Talk Composites - The Forum for Advanced Composites

Questions on eb700 tooling board

http://www.talkcomposites.com/Topic32224.aspx

By quinn - 3/3/2019 4:50:15 PM

So far having bad luck with high temp tooling. Mostly issues with post curing off the plug causing surgace issues. Anyway, out of fruatration im ready to just machine some solid molds. The price isn't all that bad considering what I've spent so far on high temp surface coat and epoxy. 
So I watched the video on this tooling board and it says it's great for master patterns and can be used directly as a mold for "small" production runs and prototyping. What exactly does this mean? I'd like to mill a mold directly into this stuff and get some decent use out of it. Will it not last long with repetitive use? How many pulls will I get and what happens when I get beyond that point? Will it be ok for maybe 50 parts or so? Maybe recondition with more s120 at that point? 
I'm also finding it very difficult to get a pinhole free surface in prepreg with vacuum bagging. Also not really happy with the wrinkles on the inside of the part. Needs to have a not so horrible surface in there. I'd like to solve both these problems with either a custom bladder or expanding silicone, but I'm not sure what this tooling board will hold up to. It will be a 2 peice mold, similar shape to football, each half milled out of solid block of tooling board with minimum wall thickness around 25mm. Will the mold hold up to some decent pressure? Nothing crazy, maybe 25 psi, just need a bit more than what you get with vacuum. 
I realize my other option is to mill a plug from the tooling board and that would solve my problem of post curing mold off the plug since the tooling board can handle the post cure, but I would still prefer to skip all that mess and mill a mold directly since I know nothing can really go wrong. Less work and no dealing with surface coat and lay up. 
By quinn - 3/6/2019 6:03:43 PM

 
oekmont - 3/6/2019 5:51:01 PM
Have you considered infusing the molds? When I read about using jelly resin, it was unavoidable that the air pockets would ruin the mould during post cure. At least the first layer has to be absolutely perfect. And that means using a fine cloth and using thin resin. Anything much more viscous than fresh standard laminating epoxy will not wet out the cloth air free. With a fine glass cloth and black gelcoat you can see how it is getting harder to get the bubbles out as the resin starts increasing it's viscosity.

On my last try I vacuum bagged the mold after wet lay which seemed successful at removing all air, but the problem still remains that post curing off the tool (my plug was mdf and duratec) seems incredibly finicky. I didn't have positive dimples in the surface of the second mold like i did the first try, but the surface still didn't stay perfect through post cure, just kind of a wiggly surface. With another attempt of doing it on a proper tooling board plug and post cure on the plug, I could probably get the results I'm looking for, but by the time i order tooling board, more surface coat, etc., it'll cost just as much as milling these out of aluminum which is a process Im familiar with and will work perfect at making an excellent mold. Nothing can really go wrong.