I’ve been printing a lot of lithophanes while writing Hacking the Digital Print. When they lay flat, they’re pretty amazing, and when they don’t, they’re amazingly frustrating.
Originally I was working on my MakerBot Replicator 2, which has an unheated acrylic bed. Printing with PLA on Painter’s tape worked pretty well for most objects and even for small lithophanes, but as I started to scale up, they invariably curled. My first change was to move out of a cold basement closet into the new insulated printer room – that brought the ambient temperature up from about 60 degrees (this was last winter) to about 75. That helped across the board, but I was still getting lifting – both the print off the tape, and the tape off the bed. I tried everything from cleaning the plate and tape with isopropyl alcohol, to using helper discs, to printing with (and without) a raft, changing the extrusion speed. I even tried switching to Gaffer’s tape. The best combination on that printer that I found was with Gaffer’s tape on a clean bed, with helper discs and a raft – but still had lifting happening.
MakerBot was kind enough to loan us a 5th Generation Replicator while we were writing the book, and I had much better luck with my normal PLA bed prep of painter’s tape and no helper discs. The big difference is that in the 5th generation printer the bed is glass instead of acrylic. An upgrade to a glass bed for my Replicator 2 is on my list for Santa this year for sure.
When I got my LulzBot TAZ 4 with a heated bed, I gave it a go with both ABS and HIPS, just using the stock PET tape with a coating from an Elmer’s washable purple gluestick. Everything worked perfectly, but I had to be a lot more careful removing the prints from the PET film than from the painter’s tape – blue tape is cheap and easy to replace, so a bit of casual force is fine. PET tape, not so much. As always, patience until the print slowly cools is a virtue.
So the end lesson is that glass beds trump acrylic ones (at least for large flat prints), and a heated bed makes things easier to print, but may make it harder to remove. The lithophanes in the book are from the MakerBot 5th generation and the TAZ4, both in PLA (MakerBot) and HIPS (TAZ4). More on lithophanes and materials in another post.