HV-VPP stands for high-viscosity vat photopolymerization - UV light masked through an LCD panel cures liquid resin layer by layer. This machine processes dense silicone instead of thin resin, which demands a custom approach to recoating and leveling.
I joined when it was mostly a printer frame and developed the mechanical and controls architecture to turn it into a working prototype. With guidance from PhD researchers in the lab, I independently designed the PLC control system and engineered the machine's key mechanical hardware.
Bringing The Controls Online
The printer runs on a Beckhoff PLC programmed in TwinCAT. I reconfigured the system to operate as an EtherCAT master, allowing the Beckhoff controller to directly coordinate the machine's motors and actuators.
Z-axis running under PLC control during movement and repeatability testing.
Building The Mechanical System
To ensure optical stability, I locked the breadboard frame to the outer chassis using custom standoffs rather than adjustable feet. I validated the design using FEA under a 400 lbf static and buckling load. To eliminate the warping seen in early SLA prototypes during UV curing, I produced the final standoffs from SLS nylon and finish-machined them for surface flatness.
I also turned custom servo and roller couplers from 303 stainless steel, maintaining an interference/press fit for clamping. Custom dovetail gauge blocks allowed me to align the recoating rollers in-plane while still enabling rapid removal for maintenance.
UV & LCD Masking
Each UV power supply dims through a 0–10 V analog signal. By integrating an EL4001 bus terminal, the PLC directly manages power output across all ten supplies simultaneously. Layer masking is driven through LCD panels controlled by a custom Python slicer script.
PLC-driven UV light controls running via the EL4001 terminal.
Tramming & First Prints
Initial alignment showed the build plate to be approximately 1° out of plane relative to the breadboard. Precise shimming at the standoffs corrected the offset and aligned the plate parallel to the resin vat.
During initial test runs with 0.5 mm layer heights and 1-minute exposure times, the printer successfully cured three-layer test structures measuring 1.5 mm in thickness. The open items at that stage were layer-to-layer adhesion, load distribution across the build plate, and the Z-axis homing logic.
Result
The printer produced a thymine-based silicone actuator 44 layers thick: 0.5 mm layers, 22 mm final height.
Built alongside Roxy Carbonell, Matt McCoy, and Keenan Vaughn under Dr. Carolyn Seepersad at the Digital Design & Manufacturing Lab.