Pause and retract problem (Cura and Slic3r)

Hello,

Slic3r uses relative extrusion length, but Cura uses absolute extrusion length. So If I pause a model sliced by Cura and pause the print the filament gets unloaded. Is there any way to fix this problem without changing Slic3r to absolute filemant extrusion and to keep the retract in the pause command?

Regards,

Sven

Quote
Treito
Hello,

Slic3r uses relative extrusion length, but Cura uses absolute extrusion length. So If I pause a model sliced by Cura and pause the print the filament gets unloaded. Is there any way to fix this problem without changing Slic3r to absolute filemant extrusion and to keep the retract in the pause command?

Regards,

Sven

Hi Sven,

If you are using my firmware fork, then the pause/resume doesn't work properly if you are using absolute extrusion. I think the RRP 1.09 release may be OK because it uses a different pause/resume mechanism. I believe recent versions of Cura have an option for relative extrusion anyway. Relative extrusion is recommended when using RepRapFirmware, because it avoids accumulating rounding errors.

Edited 2 time(s). Last edit at 05/26/2015 07:34AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thanks for the reply,

unfortunately Cura does not support relative extrusion. They tell something like every printer understands the command for absolute extrusion but not all can do relative extrusion and besides they tell that absolute extrusion is more precise. There was an old version which supported relative extrusion with a trick but this does not work anymore.
RRP 1.09 does have other movement commands, right? It did not sound as smooth as your fork and the homing is very slow.
But RRP 1.09 supports this pause problem? So I have to exchange all commands?

Check out this issue in the Cura github repo: [github.com]. It implies to me that relative extrusion is possible, at least in the dev version. Somebody also did a plugin for relative extrusion well over a year ago.

I'll also look at whether I can have the firmware save the absolute/relative extrusion state on a pause, along with the absolute extrusion value, and restore those values on a resume.

Edited 1 time(s). Last edit at 05/26/2015 07:54AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Hello,

many thanks that you will check your firmware. BTW I found this:

Quote
dc42
btw using my fork of RepRapFirmware, you don't have to use the relative extruder plugin for Cura, because I fixed the bug with absolute extruder moves in the original firmware many months ago. Also, you can get round the T1/T0 numbering using the an extension to the M563 in your start gcode - see the note towards the end of [reprap.org].

I also use Cura and your firmware and would love to not have my filament unload on pause. Most of the time if I pause a job I'm intending to cancel it too, but its not much fun waiting for it to 'reverse' 3 meters of filament before you can move the head off the melting, fouled up, print.

The plugin works fine but I cannot decide which slicer I should use.

I switched to Cura months ago, and haven't looked back.I haven't tried Slicer in probably 6 months, but the print quality between the 2 were day and night for me. Cura's prints looked far better.

The pausing thing is strange - I use DC's fork, and in the past (before I realised my Ormerod can easily print at 250% via DC's print speed slider ), I often paused a large print in the middle of the night to go to bed, and continue the next day, and I never had the filament unload on me.
But to be honest, I can't remember whether I was using relative extrusion via the plugin, or absolute extrusion, so it may have been while I was using the relative extrusion.

Why does absolute extrusion cause an unload?

Quote
pandionx
Why does absolute extrusion cause an unload?

It's because my fork restarts a paused print by rewinding the file to the first instruction that was queued but not executed; but it doesn't yet reset the absolute extrusion value to the right amount at that point. I have a fix for that ready for testing.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

The second problem is that on the beginning the pause command retracts the filament by 4.5mm or so. Cura switches to absolute extraction so the command not causes the filament to retract by 4.5mm but it retracts to -4.5mm that means that the filament is retracted by the length printed so far and additional 4.5mm. So if you have printed more than 395mm the filament gets loaded off the extruder.
I am testing Cura. Slic3r and Kisslicer at the moment. I cannot see any real differences by now (Slic3r 1.2.7), but what I like at Cura is that it shows the printing time for example and it is easier to choose if you should prefer more quality or speed. Doubling the speed does not end in having only half of the printing time. Sometimes this is only 10% and so I can decide not to speed up things.
Besides I think that the printing quality of Slic3r is slightly better especially regarding screw holes. Slic3r added a new function to print these holes a little bit larger and so the screws does fit much better.

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Slicer: Simplify3D 4.0; sometimes CraftWare 1.14 or Cura 2.7
Delta with Duet-WiFi, FW: 1.20.1RC2; mini-sensor board by dc42 for auto-leveling
Ormerod common modifications: Mini-sensor board by dc42, aluminum X-arm, 0.4 mm nozzle E3D like, 2nd fan, Z stepper nut M5 x 15, Herringbone gears, Z-axis bearing at top, spring loaded extruder with pneumatic fitting, Y belt axis tensioner
Ormerod 2: FW: 1.19-dc42 on Duet-WiFi. own build, modifications: GT2-belts, silicone heat-bed, different motors and so on. Printed parts: bed support, (PSU holder) and Y-feet.
Ormerod 1: FW: 1.15c-dc42 on 1k Duet-Board. Modifications: Aluminium bed-support, (nearly) all parts reprinted in PLA/ ABS, and so on.

Quote
Treito
The second problem is that on the beginning the pause command retracts the filament by 4.5mm or so. Cura switches to absolute extraction so the command not causes the filament to retract by 4.5mm but it retracts to -4.5mm that means that the filament is retracted by the length printed so far and additional 4.5mm.

That's easy to fix. Put a M83 command to switch extrusion to relative mode in the pause.g file, ahead of the retraction command. The mode will automatically go back to absolute when pause.g finishes, if it was absolute to start with.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Oh thanks. I was afraid that it stays relative and after the resume the printer extrudes thousands of mm filament. Nevertheless the holes in Cura are not as good as in Slic3r 1.2.7. especially regarding the mod from dc42 of iamburnuning Extruder gears. After printing with Cura the head of the screw die not fit. Using Slic3r I Bad a perfect fit. Second Problem: I accidentally had too mich perimeters in Cura so the screw connection was not hexadecimal but nearly round. Slic3r drops Perimeters in this case.

Edit: Damn autocorrection. It does not recognize that I use English here.

Edited 2 time(s). Last edit at 06/05/2015 07:08AM by Treito.

Quote
dc42
That's easy to fix. Put a M83 command to switch extrusion to relative mode in the pause.g file, ahead of the retraction command. The mode will automatically go back to absolute when pause.g finishes, if it was absolute to start with.

When it switches back to absolute, does it also remember the absolute value prior to the switch to relative?

Dave

Quote
dmould

Quote
dc42
That's easy to fix. Put a M83 command to switch extrusion to relative mode in the pause.g file, ahead of the retraction command. The mode will automatically go back to absolute when pause.g finishes, if it was absolute to start with.

When it switches back to absolute, does it also remember the absolute value prior to the switch to relative?

Dave

No. However:

1. If the resume macro file undoes the retraction in the pause macro file by the same amount, the absolute value will be unchanged.

2. When I have fixed the original problem with resuming, it won't matter anyway, because it will restore the original absolute value as after the last completed move.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
dc42

Quote
dmould

Quote
dc42
That's easy to fix. Put a M83 command to switch extrusion to relative mode in the pause.g file, ahead of the retraction command. The mode will automatically go back to absolute when pause.g finishes, if it was absolute to start with.

When it switches back to absolute, does it also remember the absolute value prior to the switch to relative?

Dave

No. However:

1. If the resume macro file undoes the retraction in the pause macro file by the same amount, the absolute value will be unchanged.

2. When I have fixed the original problem with resuming, it won't matter anyway, because it will restore the original absolute value as after the last completed move.

I was not thinking so much about the retract/unretract while in relative mode, but the operation in principle. e.g. the move prior to switching to relative was an absolute extrusion value of (say) 12345. I now switch to relative mode. In relative mode the present absolute value of 12345 has no meaning, so it would be reasonable for the firmware to "forget" it. If it does so, then switching back to absolute mode would result in an extrusion of, say, 12346 not extruding the expected 1mm of filament even if there had been no extrusion commands while in relative mode.

Dave

Dave, I had the problem that at the end of the printing that the filament was completely unloaded. I thought of changing the pause.g but I assumed that in this case I have to set Slic3r to absolute mode, too. But however as long as there is another problem with the absolute mode and the pause, I will keep Cura in relative mode even though it makes also some trouble.

Quote
Treito
I am testing Cura. Slic3r and Kisslicer at the moment. I cannot see any real differences by now (Slic3r 1.2.7), but what I like at Cura is that it shows the printing time for example and it is easier to choose if you should prefer more quality or speed. Doubling the speed does not end in having only half of the printing time. Sometimes this is only 10% and so I can decide not to speed up things.
Besides I think that the printing quality of Slic3r is slightly better especially regarding screw holes. Slic3r added a new function to print these holes a little bit larger and so the screws does fit much better.

I will give the new Slic3r a shot, but my experience was the exact opposite - Slic3r's quality was terrible, and I even though I found Cura to also make the holes slightly smaller, I found it far less so than Slic3r.

Slic3r has better support options, but I seldom pretty anything that needs that level of support, the normal Cura support works just fine for me.

Quote
dc42

Quote
pandionx
Why does absolute extrusion cause an unload?

It's because my fork restarts a paused print by rewinding the file to the first instruction that was queued but not executed; but it doesn't yet reset the absolute extrusion value to the right amount at that point. I have a fix for that ready for testing.

Will be happy to test once you release it.

I was hoping to release it yesterday, but the tests I did with absolute extrusion and pause/resume suggested there was still something not quite right. Looks like I need to do some more work on it.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].