Pause and Resume creates gap

Hi,

I am using RepRapFirmware-1.12-dc42. I am trying to use Pause and Resume function. When I am pausing, it is pausing the print and going to the given XY location. Again when I press Resume, it starts the print.

But, it is creating gaps in the print. Please see the attached photo. I have attached the Pause and Resume gcode files also.

Thanks
Selva

my bet is that the pressure in your hotend doesn't reach normal levels fast enough... so maybe look for the resume.g and add some extra feed on resume?

I am using Bowden setup with 400mm length. I have tried this different types of extruder. The same gap appears in all the prints with all type of extruder.

Extra feed - Making extruder to extrude more filament or make the Z come to minus value?

It looks like when it resumes, the Z is not positioning correctly to the required height.

Edited 1 time(s). Last edit at 07/25/2016 04:59AM by selva_tvi.

Extrude extra filament after pausing to prime the extruder.

how about this:
Print two test cubes. Pause one multiple times. The other you leave it alone.

Does the final z height remain the same?

Are you doing the pause/resume while it is printing perimeters, or after it has printed perimeters and is printing infill?

If there is any backlash in your Z axis, then after resuming and in the absence of bed compensation, the nozzle will be higher than before pausing by the amount of backlash. However, if you only pause when all perimeters for that layer have been completed, then only the infill will be affected, which is unlikely to matter.

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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].

@ Bob64: I have printed two test cubes. One without pausing. The height was 19.71mm

The other was printed with multiple pause and resumes. The final height was 19.96mm. So, the difference is almost 0.25mm.

@DC42 - These test prints were printed without any infill and printing with 3 perimeters. I am using DUET 0.6 board with IR sensor (from Replikeo) for bed compensation. Having 6mm Leadscrew with Antibacklash nut in Z axis. How this can be eliminated?

Edited 1 time(s). Last edit at 07/26/2016 12:41AM by selva_tvi.

Sounds like some sort of mechanical problem... check current voltage on your steppers, check to make sure your grub screws are tight, do some z tests by affixing a sticker or something on your z rod, and checking to make sure it goes to the same spot after a few dozen repeated turns up and down.

Quote
selva_tvi
@DC42 - These test prints were printed without any infill and printing with 3 perimeters. I am using DUET 0.6 board with IR sensor (from Replikeo) for bed compensation. Having 6mm Leadscrew with Antibacklash nut in Z axis. How this can be eliminated?

Please can you run M114 just before pausing, and again just after pausing to check that the firmware thinks it has restored the head to the same Z step count.

Another possibility is missed steps during the resume process, causing the head not to travel down as much as it should. If this were the case, the error in the Z height would be a multiple of the distance moved by 4 full steps of the Z motor, and you might be able to see the motor jumping back by 7.2 degrees.

I'll run some tests on my 2 printers when I get time.

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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].

I had a similar problem when I had my motor current idle timeout set too low inadvertently, and the steppers were dropping slightly when the driver reduced the current.

Edited 1 time(s). Last edit at 08/04/2016 04:03AM by n8bot.

@Bob64, @DC42 - Sorry for late reply. I am using Lead screw with antibacklash nut in the Z-axis. The nut is having pre-adjustment screw to eliminate the backlash. I adjusted and did the sample print. Perfectly came without any issue. Thanks for the suggestions.