Injection Molding

[Tree Reaper]

I was playing with this idea of using expanding insulating foam to wet form leather projects.

This is going to be a guitar pick case, it just requires trimming now and I'm pleased with the results.

[HellfireJack]

You actually used the force of the expanding foam to mold the leather?

Not only an awesome idea but you wind up with a A:B mold if you don't want to use the foam injection later.

I used to work with the urethane marine foam when I worked at a fiberglass boat shop as a kid. I remember it being as hard as cement when fully cured. Is the spray can stuff the same way?

[particle]

That's impressive! I can't believe it exerted enough pressure to form the leather that well!

[Tree Reaper]

Yes, I used the foam to expand the leather and now I have a foam mold that will seat the leather into the wood mold time after time.

The top block was screwed to the bottom block, I had two holes pre drilled in the top block to insert the plastic tube from the can of foam.

I placed a piece of plastic bag over the leather to protect it from the foam and filled the block with foam, sealed the two holes and let it expand.

The foam is rigid but not real hard although it's hard enough for repeated use.

Edited July 13, 2012 by Tree Reaper

[LNLeather]

Hey TR, that was Very Clever... Are you an Engineer?

I think you might have come up with an idea, with different designs for different items,

that could make you a lot of $$... ??

Edited July 14, 2012 by LNLeather

[cem]

This is a cool idea thanks for sharing Tree Reaper, I've got an interest in this sort of stuff after making silicone molds and the like for a number of years.

Cheers,

Clair

[Tree Reaper]

Thank you all, not an engineer but I think it's in everyone to dream stuff up.

Just know that this foam can be messy, requires acetone for cleaning and rubber gloves.

[BIGGUNDOCTOR]

Expanding foam can exert tons of pressure. Im high school one of the students made a mold for a larger item, and braced it with 2x4's. He mixed the foam's A & B, and poured it in. Soon afterwards the 2x4's were breaking under the pressure.

Look into Smooth-On's products for mold building. They have lots of options.

A friend used a can of expanding foam to get home after one of the airbags of his truck's suspension had a fatal air leak form. The airbag was toast, and the foam held for a long time, even after getting back home hundreds of miles away.

Edited July 14, 2012 by BIGGUNDOCTOR

[Tree Reaper]

The case is finished and should work well.

Edited July 14, 2012 by Tree Reaper

[Tree Reaper]

I tried a round mold and it works just as well.

I can cut this in half and get two pouch faces with it.

[DoubleC]

Kevin that is just too clever for words. I never know what you're going to come up with next. I'm surprised you're not running NASA or something. Cheryl

[Tree Reaper]

Thanks Cheryl, I don't think these will get that far off the ground but it sure makes my molding life easier.

[DoubleC]

That far off the ground? ROFL, like space? I tell you if I needed anything, and couldn't figure it out, I know you could. You're just so freakin talented. c

[Tree Reaper]

The ability to make things cheaper than dirt and cowboy simple is what drives me.

[DoubleC]

Yet the things you come up with are so simple they are absolutely genius. Don't know about the dirt cheap stuff but I am the queen of cheap so I'll have to find out about this!!!!

[WinterBear]

I might have to try this. I wonder if I could lay a piece of fiberglass cloth and coat it with resin into the negative side of the mold before (lining the negative with a release gel or plastic sheet first) and then using the expanding foam, so the foam attaches to the fiberglass. If I have imagined right, I think I'd wind up with a wooden mold half (negative side), and a foam positive with a fiberglass shell for added strength for the other half. Hope I'm making sense.

[Tree Reaper]

What I use is cedar for the mold then for strength I use a PL Premium construction adhesive and glue on a piece of plywood to the bottom and to the top of the mold.

What are you thinking of molding?

I used the foam on the new mold and duplicated that round pouch face today.

I have a cigar lighter that I use for melting rope ends and starting propane appliances, I'm making a case from the two halves.

[WinterBear]

This opens all sorts of possibilities.

I'm considering a mold for some super nice camp utensils I got for my sister and her husband. I'd covered the sets with tape and foam to make a sort of approximate shape to mold over, but was unable to get a good and consistent rim/edge, let alone repeat it. It'll be at least August before I can experiment though. Frontier Days starts Friday (and ends pretty much at the end of the month) and things are going to be a zoo. If I don't get supplies by Thursday, I'll have to wait until the 31st when things calm down again.

[Tree Reaper]

Would this be a pouch for a knife,fork and spoon set?

I'd like to see the desired shape you would require, any chance of posting a picture?

[WinterBear]

Yeah, I'll sketch something out and post some pictures. Not today though. I have Scout meetings and likely won't get home until after 11.

[Tree Reaper]

Got this one finished.

[TZHunter]

Hey, how did you plug the holes ? My mind is thinking....squirt a bunch of foam, then pull the can out, and stick something in there REALLY fast before the foam expands and comes out the hole. . . . for those from that generation, couldn't you just imagine Lucy (I Love Lucy) trying to do this and all the foam coming out everywhere ?

Anyway, would appreciate hearing how you managed to get the holes plugged before the foam came out and how you plugged. Thanks, TZHunter

[Tree Reaper]

I drilled the two holes, one for foam and the other for the air to escape.

The holes are the exact same size as the straw you get with the foam.

From the outside of the form I counter bored the two holes out about one inch in, one size under 1/4" to match two dowel plugs that I cut with tapered ends.

When the foam starts to exit the holes, drive in the plugs, cut them flush and put the mold into a wood working vise.

[WinterBear]

Ok, the lighter case is great, I love the idea, and it looks like it really made a strong case. I see some similar sharpie holsters in my future as soon as my friend sees this.

[DoubleC]

Hey, how did you plug the holes ? My mind is thinking....squirt a bunch of foam, then pull the can out, and stick something in there REALLY fast before the foam expands and comes out the hole. . . . for those from that generation, couldn't you just imagine Lucy (I Love Lucy) trying to do this and all the foam coming out everywhere ?

Anyway, would appreciate hearing how you managed to get the holes plugged before the foam came out and how you plugged. Thanks, TZHunter

I used the same analogy, with me being Lucile Ball :-)