troubles with G29 S2 command

Hello,

This is my first post here.
I tried the Repetier website for answers but no reaction.

I have an issue with the new firmware v0.91 concerning G29 S2.
This should messure the print area height and store it in Eeprom.

First the printhead is probing the 3 points then goes up to Z max endstop and goes down.
When the printhead is coming down from touching the z max endstop it touches the bed again.
Then the problem occurs.
Z axis doesn't move but X-axis and Y axis go down.
Result: printerhead crashing in bed.

any idea?

Geo Hagen
Homemade Deltaprinter.
Ultimaker electronics.

Hi Geo,

Have you found a solution for this? I am having the same problem with the latest version of the firmware 0.91.5. (delta type installation)
II issued the command a few time with the s2 option but it starts the calibration an reads the 3 points..


then it crawls slowly back to Z-MAX (can I speed this up somewhere? probing at 20mm/s but crawling to the Z at probably 2mm/s) And after hitting the Z-Max it starts moving down..and rams the hotend into the bad :-(

Perhaps we should put the last point at x0 and y0 so that it rises evenly.. (just thinking of it while typing, will try this tomorrow first thing) so in my case it would be point 1 -80,-80 then 80,80 and last 0,0 I hope it will understand this order..

Why only 3 points instead of 7 points? Just curious. perhaps the 3 points is enough. but what if you have a slight bowl because of heatbed expansion? So no critique.. just curious :-)

One final problem on which I am not done investigating.. is that at the end of the print the host never seems to find that it is ended.. I got a flashing light on the board very rapidly. but as said I need to investigate this further, perhaps something in the endcode.. (also something for tomorrow)


With kind regards,

Michael

Looks like you are both using delta printer and indeed the G29 for delta was wrong. Measured height works only for cartesian printers that way. Replaced that code part so it works now.

The command was a bit neglected in favor for the G32 command, which also corrects the bed tilt resulting normally in better positioning.

The G32 command is also the reason we use 3 points. We need 3 Points to compute bed tilt which is why we store 3 points and we simply reuse the 3 points for G29.

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I can confirm that after getting the latest version the G29 S2 responds differently and doesn't crash anymore into the bed..
The only problem now is that a wrong value is stored in the eeprom for the Z-height.. My height should be 170.. with a probe offset of 3.7 but it stored 22 in the eeprom as z-height..

So when I issue G28 for home it goes up to the endstops (max) and comes down to 22..
So I think there is a minor calculation error ,, (will try to find it myself, perhaps I can :-))

Edited 1 time(s). Last edit at 02/23/2014 12:00PM by mhensen.

I have checked it again. Also I got reasonable values they were off a mm. Looks like some coordinate transformations were at the wrong place. With the latest fix I now get identical values every run and error is only 0.3mm to the G32 result, which is acceptable as I know my bed has a light tilt.

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Hi,

This is my first message. Well, I have trouble with the G32 S1 in my cartesian printer Prusa Mendel. The Z-probe touches the bed in 3 points then the Z axis goes up to Z max endstop and goes down. When the printhead is coming down from touching the z max endstop, it goes down until crashing in the bed.

I'm not using the eeprom memory because I want that the printer do the measure of the table always that it will begin to do a printer work.

With the G29 S1, the same problem occur.

Without the S1, only G32 comand, the printhead touches gently in the bed with wrong leveling.

I am using the firmware version 0.91 of Repetier Host.

I don´t have idea I need to do to correct it.

What sub verison of 0.91 are you using. There was definitely an error in one of the versions, so you should test 0.91.6 or higher.

After going to z-max it should go to start height and not lower.

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Hi Repetier,

There is no subversion number in the firmware that I got of Repetier web site downloaded in the last Friday. Only appear Repetier version 0.91 in the Repetier.h file. Where can I get the new 0.91.6 or higher version ?

#define REPETIER_VERSION "0.91"

Attached are the configuration.h and Repetier.h from the Repetier firmware that I am using now.

I Thank Your Help.

Sorry, English is not my native language. : )

The subversion is the REV number in the online calculator. It is not written anywhere else, except in the version string if Configuration.h. There you have

    "version": 91.5

so it was is the version with broken z leveling.

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Ok.

So when the firmware from the Repetier web site will be updated?

There is no indications about newer versions.

The servo is changing a little the position previously adjusted in the configuration.h file. When I do M340 P0 S1500, the position must be 90 degrees, but sometimes it changes a little. It can be another problem from firmware?

Hello?

You used 0.91 REV 5 and current version online is 0.91 REV 6. Soon you will get 0.91 REV 7.

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Hi,

Ok. I will try the 0.91Rev 6.

This is a Good news about the 0.91 Rev 7.

I thank Your help.

Is it possible to define more than 3 points in the Z-probing? I would like to probe a grid of my bed to account for any slight warping.

Quote
repetier

You used 0.91 REV 5 and current version online is 0.91 REV 6. Soon you will get 0.91 REV 7.

Can I slip in a small thread-hijacking question here and request that you post a new thread on this forum whenever you release a new REV? Please also include the release notes, so that those of us who don't check the auto configuration site every day will get notified of new versions and what the fixes are. Thank you from somebody still on REV5 with a Delta.....

I also would like to see an offset matrix applied to the bed leveling routine (similar to runninfarmer's observation). This would allow the system to measure z offsets at specific grid intervals to fill the matrix. Then when printing the first 5 layers or so, you would apply the offsets (interpolating between the matrix points in x-y to obtain z estimates). Also you could apply an offset matrix reduction routine, reducing the offset weight of each of the 5 layers by 20% untill at layer 6 no more offset is applied. This would allow you to print on fairly warped platforms (potato-chip shaped) and by layer 6 be fairly flat. to disable the feature fill the matrix with zero's. The calculations to dynamically apply the matrix may exceed the mega 2560's ability to keep up during printing, maybe this is suited to the DUE version, or just run the first 5 layers slower and resume to normal speed at layer 6. I would envision a few firmware settings to allow some tweaking. A parameter to define the size of the matrix (and thus resolution). A parameter to define the layer reduction to zero (20% would remove offset compensation after layer 5, 50% would remove compensation by layer 3 etc...) An auto populate matrix function to take the z probe on a path around the print bed sampling heights in the grid and storing in the matrix. This could be an enabling feature to allow low cost expansion of the print bed to 400mm and larger. Its pretty easy to get AL plate that large but common to see up to .5mm warp. offset matrix to the rescue!!

by the way, I have a printer capable of printing in a 500mm x 500mm x 500mm volume. be glad to code, test and tweak. it's currently setup for abs at 200x200x500

That is an idea I had always thought of. It is the reason I left 2048 bytes in eeprom free. Assuming we use 2 byte per point as int16_t storing the offset to z perfect as steps we could store a grid of 32x32. What we need is a defined grid area which is normally smaller then print area. On my delta for example I can not reach all positions with my z probe, because of the position. So leaving that area would stall at the latest value of the grid.

Measuring is then no problem only a bit time consuming, but you normally do this only once per bed.

The biggest problem is speed. If it is quite even only minor corrections are necessary and we have nor problems. But for fast moves we need to change z faster.

Implementation depends on the drive system. For cartesian printers we can store a z corrected counter and drive always towards the nearest attractor. No complex computations as we need to be fast.
Correction can be 100%, 50%, 25%, 12.5% or none so we can solve it with simple integer shifting. Divisions are too slow. On the due we can use divisions.

For delta printer we should do it in the delta transformation. You can not move z during print. Tried that when I implemented babysteps and the result was loosing even more steps.

Well, thats the coarse direction it should go. Maybe some more tweaks for avr are necessary to handle it in a fast way.

If you think you can do it, try. If it works good I will add it. But I have only a probe for delta to test. Please use the work092 branch if you do so. It will be included in that version and there are many modifications as it is the upcoming version.

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