Auto bed probing and compensation with G29 Development

Want to use the Open Source Hardware documentation to make your LulzBot 3D Printer do even more? Start here!
bam
Posts: 117
Joined: Thu Sep 19, 2013 11:37 pm

Re: Auto bed probing and compensation with G29 Development

Post by bam » Mon Aug 04, 2014 6:32 pm

TomsCables wrote:Hey All,

I was able to get this thing printed and installed on my TAZ4. Following the instructions from here http://blog.yuliyruzin.com/2014/06/lulz ... eling.html
Awesome! :)
TomsCables wrote:Now when printing it measures the bed with the probe but stops at about 3mm from the glass and starts printing. Its acting like the Z_Probe_Offset is zero.

I tried editing the Z value in the, M206 X0.0 Y0.0 Z0.0; offset home position for fine tuning line of the custom code, but that didn't seem to make a difference. Can anyone help me?
iinteresting... I'm not sure what's going on with the offset, it could be that the minimum software endstop function is stopping it from going below 0 even though there's an offset? I'll have to check it out.

You might try changing the z-offset in slic3r: printer settings --> General ---> Z-offset. It seems to work a bit better.
TomsCables wrote:Oh and I noticed my X motor making a clunking sound when printing now. Could this have something to do with the firmware?
Could it be the z steppers? With compensation they're constantly moving to keep the nozzle at the right height over the non-level bed. They move way slower than the other steppers and make a much lower tone than the other steppers, to the point where you can hear the individual steps. I kinda like it, adding some base notes to the song your printer sings while it's making your cool stuff 8-)

Hope that helps
-bam

bam
Posts: 117
Joined: Thu Sep 19, 2013 11:37 pm

Re: Auto bed probing and compensation with G29 Development

Post by bam » Mon Aug 04, 2014 8:15 pm

We've been working for some time now on bed leveling, and have working prototypes featuring a neat way to tackle bed compensation.

The hack uses the nozzle as the probe to find the bed, so the probe-nozzle offset doesn't need to be measured and accounted for. We've taken the 2 leads to the z-endstop and wired one to metal corner pieces of a rigid mounted bed, and the other to the hotend itself. That way, when the printer homes or probes at any of the corners, it can accurately measure the plane AND z-position of the bed with a small offset.

This method is working pretty well, but has some significant challenges:

-the metal contacts on the corners need to be as close to the same thickness as possible so they match the plane of the bed. We used shim washers in the first tests, and have moved to custom machined discs. For a quick hack, you could probably use tin foil or shims spread over the corners.

-the nozzle and pads have to be really clean. A good first step is setting up your end g-code to retract the filament ~45mm at the end of each print, and the start g-code to extrude that much before printing. This will keep oozing to a minimum,and a good wire brush is also handy for getting the stubborn buildup off of a nozzle. It also helps to have the nozzle at at least 170C while homing and probing so that any plastic that is there can squish out of the way.

The begonia prototypes have an integrated wiping pad so we can have the printer vigorously scrub it's nozzle before probing, it's a pretty great thing to see :)

-You either need to keep your z-min endstop as a backup, or be really sure that your printer won't drive it's extruder through the middle of the bed the first chance it gets. There are a lot of great firmware safeguards, but you might want to keep the endstop wired in place.
IMG_2957.JPG
Azalea 1: the first lulzbot mini prototype. Note the rear mounted wipe pad and shim washers on all 4 corners of the bed
IMG_3151.JPG
begonia phase prototype with barely visible corner probes

User avatar
Orias
Aleph Objects | LulzBot
Posts: 1447
Joined: Wed Mar 27, 2013 1:24 pm
Location: US

Re: Auto bed probing and compensation with G29 Development

Post by Orias » Tue Aug 05, 2014 9:50 am

Is there a video of the wipe motion? I'd love to see that!

TomsCables
Posts: 80
Joined: Mon Apr 14, 2014 8:45 am

Re: Auto bed probing and compensation with G29 Development

Post by TomsCables » Tue Aug 05, 2014 1:26 pm

TomsCables wrote:Now when printing it measures the bed with the probe but stops at about 3mm from the glass and starts printing. Its acting like the Z_Probe_Offset is zero.

I tried editing the Z value in the, M206 X0.0 Y0.0 Z0.0; offset home position for fine tuning line of the custom code, but that didn't seem to make a difference. Can anyone help me?
bam wrote:iinteresting... I'm not sure what's going on with the offset, it could be that the minimum software endstop function is stopping it from going below 0 even though there's an offset? I'll have to check it out.

You might try changing the z-offset in slic3r: printer settings --> General ---> Z-offset. It seems to work a bit better.
I tried changing the Z offset also. It acts like its a fail safe once the Z=0 it just won't go.
I did find this article http://airtripper.com/1799/marlin-firmw ... code-m206/ that talks about the M206 command and how to get your printer to actually do it.


TomsCables wrote:Oh and I noticed my X motor making a clunking sound when printing now. Could this have something to do with the firmware?
bam wrote:Could it be the z steppers? With compensation they're constantly moving to keep the nozzle at the right height over the non-level bed. They move way slower than the other steppers and make a much lower tone than the other steppers, to the point where you can hear the individual steps. I kinda like it, adding some base notes to the song your printer sings while it's making your cool stuff 8-)
The Knocking sound only occurs when I add all of that custom gcode to slic3r. It also does it when the carriages moves in the X direction when homing, so its not the Z steppers. When I remove the custom gcode it its as quiet as always. So its something in the custom gcode thats posted to the page. Maybe its a speed it doesn't like.

jepmn
Posts: 48
Joined: Mon May 05, 2014 8:59 am

Re: Auto bed probing and compensation with G29 Development

Post by jepmn » Thu Aug 07, 2014 2:13 pm

I've hit some weird resonances before that seem to depend on speed and where it's at on the axis (e.g. more resonances when it's high up on the z and traveling back down to the bottom at a certain speed).

nbmoretto
Posts: 243
Joined: Sat Nov 01, 2014 10:44 am

Re: Auto bed probing and compensation with G29 Development

Post by nbmoretto » Sat Nov 01, 2014 2:05 pm

I was wondering if with the most recent Taz 4 firmware if I still need to flash the firmware to get access to the G29 probe commands or if it comes stock with the Taz.

inventabuild
Posts: 163
Joined: Fri Aug 15, 2014 8:39 pm

Re: Auto bed probing and compensation with G29 Development

Post by inventabuild » Sat Nov 29, 2014 9:50 pm

bam wrote:We've been working for some time now on bed leveling, and have working prototypes featuring a neat way to tackle bed compensation.
When will the auto bed level upgrade be available for the TAZ 4?

inventabuild
Posts: 163
Joined: Fri Aug 15, 2014 8:39 pm

Re: Auto bed probing and compensation with G29 Development

Post by inventabuild » Sat Jan 10, 2015 11:13 pm

There is an enhanced version of the Auto_Bed_Leveling G29 code:

http://3dprintboard.com/showthread.php? ... 29-command

It says Marlin now allows for topographical mapping of the bed to allow for a non-planar surface. Has this been done for the TAZ 4?

Many people including myself report the center of the bed to be a different height by as much as 0.15 mm than the corners. This is significant for a 0.35 mm nozzle and makes it difficult to get a good first layer down for large prints or multiple small prints that cover the TAZ 4 build surface; hence the reason the TAZ 4 needs software to map the build surface and account for a non-planar build surface.

zhd
Posts: 54
Joined: Sun Jan 04, 2015 1:01 pm

Re: Auto bed probing and compensation with G29 Development

Post by zhd » Sun Jan 18, 2015 1:58 pm

inventabuild I feel is right - when i calibrate my TAZ on all 4 corners, the center of the bed will always be the highest point by far, didn't measure it but it must be at least 1mm height difference.

Is there something wrong or is that normal? As inventabuild is stating I reckon it could cause problems for large prints. (which I have not attempted yet)

So far I just did a manual calibration of the part of the bed which I was using for my smaller prints

saramos
Posts: 195
Joined: Fri Sep 19, 2014 1:05 am

Re: Auto bed probing and compensation with G29 Development

Post by saramos » Tue Jan 20, 2015 2:10 am

I wonder if it is the Y rails sagging under the weight of the print head rather than the bed being warped?

Post Reply