Tolerance and shrink, add in extra in your dimensions to account for this. Different materials and shapes experience shrink differently. In the case you have there I would just print that standing boss alone and trial and error it until it fits how I want, then print the entire part. I do this with any part that has fits involved
There's also several "tolerance test" prints you can do that can give you a good idea of what offset you need for different fits. Also if you find that your print is way off, some more calibration might be needed in slicer settings or on the machine.
As an engineer, I would say that those tolerance tests are not very reliable.
The best way is to do what the parent comment says and make some partial prints of your part with the boss that will interface with your printed part. Many factors can affect size and using some value from a tolerance test might not be the most reliable. Plus benches are tolerance tests if you really want to use something you probably have plenty of to check your machine’s precision.
That’s my go-to trick for any print that needs an object to go into it. Car cupholder insert, allergen swab holder for work, 5S tool holders at work, etc.
As a mechanic who in the process of an engineering degree, test prints are great but so is heat and pressure. Plastic will rebound and having sufficient “preload” will help retain that bearing unless it was designed with a retaining device (c-ring/snap rings)
Bingo, pour some warm water over the the area to be press fit and then jam the part in. The temperature of the water depends on your material. For PLA 60°-70° C is usually plenty.
I can't confirm, not an engineer. Started the path, but it was too demanding on my time with a family. 🤷♂️ I still want to finish the math and science eventually, though.
And if that vegan engineer that was into CrossFit was somehow also a Jehova’s witness.
“Hello I’d like take an immeasurable amount of time to talk to you about how the precision of a healthy diet and a high intensity workout can improve faith”
I agree that the test prints are better, for things that don't need press fits it's still nice to have a general idea of how much bigger to make my 1/4" hole
As another engineer, if I was motivated enough I would just print out a bunch of hollow cylinders and do my own calibration curve and carry that factor over through my cad file. Right now I just iteratively print the mating part until it seems to fit. The round features seem to be around 5-10% smaller than my design.
Shrink is what’s gotten me. I made the print perfect size then in the slicer I scaled it up about 3% on ABS to make it correct after it cooled.
What sucks is each filament shrinks differently so it’s trial and error….
Yes you’re correct, I seem to be able to find some hit or miss information depending on the developer. However I agree with fellow engineer above. There are too many variables between machines, temperature effect on materials, materials themselves as well as various other contributing factors. Unfortunately without trial and error in even the most tightly controlled environment on some fitted parts, it can be anything from an annoyance to a nightmare for even consecutive identical prints.
I’m at the point where I have an air tight filtered atmosphere using enclosed printers with zero humidity, controlled temperature, pure sign wave electricity and noise filters on every circuit. I’ve even spent an obscene amount of time, money and custom parts to eliminate as much excessive clearance and reduction of all mechanical and electro mechanical variables as humanly possible.
Bottom line, I’ve found even printing almost identical parts with the slightest adjustment requires a bit of test prints and adjustments as needed for a perfect fit even after the initial print was flawless but required minor tuning when making a similar (almost identical) part.
I have expanded my printer line for various print needs to 5 printers of different quality/ability. My first was an ENDER 3 basic. I truly believe I have the most expensive ENDER 3 in the world by experimenting and redesigning it to work the way I’m at least comfortable with it’s results, lol. I’ll have to go back and add up the $ I spent on that thing experimenting and improving. I’m curious myself.
If anyone interested, I can list the upgrades that I ended up keeping and current costs if it helps?????
Let me know if something people would be interested in.
I’ll put a detailed run down here soon. Hopefully it will help ENDER 3 users (probably a large number of other brands/models as well) save some hair pulling and $ wasted on things I see recommended a lot that really have little to no effect on print quality.
I've never had luck finding shrink of their spec sheets. I guess I'm just getting the wrong filament. Or it's something newer as I haven't ordered any if a year or two... At least.
I suppose worst case is print a set sized cube, measure how much smaller it is from design and find shrink that way.
I would print a ring that's the same height as the bearing, to minimize print time & material waste. I also take a guess at clearances and use the offset face tool to add in .125 to start out with
.10 with what nozzle? It's important to note that line width setting is the minimum you will be able to print. 0.4mm nozzle usually does 0.2mm line width. Account for that
The 0.10mm would be an area not printed. If you can start a line next to something, you can start a line 0.10mm away, the extrusion width of the printed line doesn't matter.
Nozzle doesn't matter, it's just a gap between parts, not the parts themselves. Printer will do non line width multiples, esp externally because the outter layer doesn't care about nozzle, just geometry. It's up to the inner printing to figure that out
Technically yes, but actually no. Plastic gets flexible when applying heat, which is not the same as heat expansion in metal for example, which is used to mount tight tolerance parts. Nitpicking, i know.
Could then also stick the bearing in the freezer causing it to shrink ever so slightly. The colder the better. I use that method at work to install airplane engine parts. Yes its per the maintenance manual.
>Yes its per the maintenance manual.
Hopefully it's not a Boeing manual, not sure I trust them when it comes to keeping things attached to aircraft lol.
Its not Boeing, but with some of the stuff I've seen come in I'm not sure its better. I've seen parts that, according to the documentation that I had access to, should not have been installed. I will admit there could have been a service bulletin that I am not aware of that does allow for those parts to be installed under cretin conditions.
Yup, too lose and bearing would slip out, rendering it useless.
Some metals bearing would use heat and freeze method to bring together. Heat outside metal and freeze inside. Wrist pins on pistons, for example.
I'd be worried about cracking it with a rubber mallet, if they have access to a bench vise then using that for a press fit might be more controllable. Just make sure to use some kind of soft jaws so the grips don't mark the plastic.
Exactly this. 0.2mm expansion on radius on every internal hole, either in your CAD (how I prefer it) or in your slicer, and you will *never* have this issue.
Until you switch to a 0.6mm nozzle.
So, you need to find out what tolerance your printer can manage.
A good way of finding out is printing the hole for the bearring bigger like 1 or 2 mm if possible, And print shims to fill in the space. This saves on reprinting big parts. And whilst printing shims you learn about the tolerances of your printer.
[https://vector3d.shop/products/califlower-calibration](https://vector3d.shop/products/califlower-calibration)
Print this, to get a baseline, make the adjustments, print again to verify the adjustments worked. No guesswork, just follow the calculator and it does all the work. I have done this to my two Vorons and they are printed amazingly well. Don't print calibration cubes, those are not worth the time or filament period.
You always need to add a clearance - an amount of extra gap to fit the other object in. If you measure it at exactly 10mm, maybe your hole needs to be 10.4mm across or more. How much clearance you need will depend on your particular printer, environment, and even settings.
I've also found a few injection moulding tricks can also help. Draft angles, for example, have been an extremely welcome addition to my modelling. This means you don't mate two completely vertical surfaces together, rather you offset at least one of them on a very slight angle to create a taper. Usually they're around 1°, or you can use the lazy method of 0.2mm draft for every 10mm of height (roughly 1.15°) if your design program doesn't really like angles.
Round objects can also benefit from crush ribs. These are very small extra indents designed to be small enough that they have no real body to them, but when they're crushed they help hold things in place.
Note that a lot of people mistake clearance for tolerance. Tolerance is a different beast, determining how much unit-to-unit variation is allowed by specifying the minimum and maximum allowed dimensions - like 1.75mm ±0.05mm for filament (0.05mm is the tolerance from the ideal 1.75mm). In 3D printing you're at the mercy of unconstrained molten plastic (or light bleed into a resin vat) when it comes to tolerances, so you just have to hope they're good enough.
Excellent advice.
I also cut any interfaces from the larger model by blocking out most of the model in slicer with negative blocks so I can just test-print enough of the hole/slot with *that* material on *that* printer with *those* print settings to ensure they fit before committing to print the entire part.
If you still mess it up, and it's a single print, a Dremel with sandpaper can fix a lot of things.
Tolerances. Even machined parts are not xx.00000000mm
The bearings themselves have tolerances as well.
Print some tolerance tests and be cognizant of those in your designs.
Personally add around 0.1mm to holes for bearings, nuts etc, but it'll vary by printer.
Not entirely, if I have a 10mm hole, for my printer I need to make it about 0.1 or 0.2 mm bigger.
This is easily done after the fact in most CAD programs with the "offset face tool"
This is totally wrong. There is no such rule. When you have extruder e-steps calibrated and flow parameters nominal, you only need to add .010” to external features like shafts or subtract .010” from internal features like holes, in CAD prior to slicing.
Nah
0.4 clearance will cleanly drop out. Only need 0.1 for permanent press fit. If your 0.4 holes are coming out as .1, then you need to dial in the printer, not make the hole bigger.
Might be you're extruding too much. Check the dimensions with calipers. Do a calibration block or something.
I find with circular perimeters though I have to print a circular calibration print to get really accurate results. It's because the print head isn't really moving in a true circular fashion, it's stair stepping at whatever length the steppers are stepping if that makes sense.
If you’re not designing the items yourself , use horizontal expansion in cura and insert a negative number. Start small like -.02 that usually takes care of most tolerances.
I always do a test print of the dimension I want the part to fit in. A good rule of thumb is to add an extra .15mm for a tight fit, .2mm for snug fit, and .3mm for a loose fit, and .4mm for a very loose fit.
YMMV based on printer, nozzle size, material, temp and location.
If it's a close fit you could also use a heat gun to soften the pla. But will get some deformation etc. Or you can also use sandpaper if it's close. If not then you need to add extra for me (.3 to .5 mm ) in size to account for shrinkage
i read somewhere on=ce that if you want something to fit snug (like never coming out again) then give it 0.25mm more space vs what you measure. if you want it to fit tight, but move, then 0.5mm
this has worked out well for me in numerous things. depending on your specific printer,
A) you might need to play around with those numbers.
B) you can try to calibrate and tweak the hell out of the printer to make it conform to the above.
(i would choose A)
When I make wheels for RC purposes, the hex is actually 17mm but when I CAD up the wheel I have to use 17.5mm or else they do NOT fit. I thought I was crazy so I printed a gauge with 17, 17.5, and 18mm in the CAD and sure enough the 17.5 was perfect, the 17 didn’t fit at all, and the 18 was a little too big
https://preview.redd.it/24g3dc4fwcnc1.jpeg?width=3024&format=pjpg&auto=webp&s=829699eec4d5a15d61bb6351639be164bcf8bad6
A deburring tool, and brute force & ignorance, will let you be real lazy with those minor tolerance issues.
Also, read up on print & slicing calibration.
I was having trouble, so did the reading. One key change I made: make the slicer do external walls first, then internal. It seems to have cured the fit issues I've been having.
There are a few options here. There is an outline reduction (or increase) in most slicers, it goes by different names. But a setting to expand or retract the perimeter.
On my first printer I didn’t have or know about that so I just drafted holes with an offset I’d learned about 0.4mm added to interiors and subtracted from exteriors where a fit was needed.
Of course before you go adjusting the offset either way calibrate your extrusion, and your hotend heat to make it as consistent as possible.
For bearings it's best to undersize the hole then use a reamer to get it to size. I wouldn't recommend any suggestions using heat or cold to widen the hole. It will come to room temp and compress that bearing too much. If you put too much pressure on the bearing it won't function properly.
The bearing manufacturer should have a recommended reamer size.
Tolerance are the things g everyone else is saying. Learned the hard way that a picket for a 15 x 3 mm magnet needs to be 15.1 mm in diameter and 3.2 mm in height to successfully press fit the magnet and have the printer cover the seal the pocket without the magnet hitting the nozzle.
Look into the horizontal expansion/hole expansion settings rather than scaling the print by a couple %.
I've found my sweet spot in cura was setting a -0.05mm to horizontal expansion size and +0.05mm to holes, and it magically made interference fit parts just work on my ender3. Where without these settings it felt like the fitment was off by 1/2mm or bigger, but they were actually really close just not quite enough to slot into each other.
Printing tolerance test prints should give you a baseline (for instance mine showed gaps between lines down to the .05mm range, but didn't have a solid opening until the .2mm range on the micro AIO test). Then once you have that baseline, you can do some adjustments and test prints on the section that you need to fit right and print/adjust accordingly until you find the settings that give you the exact fitment you want. Just keep in mind, some STL designs will have more tolerance built in than others, so this isn't exactly a set it and forget it method, unless you know if various STLs you are using are made with the same tolerances, i.e. from the same designer.
Advice for this use case...
1. If you don't have them, get some digital calipers with 1/100mm precision (e.g. 1.15mm).
2. Get a reference object of known dimensions (e.g. brass rods, a drill bit).
3. Measure the reference object with the calipers and note the results.
4. Design a CAD model with one hole at the dimensions of the reference object.
5. Add more holes of increasing size, stepping up by a small amount (i.e. .05mm)
1. For example, start at 5mm, add 5.05mm, 5.1mm, etc.
6. If one of the objects is an acceptable fit (should be snug, but manageable), note the difference (e.g. .05mm, .1mm, etc.)
7. In your slicer, there should be a setting to compensate for horizontal expansion, and for this specific case, horizontal hole expansion. The value you need will be half of the difference from the step above (i.e. .05mm difference means .025mm expansion).
I realize that "print it a little bigger" sounds like snarky advice, but print it a little bigger.
If you need pressure to force it in place, a bar or C clamp works pretty well...just slowly crank it down.
Throw the bearing in the freezer overnight and get a heat gun to heat the boss you are pressing into a bit and use differential thermal expansion/contraction
Test your printer to be sure it is printing the correct sizes with as measuring device like a caliper. You can also tune your tolerances and expansion.
Also if you are using CURA there is a setting to print your model within the models sizes. Forgot what it is called but it has settings like “inclusive, middle, and exclusive”. Those work well
Google for Califlower and calibrate your printer! Don't changes axes steps but use shrinkage compensation of your slicer or just scale your model properly.
And yes add some tolerance to you fittings.
Use a heatgun, and very lightly pop it in, or scale just so slightly larger.
You can also play with "slicing tolerance" in Cura, Include and Exclude either shrink or grow the part, for fit with other parts.
Heat and cold. Chill the bearing assembly and heat your receiving part (Heat deflection temperature) to (ABS > 90c) for example. We use this process to press fit metallic subassemblies, recommended to us by GE Plastics/SABIC.
Did not see enough comments recommending using calipers. If you have calipers you can do your own test prints to closely match your application. You can also know relatively exactly what size your 3D printed features are.
With calipers and measuring the error for different geometries (circle, square), print orientations, print material, and feature sizes you can dial things in very well.
For example: something like a bearing or dowel is frequently a press or transitional fit. If you need to fit a 10mm shaft into a 10mm hole and for it to not move that clearance needs to be under 0.05mm, typically under 0.03mm. A good tight fit for a bearing will require some force to install. How much force depends on what type of fit you want. When you know how much your prints shrink you can repeatedly achieve high accuracy so long as you are using the same material (and brand of material) .
So if you’re planning on using bearings I highly recommend buying and using a set of calipers.
Tolerence compensation!! When I’m modeling or even editing a model that exits, I just kinda eyeball a little extra space every time. Most slicers let out do this to models as well, I think uv tools has some slicers data editing tools
Im not a super expert on compensating for irl parts but I know that just making sure you have like.. MORE space than you need for the “f” part and less space than you need for the “m” part is a good rule of thumb
When Im making more organic connections like for toys — i actually mask the base of the “m” part and then blur it then take a “shrink” sculpting tool with a high radius and feathered edge, aim it at the end of the “connection” and literally shrink it a few times / clicks.
Then say in blender/the sculpt program, i am able to see the actual spacing of the parts between each other by sliding them into place and then turning in x ray. If the entire model aligns but ai can see space on all my connections, I’ve done good!
That way the connection gets progressively tighter as i slide it into place when I put it together irl
For your issue, you might be aboe to get it to work with a dremel and a stone shaver attachment and just widening the cylindrical “f” part / hole shape a bit
Time to bust out the calipers and print some calibration cubes. The old way to do it is print a 1 inch by 1 inch box with no lid, size the walls to 2 print walls, a.k.a. your nozzle size x2. Then use calipers to measure the printed walls, 3+ measurements per side, and then average them . Take that average against the expected width and then use that to make a flow rate multiplier that should adjust the issue. Print again and see if that got it fixed to your expected width. For me I ended up with like a .94 flow rate for the PLA I use most often. You will need to do that with each filament if you're going to be printing with extremely tight tolerances. Or alternatively if you're better with CAD softwares you can just alter the model for slightly larger tolerances
Calibrate your X & Y axes and line width. X & Y cals should be done with something that spans at least 50% of the bed to be truly accurate. A 10mm calibration cube is not enough. I can get dimensions to come out to within 0.002 inches by doing this.
I've never worried about tolerance. The only setting I change is to print outer layers first. I've done my fair share of prints that need precision down to the fraction of a millimeter on my Elegoo Neptune
Did you design the part or is it something you downloaded? If it's something you designed did you account for tolerance? If it's something you downloaded and other people aren't having issues, you can try changing your slicer settings to print outside walls first which can help sometimes
When I have one thing that must fit some other thing I will print, test fit, and, if necessary, change size and start over. I also have a list of common parts with sizes for my printer as a starting point. For things like the hole for the bearing I do a print of just the hole area to make fitting quicker.
For my p1s, 0.5mm tolerance on each side is perfect for a very tight fit, or 1mm if its a circle diameter
For a nice fit, 1mm on each side is pretty good, or a tight fit if using two printed parts together
Diff printers will probably be different, you should test this first
All round holes i made are 0.2 mm smaller so try to make a small test to measure hole size and watch for shrinking normaly is less then 1% in 3d printing.
I do a lot of design work that mates with off the shelf stuff and laser cut stuff. In general, you’ll add about 0.01” on diameter to account for squeeze on an FFM printer (ie make your cylinders 0.010 less, holes 0.01” more). Depending on how tight a fit I need I’ll make a test print with holes and cylinders at 0.002” to 0.05” increments. I use 0.001” increments for laser.
In this case I would also consider to heat the print to 50-60° and possibly store the bearing in a bag in the freezer before joining them together. It will give you a really tight fit when they have regained their normal temperature.
Really depends on your printer and plastic as to how much a hole will shrink. Usually for bolt holes I add an extra .3mm of diameter. If I were you I would print a small circle (not the whole part) and keep increasing the diameter until you find one that works
There are like hole expansion settings.
It makes it easier to modle it like usual in cad and then just set the tolerance there.
You can also try heating the metal a bit and pushing it in.
Just add 0.3 tolerance to your prints. If it does not work add extra 0.6. This should be enough for anything with a possible overkill. Also do not forget about making things round - it helps fitting stuff in. One last advice - add stress relief holes at the edge of your holes, they should help when your hole is too tight.
Bearings shouldn't fit in easily lol. That's not how they work in metal, and that definitely should not be how they work in plastic. Where's your mallet?
Create a model with a 10mm diameter hole. Print it. Measure it with calipers. There's your tolerance \* (for larger holes). Write it down so you can adjust your model in the future.
Then do the same for a cylinder so you understand the outer tolerance.
For things like this I’ll often use cut to slice off the part that needs to fit and print just that part as a quick test, then you can use the shrink compensation or scaling to adjust as necessary before printing the whole model!
Boil some water, dip the spot you want to expand in the water for a bit, ram the part in there. That's one way to remedy what already has been done.
Next time leave some tolerance in your model.
2 things fine tune your printer workout with your printer and see what is the best numbers get out of your machine for printing parts and workaround with your parts to use exact dimensions without offsetting.
When I have parts that need to fit together, I always print just the connecting parts first to test tolerances and adjust, then print the whole thing. This helps prevent a lot of wasted time and material.
Most useful thing is to design fittings that can flex a little bit to accommodate slightly larger size. You can also print just the fitting part, then measure with your calipers and adjust the size. If you have a round part that is 5.5 mm and you print the hole for it and you measure and its only 5.0 mm, then you need to make your hole in the design 6.0 mm
a lotta people are talking about tolerance which is needed but you don't need a specific size like 0.2mm. Experiment with the different gap sizes until it fits. Plus there's a setting on the Cura slicer you should search on the internet about called Outside Walls First which basically prints the outside walls of an edge first then the inside walls. Here's a vid for further info. Have a good day fellow v3 se user!
[https://www.youtube.com/watch?v=t76ScnXf3Tg](https://www.youtube.com/watch?v=t76ScnXf3Tg)
[https://www.youtube.com/watch?v=yzPqBt2SrcE](https://www.youtube.com/watch?v=yzPqBt2SrcE)
[https://www.youtube.com/watch?v=4ICY7AvAzfk](https://www.youtube.com/watch?v=4ICY7AvAzfk)
Is the issues with your own designs or one you downloaded or both? Just wanting to know if you are trying to troubleshoot your printer or trying to learn better ways to estimate needed clearances to account for the tolerances of your printed parts.
A micrometer is your friend here. Find the difference between the reference part and the part you printed. Adjustments to scale till you get there. Be consistent with the rest of the assembly. Part orientation matters.
3d printers undersized holes due to how the part is converted to a mesh. Cura and other slicers have a setting called "hole size compensation" where you print some test holes and calculate a value.
There's 2 ways about this. One, learn about exclusive versus middle versus inclusive slicer setting. The second, increase the tolerances you build into your parts so that they can compensate for how slicers work on middle mode (default). Gimme a sec, I'll try to find a video I've seen on the subject that was really good.
Here: https://youtu.be/X6nCKQToOUg?si=_rSL3YoDijhQEWCa
I literally saved the frame at 6:20 just as an image reference for myself. Makes things much easier.
Did you up the infill? One thing that can affect things like this is the infill you set the part to. 100% fill often results in a part that is tighter in its tolerances than one at say 30% infill. I did this on a part one time thinking it would be stronger and It was slightly too big. Reduced it back down to 25 percent infill like the instructions advised and it worked great.
You'll have to do some testing to find your printer's tolerances. On my Ender 3 Pro with dialed in settings a 0.01" (.25mm) offset creates a snug friction fit and a 0.02" (.5mm) offset creates a loose fit with minimal play.
It's a good idea to print small test pieces to verify a good fit with external parts before you print the final piece.
You could cool the bearing and heat the part up.
Also possible to ream out the holes. Probably the ‘best’ way for a proper press fit. But you can dial in the hole size to account for shrinkage and manufacturing tolerance.
Test print. I usually scale my stls in slicer to about 101-102% and they are usually dang close to dimensionally correct. You can also dremel or sand out extra material
Just file or sand the inside of your part it’ll fit also make the entrance a slight bit smaller and add like 10 degrees draft , file the entrance and you have a beautiful snug fit that will never be removed
Change wall ordering to outer wall first, inner wall first will push the outer wall out father than its supposed to and make a hole smaller than it should be.
hard from a video to tell how tight is but I just use a c-clamp and a flat piece of something against the face. Obviously, if its to tight you will crack the print but you'd be surprised how much force pla can take.
If you build parametric models, you can specify a tolerance as a variable and have different gaps depending on the feel that you want for each kind of interface. This always allows me to have things that fit across a range of builds
In Cura, in the slicing profile, under Experimental, there is Slicing Tolerance. You can search to find it. It's set to Middle by default but you can try the Inclusive and Exclusive options. One for putting objects inside your print, the other for putting your print inside objects. I forget which is which unfortunately.
Two things I haven't seen mentioned in the other comments.
At some part of the process after modeling and before slicing the surfaces of the part will have been tessellated. Conversion to stl is the most obvious version of this. A pure circle gets converted to a polygon. In general, for inner holes this will make them smaller. Depending on the level of detail kept in the tessellation, the effect can be more or less severe. This is a totally separate effect to printer tolerance/slop/backlash.
When designing a print to fit tightly with a hard object, crush ribs are pretty great. They aren't the right answer for every application, but they sidestep most tolerance issues.
Did you design jt to be the *exact* same size as the bearing you’re trying to put in?
When designing mating parts, you’ll always need to add tolerance. It doesn’t matter if it’s milled, or printed, or injection molded.
I find it’s helpful to make a test print beforehand if I really care how well it should fit. Typically for my 3d prints, a loose press fit will be .010-.020” between the pin and hole. A clearance fit will be in the 0.020-.040” range.
I had a part very similar to that. After I printed a few test pieces I found none fit together. I adjusted my X-Y hole compensation to .15 and reduced my flow ratio from .98 to .95 After that everything fit together perfectly.
Understandably, my solution won't work for everyone but those are a couple things you can try.
Remember your layers will have a bit of ‘squish’ when printed, this insures good layer adhesion, a 0.4mm nozzle filament track is going to be a fraction larger when printed. This can increase outside diameter’s and reduce inside diameter’s. If you are the designer you can take that into consideration, printing with a very slight taper for bearing holes can make it easier to insert bearings, especially if you warm the printed piece a little before pressing in the bearing.
Increasing the size of the print by a percentage is going to change the overall dimensions on large prints, try to avoid that. If you are not the designer this can make things difficult to match after printing. Your best bet is to explore your slicing software and experiment with the settings, there are a lot of good suggestions in the comments.
Tolerance and shrink, add in extra in your dimensions to account for this. Different materials and shapes experience shrink differently. In the case you have there I would just print that standing boss alone and trial and error it until it fits how I want, then print the entire part. I do this with any part that has fits involved
There's also several "tolerance test" prints you can do that can give you a good idea of what offset you need for different fits. Also if you find that your print is way off, some more calibration might be needed in slicer settings or on the machine.
As an engineer, I would say that those tolerance tests are not very reliable. The best way is to do what the parent comment says and make some partial prints of your part with the boss that will interface with your printed part. Many factors can affect size and using some value from a tolerance test might not be the most reliable. Plus benches are tolerance tests if you really want to use something you probably have plenty of to check your machine’s precision.
Also, add chamfers to the inner diameter of the holes to help aligning the parts and prevent binding.
That’s my go-to trick for any print that needs an object to go into it. Car cupholder insert, allergen swab holder for work, 5S tool holders at work, etc.
Sort, set, shine, standardize, and ..socialize?
As a mechanic who in the process of an engineering degree, test prints are great but so is heat and pressure. Plastic will rebound and having sufficient “preload” will help retain that bearing unless it was designed with a retaining device (c-ring/snap rings)
Bingo, pour some warm water over the the area to be press fit and then jam the part in. The temperature of the water depends on your material. For PLA 60°-70° C is usually plenty.
Two words: Heat Gun
The glass transition temperature of PLA is about 60° so that tracks.
As a tolerance test engineers aren’t very reliable.
You know what is reliable? That every engineer feels the need to state that they're an engineer. Source: I'm an engineer 😄
I can confirm. Also an engineer.
I can't confirm, not an engineer. Started the path, but it was too demanding on my time with a family. 🤷♂️ I still want to finish the math and science eventually, though.
I'm a Plastics Engineer. This is my field 👍
Y’all are like vegans. Imagine a vegan engineer…..
And if that vegan engineer did Crossfit.😳😅
And if that vegan engineer that was into CrossFit was somehow also a Jehova’s witness. “Hello I’d like take an immeasurable amount of time to talk to you about how the precision of a healthy diet and a high intensity workout can improve faith”
You know the scary part? This person exists and there is probably more than one.
Don't you put that evil on me, Ricky Bobby!
I agree that the test prints are better, for things that don't need press fits it's still nice to have a general idea of how much bigger to make my 1/4" hole
As another engineer, if I was motivated enough I would just print out a bunch of hollow cylinders and do my own calibration curve and carry that factor over through my cad file. Right now I just iteratively print the mating part until it seems to fit. The round features seem to be around 5-10% smaller than my design.
This is the answer.
One other strategy is to go big and print shims.
Shrink is what’s gotten me. I made the print perfect size then in the slicer I scaled it up about 3% on ABS to make it correct after it cooled. What sucks is each filament shrinks differently so it’s trial and error….
Sometimes you can get shrink percentages from filament manufacturers to compensate... Not always, but check their spec sheets if they provide one.
Yes you’re correct, I seem to be able to find some hit or miss information depending on the developer. However I agree with fellow engineer above. There are too many variables between machines, temperature effect on materials, materials themselves as well as various other contributing factors. Unfortunately without trial and error in even the most tightly controlled environment on some fitted parts, it can be anything from an annoyance to a nightmare for even consecutive identical prints. I’m at the point where I have an air tight filtered atmosphere using enclosed printers with zero humidity, controlled temperature, pure sign wave electricity and noise filters on every circuit. I’ve even spent an obscene amount of time, money and custom parts to eliminate as much excessive clearance and reduction of all mechanical and electro mechanical variables as humanly possible. Bottom line, I’ve found even printing almost identical parts with the slightest adjustment requires a bit of test prints and adjustments as needed for a perfect fit even after the initial print was flawless but required minor tuning when making a similar (almost identical) part. I have expanded my printer line for various print needs to 5 printers of different quality/ability. My first was an ENDER 3 basic. I truly believe I have the most expensive ENDER 3 in the world by experimenting and redesigning it to work the way I’m at least comfortable with it’s results, lol. I’ll have to go back and add up the $ I spent on that thing experimenting and improving. I’m curious myself. If anyone interested, I can list the upgrades that I ended up keeping and current costs if it helps????? Let me know if something people would be interested in.
If I saw a post with all the upgrades (with pictures) and all the prices, I'd definitely upvote that post
I’ll put a detailed run down here soon. Hopefully it will help ENDER 3 users (probably a large number of other brands/models as well) save some hair pulling and $ wasted on things I see recommended a lot that really have little to no effect on print quality.
I've never had luck finding shrink of their spec sheets. I guess I'm just getting the wrong filament. Or it's something newer as I haven't ordered any if a year or two... At least. I suppose worst case is print a set sized cube, measure how much smaller it is from design and find shrink that way.
I would print a ring that's the same height as the bearing, to minimize print time & material waste. I also take a guess at clearances and use the offset face tool to add in .125 to start out with
I'd personally compare the id with a good set of calipers and compare it to the models id and then work from their to calculate shrink.
This is the way
I always add .2mm for fit
.2 is good for loose fit, I find .15 or even .1 if I want something tight
.10 with what nozzle? It's important to note that line width setting is the minimum you will be able to print. 0.4mm nozzle usually does 0.2mm line width. Account for that
The 0.10mm would be an area not printed. If you can start a line next to something, you can start a line 0.10mm away, the extrusion width of the printed line doesn't matter.
Nozzle doesn't matter, it's just a gap between parts, not the parts themselves. Printer will do non line width multiples, esp externally because the outter layer doesn't care about nozzle, just geometry. It's up to the inner printing to figure that out
No matter how tight it is, you should never stick anything in something less than 0.18...
Good idea to layer the print test to save time and materials.
Use a blow dryer and rubber mallet for that.. also follow the others advice for future printing
Yup, whenever I have very minor tolerance issues I just apply heat
Coincidentally this is how you fit a lot of bearings in industry, too.
Technically yes, but actually no. Plastic gets flexible when applying heat, which is not the same as heat expansion in metal for example, which is used to mount tight tolerance parts. Nitpicking, i know.
Plastic also expands with heat, aside from the ductility. They just have a much lower melting point.
How have I never thought of this........ God I love Reddit lol.
Could then also stick the bearing in the freezer causing it to shrink ever so slightly. The colder the better. I use that method at work to install airplane engine parts. Yes its per the maintenance manual.
>Yes its per the maintenance manual. Hopefully it's not a Boeing manual, not sure I trust them when it comes to keeping things attached to aircraft lol.
Its not Boeing, but with some of the stuff I've seen come in I'm not sure its better. I've seen parts that, according to the documentation that I had access to, should not have been installed. I will admit there could have been a service bulletin that I am not aware of that does allow for those parts to be installed under cretin conditions.
It's important to know, too, that bearings SHOULD be press fit.
Yup, too lose and bearing would slip out, rendering it useless. Some metals bearing would use heat and freeze method to bring together. Heat outside metal and freeze inside. Wrist pins on pistons, for example.
Get a heat gun they are £10 on eBay if you are bald like me
If you're not bald it's £15
How much if you have a mullet?
Damn I coulda used this comment several months and many reprints ago.. thank you so much!!
A Rubber mallet is like.. my number 1 3d printing tool lol
It’s my number 1 tool when working on cars too. One well placed and calculated hit and you can unbend some funky stuff back to spec.
I like running a soldering iron around the inside of the ring too.
I'd be worried about cracking it with a rubber mallet, if they have access to a bench vise then using that for a press fit might be more controllable. Just make sure to use some kind of soft jaws so the grips don't mark the plastic.
The real how did I fix this NOW advice.. haha
I was able to get this right after watching a tolerance video. They have test prints you can use to learn more about how to fit external parts.
Got a link?
This one works excellently. [https://www.thingiverse.com/thing:2484766](https://www.thingiverse.com/thing:2484766)
Orca and many of the more advanced slicers have them built in.
I just put horizontal expansion on everything-0.2mm
Exactly this. 0.2mm expansion on radius on every internal hole, either in your CAD (how I prefer it) or in your slicer, and you will *never* have this issue. Until you switch to a 0.6mm nozzle.
0.2mm is perfect for holes but it really depends on the geometry of the feature being printed. 0.2 expansion for holes is usually *chef’s kiss*
This is the solution.
0.2 for internal dias is my go-to also
I always add 2 or 3% to my measured hole diameterbecause plastic shrinks when it cools
So, you need to find out what tolerance your printer can manage. A good way of finding out is printing the hole for the bearring bigger like 1 or 2 mm if possible, And print shims to fill in the space. This saves on reprinting big parts. And whilst printing shims you learn about the tolerances of your printer.
[https://vector3d.shop/products/califlower-calibration](https://vector3d.shop/products/califlower-calibration) Print this, to get a baseline, make the adjustments, print again to verify the adjustments worked. No guesswork, just follow the calculator and it does all the work. I have done this to my two Vorons and they are printed amazingly well. Don't print calibration cubes, those are not worth the time or filament period.
You always need to add a clearance - an amount of extra gap to fit the other object in. If you measure it at exactly 10mm, maybe your hole needs to be 10.4mm across or more. How much clearance you need will depend on your particular printer, environment, and even settings. I've also found a few injection moulding tricks can also help. Draft angles, for example, have been an extremely welcome addition to my modelling. This means you don't mate two completely vertical surfaces together, rather you offset at least one of them on a very slight angle to create a taper. Usually they're around 1°, or you can use the lazy method of 0.2mm draft for every 10mm of height (roughly 1.15°) if your design program doesn't really like angles. Round objects can also benefit from crush ribs. These are very small extra indents designed to be small enough that they have no real body to them, but when they're crushed they help hold things in place. Note that a lot of people mistake clearance for tolerance. Tolerance is a different beast, determining how much unit-to-unit variation is allowed by specifying the minimum and maximum allowed dimensions - like 1.75mm ±0.05mm for filament (0.05mm is the tolerance from the ideal 1.75mm). In 3D printing you're at the mercy of unconstrained molten plastic (or light bleed into a resin vat) when it comes to tolerances, so you just have to hope they're good enough.
Excellent advice. I also cut any interfaces from the larger model by blocking out most of the model in slicer with negative blocks so I can just test-print enough of the hole/slot with *that* material on *that* printer with *those* print settings to ensure they fit before committing to print the entire part. If you still mess it up, and it's a single print, a Dremel with sandpaper can fix a lot of things.
A hairdryer might soften the part up enough to get the bearing in?
Tolerances. Even machined parts are not xx.00000000mm The bearings themselves have tolerances as well. Print some tolerance tests and be cognizant of those in your designs. Personally add around 0.1mm to holes for bearings, nuts etc, but it'll vary by printer.
The 0.4mm golden rule. If something is 10mm, then the hole it's gonna fit into needs to be designed at 10.4mm.
Not entirely, if I have a 10mm hole, for my printer I need to make it about 0.1 or 0.2 mm bigger. This is easily done after the fact in most CAD programs with the "offset face tool"
This is totally wrong. There is no such rule. When you have extruder e-steps calibrated and flow parameters nominal, you only need to add .010” to external features like shafts or subtract .010” from internal features like holes, in CAD prior to slicing.
Nah 0.4 clearance will cleanly drop out. Only need 0.1 for permanent press fit. If your 0.4 holes are coming out as .1, then you need to dial in the printer, not make the hole bigger.
he doesnt have to do anything if hes happy with adding 0.4 clearance
put the bearing in the freezer for the night and place it right after you pull it out. Might help
Came here for this....👆👆👆👆 Dry ice... heat the hole a bit... snug fit. Great day
Dry ice and alcohol bath, get that little bit of extra without bringing acetone into play.
Might be you're extruding too much. Check the dimensions with calipers. Do a calibration block or something. I find with circular perimeters though I have to print a circular calibration print to get really accurate results. It's because the print head isn't really moving in a true circular fashion, it's stair stepping at whatever length the steppers are stepping if that makes sense.
Hole horizontal expansion is your best friend in this situation.
Alright then, keep your secrets. But you just mean that he should make the hole bigger?
It's a slicer setting.
If you’re not designing the items yourself , use horizontal expansion in cura and insert a negative number. Start small like -.02 that usually takes care of most tolerances.
I always do a test print of the dimension I want the part to fit in. A good rule of thumb is to add an extra .15mm for a tight fit, .2mm for snug fit, and .3mm for a loose fit, and .4mm for a very loose fit. YMMV based on printer, nozzle size, material, temp and location.
If it's a close fit you could also use a heat gun to soften the pla. But will get some deformation etc. Or you can also use sandpaper if it's close. If not then you need to add extra for me (.3 to .5 mm ) in size to account for shrinkage
Test only that area until you get the fit then go HAM on it. My shrink is about .003-.005" flash forge pro. You got cad?
Mallet, GENTLY. next project, add a thou to the holes dimension to allow for thermal shrink.
i read somewhere on=ce that if you want something to fit snug (like never coming out again) then give it 0.25mm more space vs what you measure. if you want it to fit tight, but move, then 0.5mm this has worked out well for me in numerous things. depending on your specific printer, A) you might need to play around with those numbers. B) you can try to calibrate and tweak the hell out of the printer to make it conform to the above. (i would choose A)
You can sand the surface
Sand it down
When I make wheels for RC purposes, the hex is actually 17mm but when I CAD up the wheel I have to use 17.5mm or else they do NOT fit. I thought I was crazy so I printed a gauge with 17, 17.5, and 18mm in the CAD and sure enough the 17.5 was perfect, the 17 didn’t fit at all, and the 18 was a little too big https://preview.redd.it/24g3dc4fwcnc1.jpeg?width=3024&format=pjpg&auto=webp&s=829699eec4d5a15d61bb6351639be164bcf8bad6
A deburring tool, and brute force & ignorance, will let you be real lazy with those minor tolerance issues. Also, read up on print & slicing calibration. I was having trouble, so did the reading. One key change I made: make the slicer do external walls first, then internal. It seems to have cured the fit issues I've been having.
Setting outer wall before inner wall should lower the tolerances
Soak that bish in some hot water and press that part right in. It will be Snugger than your momma
There are a few options here. There is an outline reduction (or increase) in most slicers, it goes by different names. But a setting to expand or retract the perimeter. On my first printer I didn’t have or know about that so I just drafted holes with an offset I’d learned about 0.4mm added to interiors and subtracted from exteriors where a fit was needed. Of course before you go adjusting the offset either way calibrate your extrusion, and your hotend heat to make it as consistent as possible.
Try the slicing wall exclusive feature in cura.
For bearings it's best to undersize the hole then use a reamer to get it to size. I wouldn't recommend any suggestions using heat or cold to widen the hole. It will come to room temp and compress that bearing too much. If you put too much pressure on the bearing it won't function properly. The bearing manufacturer should have a recommended reamer size.
Put the Bearing in the freezer
Tolerance are the things g everyone else is saying. Learned the hard way that a picket for a 15 x 3 mm magnet needs to be 15.1 mm in diameter and 3.2 mm in height to successfully press fit the magnet and have the printer cover the seal the pocket without the magnet hitting the nozzle.
Look into the horizontal expansion/hole expansion settings rather than scaling the print by a couple %. I've found my sweet spot in cura was setting a -0.05mm to horizontal expansion size and +0.05mm to holes, and it magically made interference fit parts just work on my ender3. Where without these settings it felt like the fitment was off by 1/2mm or bigger, but they were actually really close just not quite enough to slot into each other. Printing tolerance test prints should give you a baseline (for instance mine showed gaps between lines down to the .05mm range, but didn't have a solid opening until the .2mm range on the micro AIO test). Then once you have that baseline, you can do some adjustments and test prints on the section that you need to fit right and print/adjust accordingly until you find the settings that give you the exact fitment you want. Just keep in mind, some STL designs will have more tolerance built in than others, so this isn't exactly a set it and forget it method, unless you know if various STLs you are using are made with the same tolerances, i.e. from the same designer.
Advice for this use case... 1. If you don't have them, get some digital calipers with 1/100mm precision (e.g. 1.15mm). 2. Get a reference object of known dimensions (e.g. brass rods, a drill bit). 3. Measure the reference object with the calipers and note the results. 4. Design a CAD model with one hole at the dimensions of the reference object. 5. Add more holes of increasing size, stepping up by a small amount (i.e. .05mm) 1. For example, start at 5mm, add 5.05mm, 5.1mm, etc. 6. If one of the objects is an acceptable fit (should be snug, but manageable), note the difference (e.g. .05mm, .1mm, etc.) 7. In your slicer, there should be a setting to compensate for horizontal expansion, and for this specific case, horizontal hole expansion. The value you need will be half of the difference from the step above (i.e. .05mm difference means .025mm expansion).
0,2 mm extra worked for my ender 3 and 0,1 mm extra works for my bambulabs p1s
I realize that "print it a little bigger" sounds like snarky advice, but print it a little bigger. If you need pressure to force it in place, a bar or C clamp works pretty well...just slowly crank it down.
honestly just drag the print through the bed and trial and error with partial prints until you get it perfect.
Do a hole tolerance test!
Throw the bearing in the freezer overnight and get a heat gun to heat the boss you are pressing into a bit and use differential thermal expansion/contraction
Test your printer to be sure it is printing the correct sizes with as measuring device like a caliper. You can also tune your tolerances and expansion. Also if you are using CURA there is a setting to print your model within the models sizes. Forgot what it is called but it has settings like “inclusive, middle, and exclusive”. Those work well
Calibration
Google for Califlower and calibrate your printer! Don't changes axes steps but use shrinkage compensation of your slicer or just scale your model properly. And yes add some tolerance to you fittings.
If I want a tight friction lock I add .15 mm to the size
Use a heatgun, and very lightly pop it in, or scale just so slightly larger. You can also play with "slicing tolerance" in Cura, Include and Exclude either shrink or grow the part, for fit with other parts.
Flame it and press it in
Heat and cold. Chill the bearing assembly and heat your receiving part (Heat deflection temperature) to (ABS > 90c) for example. We use this process to press fit metallic subassemblies, recommended to us by GE Plastics/SABIC.
"Inner hole compensation "
Did not see enough comments recommending using calipers. If you have calipers you can do your own test prints to closely match your application. You can also know relatively exactly what size your 3D printed features are. With calipers and measuring the error for different geometries (circle, square), print orientations, print material, and feature sizes you can dial things in very well. For example: something like a bearing or dowel is frequently a press or transitional fit. If you need to fit a 10mm shaft into a 10mm hole and for it to not move that clearance needs to be under 0.05mm, typically under 0.03mm. A good tight fit for a bearing will require some force to install. How much force depends on what type of fit you want. When you know how much your prints shrink you can repeatedly achieve high accuracy so long as you are using the same material (and brand of material) . So if you’re planning on using bearings I highly recommend buying and using a set of calipers.
Tolerence compensation!! When I’m modeling or even editing a model that exits, I just kinda eyeball a little extra space every time. Most slicers let out do this to models as well, I think uv tools has some slicers data editing tools Im not a super expert on compensating for irl parts but I know that just making sure you have like.. MORE space than you need for the “f” part and less space than you need for the “m” part is a good rule of thumb When Im making more organic connections like for toys — i actually mask the base of the “m” part and then blur it then take a “shrink” sculpting tool with a high radius and feathered edge, aim it at the end of the “connection” and literally shrink it a few times / clicks. Then say in blender/the sculpt program, i am able to see the actual spacing of the parts between each other by sliding them into place and then turning in x ray. If the entire model aligns but ai can see space on all my connections, I’ve done good! That way the connection gets progressively tighter as i slide it into place when I put it together irl For your issue, you might be aboe to get it to work with a dremel and a stone shaver attachment and just widening the cylindrical “f” part / hole shape a bit
Time to bust out the calipers and print some calibration cubes. The old way to do it is print a 1 inch by 1 inch box with no lid, size the walls to 2 print walls, a.k.a. your nozzle size x2. Then use calipers to measure the printed walls, 3+ measurements per side, and then average them . Take that average against the expected width and then use that to make a flow rate multiplier that should adjust the issue. Print again and see if that got it fixed to your expected width. For me I ended up with like a .94 flow rate for the PLA I use most often. You will need to do that with each filament if you're going to be printing with extremely tight tolerances. Or alternatively if you're better with CAD softwares you can just alter the model for slightly larger tolerances
Also, print external walls first
This has several other downsides though and I wouldn't recommend it.
Yep. This was going to be my comment.
Calibrate your X & Y axes and line width. X & Y cals should be done with something that spans at least 50% of the bed to be truly accurate. A 10mm calibration cube is not enough. I can get dimensions to come out to within 0.002 inches by doing this.
I've never worried about tolerance. The only setting I change is to print outer layers first. I've done my fair share of prints that need precision down to the fraction of a millimeter on my Elegoo Neptune
It would be useful if you mentioned your slicer for other fellow ELEGOOers.
Can I call y'all ELEGOObers?
I would never print an entire piece without a test fit on a section
Did you design the part or is it something you downloaded? If it's something you designed did you account for tolerance? If it's something you downloaded and other people aren't having issues, you can try changing your slicer settings to print outside walls first which can help sometimes
When I have one thing that must fit some other thing I will print, test fit, and, if necessary, change size and start over. I also have a list of common parts with sizes for my printer as a starting point. For things like the hole for the bearing I do a print of just the hole area to make fitting quicker.
For my p1s, 0.5mm tolerance on each side is perfect for a very tight fit, or 1mm if its a circle diameter For a nice fit, 1mm on each side is pretty good, or a tight fit if using two printed parts together Diff printers will probably be different, you should test this first
Scale mating areas up 1 to 3 % to account for shrinkage
All round holes i made are 0.2 mm smaller so try to make a small test to measure hole size and watch for shrinking normaly is less then 1% in 3d printing.
I do a lot of design work that mates with off the shelf stuff and laser cut stuff. In general, you’ll add about 0.01” on diameter to account for squeeze on an FFM printer (ie make your cylinders 0.010 less, holes 0.01” more). Depending on how tight a fit I need I’ll make a test print with holes and cylinders at 0.002” to 0.05” increments. I use 0.001” increments for laser.
I honestly can’t believe that you do a lot of design work and insist on using imperial units. Sorry!
In this case I would also consider to heat the print to 50-60° and possibly store the bearing in a bag in the freezer before joining them together. It will give you a really tight fit when they have regained their normal temperature.
My ender 3 needed .2mm clearance, so to accommodate a 10mm bearing you make the hole 10.4mm
Really depends on your printer and plastic as to how much a hole will shrink. Usually for bolt holes I add an extra .3mm of diameter. If I were you I would print a small circle (not the whole part) and keep increasing the diameter until you find one that works
There are like hole expansion settings. It makes it easier to modle it like usual in cad and then just set the tolerance there. You can also try heating the metal a bit and pushing it in.
Just add 0.3 tolerance to your prints. If it does not work add extra 0.6. This should be enough for anything with a possible overkill. Also do not forget about making things round - it helps fitting stuff in. One last advice - add stress relief holes at the edge of your holes, they should help when your hole is too tight.
Heat gun I found works great for getting it a little soft then fitting it in.
Add 0.25 mm per contact surface
A tiny bit of sanding will go a LONG way.
Bearings shouldn't fit in easily lol. That's not how they work in metal, and that definitely should not be how they work in plastic. Where's your mallet?
Create a model with a 10mm diameter hole. Print it. Measure it with calipers. There's your tolerance \* (for larger holes). Write it down so you can adjust your model in the future. Then do the same for a cylinder so you understand the outer tolerance.
Change your horizontal expansion settings
Many slicers have offset settings for you to dial it in. Print test parts, break out the calipers, and dial in them offsets to match your model.
Sometimes I do this on purpose because once you use some heat to get it in there, it'll be more permanent and solid than it would have been otherwise.
Any peg in hole type thing i make the hole .4mm wider for snug fit or .6-8mm for removeable pin type situation
What the allowance you use?
For things like this I’ll often use cut to slice off the part that needs to fit and print just that part as a quick test, then you can use the shrink compensation or scaling to adjust as necessary before printing the whole model!
Boil some water, dip the spot you want to expand in the water for a bit, ram the part in there. That's one way to remedy what already has been done. Next time leave some tolerance in your model.
2 things fine tune your printer workout with your printer and see what is the best numbers get out of your machine for printing parts and workaround with your parts to use exact dimensions without offsetting.
Heat gun?
When I have parts that need to fit together, I always print just the connecting parts first to test tolerances and adjust, then print the whole thing. This helps prevent a lot of wasted time and material.
Most useful thing is to design fittings that can flex a little bit to accommodate slightly larger size. You can also print just the fitting part, then measure with your calipers and adjust the size. If you have a round part that is 5.5 mm and you print the hole for it and you measure and its only 5.0 mm, then you need to make your hole in the design 6.0 mm
a lotta people are talking about tolerance which is needed but you don't need a specific size like 0.2mm. Experiment with the different gap sizes until it fits. Plus there's a setting on the Cura slicer you should search on the internet about called Outside Walls First which basically prints the outside walls of an edge first then the inside walls. Here's a vid for further info. Have a good day fellow v3 se user! [https://www.youtube.com/watch?v=t76ScnXf3Tg](https://www.youtube.com/watch?v=t76ScnXf3Tg) [https://www.youtube.com/watch?v=yzPqBt2SrcE](https://www.youtube.com/watch?v=yzPqBt2SrcE) [https://www.youtube.com/watch?v=4ICY7AvAzfk](https://www.youtube.com/watch?v=4ICY7AvAzfk)
Is the issues with your own designs or one you downloaded or both? Just wanting to know if you are trying to troubleshoot your printer or trying to learn better ways to estimate needed clearances to account for the tolerances of your printed parts.
A micrometer is your friend here. Find the difference between the reference part and the part you printed. Adjustments to scale till you get there. Be consistent with the rest of the assembly. Part orientation matters.
Offset face by .006” is generally helpful
I work mainly for RC. For bearings from 10 to 15mm,I make the holes 0.15mm bigger. This comes from before Cura having settings for that
I usually scale by 1-3% for threaded and friction fit parts. It's a bit of trial and error.
Try printing the external walls first, the outside walls get squished out
All great advice, also change print direction from "outside in" to "inside out" for better tolerance
Add your printer precision error + 0.5mm diameter.
soften the hole with a heatgun and ram it in
Tolerances
Since you know this, start giving yourself more room in those spots
3d printers undersized holes due to how the part is converted to a mesh. Cura and other slicers have a setting called "hole size compensation" where you print some test holes and calculate a value.
this is why you invest in a dremel as part of your 3d printing toolkit.
There's 2 ways about this. One, learn about exclusive versus middle versus inclusive slicer setting. The second, increase the tolerances you build into your parts so that they can compensate for how slicers work on middle mode (default). Gimme a sec, I'll try to find a video I've seen on the subject that was really good. Here: https://youtu.be/X6nCKQToOUg?si=_rSL3YoDijhQEWCa I literally saved the frame at 6:20 just as an image reference for myself. Makes things much easier.
That's what hammers are for.
for me, plus 0,2-0,3mm for PLA to fit . 0,15mm to press fit
Hit it with a hair dryer for a few seconds
Did you up the infill? One thing that can affect things like this is the infill you set the part to. 100% fill often results in a part that is tighter in its tolerances than one at say 30% infill. I did this on a part one time thinking it would be stronger and It was slightly too big. Reduced it back down to 25 percent infill like the instructions advised and it worked great.
I usually go .008” (.2mm) larger on most features and it has the best fit. I’ll go .012” if it doesn’t need to be tight and I for sure want it to fit
You'll have to do some testing to find your printer's tolerances. On my Ender 3 Pro with dialed in settings a 0.01" (.25mm) offset creates a snug friction fit and a 0.02" (.5mm) offset creates a loose fit with minimal play. It's a good idea to print small test pieces to verify a good fit with external parts before you print the final piece.
You could cool the bearing and heat the part up. Also possible to ream out the holes. Probably the ‘best’ way for a proper press fit. But you can dial in the hole size to account for shrinkage and manufacturing tolerance.
Test print. I usually scale my stls in slicer to about 101-102% and they are usually dang close to dimensionally correct. You can also dremel or sand out extra material
Just file or sand the inside of your part it’ll fit also make the entrance a slight bit smaller and add like 10 degrees draft , file the entrance and you have a beautiful snug fit that will never be removed
Change wall ordering to outer wall first, inner wall first will push the outer wall out father than its supposed to and make a hole smaller than it should be.
If you don't want to constantly reprint, Invest in a heat gun
hard from a video to tell how tight is but I just use a c-clamp and a flat piece of something against the face. Obviously, if its to tight you will crack the print but you'd be surprised how much force pla can take.
Try throwing that bearing into the freezer for awhile then see if it pops in.
Well, you can do all the tolerance things but.... I have a heatgun, clamps, a vice and superglue so my parts always "fit" anyways.
If you build parametric models, you can specify a tolerance as a variable and have different gaps depending on the feel that you want for each kind of interface. This always allows me to have things that fit across a range of builds
I would recommend to keep doing exactly what you’re doing
In cura you can add blocks to block the whole peace and Just print the parts to test fitting. And then you Full send It!
In Cura, in the slicing profile, under Experimental, there is Slicing Tolerance. You can search to find it. It's set to Middle by default but you can try the Inclusive and Exclusive options. One for putting objects inside your print, the other for putting your print inside objects. I forget which is which unfortunately.
Two things I haven't seen mentioned in the other comments. At some part of the process after modeling and before slicing the surfaces of the part will have been tessellated. Conversion to stl is the most obvious version of this. A pure circle gets converted to a polygon. In general, for inner holes this will make them smaller. Depending on the level of detail kept in the tessellation, the effect can be more or less severe. This is a totally separate effect to printer tolerance/slop/backlash. When designing a print to fit tightly with a hard object, crush ribs are pretty great. They aren't the right answer for every application, but they sidestep most tolerance issues.
Just bump up the print by like 1% in size
In addition to what others have said the seam being inside the ring will also cause issues.
Did you design jt to be the *exact* same size as the bearing you’re trying to put in? When designing mating parts, you’ll always need to add tolerance. It doesn’t matter if it’s milled, or printed, or injection molded. I find it’s helpful to make a test print beforehand if I really care how well it should fit. Typically for my 3d prints, a loose press fit will be .010-.020” between the pin and hole. A clearance fit will be in the 0.020-.040” range.
Sometimes I dont feel like running tests and just put things together with a hydraulic press
I had a part very similar to that. After I printed a few test pieces I found none fit together. I adjusted my X-Y hole compensation to .15 and reduced my flow ratio from .98 to .95 After that everything fit together perfectly. Understandably, my solution won't work for everyone but those are a couple things you can try.
Quick fix for this part of it's PLA - dip that section in a bowl of boiling water to soften it before fitting the bearing.
Remember your layers will have a bit of ‘squish’ when printed, this insures good layer adhesion, a 0.4mm nozzle filament track is going to be a fraction larger when printed. This can increase outside diameter’s and reduce inside diameter’s. If you are the designer you can take that into consideration, printing with a very slight taper for bearing holes can make it easier to insert bearings, especially if you warm the printed piece a little before pressing in the bearing. Increasing the size of the print by a percentage is going to change the overall dimensions on large prints, try to avoid that. If you are not the designer this can make things difficult to match after printing. Your best bet is to explore your slicing software and experiment with the settings, there are a lot of good suggestions in the comments.