A couple of weeks ago I cracked a pretty big personal milestone with 3D printing; extruding PLA straight onto glass. Without blue painters, or kapton tape. This had been a pretty tricky problem to solve - as getting the first layer of plastic to bond to your print platform is one of the hardest nuts to crack when you first embark on the 3D printing journey. I had all manner of issues with plastic curling, knotting and perfectly good prints getting knocked out of place mid print. But no more!

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So here is how I am able to reliably print directly in PLA to glass:

The build platform

My build platform is made of the following (top to bottom):

  1. 6mm acid etched glass
  2. Heated build PCB, version 2.
  3. 10mm plywood.

The first part of my platform is a nice thick sheet of glass, this creates a nice thermal mass to evenly distribute the heat from the heated build PCB across the entire build area. It does take a little while to warm up for your first print, but also makes it fairly easy to keep at the desired temperature. The glass plate is also acid etched, giving the surface a little bit of grip that helps make that quirky first layer of plastic stick to the build platform.

The heated middle part of my platform is pretty standard these days, and in my opinion another mandatory component of any fused deposition modelling printer (aka RepRap). Heating the build platform has a bunch of advantages, it reduces or eliminates any curling during printing, it also makes it much easier to consistently print that first layer of plastic. The temperatures that I set for the heated build platform when printing is:

  • First layer of plastic - 80°c
  • Rest of the print - 70°c

The bottom part of my platform is 10mm plywood. This is actually a bit different from most RepRap builders who often use a sheet of aluminium. However, I actually prefer the plywood for a couple of key reasons - it is a better insulator than aluminium. This means that more of the heat from the heated PCB goes up into the glass, rather than being wasted heating up the bottom support. The plywood is also lighter, so it makes it much easier for your y-axis stepper motor to move it around.

The material

Not all PLA is created equal! The only PLA that I have found to reliably print to glass is the awesome plastic from Diamond Age Solutions. I am not exactly sure what secret herbs and spices Vik puts into his PLA, but with the exact same temperatures and configuration I could not get the PLA from a local Australian supplier to stick to the glass sheet. The extruded PLA would instantly bundle and wrap around the hot end. So seriously, get the stuff from Diamond Age, you will radically increase your printer reliability. Plus to quote a friend “their colours are delicious”.

The hot end temperatures I use when printing directly to glass is the following:

  • 189°c for the first layer.
  • 185°c for the rest of the print.

Process

After each print, I lower the temperature of the heated build platform down to 50°c, this is to allow the PLA to harden and to make it easier to remove the print from the platform. After removing the print, I squirt a bit of window cleaner onto the glass plate and wipe it down. This is to remove any PLA residue that may still be left on the glass plate. Acetone would probably work better, but I have found the window cleaner to be cheaper and to do a remarkably good job.