Repair of tooling gel on a mold?

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#1

Hi folks, very new to the site here and of course my first post is a duzy. Intro first. Name is Adam Hennessy. I run a fabrication shop specializing in tube chassis/roll cage design and fabrication for kit cars and race cas alike, as well as CNC mold production for composites and resin casting amongst other things. While I’m not new to the composite field I am still learning quite a bit, which brings me to my issue.

I was making a mold of a part in the standard fashion i’ve always used with no issues, except this time I tried out a new form of PVA(FibRelease via Fibreglast). Material atomized well and seemed to get good coverage but upon mold separation from the plug I had ruh roh…sticking. Most was along the sealing flange surface for the v-bag tape, but there are a couple spots on the actual tooling surface for the part itself and I need to repair them.

Having never had to repair tooling gel in this fashion, I’m curious to know for the experts and more knowledgeable members on how to go about repairing the surface. A basic rundown from start to finish would be nice, and TG will be sprayed on.

Any help you guys have would be great! I would typically just make another mold but time is not on my side for this particular part(CF sunroof panel for a racecar going out to track in ~week.)

#2

Fibrelease :notrust:
Frekote :smiley:

Sorry no tips on mold repair. I would just make a new one.

#3

i use thickened epoxy to repair small imperfections in molds.if its a pit.grind out the area with a pencil grinder.then clean,fill with thickened epoxy,let cure.carefully sand.then wet sand and polish.i use black tooling gel coat,so i use black dye with the thickened epoxy.its always worked great for me.

#4

I’m going with you on this one. The fibrelease is too damn watery and doesn’t hold well to anything other than a horizontal surface :mad: I thought I’d give it a shot due to it’s “ease” of application. Not again! I will try this frekote you mentioned in the future.

After reading up on the minimal info online I went ahead and started to do just this. Put an 80 scratch to the #$%#$^@ areas and started filling in with some Devcon quick set epoxy. Typically i’ll use two different colored layers of TG so I know when the stuff is getting thinned out over use but on this one-time mold I just used a single color orange coat

I’m just wondering if I should scuff the whole thing and shoot an entire covering layer of TG over the whole mold(after this whole epoxy thing) then sand/buff/polish it out.

My other question is whether if I DO end up shooting another layer of TG over the whole thing, do I need to overspray that coating with something like wax or PVA to get the TG to set up on that exposed surface?? I’m assuming yes.

Appreciate all the help and info thus far folks :tongue:

#5

i use west system and micro balloons for my repairs.i have never used any coatings over the top though.so i dont have any info for you on that.i just carefully sand to the surrounding areas.then polish it out.most of the time,you cant really see the repairs.

#6

Ideally you would use the same surface coat or gelcoat you used on the mold to repair it.

#7

It’s easier to use top coat as it’s better to sand down and polish.

#8

Well I ended up repairing the major spots with thick epoxy as suggested and sanded them, sanded the whole surface at a light 80 grit scuff and shot a thin layer of the tooling gel over it with duratec HG additive mixed in. Flowed out and cured well, minimal orange peel which surprised me. Just have to sand and buff now.

Big thanks for the suggestions folks!

-Adam

#9

call Express Composites in Missouri. They have a special mold repair putty. Its like automotive putty, (bondo) and is catalyzed with the same creme hardener used with automotive putty. But its a vinyl ester material. I believe they might also have epoxy? Its very very thick but super smooth to spread on. So its easy to apply, and will not run even on vertical or upside down surfaces. Its not easy to sand, but that means its a very durable material. cures to sand in 15 min or so.

#10

The problem with repairing moulds is that when sanding 2 different materials, you end up cutting away one of them faster than the other. This is not really a problem if your tougher material is the original mould, but if it is the repair, you have a hard time getting things nice.

Perferably, use the same tooling gel, spray some layers or even brush them on, wait for them to kick, and do the next layer when needed. In the last layer, add a bit of parafin wax, to prevent sticking (or wash down the sticky stuff with acetone)

Now sand, perhaps do a small refill, sand again and buff. This should give you near perfect results.

As for the Frekote, ask for a small sample and do a test. It is not working for everyone.

Also, on paints and tooling materials, use a sealer. Get a look into the Zyvax range of materials, their sealer GP is very good.