Bed levelling issue

Here is one that will surely trip you up if you're trying to be clever: I changed the maximum limits in the Marlin code to 15 minimum and 185 maximum in both X and Y axes. The reason is that my bed is exactly 200 x 200, and running a calibration procedure pretty much always puts the J-head off the glass at at least one corner. By changing the edges to 15mm in on all sides, the levelling calibration procedure (M371, M372 and M373) stays on the glass, making calibration easy. Only, the table that gets generated seems to be off. I changed back to 0 and 200 and it LOOKS better (moving to X100 Y100 Z0 is spot on). Printing now to see how the first layer will look.

More calibration factors

I learnt something new yesterday - having spot-on Theta and Psi steps-per-degree values from the calibration procedure, does not mean your prints are on scale. There are two more factors (the M365 X and Y scaling factors), also calibrated using the spreadsheet and calibration phantom, but not explicitly mentioned in the calibration webpage. I tried printing some Morgan parts (those I broke early on), and I could see that the calibration must be out. Printing a round gear (extruder large gear) also produced a non-round shape. I have now calibrated the factors and I am printing a new phantom as I type here. Currently I'm struggling with getting a good first layer, my bed levelling calibration is acting up.

Noteworthy thing #4

I found this - the Dremel Devil - on Thingiverse today. There is a link to the magazine article (with video) in the Thingiverse description. We used to play with pull-string "helicopters" when I was a kid, this is the grown-up version. And if you don't have a Dremel tool (or clone), another reason to get one. This is definitely on the Things-To-Print list.

PLA calibration

If there is one thing my Morgan has battled with, it is plastic being soft (and sagging if on an overhang). The cure for this is cooling (via the fan) and playing with the cooling settings in Slic3r. Up to this morning, I did not HAVE a fan, but with PLA I can see that it is necessary. Firstly, ABS-Filament (from whom I got my PLA) suggests both their PLA and ABS prints best at 230. This is warm for PLA in my opinion, but this is what I use at this moment (after the first layer I drop to 220). I am down to 60 degrees on the bed temperature and printing on bare glass. I have to extrude the PLA faster (I use the extruder multiplier setting) than the setting that worked for ABS.

Reinforcements

It seems as if the damage from the recent disaster includes the Arduino Mega, three of my old (4988) stepper driver boards, and possibly one of my laptop USB ports. I picked up a replacement Mega from Micro Robotics on Monday, and spent another long night sorting out the printer. The 8255 stepper drivers are OK, the originals NOT. I THINK what happened is that I replaced the originals with the better ones, which was not properly adjusted for current. When I replaced the originals, I must have inserted them incorrectly (the 4988 and 8825 boards have their pots on opposite ends of the board so they look different when installed). Anyways, a slightly expensive exercise. As I have at least two friends who are considering building (or having me build) Morgans, I have ordered a lot of vitamins of e-bay, in packs of 5 or 10. I will therefore have a lot of surplus (stepper motors, RAMPS boards, controllers, stepper drivers and more). I am considering starting a "web surplus store" to recover some of my expenses (and have the advantage of bulk pricing). But first, I'm calibrating for PLA...

Crash and BURN

The stepper motor driver upgrade was a spectacular failure. The printer made funny noises, the smoke came out, and it is dead. The new stepper motors came with pin strips loose, which I neatly soldered on, and after installing, the electronics made funny, strained noises. Clicking the "Motors OFF" button quitened it down, but after the HOME command (G28) the noise would intermittently come back.

The mechanicals also started acting weird, during the re-calibration procedure. Next, the smoke came out and the PC crashed (so much so that I needed to disconnect power and take out the laptop battery to get it to start up again). The Arduino Mega now does not speak to the PC at all (RAMPS unplugged). My Arduino Uno works, no problem.

So the controller at least is kaput, possibly more. Eish...

PLA filament and microstepping upgrade

There were two parcels in the post box this morning. One contained three rolls of PLA filament, white, red and yellow (the last two nice and bright) from ABS-Filament (.co.za) in Nelspruit. I'd like to compare the printing performance of the Morgan on PLA vs ABS. But I expect a bit of experimentation to get the optimum settings before we're at best performance.

The second parcel (from Micro Robotics) contained amongst others two stepper motor driver boards, based on the DRV8825 driver chip. This is intended for the X and Y channels on the RAMPS board, to get full resolution. I am already running 0,9 degree motors, with 1/32 microstepping I am doubling the resolution on Theta and Psi angles.

All that SHOULD be required is to plug the new boards in and doubling the steps on the M92 command, but I will check the calibration afterwards to confirm the aspect ratio stayed preserved.