There I was, stranded between two sources of 3D printing pain.
First, my only 3D printer was the horribly slow 101Hero, which insists on revealing more of its limitations as my skills have grown.
Second, nearly a year ago I backed the BuildOne 3D printer Kickstarter campaign. Production and delivery are 6 months late at this point (due to bad part vendors that in turn caused a complete printer redesign), though I expect to have it before the end of this year.
But that's way too long to persist with the 101Hero, which was only meant to be a disposable "training wheels" printer.
Last week I snapped. I desperately needed to print faster than the 10 mm/sec (yes, that's right) best rate I was seeing on a printer that had lousy positioning accuracy. It was ruining over half of my prints, and that's accounting for the great strides I've made in getting past many of the 101Hero's other limitations.
I really wanted my next printer to be a Creality CR-10, but I didn't want to order one just yet. I really wanted another small printer, just one that would print faster and better.
On paper, the $159 Monoprice Mini Delta (MPMD) was exactly the machine I wanted: A small fast delta that included a heated bed, a color LCD control panel and even WiFi support. It arrived 3 days after I placed my order, and I had started the test print provided on the uSD card less than 30 minutes after first touching the box. There was literally no setup to do other than getting it out of the box, loading the filament, inserting the provided uSD card, and plugging it in.
The test print, a waving cat (that didn't wave), came out perfect!
My next task was to configure Cura for the MPMD. This proved to be unexpectedly cumbersome, since no Cura configuration was provided that would work with the latest Cura (3.3.1). Cura version 15.04.6 is included on the uSD card, but it lacks features I've come to rely upon. The Cura configuration was soon complete, thanks to the abundant community help online, which is fortunate since Monoprice support seems not to exist (or, more likely, is overwhelmed).
I loaded up the STL for the single-layer delta calibration print I've been using with the 101Hero, scaled it to fit the MPMD, saved it to the uSD card, then started the print.
I watched the system first warm up the bed then the hot-end (done in sequence to limit power supply loading), Next I saw the system do it's auto-leveling process (double taps near each tower). Then I watched the effector slam into the print bed and start digging gouges into the bed's plastic surface. It took me a moment to figure out how to abort the print, during which time more ruts were dug.
Were I thinking a little faster, I would have simply cut the power instead. Which would have required pulling the cord, since the MPMD has no power switch. Something that even the crippled 101Hero has!
A tiny bit more research revealed the MPMD "auto-leveling" feature is completely broken. There is a work-around, but it requires repositioning the end-stops to be within a fraction of a millimeter of each other. Which I did, over and over again, for nearly an hour, with much cursing.
After which I had to update the Cura printer start gcode to use a slightly different auto-level command that was far more reliable than the one recommended by Monoprice.
And that was the end of the major drama. My MPMD has been printing nearly non-stop since then, with great results.
But not perfect! Most of the print defects are due to the MPMD's floating print bed: It literally rests on top of three spring switches that are used for auto-leveling, which, despite having alignment pegs, means the bed has nearly 1 mm of sideways slop, which is enough to create a noticeable layer shift.
The MPMD has other minor imperfections. The first is the noise. Even when not running, the fan in the bottom is surprisingly loud. I modified a 60 mm fan mount design that is in the queue for printing. The noise gets far worse when printing, mainly due to the bushings on the steel rods. My plan is to clean them then lubricate with lithium grease.
The final significant noise source is conducted sound from the steppers. I haven't yet selected a remedy for that, mainly because there are so many to choose from! There are sound-isolating mounts, stepper smoothers, and switching to improved driver chips, such as the Trinamic drivers. There are also things the slicer can do to reduce noise, starting with the acceleration, but also by limiting travel speed. I'll try those first.
As I learn more about 3D printing, I want to twist more of the knobs. On a Marlin system I can permanently tweak the configurations in the source code, and can tweak settings stored in EEPROM, as well as tweak settings during each individual print. The MPMD doesn't use Marlin, though the gcode does appear to be very compatible.
The display on a Marlin system can be used to tweak many settings while the printer is printing, making it much faster and easier to get things dialed-in. The MPMD display does permit a few things to be tweaked, but almost none compared to Marlin. Still, the MPMD display does all the basics quite well, and does so while looking fantastic. It's really great to have a printer display I can read from across the room!
One odd thing is the location of the spool holder onthe back of the printer: The filament has to take a needlessly tortuous path to the extruder I printed a quick bracket that lets my use a paint roller as a spool holder, placing the spool above and in line with the extruder, as well as closer to the printer's center of gravity. A paint roller really is an awesome spool holder.
That loud fan in the base also causes another problem: It blows air directly on the bed heater, meaning it takes longer for the bed to heat up. The hole under the bed heater is easily filled by printing a cup designed for the job, which I found on Thingiverse. The performance difference was immediately noticeable.
Once you adjust the limit switches and get auto-leveling to behave, the MPMD is truly a fantastic value, despite the other minor annoyances (all of which have solutions, or at least work-arounds).
Then again, I'm coming from a 101Hero: ANYTHING else would be a huge step up for me!
