Step 2: Vacuum Form the molds
I placed the positives in the vacuum former, secured the PET-G food-safe plastic, heated it and vacu-formed the molds. The hardest part was extracting the gears from the plastic, as the sides were perfectly vertical. Normally one adds a bit of a "draft angle" to the positives, so that they are larger at the base than at the top to ease extraction. Since I was not in a hurry, nor was I doing a production run of the molds I just dealt with the annoyance.
After a few minutes of flexing and pushing, I had molds for my gear-shaped burgers.