molding/Casting Problem

[ChiCubsGordon24]

Hey guys,

I'm having a small problem with casting a piece. I made a 1 part mold of a wolverine claw I had printed and every time or almost every time i cast it the tip does not come out. It looks like possibly an air bubble. Whats the best way to avoid it and get the tip to cast properly? Hopefully I wont need to remake the mold.

Thanks for any suggestions.

 

[division 6]

Sprinkle in some talc (baby powder) and see if that helps.

 

[RocketNerd]

i will generally put a small cut/cavity on the tips of items that extends an inch or two. That way if air is trapped in the tip, it has somewhere to go. you wind up with a little flash at the end that is easily cut off.

 

[ChiCubsGordon24]

I thought about using a toothpick to make a hole for the air. I'll try that and the baby poweder. Thanks guys.

 

[lmgill]

You are correct in getting air trapped. This is most likely what is happening. While the talc may help, you really need to give the air an escape route. Cutting vents in molds can be one of the quickest ways to ruin a mold if done heavy-handedly. You want a vent to be as small as possible at the wall of the mold cavity, and then get larger as it reached the outer surface of the mold. The best is a "gate vent" but that is difficult to explain without visuals. Remember to open up a larger hole in any jacket/ matrix you have around the mold.

Being a one piece mold, it is likely difficult to get too the tip of the claw.

If you get a piece of tiny (less then 1/8") brass tube (K&S brass is a usual at hobby shops) then you take an Xacto, with a #11 blade and cut a bevel on the inside edge of the tube, by spinning the tube by hand around the tip of the blade, you can make the tube into a core drill. You can then use this to cut a vent into the very tip of the claw an give the air a way out. Do this by pressing and simultaneously spinning the tube as it cuts through the silicone. Practice on a scrap of silicone so you can see how it works. Note: If you cut the bevel on the inside of the tube, the whole in the silicone will gradually get larger, as the silicone becomes compressed into the tube. If you cut the bevel on the outside, the hole will get smaller, as the silicone is spread by the bevel.

 

[ChiCubsGordon24]

You are correct in getting air trapped. This is most likely what is happening. While the talc may help, you really need to give the air an escape route. Cutting vents in molds can be one of the quickest ways to ruin a mold if done heavy-handedly. You want a vent to be as small as possible at the wall of the mold cavity, and then get larger as it reached the outer surface of the mold. The best is a "gate vent" but that is difficult to explain without visuals. Remember to open up a larger hole in any jacket/ matrix you have around the mold.

Being a one piece mold, it is likely difficult to get too the tip of the claw.

If you get a piece of tiny (less then 1/8") brass tube (K&S brass is a usual at hobby shops) then you take an Xacto, with a #11 blade and cut a bevel on the inside edge of the tube, by spinning the tube by hand around the tip of the blade, you can make the tube into a core drill. You can then use this to cut a vent into the very tip of the claw an give the air a way out. Do this by pressing and simultaneously spinning the tube as it cuts through the silicone. Practice on a scrap of silicone so you can see how it works. Note: If you cut the bevel on the inside of the tube, the whole in the silicone will gradually get larger, as the silicone becomes compressed into the tube. If you cut the bevel on the outside, the hole will get smaller, as the silicone is spread by the bevel.

Awesome I appreciate the tips