audi, carbon fiber, production03.17.2011
Over the past few weeks I’ve been working on various improvements to help with the production of the B8 “OEM” carbon fiber vent and MMI pieces. I spent the last day or so making simple foam molds that help support the pieces under vacuum. Previous brackets would cave in under full vacuum. Running the pump at half vacuum meant sometimes the edges of carbon fiber wouldn’t be totally conformed around the part because the seal wasn’t as tight as it could be. After having to redo a few pieces, I decided it was time to make some molds.
To make our foam mold, I’m going to use a pour foam. It is very similar to the expanding insulating/sealing foam sold in cans at the hardware store. It comes in two parts, and you mix them 1:1 to start making your foam.
For demonstration purposes, I’ll do a small test run first with 1oz of each of the materials.
After 60 seconds of mixing, the foam turns from dark brown to a light brown and starts to thicken up.
15 seconds later and the expansion starts
Within 2 minuets the foam has engulfed the cup.
The foam also emits a massive amount of heat.
5 minutes later and the foam is sold.
As you can see I’ve had a bit of fun testing out various mixing techniques and amounts to try to get a solid foam that I was happy with.
Time to get serious with our MMI mold. I lay plastic wrap in the oven tray so that the foam doesn’t stick to it.
The B8 S5 MMI piece gets the same treatment.
A 1:1 mixture, this time 12 total ounces.
You really have to whip it quickly, as it starts to start foaming within a minute or two.
Once its ready, pour the mixture over the part.
Same rapid expansion as before, just on a bigger scale.
I want to compact the foam a little bit to ensure that it fills in all the gaps around the part, so I place some plastic wrap on top of the foam and pat it down a bit.
This one gets up to 160F.
A couple of minutes later, the foam is hard and ready to be popped out.
Now comes the fun part of shaping the mold, this time with a B8 S4 piece that was made earlier in the day and is a little more firm.
After picking off the foam around the top of the part, I slowly sand away at the bottom edge, making enough room for the fabric to wrap all the way around,
Next I start to cut away at the speedometer area, picking out large chunks.
Then going back for more detailed work and cleaning it up a bit.
Finally started to look respectable.
Same treatment for the inside. I have to remove this inside area because the fabric needs to wrap all the way around the edges of the long skinny parts.
All done. It’s not pretty, but it works perfectly.
After placing the mold, along with the piece wrapped in fiber in the bag, the edges are carefully sealed.
After the pump is turned on, all of the air is removed and the fabric is perfectly contoured to all the complexities of the part.
