Question about how @Printrbot utilizes the G29 homing code. Can I change the 3 points used to determine the bed plane?
I’m not sure if my bed is warped (possible, but unlikely - its a very well machined aluminum plate - the X axis upgrade for the Smalls) or if interference is skewing results, but I my printer is practically scraping the bed at one corner, and barely sticking at the opposite corner.
From my PCB milling days, I seem to recall a homing technique that probed a grid pattern - is there something similar for the Smalls?
There is a 9 point firmware you can flash that has been floating around. I’m currently suffering from a similar issue, but the 9 point didn’t help me. If you want it I can make a Dropbox link for it.
To my knowledge, the points themselves cannot be changed by M-codes
@Alex_Wiebe I have helped with 30+ Printrbot/printrbot component printer’s and have yet to have an issue myself until now. My unit was used and abused before I got it (it’s 2 or 3 years old) so I’m not surprised it’s run into a few issues.
What I would do is flip your bed over. See if the issue continues to persist. If I remember correctly the smalls beds are not orientation specific.
I used to use a 4 point on the Printrboard. Required recompiling the firmware and extracting the hex, but got the job done. I assume you did similar for the 16 points @Matthew_Del_Rosso ?
@Brook_Drumm nope its a printrboard😁 actually its the replacement board you sent me awhile back. Had to remove some other features for it to fit on the board’s memory but I can send you a video of it probing if you want. By sixteen I mean how many points the printer actually probs, in the firmware it’s only 4 (4x4 prob mesh )
@Griffin_Paquette ya, took the sample marlin and removed some stuff and add 16 points, it’s not to hard. By 16 points I mean where it actually probs, in marlin it reads as 4. (4x4 probing point mesh)
Just a bit of data from my printer. If we picture a square, with the front left corner being #1, and number around counter clockwise (front right = 2), then the 3 probe points after initial homing measure: #1 = -1.56 #2 = -0.36 #3 = -0.59
There’s about a 1mm tilt up from far left to far right, and a slight tilt down from front to back.
Point #4 (back left) is not measured.
I’m printing 0.2mm layer height with a 0.2mm nozzle. Printing a 2mm thick calibration square (100x100mm) I get the following results:
#1 = 1.85mm thick #2 = 1.95mm thick #3 = 1.95mm thick #4 = 1.60mm thick - and in fact, the first 2 layers (Z=0.15, 0.35mm) basically do not print at all (extruder is skipping due to back pressure).
The desire is to reliably print at a 0.1mm layer height.
@Alex_Wiebe There still might be an issue with your bed and Z probe but trying to print 0.2mm layers with a 0.2mm nozzle is asking for trouble. The maximum layer height you can reliably print is about 75% of the nozzle width. Much of the time it won’t squish or stick if layer size matches nozzle width. Unless you are running 10- 15 C hotter than normal you likely won’t be able to extrude without running into back pressure issues. With a 0.2mm nozzle your first layer should be no thicker than 0.15 which you already stated isn’t working. Bump you temp by 10C and see if it helps. Otherwise start your first layer at 0.1.
@Jeff_Parish Points noted. The 0.2mm layer height was more for draft printing. The issue I’m having is that after probing, and even during the 2nd layer (which should in this test be 0.35mm off the deck) the head is so tight to the bed in one corner that the extruder is skipping steps and no filament can squeeze out. But it is fine in the opposite corner.
That is, the 3 point probe + math is either insufficient for the detail I’m trying to squeeze out, or my bed is warped in that corner by ~0.3-0.4mm.
I was hoping there was an easy solution to probe more points and better map the bed.
@Brook_Drumm no, but I can send you a copy. I’ll email it to you . Just one thing about my hex, it leaves the bed sizing to the actual slicer software, so don’t be like me and not set its boundaries then check to see if the printer knows it limits
@Griffin_Paquette ya there is, it’s actually a line right in the marlin, but for some reason it wouldn’t work when I set it to 250x. It would keep the original 150x
The 3 probes from G29 match the same points when doing a G30.
Feeding the G29 numbers into Wolfram, I get this formula for Z:
z = -0.00176471 x - 0.0101538 y - 0.760814
And putting the missing point in:
z = -0.00176471 (140) - 0.0101538 (140) - 0.760814
z = -2.43
Not -1.88.
Over 0.5mm out. Which agrees with my observations (head crashing)
Not good when trying to print < 0.2mm layers…
I’d be interested in playing with multi-point probing firmware for the Smalls.
I don’t plan on putting any LCD style controller if that helps manage the memory footprint.
@Alex_Wiebe if you use the sample firmware that printrbot has on there forum, most of the unessesary things are already removed. I wish I had documented what I did so I could direct you better
is it posted anywhere?
. Just one thing about my hex, it leaves the bed sizing to the actual slicer software, so don’t be like me and not set its boundaries then check to see if the printer knows it limits