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"Inverted" ABL Correction Matrix?

Posted by bcsteeve 
"Inverted" ABL Correction Matrix?
February 12, 2018 05:26PM
I'm having a frustrating experience.

First off, things have gone well for a long time. But I changed my print surface so I had to run the ABL routine again. I have it set to Bilinear. My bed is pretty flat as it is, but I have it ABL anyway.

Now with my new print surface, I'm less level (go figure), but I figure ABL will correct.

However, when I print... the left side is tight and the right side is loose. When I bring the Z down, the left side is SUPER tight and the right side is even more loose. Huh?

I started to wonder if the matrix that's being measured isn't being applied right? Like something is inverted that shouldn't be (or vice versa). I'm not sure what to check. Honestly, I'm not even sure what info you would need to help me check. So please be kind and let me know what you need to know to get me where I need to be.

I'll start with the M420 -V output, though I doubt on its own that's any help to you:

Send: M420 V
Recv: Bed Level Correction Matrix:+1.000000 +0.000000 -0.000136
Recv: -0.000000 +1.000000 -0.000970
Recv: +0.000136 +0.000970 +1.000000
Recv: echo:Bed Leveling On
Recv: ok

This is a CR-10 running stock Marlin. This is the output from M115:
Send: M115
Recv: FIRMWARE_NAME:Marlin 1.1.8 (Github) SOURCE_CODE_URL:[github.com] PROTOCOL_VERSION:1.0 MACHINE_TYPE:Thinger EXTRUDER_COUNT:1 UUID:cede2a2f-41a2-4748-9b12-c55c62f367ff
Recv: Capconfused smileyERIAL_XON_XOFF:0
Recv: Cap:EEPROM:1
Recv: Cap:VOLUMETRIC:1
Recv: Cap:AUTOREPORT_TEMP:1
Recv: Captongue sticking out smileyROGRESS:0
Recv: Captongue sticking out smileyRINT_JOB:1
Recv: Cap:AUTOLEVEL:1
Recv: Cap:Z_PROBE:1
Recv: Cap:LEVELING_DATA:1
Recv: Cap:BUILD_PERCENT:0
Recv: Capconfused smileyOFTWARE_POWER:0
Recv: Cap:TOGGLE_LIGHTS:0
Recv: Cap:CASE_LIGHT_BRIGHTNESS:0
Recv: Cap:EMERGENCY_PARSER:0
Recv: ok
Send: M155 S2
Recv: ok
Thanks.


(ps. Grr. ALL forums should have smileys disabled in CODE tags)

Edited 2 time(s). Last edit at 02/12/2018 05:28PM by bcsteeve.
Re: "Inverted" ABL Correction Matrix?
February 13, 2018 03:50AM
What is the new bed material, and what type of probe are you using ?
Re: "Inverted" ABL Correction Matrix?
February 13, 2018 09:03AM
You may be running into this issue: [github.com]

The reason for the flaw is not currently known. You might want to switch to a different bed leveling system until this is fixed.
Re: "Inverted" ABL Correction Matrix?
February 13, 2018 09:05AM
Quote
obewan
What is the new bed material, and what type of probe are you using ?

Glass vs glass... just a different sheet. Using capacitive sensor.
Re: "Inverted" ABL Correction Matrix?
February 13, 2018 09:48AM
Quote
Roxy
You may be running into this issue: [github.com]

The reason for the flaw is not currently known. You might want to switch to a different bed leveling system until this is fixed.

Yeah, that sounds like what I'm experiencing.

FYI Linear and Bilinear both have the "effect". I haven't tried 3 point and my system (CR-10) can't handle UBL. At least not without some serious feature trimming (I tried axing beeper and SD but that wasn't even close to enough).
Re: "Inverted" ABL Correction Matrix?
February 13, 2018 09:54AM
Quote
bcsteeve
Quote
obewan
What is the new bed material, and what type of probe are you using ?

Glass vs glass... just a different sheet. Using capacitive sensor.


Are capacitive proximetry sensors accurate enough with glass ?

Is it possible the capacitive sensor is actually getting reflections off your alluminium bed.
Re: "Inverted" ABL Correction Matrix?
February 13, 2018 10:09AM
Quote
obewan
Quote
bcsteeve
Quote
obewan
What is the new bed material, and what type of probe are you using ?

Glass vs glass... just a different sheet. Using capacitive sensor.


Are capacitive proximetry sensors accurate enough with glass ?

Is it possible the capacitive sensor is actually getting reflections off your alluminium bed.

Sure they are. Inductive wouldn't be (well, it would be, it would just be measuring the wrong surface). These things don't "reflect", per se. A capacitive sensor is the appropriate tool for a glass bed. It would be fine for metal too, but if you have metal then I'd suggest inductive because it doesn't suffer as much from environmental influences (humidity, primarily).
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