Z height behavior

pc-6 · 21 Dec 2018, 15:28

Never mind about the first issue of printing at Z0.7. I was so focused on the firmware I did not notice that I had accidentally had a Z height offset in my slicer settings. Ah the silly things one does when they are frustrated and tired. This is one issue a good nights sleep fixed.

Still have the mesh bed issue.

Phaedrux · 21 Dec 2018, 17:17

Most BLTouch issues Have been documented here: https://duet3d.dozuki.com/Wiki/BLTouch_Troubleshooting

Give that a look and see how your configuration compares.

How accurate is the heightmap? If you move your nozzle along close to the bed with mesh compensation active does it keep it close to the bed or is it obviously far off?

pc-6 · 22 Dec 2018, 18:20

@phaedrux
When I move the nozzel across the bed with the mesh bed leveling on, the nozzle is slowly lifted from the bed. With the mesh bed off the nozzle keeps a consistent distance above the bed.

Phaedrux · 22 Dec 2018, 18:30

It would seem that your probe isn't giving you repeatable results leading to an inaccurate height map.

If you do a test print with mesh compensation off does it print well? If your bed is flat enough you don't really need to use mesh compensation at all.

0_1545503269052_bedlevel_nozzle_0.4_200x200-0.3-0.8.stl

https://duet3d.dozuki.com/Wiki/Test_and_calibrate_the_Z_probe

When you measure the trigger height to do you get repeatable results across several tests?

Can you post your G31 and M558 commands from config.g?

dc42 · 23 Dec 2018, 10:36

Which firmware version are you using?
High amounts of slope in the height map can mean that you are probing too fast. Try reducing the F parameter in the M558 command.

pc-6 · 24 Dec 2018, 08:01

@phaedrux
When I do multiple mesh bed compensation the map turns out very consistent every time, so I would guess that the BL touch is consistent.
If I print with the mesh bed on it will push the nozzle into the bed in most areas of the bed. If I do a print with the mesh bed off it is much better but not perfect yet. I am printing on glass but so far have not been able to achieve what I would expect.
Here is the G code:
M558 P9 H5 F320 T6000 ; Set Z probe type to bltouch and the dive height + speeds
G31 P500 X14 Y35 Z0.92 ; Set Z probe trigger value, offset and trigger height

pc-6 · 24 Dec 2018, 08:40

@dc42
I'm using firmware 2.0(RTOS) (2018-06-05b3)

I Changed in the M558 the F320 to F120 and the result is better. Here is a screen shot.

Running another print with the mesh bed on and it is much better but still puts the nozzle into the bed in a few spots. Overall this is better than without mesh bed compensation but still not acceptable.

dc42 · 24 Dec 2018, 16:56

Try upgrading to later firmware, such as the 2.02 version just released. There was a known issue in 2.0 that sometimes caused Z height errors.

Phaedrux · 24 Dec 2018, 17:41

M558 F100 R0.5
G31 P25

Along with updating the firmware, try these changes. I think you're basically probing way too fast for the BLTouch to settle properly. You may want to reduce your Z axis top speed, jerk, and acceleration also while doing a G29. You want htings to be nice and smooth and stable while doing it.

pc-6 · 15 Jan 2019, 02:58

Got replacement BL touch (First one was apparently faulty) and that has significantly improved things, still not perfect but almost acceptable.

I am going to rebuild with stout linear rails and with busy work schedule should be back at it in a couple months. Hopefully that might improve things.