TL;DR: It blew up ages ago, now it's mostly fixed. If you know how to stop the motors overheating, let me know.
As an original backer of the eMaker IndieGoGo project, I got my Huxley a while ago and enjoyed it very much. I'm more interested in the things 3D printers can make than the printers themselves, so I adopted a need-to-know approach to the stack of technologies that these printers are built on. As such, when it finally failed (the Arduino chip was attacked by the blue smoke monster) I was unable to fix it quickly and it went into a cupboard for a year and half.
Fast forward to now, and my renewed
masochism optimism encouraged me to repair it. I thought I would include some brief notes on my experience for people in similar situations or if people have comments on things I might have done differently.
The root cause of the Arduino (the big ATMega chip on the PCB ) failure is not know, but I believe it was something like this: the thermistor failed (the original design for this was a weak point), which caused the head to overheat and the heating resistor baked possibly shorted out. Something about this caused the Arduino to fail with a sharp crack and puff of smoke (current surge from the 19V lines to the 5V logic supply perhaps?). Hoping this was all that was at fault, I looked to replace these three elements. Things have moved on since the early days of Huxley, but there is no easy way to plot a path from the old version to the new version unless you have been paying attention as things evolved, which of course I haven't.
I bought a new Arduino (128MB instead of 64MB, which you can't seem to get anyway), a fancy ceramic heater with a metal body that just slotted into my hot end, and a glass-bead thermistor, which is far superior to the belt-and-braces version originally specified. All of these things went together (slowly) into the old rig and work well.
First time around, I never compiled the firmware or dug into that side of things much (too much like my day job), but this time I needed to. Getting a new version of the Marlin firmware from the RepRapPro GitHub worked fine, but I had to make some changes because that firmware only has options for the current Huxley models. Here are the relevant changes:
My Huxley uses nichrome wire to heat the bed (a design that has been replaced with a PCB heater with the mosfet mounted on the bed PCB ), so in pins.h I had to change HEATER_BED_PIN to 12 and FAN_PIN to -1 (I think it has been allocated to the old bed MOSFET in later versions to give a software controllable fan).
The values for DEFAULT_AXIS_STEPS_PER_UNIT needed to be changed to the 14-tooth pulley presets. I also modified the extruder rate manually as part of the calibration based on this excellent blog pos by @richrap [
richrap.blogspot.co.uk]
I started using Slic3r for the STL > GCODE conversion because it seems to be what the cool kids are doing, and it looks good. I had to slow the flow rate down because the print head cools down too much with the defaults (possibly because my PLA is old and damp?). The retraction was too low I think at 1mm so I pushed it up to 3mm.
One problem I've had is that the defaults for the flow rate for infill were so high that the hot end was being overwhelmed and cooled down too much, which put tension into the filament feed and made the feeder bolt slip. I'm experimenting with feeding in more slowly.
My only remaining problem now seems to be that the X axis motor overheats halfway through printing and it's motion becomes limited, leading to filament being deposited in the wrong place. Not sure how I'm going to tackle that one so I would be interested to know if there are any relevant settings that can lighten the load on the motors.
Edited 2 time(s). Last edit at 10/26/2014 04:09PM by rupert.