DC42 firmware: dimensions and stuttering

Hi Dave. Been using the Duet/delta firmware and starting to get some very nice looking parts, best ever in fact! (after endlessly dialing in the print settings)
Two questions:
1) My dimensions seem to be a hair off; would this be caused by the wrong rod length?
2) I sometimes see stuttering of the nozzle motion. Is the web interface streaming the g-code and if so how can I make sure it runs at full bandwidth with minimum lag?
(other than running off of the SD card)
thanks

Edited 1 time(s). Last edit at 09/11/2015 07:05PM by shadowphile.

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shadowphile
Hi Dave. Been using the Duet/delta firmware and starting to get some very nice looking parts, best ever in fact! (after endlessly dialing in the print settings)
Two questions:
1) My dimensions seem to be a hair off; would this be caused by the wrong rod length?

Is the entire scale of the model off, or is the dimensions off?
A printed cube, is it off by the same amount in both the X- and Y-plane (Z as well, but that's another setting) or do you get different measurements in the X- and Y-plane?
If all axis are off, X, Y and Z check your steps/mm, if Z is correct but X and Y are off by the same amount, adjust your rod-length, if you have correct Z and one of the X or Y correct but not the other then it is a harder nut to crack, auto-calibration will get you a bit but not all the way in my experience.

Quote
shadowphile
2) I sometimes see stuttering of the nozzle motion. Is the web interface streaming the g-code and if so how can I make sure it runs at full bandwidth with minimum lag?
(other than running off of the SD card)
thanks

Not really sure what you mean here, but as far as I know the web-interface only allows you to upload a gcode file to the SD-card so that the printer can read it from there, no streaming done.

Thanks. I am collecting data to separate out the variables such as offset vs scaling vs noise vs extrusion width. Z axis and steppers are correct.
The steppers stuttering does not seem to affect the printing quality so I guess I will ignore it for now. It is random and infrequent, more audible than visible. I should do a large spiral to get a better observation.

Are you driving your printer via the USB port instead of printing from SD card? If so, the stuttering is probably caused by the host program failing to supply the data fast enough. This can be fixed by configuring the host program not to wait for the "OK" response to each gcode command, as this slows data transmission down a lot. and it isn't necessary on the Due because of its native USB port.

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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].

no, haven't touched the USB in quite a while. Now I only use it update the firmware.

So you are printing from the SD card then, either directly or using the web interface "Upload & Print" button. If the pausing happens repeatably at sharp corners, then it could be that you have the maximum acceleration or jerk speed set too low in config.g. If it happens just occasionally, about once per layer, try changing your slicer to generate relative extruder coordinates instead of absolute ones, and/or upgrade to version 1.09j of my firmware fork if you haven't already.

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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].