Auto_Bed_Leveling: Z-Probe Repeatability code

It is easier to see the imperfections in the 'flatness' of the bed when you have the bed closer to level. Here is the topography for a print I'm doing right now:

Mean of sampled points: 4.498123

Bed Height Topography:
--0.10869 +0.02526 +0.07123 --0.07925
--0.13349 +0.01203 +0.03584 +0.05469
--0.14705 --0.00054 +0.06495 +0.10530
--0.12225 +0.00277 +0.12745 +0.09174

Notice the first row starts negative, goes positive, and then goes back negative. And notice the second column. It starts positive, goes negative and comes back to positive.

Right now, your bed is tilted pretty hard from left to right. If you can get it more level, the imperfections will jump out at you. But with that said, looking down your 3rd, 4th and 5th column, the 4th row jumps up in value and then back down when it goes to the 5th row. But the 1st and 2nd column is the opposite. On the 4th row it jump down in value and then back up.

Hi Roxy sorry I havent got back to you for a couple of days but work has been crazy and I needed a rest. I'm just about to try a print with pronterface and your code and thought i'd just add the M48 code first. When I added in the code it wouldnt compile saying #endif without #if at the very end of your code, I tried just removing the #endif line and it compiled and seems to work but don't really know if i've done something stupid. Here are my first results just sending an M48 command
>>>M48
SENDING:M48
M48 Z-Probe Repeatability test. Version 1.85
Mean: -0.167070
Standard Deviation: 0.002544
echo:endstops hit: Z:-0.17

I will have a go at printing something now and see how it goes but when I ran G29 last time this was my result
Bed Level Correction Matrix:
0.999998 0.000000 0.002131
0.000000 0.999999 0.001302
-0.002131 -0.001302 0.999997
isnt the last line supposed to be positive numbers? Or have I got that confused? Thanks again in advance

*Just wanted to try it one more time just to make sure
>>>M48 n10 V4
SENDING:M48 n10 V4
M48 Z-Probe Repeatability test. Version 1.85
Positioning probe for the test.
1 of 10 z: -0.791797 mean: -0.791797 sigma: 0.000000
2 of 10 z: -0.793750 mean: -0.792773 sigma: 0.000977
3 of 10 z: -0.792187 mean: -0.792578 sigma: 0.000844
4 of 10 z: -0.794531 mean: -0.793066 sigma: 0.001118
5 of 10 z: -0.793359 mean: -0.793125 sigma: 0.001007
6 of 10 z: -0.798828 mean: -0.794075 sigma: 0.002316
7 of 10 z: -0.807422 mean: -0.795982 sigma: 0.005139
8 of 10 z: -0.805469 mean: -0.797168 sigma: 0.005740
9 of 10 z: -0.800781 mean: -0.797569 sigma: 0.005530
10 of 10 z: -0.800000 mean: -0.797812 sigma: 0.005296
Mean: -0.797812
Standard Deviation: 0.005296
echo:endstops hit: Z:-0.80

Quote:

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Originally Posted by brainscan

Hi Roxy sorry I havent got back to you for a couple of days but work has been crazy and I needed a rest.

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No Problem!!!

Quote:

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Originally Posted by brainscan

I'm just about to try a print with pronterface and your code and thought i'd just add the M48 code first. When I added in the code it wouldnt compile saying #endif without #if at the very end of your code, I tried just removing the #endif line and it compiled and seems to work but don't really know if i've done something stupid. Here are my first results just sending an M48 command

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It looks from the printout later that everything is good... But if you attach your current Merlin_Main.cpp I'll do a quick DIFF and make sure that #endif was safe to take out.

Quote:

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Originally Posted by brainscan

>>>M48
SENDING:M48
M48 Z-Probe Repeatability test. Version 1.85
Mean: -0.167070
Standard Deviation: 0.002544
echo:endstops hit: Z:-0.17

I will have a go at printing something now and see how it goes but when I ran G29 last time this was my result
Bed Level Correction Matrix:
0.999998 0.000000 0.002131
0.000000 0.999999 0.001302
-0.002131 -0.001302 0.999997
isnt the last line supposed to be positive numbers? Or have I got that confused? Thanks again in advance

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Adding a 't' or 'T' to the G29 is helpful because you can see how flat the bed is from the Bed Height Topology map. Ideally, you should have a '0' after each decimal point. Like +0.0xxx or -0.0xxx The last line isn't supposed to be positive. I bet you are thinking about previous discussions where people's Z-Axis was going the wrong direction. The DIAGONAL of the matrix should be POSITIVE!!!!

Quote:

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Originally Posted by brainscan

*Just wanted to try it one more time just to make sure
>>>M48 n10 V4
SENDING:M48 n10 V4
M48 Z-Probe Repeatability test. Version 1.85
Positioning probe for the test.
1 of 10 z: -0.791797 mean: -0.791797 sigma: 0.000000
2 of 10 z: -0.793750 mean: -0.792773 sigma: 0.000977
3 of 10 z: -0.792187 mean: -0.792578 sigma: 0.000844
4 of 10 z: -0.794531 mean: -0.793066 sigma: 0.001118
5 of 10 z: -0.793359 mean: -0.793125 sigma: 0.001007
6 of 10 z: -0.798828 mean: -0.794075 sigma: 0.002316
7 of 10 z: -0.807422 mean: -0.795982 sigma: 0.005139
8 of 10 z: -0.805469 mean: -0.797168 sigma: 0.005740
9 of 10 z: -0.800781 mean: -0.797569 sigma: 0.005530
10 of 10 z: -0.800000 mean: -0.797812 sigma: 0.005296
Mean: -0.797812
Standard Deviation: 0.005296
echo:endstops hit: Z:-0.80

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Those are super good numbers!!! Trike is the only one with better numbers so far. You might want to use the 'L' parameter to stress the X & Y axis a little also and see if there is much additional extra slop there. Like M48 L 7 but my guess is your machine is very tight and crisp! I wish mine could do those numbers!

Quote:

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Originally Posted by Roxy

No Problem!!!



It looks from the printout later that everything is good... But if you attach your current Merlin_Main.cpp I'll do a quick DIFF and make sure that #endif was safe to take out.



Adding a 't' or 'T' to the G29 is helpful because you can see how flat the bed is from the Bed Height Topology map. Ideally, you should have a '0' after each decimal point. Like +0.0xxx or -0.0xxx The last line isn't supposed to be positive. I bet you are thinking about previous discussions where people's Z-Axis was going the wrong direction. The DIAGONAL of the matrix should be POSITIVE!!!!!

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Yes now you've said it you're right I am thinking about the delta being positive (my maths is bad anyway so I get confused easily), I will add in a T to the G29. I am still having problems with it though, tried a print and the nozzle still just air prints. The z axis move to show its using the bed level matrix but because its so far from the bed I cant tell if its following it properly. Sorry I know this is the wrong thread for this problem so I will make a new post there with any files you want? Thank you, feel so close now!!!

Quote:

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Originally Posted by Roxy;

Those are super good numbers!!! Trike is the only one with better numbers so far. You might want to use the 'L' parameter to stress the X & Y axis a little also and see if there is much additional extra slop there. Like M48 L 7 but my guess is your machine is very tight and crisp! I wish mine could do those numbers!

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Thanks I was surprised how good they were actually and I know there is play in the probe as its only a thrown together prototype(cant print my new one until I sort out the bed levelling)

Your code is 'safe'. But you are missing both the #ifdef and #endif in the following code snippet. Everything is fine except this code won't disappear like it should if you ever turn the Auto_Bed_Leveling off. Go ahead and post in the previous thread and we can start working on getting the Z-Axis height right. Does your Z-Probe really fire .8mm below the nozzle?

#ifdef ENABLE_AUTO_BED_LEVELING // <---<<< Missing
case 48: // M48 Z-Probe repeatability
{
#if Z_MIN_PIN == -1
#error "You must have a Z_MIN endstop in order to enable calculation of Z-Probe repeatability."
#endif

double sum=0.0;
....
Sigma_Exit:
break;
}
#endif // ENABLE_AUTO_BED_LEVELING // <---<<< Missing

ahh I wondered if adding #ifdef ENABLE_AUTO_BED_LEVELING at the beginning would help but wasnt really sure if that was missing for some reason or if the #endif somehow got pasted into the end, i'll add both of those back in now. No my probe offset is x 13 y 0 z -7.4 but it shows endstop hit between -0.4 and -0.8

Quote:

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Originally Posted by brainscan

ahh I wondered if adding #ifdef ENABLE_AUTO_BED_LEVELING at the beginning would help but wasnt really sure if that was missing for some reason or if the #endif somehow got pasted into the end, i'll add both of those back in now. No my probe offset is x 13 y 0 z -7.4 but it shows endstop hit between -0.4 and -0.8

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OK... This isn't going to be that hard to figure out! (Famous last words!!!!) Because the Z number should be very close to your Z_PROBE_OFFSET_FROM_EXTRUDER

And yours is 1/10 of it...

1 of 10 z: -0.791797 mean: -0.791797 sigma: 0.000000

I'm guessing this is pretty good, then?

>>>M48 x 100 y 100 n 15
SENDING:M48 x 100 y 100 n 15
M48 Z-Probe Repeatability test. Version 1.85
Mean: 10.933267
Standard Deviation: 0.000403
echo:endstops hit: Z:10.93

I'll try again with the E included.

Edit:
>>>M48 x 100 y 100 n 15 e
SENDING:M48 x 100 y 100 n 15 e
M48 Z-Probe Repeatability test. Version 1.85
Mean: 10.933835
Standard Deviation: 0.006625
echo:endstops hit: Z:10.94

Yes... That first number is so good I doubt you can get it that good every time you run the test! Your mechanics must be very precise!

Hi Roxy,

Thanks for writing this nice feature for testing the Auto_Level sensor. I noticed your post at the Marlin GitHub and hence found this forum. Next i patched the Marlin_Main.cpp and tested my setup.

The results are very interesting indeed. Without retraction the deviation is at what I consider at the theoretical limit of the Z-Probe design I have as I get an astonishing 0.000691 (yes that’s right, 3 leading zero’s) i.e. better than 1 Mill accuracy. (1/1000mm).

However when adding ‘Retract’ this drops to 0.004797. This indicates that the ‘shaft-rotation’ in my design still induces a small deviation or I need to make a more accurate ‘head’ for the sensor probe. However if you then think about the BED flexing up and down when being heated even when this is done under PID control, then I believe that any further improvements will be futile as Bed Bending caused by temperature fluctuation and moving cooling fan’s around while printing will most likely be a bigger factor.

FYI: I use a M5 Ultra-Mini Proximity Sensor in combination with a bronze probe with a small metal nut on top, retracted by a mini servo. However the Servo is not part of the measurement and only used to lift the probe. Still I noticed that due to the lifting the probe, it slightly rotates each time its gets lifted and retracted, hence the difference in results when adding ‘retract’ to the M48 test command.

This Z-probe design I made can be applied to many extruder setup’s so if anybody is interested you can find a description of the setup at the following link: http://creatrtips.freeforums.org/vie....php?f=8&t=160

Here is a link for the mini proximity sensor I use: http://jimou.en.alibaba.com/product/...ty_sensor.html Type 10-30V NPN N.O. with a switching distance of 0.8mm

I also noticed (especially when using mechanical switches) that slowing down the second and final probe movement increases the accuracy significantly. I therefor patched the ‘homing_feedrate[Z_AXIS] ‘ lines within marlin_main.cpp to be divided by 8 where the default is only 2. This makes a notable difference. Even for a non-mechanical sensor such as an induction proximity sensor.

Results from M48 testing:
Without Retract:
10:25:02.150 : M48 Z-Probe Repeatability test. Version 1.85
10:27:22.410 : Mean: 12.281874
10:27:22.410 : Standard Deviation: 0.000691
10:27:22.410 : echo:endstops hit: Z:12.28

With Retract:
10:33:23.254 : M48 Z-Probe Repeatability test. Version 1.85
10:36:09.816 : Mean: 12.280522
10:36:09.816 : Standard Deviation: 0.004797
10:36:09.816 : echo:endstops hit: Z:12.29

Thanks again for sharing this nice feature with the 3D community,

Rgds, Arno