Posts made by andymoz

With the IR probe, depending on age or last cleaning, 1 /2 /3 layers of elmers glue stick randomly. But different thickness in different places over the bed as I am not exactly an artist, it comes off with print etc.
Seems to make a big enough difference to mean first layer is either too low or too high and needs baby stepping by up to 0.1-0.12mm sometimes.

@phaedrux said in 4 point bed levelling question:

Have you tried doing a single detailed probe run with the bed clean and then just loading it when printing rather that rerunning it before each print?

Hi Phaedrux, Yes this works fine and I have been doing this for some time and it lasts for a fair few prints, but this is a slightly different use case.
I have learnt over time that the printer is not repeatable over long periods.
What I mean by that is that the corners can end up in very slightly different places due to factors like heat, stretch of belts, even a little too much pressure removing a print etc, which then throws the bed mesh out very slightly because the corners are tilted differently.

• So , think of this as a measurement at each corner so I know what angle the bed is at today.
  Actually the bed is near enough perfectly flat - lucky maybe but it doesn't need a mesh to level it out when printing, - I am just trying to account for the un-guessable tilt changes when moving the really heavy bed 370mm up and down frequently.

Halving the mesh worked better - and shows that the bed center is at z=0 when measured.

But it now starts adjusting for the slightly different layers of glue etc in those different places.

• I know I could bed mesh with it totaly clean, but I can't do this every time I turn on the printer, so I am trying to use this as the 'calibration' when turning on.

The printer design is not tolerant of room heat changes or stretching of belts etc on the z axis, so I am trying to do this regularly at print start / power-on to counter any 'skew' changes, but I already know the bed itself is flat so trying to avoid the errors introduced because my gluestick coating is uneven.

The maths involved are probably beyond me, but I wonder why when only 4 points are done it doesn't calculate it through the z=0 at the center?

Hi,
It doesn't have levelling screws, it has rails and belts on all four corners. The bed is fixed and if I notch it up the z-sliders, the adjustment is 2mm so it just goes to far the other way. ( Bed moves down from 0 at the top, print head is fixed on the z plane ).

• M3D Promega.

For homing, I am/have been using IR probe at centre to set z=0, using G30 single probe.

• the actual probing works well, I have black card behind flat borosilicate glass (4mm).
  I can repeatedly home at X190 Y160 ( probe at roughly bed centre ). The probe offset is correct and I can move to this position, set Z0.1 and just slide 0.1mm paper underneath etc.....this survives a restart as well and works with home Z and home all, so I am happy this is correct at bed centre
• just to be clear, I can print ok at the centre of the bed as well if I don't run the G29.

I edited the config files to zero out any homing by switch at the far end and I just reset z=0 using the IR probe and G30 at bed centre.

Printer is using duet maestro.
Running 2.02 release.

I did try just doing 5 point compensation using G32 and bed.g - but got told it was being deprecated and I should use G29. Should it work this way though, because it doesn't seem to be including the 5th centre point (Z=0) in the calculation like the G32 and bed.g would.

Everything works fine and prints well, But I am just trying to avoid the need to babystep so much when I have too much glue or different coatings on the bed by controlling the 4/5 main measured points only. As I know the bed is pretty good.

If you still need configs, I will have to attach tonight, sorry IT problems connecting back home.

I have a large glass bed which I know is flat as it's come off another printer.
So, I only need to correct for skew in the z axis (as there isn't any in-built adjustment).
I am trying just to corner mesh 4 points and then have this used as the tilt correction.
Using G29 with a defined grid which dimensions this out correctly and I can measure roughly 4 corners ( as per picture).

I am using an IR probe, which measures differently for different thicknesses of glue etc, so this is the way I want to level so I only have to worry about 4 key corner points and the center when worrying about the coating and differences reading the points etc.

The issue I am having is that even if I G30 at the bed center and remove all existing calibrations and offsets before doing the G29, when I do the G29 the resulting graph never dissects the center point ( which it should right if this is the z=0 offset that I am starting from? )

I get this graph ( which does match the skew and is actually less than 1mm across corners so not too bad).
But it never dissects the measured Z=0 point in the center, so it looks like it will compensate wrongly for the center of the bed?
Am I missing something obvious ?
I have repeated this many times and it never hits the center point z=0 calibration G30 I am doing before I run the G29.

If duet folks are interested in trying what was built as a proof that this would work: https://github.com/smartavionics/Cura/issues/8 is a feedback place with builds that add this feature in to a test version of Cura.

It adds in a checkbox to mark the printer as having a shared heater.

The checkbox then alters / blocks the behaviour of any temp change calls which would adversely affect the currently selected tool. Is that right @burtoogle ?

• Please test, feedback and comment in smartavionics GitHub directly if you get a chance to test.

I have been printing all day - small models which turn off various tools and change the temp of different tools all good for me.

andymozza created this issue in smartavionics/Cura

open Dual extruder, single heater, mixing nozzle gcode order causes failure #8

@burtoogle. I think this will work. I need to slice a few models to make sure.

@burtoogle - Indeed. Maybe I should re-word as low on their priority so they may not find the time to do it themselves. I have read multiple bug reports on the cura GitHub where they are just shut as will not do. This gives a pretty strong indication to me.

I realise this is old.
I noticed this while reading through - I have been hitting this issue with M3D Promega (Duet Maestro) and three tools defined in CURA.
There is also another issue to consider which is that CURA 4.0 decides to turn off un-used tools, so if a tool is not used again for the rest of the print ( for example you finish with white filament and only carry on in black), then CURA sends an M104 TX S0.
It sends this 'after' it has selected the new tool so that all temps suddenly go to 0 and you can't extrude.

You can get around this by:

1. Settings all tools standby temps to the same as the printing temp - so any standby set doesn't cause issues.
2. You can use regex as way to parse the gcode automatically in cura and remove any M104 tX s0 commands

This works correctly without issue for me...…..

However I have been conversing with smartavionics who helps out on CURA code and he has produced a proof of concept build which changes the order of the TX S0 commands so they are sent 'before' the new tool temp command.

• However CURA main devs are not keen on the change.

Obviously an ideal fix in CURA is a check box that acknowledges that all tools share a heater - and then this stops sending the Tool OFF and Tool standby messages during the print.

• This also is getting resistance from CURA devs as all the Ultimaker printers are independent heaters.