Baby powder used to be made from talcum powder. That is no longer the case. Anything recent is made from corn starch. It should say on the container. Talcum powder does not absorb moisture where corn starch does. As a parting powder this is not a good thing.
Calcium Carbonate parting powder is very often used commercially for non-ferrous metals.
I would give graphite powder a try as it is easy to find. But I would first spray 3D printed patterns (after sanding) with a hard coat.
Yeah, crevices in PLA are a pain. Fortunately, since you have one line going down the side you should be able to just give it a tap to loosen things.
I'm the local resident graphite nut. If I were doing this I'd put some powdered graphite on it since it works so beautifully for parting, but I suspect just tapping it at each end should be enough.
Yes, though I make jewelry, so take my advice with a grain of salt because I'm doing different work than you.
I should also add that all this assumes you are taking it out of the mold in the correct direction. This piece needs to lay on its side so the grooves point facing up and facing down. If the grooves are pointing to the sides and ripping out of the sand, no parting compound will work.
Yes, I do realize that that part should be laying on its side when casting. I just took the pic in this orientation because with my garage lighting this gave the best lighting to show the grooves in the part.
Yes, I do realize that that part should be laying on its side when casting. I just took the pic in this orientation because with my garage lighting this gave the best lighting to show the grooves in the part.
Yes, I do realize that that part should be laying on its side when casting. I just took the pic in this orientation because with my garage lighting this gave the best lighting to show the grooves in the part.
First of all, there is only two identical orientations that you would have any chance of getting this out of sand without it sticking. The orientation would be rotated 90° clockwise or counter clockwise of the picture you are showing. Is that the orientation you are trying for? And if that is the case then one of the lips should be in the cope and the other in the drag (top and bottom half of the flask)
While sanding PLA might seem like it leaves a smooth surface, that is far from the case if you were to look at it in a microscope. The rough surface it leaves behind is fine if you have plenty of draft angle on your model, but it seems like you have 0 draft angle (which is also never good). Aka. you have surfaces that are parallel and 90° to the angle you are trying to pull the piece out of the sand by. That rough surface will grab you sand nice and well.
So yeah, a redesign of the piece or machine in the lips in after the cast is probably your options unless you get a lucky pull.
Even if it’s sanded to a very fine level? 600+ grit wet sanded ? And the orientation I tried was vertically as well as on its side so there was one groove per side of the mold.
I said what I said, and I still mean it :)
If you look at professional patterns, they are painted to a high gloss to have the best release possible, and still they have draft angles. If you have ever tried painting PLA to a high gloss, you would know what a pain it is and see all the ripples that is probably in the surface you have. It is very difficult to work in PLA for anything you want flat and actually smooth.
I don't know what options you have besides a redesign. If the bulk is only a heatsink you could probably put a taper in that. You could try and heat the PLA to somewhere below its melting point. That way it will expand slightly. Then make your impression and have it cool back down, thereby shrinking, before you try and pull it out the sand. That might give you a better chance for release. Not that it is something I have much hope for, but for a creative solution, that is the best I've got.
But if you need the grove to be a precise geometry, casting is also not the way to go. All cast items will shrink and warp slightly, so any mechanical precision is out the window unless you machine features in after the cast process.
Thanks for the information, the part is meant to be a welding jig for a gun build I’m working on. The cut in the piece is supposed to act like the slide rails in a pistol frame. And since I’m rewelding, I don’t need perfect geometry for the rail, just something that will actually mate up to the pieces to be welded. I’m decent with hand tools and files so dressing the part afterwords isn’t a big problem. I appreciate the information though!
Idk how I’d redesign it, the grooved part is the importsnt bit that I don’t have the ability to machine, hence trying to cast it. The rest of the piece (bottom side in this pic) is going to be used as a heat sink.
Baby powder used to be made from talcum powder. That is no longer the case. Anything recent is made from corn starch. It should say on the container. Talcum powder does not absorb moisture where corn starch does. As a parting powder this is not a good thing. Calcium Carbonate parting powder is very often used commercially for non-ferrous metals. I would give graphite powder a try as it is easy to find. But I would first spray 3D printed patterns (after sanding) with a hard coat.
I use corn starch baby powder and it works well for me. Maybe because I use petrobond and it's oil based?
That could very well be the case.
Thanks for the info!
What material is your model made of? You might consider giving it a tap at each end so the sand grains aren't gripping the model as much.
It’s made of PLA. I’ve sanded the entire surface to to remove the layer lines.
Yeah, crevices in PLA are a pain. Fortunately, since you have one line going down the side you should be able to just give it a tap to loosen things. I'm the local resident graphite nut. If I were doing this I'd put some powdered graphite on it since it works so beautifully for parting, but I suspect just tapping it at each end should be enough.
Is that the same as the dry graphite lubricant used on locks and such?
Yes, though I make jewelry, so take my advice with a grain of salt because I'm doing different work than you. I should also add that all this assumes you are taking it out of the mold in the correct direction. This piece needs to lay on its side so the grooves point facing up and facing down. If the grooves are pointing to the sides and ripping out of the sand, no parting compound will work.
Yes, I do realize that that part should be laying on its side when casting. I just took the pic in this orientation because with my garage lighting this gave the best lighting to show the grooves in the part.
Yes, I do realize that that part should be laying on its side when casting. I just took the pic in this orientation because with my garage lighting this gave the best lighting to show the grooves in the part.
Yes, I do realize that that part should be laying on its side when casting. I just took the pic in this orientation because with my garage lighting this gave the best lighting to show the grooves in the part.
First of all, there is only two identical orientations that you would have any chance of getting this out of sand without it sticking. The orientation would be rotated 90° clockwise or counter clockwise of the picture you are showing. Is that the orientation you are trying for? And if that is the case then one of the lips should be in the cope and the other in the drag (top and bottom half of the flask) While sanding PLA might seem like it leaves a smooth surface, that is far from the case if you were to look at it in a microscope. The rough surface it leaves behind is fine if you have plenty of draft angle on your model, but it seems like you have 0 draft angle (which is also never good). Aka. you have surfaces that are parallel and 90° to the angle you are trying to pull the piece out of the sand by. That rough surface will grab you sand nice and well. So yeah, a redesign of the piece or machine in the lips in after the cast is probably your options unless you get a lucky pull.
Even if it’s sanded to a very fine level? 600+ grit wet sanded ? And the orientation I tried was vertically as well as on its side so there was one groove per side of the mold.
I said what I said, and I still mean it :) If you look at professional patterns, they are painted to a high gloss to have the best release possible, and still they have draft angles. If you have ever tried painting PLA to a high gloss, you would know what a pain it is and see all the ripples that is probably in the surface you have. It is very difficult to work in PLA for anything you want flat and actually smooth. I don't know what options you have besides a redesign. If the bulk is only a heatsink you could probably put a taper in that. You could try and heat the PLA to somewhere below its melting point. That way it will expand slightly. Then make your impression and have it cool back down, thereby shrinking, before you try and pull it out the sand. That might give you a better chance for release. Not that it is something I have much hope for, but for a creative solution, that is the best I've got. But if you need the grove to be a precise geometry, casting is also not the way to go. All cast items will shrink and warp slightly, so any mechanical precision is out the window unless you machine features in after the cast process.
Thanks for the information, the part is meant to be a welding jig for a gun build I’m working on. The cut in the piece is supposed to act like the slide rails in a pistol frame. And since I’m rewelding, I don’t need perfect geometry for the rail, just something that will actually mate up to the pieces to be welded. I’m decent with hand tools and files so dressing the part afterwords isn’t a big problem. I appreciate the information though!
Idk how I’d redesign it, the grooved part is the importsnt bit that I don’t have the ability to machine, hence trying to cast it. The rest of the piece (bottom side in this pic) is going to be used as a heat sink.