Following is a reply to my question on FEP to Kevin Chen of ALW resin suppiers.
FEP vs. PDMS
FEP film, that is what LT resin tray is (FEP film on top of PDMS). FEP is DuPont Teflon film, FEP is more chemical & heat resistant than PDMS. However, when it comes to “release” PDMS is better than FEP, meaning it takes less peel force to detach the printed layer form PDMS than FEP. With better “release”, PDMS gives the Form2 an edge on fine print detail over FEP film printers. Because FEP requires greater peel force to release, the fine details get deformed or detached, possibly resulting in fail prints.
From2 Resin Tray
After the printer is properly leveled, most of the time when you swap out resin trays for color change or resin type, Z axis calibration is not required. This is because:
- Trays have standard bottom thickness: PDMS + clear acrylic window
- Form 2 is equiped with pressure sensor to compensate for the thickness fault tolorance
- FL recommend to print with base-raft & supports (some time you will notice the base-raft is thicker from one printer than other)
However, when the tray bottome thickness is out of the set tolorance range, manual recalibration of Z hight is required.
FEP film in From2 Tray
One can not directly glue the FEP film on to the acrylic window without PDMS film because of the hight difference would be out of tolorance range that the Form2 is desinged for. Putting the FEP film on PDMS is “tricky” because both materials are designed for none-stick surface. Achieving a solid bonding of FEP and PDMS is timing, when the PDMS is not in liquid form and mixed solution is clear of tiny air bubbles, lay down the FEP quickly without any bubbles traping in between and without deforming the PDMS (is it still soft to touch) then cure the PDMS fully. Due to this difficult process, FL had a long delay on the LT Resin Tray moreover many defective LT Resin Trays did performing as FL had hoped for. During printing, when laser hits the resin, the chemical reaction would quickly heat up to hundres of degrees to solidify. Any tiny air bubbles traped in PDMS or in-between would quickly expand and causes delimination. Not all deliminations are caused by chemical reactions, rather it is a physical air bubble expansion pushing agaist the PDMS.
FEP self-adhesive sheets
From our experience, the self-adhesive sheet would face the challenges of:
- High temperature during print
- PDMS’s non-stick nature
- Possibility of trapped air bubbles
FEP film use in other printers
Most of the FEP film printers do not glue the film to any backing. The Film is tentions around all edges, like a trampolien/drum so it is flexible. This even tention and flexibility is important to enable the pressure sensor to auto calibrate the Z hight evenly.