Posts made by gloomyandy

@effnish Have you tried reverting to 3.5.4 and retesting? If not I think it would be worth doing that. This would confirm that the problem is not some sort of hardware problem.

@aria_james It would probably help if you could post a screenshot showing the sort of temperature variation you are seeing during a print.

@handyandy I suspect it will be as good as you are prepared to calibrate it. The thing is that Prusa will have probably thousands of hours of calibration tests and data all on the same hardware and will have had a lot of engineers analysing that data and tuning the firmware to get the best out of the hardware. You have a single example of your hardware and just you to calibrate and tune it...

@caviara Are you seeing this movement show up in the X/Y position displayed by DWC?

@marvineer What exactly are you seeing happen? As reported by dc42 he sees an initial diagonal move followed by a Y direction move for the homing move. Is that different to what you are seeing? Perhaps if you post a video of what you are seeing that will help? My understanding is that you should see what dc42 has reported and that is the expected movement.

@vaike_peeter I would not expect re-initialising the probe to cause the board to reset, but it looks like there was a "HardFault" reset in your M122 output. One for @dc42 to comment on I think.

@vaike_peeter Can you post the M558 command you were using before and the one you are using now so we can understand what the problem was?

@droftarts Just to be clear, the key thing to test for touch probing is....

1. With the nozzle in contact with the bed. Determine a coil current that gives good readings (probably using the auto calibration process).
2. Now raise the probe and see at what height above the bed you no longer get valid readings. A value slightly lower than this is in effect the maximum dive height you can use for touch probing.

From what I've seen the closer the coil is mounted to the nozzle tip the narrower is the working range of the coil (and hence the dive height for touch probing is closer to the bed).

The tricky part is that you need to get the probe to within that dive height. At the moment the best way seems to be to use the two stage process described above. However the problem is that the first stage relies on you manually calibrating a trigger point that works reliably and that gets you within that dive height. The closer the dive height is to the bed the more likely it is that issues like temperature drift are going to cause problems and possibly a crash into the bed. Heating the nozzle (to allow more accurate touch probing even with plastic on the nozzle), may make it more likely that you get temperature drift in this first stage.

I'm not sure but I don't think dc42 has been testing with the full two stage process, I think he has been using the switch probe on his toolchanger for initial Z homing and then just testing the homing touch homing operation (that's also how I ran a lot of my tests). I think we still need to gather more data on the best compromise.

Note that there is a possible alternate stage 1 homing process. This is to basically set things up with the drive current needed for touch homing and then to simply keep lowering the probe say 1mm at a time and then check to see if the probe has started to return valid readings yet. This should bring the probe to a point that it can now be used for touch probing. We don't currently have any way to actually trigger the probe based on a change from invalid to valid reading, but it may be something to consider. If it turns out that temperature drift for initial probing is a problem it may be that a 3 stage sequence would be best. Use normal threshold homing to get to a point say 6mm above the bed, then switch drive current and drop 1mm at a time until we start to get valid probe readings.

Finally you probably want to start the touch probe operation as close to bed as possible. This is because any "rough spots" in the Z motion system can cause a false touch trigger, which will require an increase in the touch threshold to avoid. This in turn results in a higher force touch, which is more likely to cause damage.

@fcwilt There are other considerations.

Depending upon how you want to use the probe you need it to return valid readings for all of the heights above the bed you wish to use it. But this is not always possible. If the coil is close to the bed then it needs a higher drive current to function, but this higher drive current often means that you get invalid readings if you move the probe to be some distance above the bed. This is particularly important if you want to use the probe for touch homing as the probe will need to operate very close to the bed but also needs to be usable when some distance from it. The current solution is "two stage homing" in which you use a lower coil current to "home" at a point that is actually say 3mm above the bed followed by a seconded stage touch operation using a higher drive current.

From the large number of tests I've run on both scanning and touch probing I'd say that having the coil mounted at about 4mm above the nozzle tip is a good compromise. Just for full disclosure most of my tests have been using a Fly toolboard and coil. It looks like the results with a Duet SZP are very similar, but touch probing is still an experimental feature so we are still gathering data.

@guitartoys You can't do G30 X0 Y20 (the X and Y are ignored in that case), so you will need to move to your homing X/Y first and then run G30 (with no parameters). Where on the bed do you normally print things? If like most people you normally print in the centre of the bed I would change the point you use to home z (ser z=0) to be that location.

@smaaash Just to be clear with 3.5.4 you will need both probes (or at least some way to home Z and set Z=0 other than the SZP). 3.6 adds support for homing by touching the nozzle on the bed and detecting this using the SZP, but be aware this feature is still classed as experimental.

@droftarts Did you resolve the question I raised above (https://forum.duet3d.com/post/327871) about the units used to set jerk and acceleration?

Perhaps @dc42 could comment?

@arturolaz See: https://forum.duet3d.com/topic/37806/revo-roto-and-z-probe-spacer

@marvineer Try removing the colon ":" at the end of each of the if statements. See: https://docs.duet3d.com/User_manual/Reference/Gcode_meta_commands#conditional-construct

@Gamefanatic3D Are you running in standalone mode or using an SBC?

@steezebe Can you post a link to the photo showing the spacer you are referring to?

@jltx said in SZP for bed level in 3.6-RC1:

G31 K1 X0 Y36 Z3 ; define probe 1 offsets and trigger height
M558.2 K1 S16 R120000 ; set drive current and reading offset

You are not setting the probe threshold/trigger value in config.g (the P parameter to G31), so it will be using whatever the default is (which is almost certainly not correct) until you have performed a M558.1.

As to the mesh not reading zero at the centre of the bed. I would expect the scan to return 0 for wherever you have homed/set Z=0, ideally you will be homing and calibrating the probe at the same location, which again is ideally probably in the centre of the bed. I don't think you have posted your homez.g file so I'm not sure what you are doing to set z=0. Depending upon how you are setting Z=0 you may need to adjust the position of the nozzle to place your szp coil over the same location used to set z=0 before carrying out the calibration of the szp.

@jltx said in SZP for bed level in 3.6-RC1:

The trigger threshold is set in my config.g

Please post your config.g file so we can see what you are setting.

@jltx said in SZP for bed level in 3.6-RC1:

I don't understand the DWC feedback. I was seeing red Z values for heights above the trigger, like 6mm. And sometimes I see yellow. Right now it is behaving.

Are you sure it was red when that far above the trigger height? That is not normal unless the probe is returning an invalid reading (in which case it will read 99999). The colour will change as you get close to the trigger threshold. Had you actually set the trigger threshold when you saw the DWC reading go red? You can find out what the current trigger height and threshold are by running G31 k<probe number> with no other parameters.

The threshold is set either by using the P parameter to G31, when you do that you are basically saying set the trigger threshold to be <xxxx> (the P parameter value) and that this value will be reported at the Z height set with the Z parameter of G31. The alternate way to set the threshold with a SZP is to set the Z trigger height with G31 and then to use M558.1 to run a calibration pass. This will move to the Z trigger height plus the calibration range set by the M558.1 S parameter and will then move down to the trigger height minus the calibration range, taking a series of readings. This data is then used to calibrate the conversion of readings to actual height above the bed. As part of the process the probe trigger threshold will also be set to match the trigger height.

I am currently trying to get mesh.g to work but it fails every time on the first point with an error that I need to recalibrate the probe, despite the ABL working correctly now. The G29 starts with a high Z value that I cannot seem to control.

What is the full error message you are getting when you try to perform the scan? You probably need to post your updated bed.g and mesh.g files so we can see what it is you are doing.

After running ABL you should rehome Z and probably recalibrate the SZP using M558.1 then run the scan using G29, this scan will move the probe to the trigger height as set by G31 and will then perform the scan. So you need to be sure that that drive current is set to ensure that you have valid readings with the nozzle at the selected trigger height and at all heights above/below this needed to obtain a scan.

@jltx I'm glad you have it working. I was in the process of typing up the following reply. You may find some of it of use...

What height from your nozzle (or other z=0 point) do you have the coil mounted? You may find that mounting it higher gives you a better working range. At the moment you are setting the trigger height to 2mm in your G31 command and are calibrating with M558.1 over a range of +/-1.5mm this means you will need the probe to provide valid readings with the nozzle 0.5mm above the bed and all points from there to above your dive height of 15mm. This may not be possible.

You may be able to make it work by setting the trigger height to a higher point. I'd try increasing that to say 3 or 4mm. Try changing the G31 Z parameter to 4 and then re-run the coil drive calibration with the nozzle at Z=2.5, then check that you still get valid readings at z=17.5. If all of that looks ok, then rerun M558.1 which should now calibrate at a height of 4mm rather than 2mm.

What amount of bed tilt are you looking to handle, so how far above/below Z=0 do you need to measure for a tilted bed? The szp is not really good at handling a wide range of heights when used in "scanning mode", probably only a range of a few millimetres.

The probe will be triggered (red in DWC) if the coil is ever in a position in which it is closer to the bed than its height above the bed when you calibrated the threshold using M558.1. You have set your trigger height to be 2mm using G31 so the probe will show as triggered if the nozzle is below 2mm above the bed. It will also show red (and display 99999) if the coil is too high/low for the drive current you have set.

To have the probe, probe multiple times you need to set the A parameter in M558 I can't see you doing that. You may also need to set the S parameter.