HELP: Aluminum Filled Epoxy Casting Resins

General Composites Discussions Products Talk
#1

Looking for advice on which products are better/different.
I’ve used Smooth-On’s Epoxa-cast resin for rigid tooling. It processes at 150F with prepreg. Tool surface polished out well, BUT…I don’t like its thermal conductivity or its stability.
My mold is a puzzle mold and the pieces don’t fit well anymore, despite the indexing.

There’s: ADTech aluminum filled systems
Freeman Supply’s Ren-Cast

Are any of these more stable than Smooth-On’s product?
Should I switch to an Iron Filled System instead?

I need a casting resin system that is Stable under process temp.
I need it to have excellent thermal conductivity (for my strip heaters).

#2

BJB has a few. I’ve made some small molds from them and they seem to be really nice. The spec xxxx lists cte as 2.02x10^-5 (0.0000202)

http://www.bjbenterprises.com/epoxy/casting-epoxy/tc-1651-a-b-1/

the rencast 3269 lists CTE at 3.76 x 10-5

#3

thanks for the lead on a different manufacturer.

Anyone else have experience working with metal filled casting epoxies from different companies?

#4

150 F is really low - i think to have problems like the ones you describe …i have processed vac cast from easy composites until 100 c with no problems …it gets little bit soft but ok …actually i like it because it helps with the demoulding

#5

Was that single-piece or multi-piece tooling?

I recently made a 4-part, twin-plane s-shaped inlet tube using the uni-mouls system and it seems each part wants to expand/contract differently with heat, so is difficult to bolt together. I am wondering if there are more stable alternatives I can use, before getting serious and using CNC milled tooling!

#6

If you want a low CTE tool, then you should be using carbon/epoxy

#7

Yeah I guess you are right, I’m just not sure how well I can afford the expense…

#8

of course budget should play in what tooling you choose, however it can be difficult to achieve high tolerances without throwing down some cash. What exactly are you trying to achieve? what are you making? how many parts? If you could provide more details I can try to give you better advise.

#9

I’m making an air inlet tube for a track car (Pre filter so low pressure). Initially it’s a 1 off to let us learn some new techniques, but we’d like to be able to sell it in the future if there is interest, so in an ideal world I’d like to get 20ish pulls from it. The part is made in a 4 part female mould to give an external A-surface.

We’ve made it out of easy composites Uni mould tooling system, which has been good so far for more open shapes, but this part doesn’t want to bolt together very nicely at all. It went a bit wrong from the start in that I had some advice from a friend who uses carbon epoxy tooling who suggested breaking the 1st 2 quadrants of mould off the pattern to get the joint edge really nice, but (it would seem) because it cures with an exotherm at 60degC it wouldn’t go back together nicely with the pattern. With the complete mould made I needed to use a clamp to pull the parts together. We used small pyramid locators, but they don’t engage very well, exacerbating the issue. Understandably, the tool is suffering quite a lot after just a could of pulls, I’ll be surprised if it lasts more than 5, let alone 20.

Obviously we won’t break apart future efforts until the whole mould is made, and we’ll also use a better location system. But basically I’m trying to figure it if the tooling system is OK, and it was our execution that was wrong, or if I should be looking at other techniques before having another punt…

#10

Using a good tooling VE system, and with an accurate plug to make your tool off of. The moulds should be pretty accurate for a low production run at 150F.

Otherwise, if you need higher tolerance, I would suggest switching to carbon/epoxy tool, generally speaking its not that expensive by area, but it does require you to keep a stock of material which can get pricey.

#11

Thanks for the advice!
The mould we are using is VE, so if this is OK for the application then I suspect the part-way-through removal and the poor locators are the cause of the problem.

Next time we try a mould like this we will use better locators and also make it as a 2 part mould, not 4 part, as this extra complexity doesn’t really do us any favours!

#12

Old-ish thread, but for future reference maybe consider some of these options.