5 years later....
Look, I'm actually making progress this time:
11 Gallon tank drawn down to 26in HG. It's not perfect, and there's so many fittings that it slowly leaks, but it's a great start. I absolutely can't have any leaks, since I don't want to run the oven and the pump at the same time, so I have to draw down the tank, switch off the pump, and then heat the plastic, which could take several minutes. That means the tank has to hold at 26+in HG for 3-5 minutes until I need it. I'm still going to try to put a tee connector and a shop vac on a sprinkler solenoid up by the hole in the platen. When the hot plastic gets pulled over the mold, the shop vac will pull out 70% of the air at a low vacuum pressure and then I can switch over to the tank to pull the remaining 30% of the air under the plastic at a higher vacuum pressure.
11 Gallon tank drawn down to 26in HG. It's not perfect, and there's so many fittings that it slowly leaks, but it's a great start. I absolutely can't have any leaks, since I don't want to run the oven and the pump at the same time, so I have to draw down the tank, switch off the pump, and then heat the plastic, which could take several minutes. That means the tank has to hold at 26+in HG for 3-5 minutes until I need it. I'm still going to try to put a tee connector and a shop vac on a sprinkler solenoid up by the hole in the platen. When the hot plastic gets pulled over the mold, the shop vac will pull out 70% of the air at a low vacuum pressure and then I can switch over to the tank to pull the remaining 30% of the air under the plastic at a higher vacuum pressure.