DLP Tests: smallest positive features

BUGSS Lab Notes – 8/1/16

Analysis of Prints from the Previous Lab Session:

150µm post with 100µm layer height 10 sec/layer

Our tests on 7/20/16 showed that increasing print time enabled us to print smaller posts. Increasing print time to 10 sec/layer  allowed us to print posts down to 150µm x 150µm in the x&y.  Looking at these prints under the microscope to determine the accuracy of the print dimension revealed that this feature size is effected considerably by the scalloping effect common to photopolymer based printing.   A 150µm wide feature printed with a 100µm layer height created a print with a 26% variation in width within a single layer. We determined that the simplest way to address this would be to half our layer height to 50µm.

New Test Prints:

2016-08-02_SC_postsWithLablesWe also expanded our test stamp to include 18 posts, ranging from 60µm to 400µm. Printing the posts at 6 sec/layer yielded a 160µm post as the smallest feature. However, the 180µm post did not print, suggesting that the light is may still not be perfectly even. This theory seemed to be confirmed by rotating the print 180 degrees and reprinting and by printing a field of 180µm posts.

These tests need to be repeated and tried with lateral shifts to the print (in software) to confirm that the issue is not due to where the features fall in relation to the pixels. Also several posts in the top row seemed to print fine but were pushed over at some point.

We will examine these prints under the microscope in hopes of determining:

  1. Did the change of layer height decrease the impact of scalloping?
  2. How does increased exposure time effect the accuracy of the size in x&y?
  3. Are the post from the single-size test all the same size?

Next Steps:

The results of this examination will guide the next test prints. Modifications to the digital mask used to even out inconsistencies in the projector may need to be adjusted. After any such errors are corrected, we plan to run a series of tests at different exposure times. This will help us to more fully determine the range of printable sizes, and optimum exposure times for each size feature. The goal is to be able to plot this data on a curve and then add a new capability to the DLP tools in Xylinus – detecting small features and adjusting the exposure time of those particular areas.






















About the author: Ryan Hoover

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