Anyone who uses a SLA 3D printer has had to deal with vat floor release layers of one sort or another. Every since I built my printer I have been using Sylgard 184 or Qsil 216 2-component silicones. These materials have very good release characteristics but they have a big downside, the coatings do not last long. To renew my vats release layer I would mix the silicone, pour the silicone into the vat then I would put the vat in my vacuum rig and place it under vacuum until all of the bubbles had disappeared I would then place the vat in a leveled toaster oven for about 2 hours until the silicone had cured, total elapsed time at least 3 hours. I tend to print objects that use most of my printers 68mm x 120 mm build area (my current settings, the usable area on my printer is about 100mm X 150mm) with prints that have large flat areas and bed of nails type supports, both of which are murder on vat release layers, so I would have renew my vat floor quite often.
For a while now I have been looking at the FEP “flexvats” people have been building over at buildyourownsla.com and I finally found some time to build one. The first hurdle was finding the FEP film at a reasonable price so I started looking for it some time ago and was able to purchase a considerable quantity of .005” FEP at a decent price a couple of weeks ago. It became clear to me after messing around with some quick vat designs that a vat that had an adjustable tensioning system for the FEP vat floor was the only real solution for me (because of the type of printing I do). I also felt that the ability to quickly change the FEP would be a real plus. The design I came up with uses a silicone gasket to tightly clamp the FEP film so that it’s reasonably flat before tensioning and a tensioning “riser” that the clamped FEP is pulled down on to which allows me to tension the FEP film, the silicone gasket also serves to prevent the vat from leaking. My flexvat consists of 6 parts: the top and bottom FEP clamp frame, a silicone gasket (cast from RTV SILICONE), the vat wall, a base that mounts to the printer that also mounts the FEP tensioner riser and the tensioner riser (plus misc. nuts bolts and threaded inserts).
I am pretty confident that this design will work well as a vat for my printer, .005” FEP is a pretty tough material so I am not really concerned about the FEP being pierced or splitting also the silicone gasket is not going to allow the FEP to come loose (the gasket is made from a shore 60a silicone which is only slightly softer than an automobile tire) the FEP clamp assembly also puts the edges of the FEP under a decent amount of clamping force. Since the FEP will stretch over time from normal use and is also subject to being dented by failed prints the design allows me to swap out the FEP by unscrewing the FEP clamp frame removing the old sheet inserting a new sheet and screwing the assembly back together a 5 minute operation.
I should have some time to run some tests this weekend and I will update this post when I have some news.