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BLTouch probing points grid off-center

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uki
Posts: 7
 uki
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Nozzle
Joined: 4 months ago

Hi!

Although I have BLTouch (v3.1) on my Ender 3v2 it's not working correctly: not compensating enough and z-offset is way off on right side of my bed. Now I just print without it - much better results... It's just worthless piece of equipment now... :((

But I have a feature request: Can You do something about BLTouch probing beeing off center? I mean it starts ~15mm from left side and probe point #5 is about ~50mm from right side - it seems that all 25 (5x5) probing points are off center. I've set my probe offset to original mounting bracket that I got with BLTouch from Creality (M851 X-43.00 Y-6.00). Maybe this off-center grid of probing points is the cause of my BLTouch issues?

Thank You!

Cheers!

uki

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Marlin Firmware Service
Posts: 195
(@marlin-firmware-service)
Stepper Motor
Joined: 6 months ago

The BLTouch can't map the entire bed - just because of the range of motion of the print head.

The left margin you mention is the safety margin to not hit any bed clips and cause damage to the nozzle or BLTouch, or have a false reading.

One of the key parts to understand is that the BLTouch can only compensate for small adjustments - usually less than 1mm - so you still have to normally level the bed before using the BLTouch.

If you haven't set your Z-Offset as yet, I would suggest this link:

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Dean3988
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Screw
Posts: 1

@marlin-firmware-service to save starting a new thread regarding this, I've only used the FW from

and it works great for my Ender 3 V2 with 3.1 BLtouch. I have the same thing where the probe is not reaching the right side of the bed, leaving around 40mm-50mm gap compared to the left side which gets near the edge.

 

I've been researching setting the probe offset as it appears that the BLtouch probe would physically reach the right edge however I am unsure of the hardware limitations of the motors etc and if this has been done for a reason? This is my first printer so learning as i go along!

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Marlin Firmware Service
(@marlin-firmware-service)
Joined: 6 months ago

Stepper Motor
Posts: 195

@dean3988 Yeah - the physical limits of where the probe can move requires this offset. The print head physically can't move far enough to the right to be able to probe the very right side of the bed.

The Probe Offset is purely to set the offset between nozzle and probe.

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uki
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 uki
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Nozzle
Joined: 4 months ago

Thank You for answer.

This is my bed:

Recv: Bilinear Leveling Grid:
Recv:       0      1      2      3      4
Recv:  0 -0.040 -0.020 +0.010 +0.062 +0.290
Recv:  1 -0.053 -0.035 +0.037 +0.125 +0.260
Recv:  2 -0.075 -0.057 -0.037 +0.020 +0.247
Recv:  3 -0.088 -0.057 +0.023 +0.120 +0.255
Recv:  4 -0.007 +0.007 +0.007 +0.057 +0.285

It way below 1mm. Still with BLTouch DISABLED - better 1st layer. When I enable BLTouch (without touching the leveling knobs) it's much much worse. 1st layer not sticking on the right side of the bed.
Which is strange, because right side of my bed is higher - so 1st layer on that side should be more flat (squished), but it's the opposite (like too much compensation from BLTouch).

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Marlin Firmware Service
(@marlin-firmware-service)
Joined: 6 months ago

Stepper Motor
Posts: 195

@uki Yeah - 0.3mm difference is still quite a bit - especially as it seems to be a step between column 3 and 4.

I tend to level my bed manually to have all values in the +/- 0.0xx range - or get as close to that as I can.

To give you an idea of what you're seeing - going towards the right side of the bed, the BLTouch will move the print head up around 0.2xx mm because the probes say that this area is much higher than the rest of the bed.

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uki
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 uki
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Nozzle
Joined: 4 months ago

I ordered another glass bed from Creality, maybe it will improve probing.

EDIT: On the other hand - I require BLTouch to compensate such irregularities, it's its purpose.

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uki
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 uki
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Nozzle
Joined: 4 months ago

According to probing points off-center - here's a video (click and it will play from mark when he talks about probing mesh off center).

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