Door cap tools
Today we made the tools for the door caps.
The original plan was to do cavity molds with a male and female side.
After studying the final geomerty of the patterns, I decided it was just too risky to do it that way, due to the fact the parts have a good deal of 'die-lock'. We opted to do a single sided tool out of silicone. It will take a little longer to make the parts, but it will be more fool-proof.
The first step is to model the surface of the tool that extends off of the pattern.
Essentially, we have to extend the surfaces of the pattern. After that, we build a box around the pattern to contain the silicone.
The other thing we need to do is determine the volume of silicone to fill the box with. The silicone we use is pretty darn expensive, so I don't want to waste any. Likewise, mixing too little is a bit of a disaster...
We fill the box with rice, dump it into a cup and thus can measure the volume of silicone required. It is essentially the opposite of what Archimedes did to measure the volume of the king's crown (that was the story, wasn't it?) Instead of measuring the part, we are measuring the volume of the area around it.
After mixing the silicone, we have to de-gas it. Any gas bubbles in the silicone could attach to the surface of the pattern and make for a poor mold. To de-gas the silicone, we put the mixed silicone into our vacuum chamber and suck all the air out of the mix.
Once the silicone is de-gassed, we now pour it into the box. The trick here is to start pouring into the lowest part of the tool. This way, any air that might be left has a chance to rise to the surface.
Here's the pattern and box after the pour. You can barely see the master model submerged under the silicone. This will take a good 12 hours or more to fully cure. After that, we dig out the clay and master model and can lay-up a carbon part.
While the cap tools are curing, I surfaced the rear window pattern. Now that the roof panel is finished and we have the hardware on it, we can fit it to the car and finish the window surface.
Here's the roof. Primed with the rear window pattern fit to the roof.
Next step is to make the tool to form the rear window.