Geeetech Rostock 301 Firmware bug #2 

Niels Johnson-Laird, I have successfully reversed the board, but I haven't yet had time to spend on porting any decent firmware to this beast.

I am fascinated to know what you discovered, please let me know if you are comfortable sharing your reverse engineering work? Based on my research around the Internet it is believed that Geeetech based their firmware on the Marlin firmware which is open-source and covered by GPL. I had been thinking of replacing the GTM32 Pro board and modding the 301 to use a Reprap RUMBA board as it supports 3 extruders and uses open-source code on an Arduino Mega 2560--I have a lot of experience with Arduinos. During my fourth attempt to print with ABS yesterday I discovered my 301's heater element has a fault (I haven't figured out if it is a fuse on the PCB or the heater element itself that is the problem). This is not too much of a surprise to me and I have accepted that the 301 is now an experimental toy--I've been using an UP! Plus 2 since December 2013 which I have printed exclusively with ABS so I can still do 3D printing.

Niels Johnson-Laird, printing with ABS on 301 requires modding the heater plate. Specifically, you need to move the sensor about 1cm away from the heater downwards (use some insulator like cork). Then it will measure the temperature close to that of the surface. Otherwise when you set it to 110 degrees C, you only get about 65 C on the surface, which is not enough for ABS to stick to it.

Thanks for sharing the tip for printing with ABS, I have seen it mentioned online. Because of this I did some initial testing with the hot-bed plate (I use a 3mm thick borosilicate glass disc on my hot-bed and add a layer of Elmer's Disappearing Purple Office Glue Stick [it is water soluble so it is easy to wash off]). When I set the hot-bed to 100 C, I recorded the surface temperature using an IR thermometer, it took 15 mins for it to reach 83 C. After this I set the hot-bed to 110C, and let it preheat. ABS adhesion has not been my problem, getting even extrusion from the nozzle over the three test prints has been the biggest problem. Partly, this has been due to the brand of ABS filament, the White ABS which came from Inventables.com (for the UP! Plus 2) will not extrude and jammed--I have since disassembled the hot-end nozzle so I can soak the metal parts in acetone (this is why I stick with ABS ;-) ). The Purple and Blue ABS (no, I wasn't planning on color mixing LOL) are both Octave brand from Amazon.com, and they would extrude, initially. The general consensus is that extrusion problems can be resolved by replacing the extruder assemblies that are attached to the extruder stepper motors at the top of the 301. I have these on order, they should be arriving in the next few days. My first print was a small test piece (~6 mins ETE) and printed OK (despite me not realizing that I had to turn on 'support' printing in Slic3r). After this I was concerned that the hot-end temperature was too low and changed it 260 C (the UP! Plus 2 won't even start moving until its hot-end nozzle hits 260 C). At this point weirdness began, with "stringing", poor extrusion and finally no extrusion--the 301 was air-printing (moving, but no filament coming out). I suspect that a setting of 260 C was the wrong choice for the 301 and for the heater element. Fortunately, I had ordered a replacement 3-in-1 nozzle set earlier this week after the white ABS jammed. Now, I am considering my options: a) replace parts with parts which are hopefully going to be better quality; or, b) dive into replacing the controller board with the Reprap RUMBA board which will involve replacing cables (that will be compatible with the connectors on the RUMBA), new firmware, and a lot more hands-on work.

Niels Johnson-Laird, it's not just replacing extruder that helps. You will also need to add some heat-resistant lubricant into bowdens for the device to start printing. There is a topic on Thingiverse that is very helpful.