Strange Y shift at the same height
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My printer was originally a Maker Select V2 that has had a lot of upgrades done over the years, but nothing to recently. The z-brace was one of my first prints, I have a Flexion extruder and upgraded the control board to Duet2Wifi just shortly after it became available and a BLtouch probe. About 6 months ago I swapped my .4 for a .6mm nozzle and swapped from a glass bed to magnetic PEI and have loved it. My main problems before were adhesion trouble on the glass bed which has completely gone away with the new bed.
About 3 years ago I printed all of the parts for an OpenAstroTracker with no issues, and am now trying to print a box for the new control module that I designed in Fusion 360 and sliced with Cura 5.3.1. This is the tallest item I have printed in awhile and is only 46mm high. It was a 4+ hour print and everything seemed to be going fine. After it finished I went back out and there was a 6mm shift only in the Y axis for the top ~4.5mm of the print. At first I thought that maybe it was some missed Y axis steps but there is no clear evidence that the printhead impacted anything and the part was stuck well to the bed.
I was able to fit the control board in what had printed so made some adjustments to the model in Fusion, re-exported it and sliced it again. This time I moved the print forward on the bed because at the far back extremes sometimes it will make a very slight contact at the front. I didn't think it was moving far enough for that, and would have expected to see issues all along if that were the case. Moving the new model back and watching it start to print I know 100% sure it is not making contact anywhere. The 2nd print came out exactly the same as the first print. It shifted the same amount at the same height, which leads me to believe it is a model or firmware issue rather than a hardware issue.
I can't attach images so I will try to describe why I don't think it skipped steps. The model is a rectangular box with rounded corners, and cylinders the full height of the corners to insert an M4 thread insert. The top 4.5mm of layers shifted uniformly in the Y direction, but oddly. On the edge that moved into the box it is a very clean bridge with a very clear gap, like it was meant to be shifted. Surprising clean but not perfect bridge since it is 130mm long. On the "front" edge where it overhangs to the outside it has a lot of single pass extrusions that are almost like it is trying to chamfer out to support the overhanging portion, which is also surprisingly good. As it built the way out those lines are loose, but then the rest of the layers are again a very surprisingly good overhang. If it had been a step skip then I wouldn't think the 2 prints would be virtually identical, or that the overhangs/bridges would come out so nice.
Not only have I re-exported the model with some slight updates for positioning of some holes, but I've also re-sliced it. I've viewed the gcode in the onboard Duet viewer, and I've also loaded the gcode into Simplify3D to look at the preview. All of those look like they should, they don't look like the gcode is the problem. When I colorize the lines based on print speed the intended bridges for square openings are slow, but all of the walls that are shifted and overhanging in my final print are the same speed as the rest of the walls like they should be.
Any help on where to look next would be appreciated. I've checked everything I can think of hardware wise (motors, belts, z-brace, even left the bed heated for 10 minutes and probed the bed again for leveling. From the same Fusion file I made a 10x10x46mm solid box and printed it with no issues. I'm at a loss so this is my last resort.
I am running Duet 2 Wifi 3.4.5 firmware and have been for months with no issues. My print speed is 50mm/s.
Thanks
; Configuration file for Duet WiFi (firmware version 3)
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool v3.1.1 on Sat Jun 06 2020 17:56:14 GMT-0700 (Pacific Daylight Time); General preferences
G90 ; send absolute coordinates...
M83 ; ...but relative extruder moves
M550 P"wanhao-di3" ; set printer name; Network
M552 S1 ; enable network
M586 P0 S1 ; enable HTTP
M586 P1 S0 ; disable FTP
M586 P2 S1 ; enable Telnet; Drives
M569 P0 S0 ; physical drive 0 goes backwards
M569 P1 S0 ; physical drive 1 goes backwards
M569 P2 S0 ; physical drive 2 goes backwards
M569 P3 S0 ; physical drive 3 goes backwards
M584 X0 Y1 Z2 E3 ; set drive mapping
M350 X128 Y128 Z128 E16 I0 ; configure microstepping without interpolation
M92 X640.00 Y640.00 Z3200.00 E93.60 ; set steps per mm
M566 X480.00 Y480.00 Z12.00 E120.00 ; set maximum instantaneous speed changes (mm/min)
M203 X12000.00 Y12000.00 Z1200.00 E3000.00 ; set maximum speeds (mm/min)
M201 X1000.00 Y1000.00 Z100.00 E5000.00 ; set accelerations (mm/s^2)
M906 X855 Y855 Z855 E855 I30 ; set motor currents (mA) and motor idle factor in per cent
M84 S30 ; Set idle timeout; Axis Limits
M208 X0 Y0 Z0 S1 ; set axis minima
M208 X200 Y200 Z120 S0 ; set axis maxima; Endstops
M574 X1 S1 P"!xstop" ; configure active-high endstop for low end on X via pin !xstop
M574 Y1 S1 P"!ystop" ; configure active-high endstop for low end on Y via pin !ystop
M574 Z1 S1 P"!zstop" ; configure active-high endstop for low end on Z via pin !zstop; Z-Probe
M950 S0 C"exp.heater3" ; create servo pin 0 for BLTouch
M558 P9 C"zprobe.in+zprobe.mod" H5 F120 T6000 ; set Z probe type to bltouch and the dive height + speeds
G31 P500 X2.3 Y-39.4 Z1.45 ; set Z probe trigger value, offset and trigger height
M557 X25:175 Y5:175 S15 ; define mesh grid; Heaters
M308 S0 P"bedtemp" Y"thermistor" T100000 B4301 ; configure sensor 0 as thermistor on pin bedtemp
M950 H0 C"bedheat" T0 ; create bed heater output on bedheat and map it to sensor 0
M307 H0 B1 S1.00 ; enable bang-bang mode for the bed heater and set PWM limit
M140 H0 ; map heated bed to heater 0
M143 H0 S120 ; set temperature limit for heater 0 to 120C
M308 S1 P"e0temp" Y"thermistor" T108746 B4226 ; configure sensor 1 as thermistor on pin e0temp
M950 H1 C"e0heat" T1 ; create nozzle heater output on e0heat and map it to sensor 1
M307 H1 B0 S1.00 ; disable bang-bang mode for heater and set PWM limit; Fans
M950 F0 C"fan0" Q500 ; create fan 0 on pin fan0 and set its frequency
M106 P0 S0 H-1 ; set fan 0 value. Thermostatic control is turned off
M950 F1 C"fan1" Q500 ; create fan 1 on pin fan1 and set its frequency
M106 P1 S1 H1 T45 ; set fan 1 value. Thermostatic control is turned on
M950 F2 C"fan1" Q500 ; create fan 2 on pin fan1 and set its frequency
M106 P2 S1 H1 T45 ; set fan 2 value. Thermostatic control is turned on; Tools
M563 P0 D0 H1 F0 ; define tool 0
G10 P0 X0 Y0 Z0 ; set tool 0 axis offsets
G10 P0 R0 S0 ; set initial tool 0 active and standby temperatures to 0C; Custom settings
M307 H2 A-1 C-1 D-1 ; Make H2 available to control LED strips; Miscellaneous
M501 ; load saved parameters from non-volatile memory
T0 ; select first tool -
Try printing a much simpler tall object like a hollow cube and see if it has the same skips at that height. From your description it sounds like there are overhangs in the area of the skip. I would bet that it's curling a bit and making contact and then pressing it down in subsequent layers, but without photos it's hard to tell.
