I had sort of noticed that out of the box the acrylic build plate of the MBot Cube was a bit warped, but for whatever reason I dismissed it. I had been told that I should make sure it was level, so I tried to figure out how to do this. I hadn’t explored the menus on the printer itself yet, so I was looking through the ReplicatorG options instead. Happily, I found a script hiding in one of the menus “The Replicator Plate Leveling.gcode”. I’ve got a clone, so it should be fine, right? Right?!?
I was surprised when I had to adjust the plate height quite a bit. Wasn’t it already sticking? Oh well, follow instructions. Seemed to be fairly level, despite the warp. Okay, start printing.
Hmm, isn’t that really close to the extruder now? In fact, it’s dragging quite a bit. Is that the surface starting to melt?? Abort! ABORT!
After a bit more fiddling and attempted prints, it was pretty clear: the acrylic build plate was doomed. A few grooves and potholes were melted into it, and it was quite obviously warped and wouldn’t level properly. It was impossible to test any of the other solutions, because nothing would print on that surface.
I researched what my options were, and it sounded like the best solution was glass, heated or not. I found a relatively cheap option on eBay for a heated plate kit, but I figured in the meantime I’d look around for a local source of glass.. installing new electronics was not really my first choice.
Many people were talking about borosilicate glass on the forums, since it’s supposed to withstand higher temperatures. When I spoke to various glass companies, however, I asked for something that could withstand the heat of the extruder (up to 250C), and they insisted I needed neoceram glass instead.. what’s used for fireplaces and such. That was going to cost me upwards of $100 for just a small piece, so I was losing enthusiasm fast. However, I read some more (that part is free, at least), and was (perhaps too easily) convinced that it really wasn’t all that important for it to be heat proof.. just completely flat. Fine, that I could do.
It was difficult to find a glass supplier open at a time when I wasn’t at work, but Preston & Lieff (who are no longer located on Preston St, as google maps led me to believe) were open on a Saturday morning, so off I went. The guy I spoke to was baffled by my needs, but since I also seemed a bit baffled, he offered me a couple of 8″ x 8″ mirrors he had put aside for another customer who never picked them up. I thankfully accepted, and ran off to see whether they would work at all.
I didn’t have any document clips large enough, and many people complained about those getting in the way anyway, so I attached the glass to my build plate with.. painter’s tape. Note: this is a bit dumb. It can’t possibly stay put for long. However, I was impatient and I still haven’t thought of a better solution. So here we go.
The extra height also meant that I couldn’t screw down the leveling knobs far enough – the springs were too stiff. Since I knew the acrylic was never going to work for me again, I figured it wouldn’t be the end of the world to just extract the springs and cut them down to size. As a hack, it’s not too bad. Did the trick.
This time I also used the correct leveling script, in the firmware of the printer. Clever how they put that right in there.. *sigh* Anyway, it worked out perfectly. My warping and nosedive extruder issues are over!
Glass may be completely flat, but it’s also completely smooth. Getting anything to stick to it was really frustrating. Thanks to the wonderful forums again, I found that a combination of acetone/plastic slurry (dissolve a few pieces of failed prints into a jar of acetone) painted onto the plate and then sprayed with Garnier Fructis extra hold hairspray worked wonders. It’s not completely perfect, and I recommend printing things that aren’t too long and thin, but it allowed me to get on with diagnosing the other problems.