What could cause this heightmap pattern
-
One of the reasons I went to indepandant z motors was that the gantry would slide down way too easy when there was no holding current so I doubt there is a stiff spot. In the great picture of things, the aberrations are immaterial but it was important to me to know why I see them. My curiosity has been satisfied and I will leave 'good enough' alone.
It has been a tremendous learning experience no matter what! -
Are you probing with bed heat on? If so, do you have the B1 parameter in your M558 command, to turn the heaters off during probing? Some bed heaters generate enough magnetic field to affect a BLTouch.
Duet WiFi hardware designer and firmware engineer
Please do not ask me for Duet support via PM or email, use the forum
http://www.escher3d.com, https://miscsolutions.wordpress.com -
If you are going to use clamps you should only use them in 3 places. 3 points determine a plane and 4 clamps over constrains a plane.
Is there anything in your wire loom that is binding the carriage? -
@dc42 , B1 is turned on
-
@4lathe , I am aware of the 3 point thing but the bed is supported at three points so I decided to keep that going to the glass plate.
No on the binding wire loom. -
Where you have the ridges and valleys in the Y direction towards the right hand end of that height map, I would be interested to see what it looks like if you probe that part of the bed with a smaller X spacing.
-
I just started a 9 hr print but I will run a mesh probe tomorrow as per request.
-
Interesting pattern ....! Just not sure what it tells me.
-
Interesting indeed! Did you try rotating the bed 90 degrees?
-
It is a CR10S-5 .... whoa .... the original post vanished
Anyway, aluminum v rails, aluminum bed, glass plate on bed.
Ha .. a new question appears
Yes, tried rotating, no difference. -
I still think your Z axis is stuck due to different movements of left and right. I would put 0.5 kg additional weight on the hotend temporarily and measure again. This will show you the problem, because it will make it worse or better.
-
I will see if there is a way of adding some weight to explore that possibility.
-
To joergs5’s point, can you probe the bed from a different direction in any way than you have been? As in always from the right or in the opposite direction in each row from what you have been been doing. That
might answer the question of whether loading from one side or the other is creating the ridges and troughs. -
@4lathe , the printer uses the standard Duet probing method starting at the front left, going to the front right, doing one step over (depending on probing density), starting on the right and probing to the left.
In other words the probing happens from both sides and no difference is seen in the bed pattern.
The pattern is seen in the Y direction and short of coding a completely manual scan, I have no idea how to tell Duet to scan 'backwards'. -
@jens55 said in What could cause this heightmap pattern:
I have no idea how to tell Duet to scan 'backwards'.
I guess you could swap your coordinate system to make the rear right corner 0,0
-
Great idea Phaedrux. When the probes happen from the opposite direction, if there is indeed a loading or stacking issue, shouldn't the valleys and ridges on the map be reversed?
-
@JoergS5 said in What could cause this heightmap pattern:
I still think your Z axis is stuck due to different movements of left and right. I would put 0.5 kg additional weight on the hotend temporarily and measure again. This will show you the problem, because it will make it worse or better.
Well it's not happening. I added a 600 gr chunk of lead and it promptly got loose . I only lost my BLTouch mount (thank God) in the process. I am not going to risk the glass plate.
-
@jens55 Sorry to hear that! I hope, it's not too much damaged.
The test was intended for:
a) if it gets worse, this may be due to stuck axis because of the difference between the two vertical aluminium extensions are too narrow or too wide. Can you test this manually?
b) if it gets better, the reason may be that you have backlash effects. This means, if Z changes, the movement changes the position at your left and right spindle with play. Alternatively, the connector between stepper and spindle is flexible too, it has backlash also. I don't know a different possibility than to make the hotend heavier to find it out without disassambling and replacing the connector.c) is possible also, as David suggested, that measuting by BLtouch has a problem
In your last screenshot the left side was lower than the right. You can move the left stepper isolated so that the distance of left and right are smaller (lift left side for about 0.25 mm) like described in https://duet3d.dozuki.com/Wiki/Bed_levelling_using_multiple_independent_Z_motors
-
@JoergS5 said in What could cause this heightmap pattern:
@jens55 Sorry to hear that! I hope, it's not too much damaged.
The test was intended for:
a) if it gets worse, this may be due to stuck axis because of the difference between the two vertical aluminium extensions are too narrow or too wide. Can you test this manually?I do not understand what you are trying to say.
b) if it gets better, the reason may be that you have backlash effects. This means, if Z changes, the movement changes the position at your left and right spindle with play. Alternatively, the connector between stepper and spindle is flexible too, it has backlash also. I don't know a different possibility than to make the hotend heavier to find it out without disassambling and replacing the connector.
I do not understand why backlash would only show up at a particular x coordinate.
c) is possible also, as David suggested, that measuting by BLtouch has a problem
Unlikely as the issue is very specific. A measuring defect would show random errors.
In your last screenshot the left side was lower than the right. You can move the left stepper isolated so that the distance of left and right are smaller (lift left side for about 0.25 mm) like described in https://duet3d.dozuki.com/Wiki/Bed_levelling_using_multiple_independent_Z_motors
Before any mesh map is run, I already do a Z axis equalization (actually 5 times). Z is within 0.005 for the ends of x travel for the given y location where the measurement is happening.
-
@jens55 it's complicated to explain better... Sorry. The backlash could show up at particular coordinates, because some micrometer differences between the vertical axis resulting in different resistance and movement.
The article https://all3dp.com/2/best-creality-cr-10-s5-upgrades-and-mods/ talks about some issues in chapter "Better bed mounting", maybe this helps.
