Z-Axis calibration with auto-leveling feature?

Hi everyone,

I just received my RoBo3D last week - it's already the upgraded model with the "auto levling" (or better described as "automatic Z-Axis calibration") feature installed. I diligently followed the instructions, and skipped the bed leveling part from the "getting started" video. Instead, I entered the predefined, manually added offset value (1.45 mm in my case) from the accompanying instruction sheet in the Z-offset field in MatterControl (and later RepetierHost).

However, with my specific printer delivery, the screws in the supports that hold the calibration switches hadn't been tightened properly, so the supports started slipping up and down while printing. When trying to fix this, I made a big mistake: I aligned the bottom face of the supports flush with the nuts on the Z-rod, and then tightened them (I hope you get the picture, even without me posting any photos). The effect was that the auto-calibration didn't work at all any more - the end-switches didn't get released, and the carriage just lifted off the nuts when moving upward, making the supports spin uncontrollably, and wrapping/pulling the cables up from the bottom, to the point of almost tearing them off. Not a pleasant experience!

It took me a while to figure out how the leveling/calibration actually works (pushing the extruder nozzle onto the bed until the switches are released), and so I sort of fixed the problem by moving the supports up a bit along the nuts (guesstimating the distance!) and tightening them again.

Since then, I've been able to come up with a few decent prints (both PLA and ABS), but most prints still go wrong - and it seems like it's often due to bed leveling issues. I have played around a lot with the Z-offset value in the software; sometimes, 1.45 seems to work, sometimes 1.39 is better, sometimes 1.42 - it's not really consistent.

So, here's my question: What's the correct procedure, in my case, for properly re-calibrating the bed? How did the team who assembled the printer get to that magical 1.45mm value? What adjustments do I need to make to the supports on the Z-Axis in order to get a consistent Z-Axis offset again?

Thanks a lot in advance!

 

I haven't even seen a picture of the auto bed leveling. It would be nice if they made an instructional video on youtube with how to put it together, adjust it and setup the software.

Sounds like some people have may have purchased it as an upgrade. I could be wrong on that. If true, how do they know how to set it up?

 

The so-called "auto bed leveling" (I'd rather call it Z-Axis calibration) that comes with the latest batch of RoBo3D R1 (not sure if there's an upgrade you can purchase separately) is nothing you need to set up in any way - it's automatic. It's also nothing much that you could take a picture of. It basically consists of some new electro-mechanical parts (basically supports with a switch on which the carriage rests, on both sides / Z-rods), and a new function in the updated firmware.

That function basically does the following: It sequentially moves the print head to 9 pre-defined probe positions on the bed, and lowers the head at each position until the nozzle hits the bed (and hence the two switches that the carriage rest upon will release). It will then calculate a plane normal from the Z values, and use that as a Z-axis calibration during the printing process.

Typically, that function gets called before every print job.

There's no actual "leveling" going on, but the level error is being measured, and taken into account during printing (which is just as good). You normally don't need to set up anything - however, there is a magic "Z-offset" value that seems to be different for each individual printer (it's manually inserted into the instruction sheet that they stick onto the bed), and that needs to be entered as the Z-offset value into your software settings.

And that's what I'm confused about, and what my question is about: How to I determine that value again, after having messed with the vertical positions of those supports on the Z-axis?

 

One thing I can see wrong with this kind of setup is if the z axis nuts move up and down in their pockets until the switches trip, then they could, once in a while hang up a little and throw off the height readings. You would think there would be light springs pulling the nuts into their pockets just to be sure they repeat position every time.

I know some people would think that the spring idea could cause the hot end to crack the bed. I wouldn't use springs that would not stretch far enough to not let the nuts pop out out of their pockets. Right now I have some rubber bands retaining the nuts on my machine. They stretch so easy that the hot end will never crack the bed.

 

I cant seem to get mine set right either. How much of the nut is showing below the switch on the z axis bolt on each side?
All of my prints start about 4mm off the bed. I raised the switches up the nut a little and it still starts high.

I wondering if when the hot end probes the bed is it supposed to lightly touch it before the switch engages or is it supposed to press down for a second.

Let me know if you make any progress.

 

The switch should barely activate with the carriage pressing on it. A slight force separating the switches with your thumb should activate and deactivate on release. If it takes too long to unseat it can be unreliable.

 

Thanks Mike. I'll keep adjusting them till i get them right. Mine pushes on the bed for at least 0.5 seconds before the switch activates.
I found this video that shows it barley touches the bed.

I will continue to modify mine.

 

On my end, it's roughly 1.45 mm on either side (it's hard to measure, even with a digital caliper). I wonder if the value we're supposed to enter as the Z-axis offset is supposed to be that very distance (how much of the bolt is showing at the bottom).

That same effect showed on my end when the switch supports were too low, so the switch never engaged during calibration. Can you hear the switches clicking at each of the 9 calibration points?

Like what Mike already said, and what the video shows.

Unfortunately, none yet. I'm still hoping for someone who can explain how to re-calibrate the bed level, and how to obtain that magical, actual Z-axis offset value that was somehow measured after my specific printer was assembled and calibrated.

 

Yes they click on each point.

The paper that came with my Robo said 0.95 as my z-offset. I have changed it from 0.5-1.5 and had no luck.

The only way i can get a print to start correctly is pause immediately and lower the z's by hand until they almost touch the bed.

 

I find myself wondering:

What software are you guys running and what version of it?

If you're running MatterControl it should say the version number at the very top of the window in the title bar.

Also, if you updated the firmware through MatterControl because it said there was an update, that might be your problem also.

 

I am using MatterControl version 1.1.0
Firmware update was through MatterControl. Using 'RoBoAuToV1'
There is actually another update now on there. Lets see what that does.


image hosting

 

I tried Matter Control (the latest version recommended from the RoBo3D website) first, then switched to RepetierHost. No firmware update so far (Matter Control kept saying it's looking for firmware updates, but never found/downloaded any). So I'm basically still running the firmware that came pre-installed with my R1, and just entered the suggested (1.45mm) Z-axis offset, both in MatterControl and then in RepetierHost. Just to clarify: In both scenarios, after adding the Z-axis offset in the printer settings, prints went pretty okay. However, not perfect.

All I'm still asking about is the standard procedure for calibrating my R1, and getting to that magical Z-offset value.

 

Started using Repetier... BOOM problem solved. Print perfect now.

Had to play around with the Z offset but 0.95 was where it looked best....

 

I've had (am having) the same issue, have you found a good solution? I don't even know where the z offset option is in MatterControl, I've had the Robo PLA/ABS (auto-print leveling) for a few weeks, produced some decent prints but when I updated the firmware and tried solving one issue the z-axis height has became messed up, my initial layer is WAY too close on the bed, any advice is greatly appreciated

 

Use Repetier... MUCH BETTER than MatterControl. The below video will help you set it up. Once it is setup keep messing with the z offset until it is dead on.

Also i would rollback to the old firmware. I did and that helped. I have attached them. Follow these steps to install.

Arduino is free to download at www.arduino.cc
Please download and install the latest arduino software.
Attached is the .zip file for the marlin auto level firmware.
Download the file. You will need to extract the files of the .zip file and put them to where your arduino software is looking for sketchbooks.
To find out the file path for where arduino is looking for sketchbooks, open the arduino software
Go to file, preferences, and see at the top of the window sketchbook location.
Make a new folder in that location and add all the files from the .zip file into that folder. Name the folder auto_level.
Steps to uploading the firmware (or flashing the arduino with the same firmware).
Make sure your computer is connected to the printer via USB cable. You can leave the power cord unplugged for this procedure.
Do not connect repetier or any other software system to your printer.
Open the arduino software.
Under tools choose board and then arduino mega 2560
Under tools choose serial port and choose the option associated with your printer (will probably be the only option, if not, unplug your printer and see which option goes away).
Under file, open Auto_Level
Now you should press the reset button on the arduino board (if you are looking at the printer from the front where the logo is, this is a small circular black button directly behind the number 3 in the logo). Press this button once.
Now hit the upload button in the arduino software. This is the green arrow pointing to the right at the top of the arduino software window.
When the firmware is finished uploading, the arduino software will say “Done uploading” at the bottom of the window.

 

Thanks for the speedy reply! Now...when you say keep messing with the Z offset is that by doing so digitally or physcially (twisting the threaded rods) and what is the "dead on" I'm aiming for? Touching the bed, so many mm from the bed etc.. I apologize I am very new to this

 

I'm new too. No worries.

You will set the z offset in the scil3r config. Under printer settings. Watch the video and you will see it.

Your printer should've came with a paper that tells you what the z offset should be. Mine was 0.95.

Also remember you need to add a few things to the custom gcode section on slic3r.

G28 ; home all axes
G1 Z5 F5000 ; lift nozzle
M109 S[temperature] ; set the extruded temp and wait
G29 ;auto calibrate bed

 

Thank you so much, I will do these steps tomorrow and report back. This forum really has great members who contribute!

 

So it seems like your solution worked! Do you use the settings that were recommended in the RoBo video or do you have any settings for repetier you wouldn't mind sharing?

 

Wow 0.95 1.45 ?????????????? On my sheet of paper it's indicate 0.10 ?????? I wondering if my issues with first layer that clogged my nozzle is the result of this extremly low value of z offset .....