Hello,
I am relatively new to this craft and I had a question. I am trying to create a simple production mold for a relatively flat piece. I was wondering if there would be any benefit to putting the mold under vacuum to cure so long as it doesnt distort its shape.
I am using fiberglass strand mat with Fibreglast brand isopthalic poly resin and their orange tooling gel coat.
If you can advise that it doesn’t matter, makes a huge difference, or is a bad idea, please do!
Thank you very much!
If your using chopped stand mat, you don’t want to vacuum. I don’t see a benefit to it really, plus by the time you get your bag setup and vacuum pulled your resin will probably be starting to gel, then your not going to be pulling any excess resin out and just waisted time/materials. What are you trying to make a mold for?
Hey Rotorage,
Thanks for the insight. I am making quite a few different molds, some of them slightly convex panels about a foot in diameter, others are brake duct and air ducting in general that are more complex. Soon I will be starting some multiple piece molds after I am situated with these first projects.
I made a pretty cool vacuum station (if you will) where my piece sits on a perforated sheet and the air is drawn down through its many holes and creates one hell of a vacuum. For the piece of I was referring to (relatively flat and simple), I think I could get it under vacuum before it was ineffective.
Im certainly not set on it, I was just curious as the literature I have read on composites/mold making/etc didnt make mention of it either way.
thanks again for your help, I appreciate it!
Also, I have a sheet metal panel that I want to make a mold from and the paint isn’t in great shape. I just soda-blasted it off and I am going to fill in any imperfections and then paint it here at work. Do you think that a high quality primer and paint will suffice in regards to holding up to temperature, etc? Last time I made a mold it was cylindrical and so I put a thermometer in it and it pegged it out at 120 degrees, I didn’t have a laser thermometer on me at the time but I am concerned that I might be exceeding the capabilities of a regular paint. perhaps powder coating is the answer?
EDIT: Is it also a possibility to just polish the bloody hell out of the sheet metal piece to a nice finish and put the gel coat right up against that? It is stamped steel sheet metal. I assume this is okay but I am open to opinions
thanks again!
polished metal release very well if properly coated. Look it to semi-permanent sealers and release agents such as Frekote.
If you have two people laying up, and vac bagging the mold it is possible to vac poly and chopped strand mat. The thing is your mat will become very compacted so a 2oz mat will end up like a 1/2 or 3/4 oz mat. The nice thing is you can use less resin.
I vacuum bagged a hood that was essentially polyester resin and fg mat. Must work fast and use little less catalyst. Try using 1.7% catalyst by volume. I also spray gel coat this way, use little less catalyst and it won’t gel in the spray gun on me.
If your vacuum bagging to save poly resin. Then how much money did it cost for the bag, breather, peel-ply, perf release, and bag tape? How much $$ in resin did you save? Cause last I checked poly resin was dirt cheap, and I would think the “extra” poly on the mold would be less expensive and time consumming then doing the entire bag process. And if your going to go threw the trouble of bagging your mold. Then why not get continous strand mat in the first place and infuse the mold. Lay materials, bag, suck resin, done… No racing against a clock and no need for another person.