There are several ways to dissipate this static. One of the fastest ways is to clean the membrane periodically. This has a dual function of dissipating the static and cleaning the membrane at the same time. Open the lid of the vacuum former and run a damp sponge over the entire membrane surface on the side that will contact the work product. You do not need to remove the membrane from the vacuum press to do this. Pay particular attention to the region on the membrane that touches the sealing edge on the vacuum former base. This only takes a few seconds to do. To determine how often to do this cleaning, periodically check to see how much debris is on the membrane. This will give you an idea of how many pressings may be done before cleaning in your specific work situation. Lift the lid of the vacuum former and run your hand across the membrane. If it feels gritty, clean it. If it feels smooth, it’s clean.
You may also ground your HD vacuum former by attaching a ground wire to the hinge rod and run it to a ground in a wall receptacle - center screw on wall plate. This should greatly reduce static build up, but you will still need to check and clean your membrane periodically.