Injection Molding

[TZHunter]

When picturing this in my mind, I also recalled some of my failed attempts at plumbing repairs, when I didn't have a cut-off valve and thought I could just unscrew that little thing and screw it back on real quick even though water was gushing out with ridiculous force. Sure glad to hear others have success when doing things like this, it gives me hope one day I may too succeed. I must admit, this idea is genius ! I'm feeling confident enough to try it.

[DoubleC]

UH TZ? I did some plumbing, well I've done quite a bit and when I couldn't find the shut off valve, I had the water company turn the water off, LOL. Are you SURE you want to try this? Cheryl

[Tree Reaper]

It's important to cover all of the leather and more with light plastic to prevent the foam from sticking to the bottom of the wood mold because it's like glue and will adhere both sides of the mold together.

The foam doesn't stick to plastic.

[DoubleC]

Yeah TZ that? You don't want to glue yourself to a wood mold, or a shut off valve, LOL.

[amuckart]

What sort of light plastic do you use?

Thanks for sharing this technique.

[Tree Reaper]

The first mold,I just used a piece of zip lock freezer bag.

Any light plastic from even a garbage bag should work.

There isn't a lot of stress on the plastic, it is supported by the leather and gets trapped between the foam and the wood top where it can be trimmed off later.

Mark your mold block with a sharpie or pen so the screw holes always line up.

[LederRudi]

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.

I'm thrilled by your invention!

Would you recommend a maximum leather thickness or a maximum size of a molding project?

[Tree Reaper]

I found the foam only works with small projects using thinner 2-3 oz. leathers.

It doesn't have enough pressure for molding thick leather.

I tried the large gap foam hoping to get more expansion from it but didn't get any better results.

There might be another product out there but insulating foam just isn't strong enough.

The advantage is you can fill shallow, odd shapes with the foam, it worked really well on the pick case.

I'm back to using wood and now wood or clay to match the mold and getting great results, a huge improvement over tacking leather around a wooden block and trying to form it.

Kevin.

[LederRudi]

I found the foam only works with small projects using thinner 2-3 oz. leathers.

It doesn't have enough pressure for molding thick leather.

I tried the large gap foam hoping to get more expansion from it but didn't get any better results.

There might be another product out there but insulating foam just isn't strong enough.

The advantage is you can fill shallow, odd shapes with the foam, it worked really well on the pick case.

I'm back to using wood and now wood or clay to match the mold and getting great results, a huge improvement over tacking leather around a wooden block and trying to form it.

Kevin.

Thank you, Kevin, for sharing your knowledge and experience!

Rudi

[BIGGUNDOCTOR]

Smooth-On has various expanding foams, and other molding products.

[Tree Reaper]

I have their specs but I can't find the specs on Great Stuff to compare lbs./ft pressure.

[Horrrk]

Hi Tree Reaper, may I say, what a brilliant way of forming leather..excellent idea.. Thankyou for sharing this..

One thing that I don't think anyone has asked yet.. I take it that you soak the leather and push it partly into the mould before the layer of plastic is added and the whole thing is clamped shut?

I can't imagine the leather, nor indeed the plastic, wanting to stretch that much from flat without tearing, is all..

Regards

Phil

[Tree Reaper]

Hi Phil;

Yes the leather is soaked under water until saturated then placed over the mold and worked into the cavity with a rounded end of a wooden dowel to get the shape started.

I wrote the company that makes Great Stuff and asked them what the lbs./cu. ft. is of their product so maybe we can get a comparison of other products on the market.

I would guess that you would require at least two to three times the force of Great Stuff in order to mold 5 oz. leather into a 1 inch deep pouch.

[Tree Reaper]

They didn't answer my question but this seems to be the general response.

we only measure it in lineal feet.

12oz can at 3/8 inch bead of Gaps & Cracks - measures theoretically 259 lineal ft.

[Horrrk]

Hi Phil;

Yes the leather is soaked under water until saturated then placed over the mold and worked into the cavity with a rounded end of a wooden dowel to get the shape started.

I wrote the company that makes Great Stuff and asked them what the lbs./cu. ft. is of their product so maybe we can get a comparison of other products on the market.

I would guess that you would require at least two to three times the force of Great Stuff in order to mold 5 oz. leather into a 1 inch deep pouch.

Thanks for your reply Tree Reaper, I figured it was something along those lines..

As far as the response from the company, it does sound like a general reply..nothing to do with a question of force or pressure..

I guess they've not had your question posed before..only for the amount of foam, people can expect out of the can..

Maybe with the tougher leathers, we're moving into the realms of hydraulics?? A little more fiddly perhaps, but not rocket science..lol

Regards

Phil

Edited September 10, 2012 by Horrrk