Monday, May 26, 2014

Adventures in 3d printing Or "I Finally Built a RepRap!"

I've wanted a 3d printer for quite some time. A few years ago I stared building one that, to say the least, was poorly engineered and under constructed. It never actually worked at all. Some of the designs could have worked, especially in a large CNC machine, but were just not a good fit for a small 3d printer. I've been eyeing the RepRap i3 models for a while now, last week I bought a kit (less electronics).

RepRap i3 with cooling fans and filament spool.
Note spool is on backwards to allow for the sloped ceiling in my lab.

Assembly was quite straightforward, there is a partial guide, though it skips (or I missed) some key steps.

A few tips:

  • Final alignment of the XZ (vertical) frame should be done after assembly. Just line it up so the extruder will reach the front and back of the Y frame and is square.
  • I printed thumbnuts to fine tune the bed leveling, it makes it really easy to get it spot on. I used these "Easy Heated Bed Leveling Thumbnuts"
  • The Z axis endstop was a pain, part of it was I used the wrong mount, but I printed this "Adjustable Z-Axis Endstop Arm" to make it easier

Fire in the Hole!

Everything I (and probably everyone else) build has some "teething" issues. I had (and am still having) a few. After I got it set up fairly good I started a print and it seemed to be working nicely, then the Sanguinololou literally caught fire (there were flames). The bug list for the Sanguinololou says the traces for the heated bed are too small, so I had reinforced them with wires before this point, it was the wires that caught fire. Turns out the mosFET shorted and the bed just stayed on continuously drawing ~16A. I salvaged the board and put a new mosFET (all I had on hand was a 12A logic level one) put it back together, set it to pwm at 50% and it lasted about 30 seconds before shorting too (I was watching this time). I swapped it again, added a reverse diode and ran it through an automotive relay (so the mosFET turns the relay on and off). That works really good.

Electronics, complete with rats nest

Now that the fires were out It was time to try some real prints. The filament won't stick to the bed. No matter what I do it won't stick. I tried cleaning really well, nope. gluestick helped, allowed me to print the upgrades I mentioned, but was hit or miss. I researched, tweaked settings, spent the better part of a day on it. Finally my brother was over and (looking on his tablet) said "they say here that Reprapper brand glossy black PLA won't stick to glass, use blue tape". Yep, I had Reprapper brand glossy black PLA filament, and yes, it sticks really well to blue tape.

A Sheep! Here's the first print that I took a picture of.

A few remain

Now I can print, I've still got a few issues left, mostly "dialing in" problems.

  • Overhangs and bridging don't work quite right. I've been lowering the extrusion temperature and it really helps. I started at 200C and am down to 180C for the first layer and 175C after that. A box fan after ~5 layers helps even more.
  • I printed some large parts and they warped, pulling the blue tape off the glass. The cooling fan bracket printed really nice with the 182C/177C and bed at 35C settings. this might be licked, but can't say yet. 
  • The first layer of big parts will bunch up a bit during infill, leaving stuff sticking up that can catch the extruder. If it gets 3 layers or so it will bury the problem and will complete fine. I might still be a touch close on my z-axis start point or it might be something else.

Future plans

  • Upgrade to optical endstop for Z-axis. It should be considerably more repeatable than a mechanical endstop, so I think it would be a big improvement. The X and Y axis are not nearly as critical, so I don't see any need to change those endstops.
  • Upgrade the electronics so I don't need a computer hooked to it and add cooling fan support. I've got several options: MosFET board and sd adapter, MosFET board and android tablet, Panelolou (includes Mosfets on the interface board and SD on the panel). I'm leaning toward the tablet option. The software looks really cool. I need to try it sometime.
UPDATE: I printed a bracket to mount some 40mm cooling fans, but all my small fans are 50mm, so I printed a 50mm bracket. Seems I chose one bad fan (rattles) so I'll have to replace that at some point. It makes a huge difference. I'll do another post on integrating it with the electronics.

Links - thumbscrews - Z-Axis Endstop Arm