Y AXIS NOT RETURNING TO SAME SPOT
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I am running a custom built cnc machine with a duet wifi utilizing the Workebee CNC web controller.
I home the machine, instruct it to go to a point on the Y axis, then mark that point, If I then instruct the machine to go in the positive direction (G1 Y800 for example) and then I command the machine to return to the original spot, I am off about 1.5 mm. ( it will be short of the spot) So the the machine will move 700mm in one direction correctly, then come back 699 instead of 700 on the return trip.
If I repeat the process but come back to the point I have marked from the negative direction it returns to the correct location. So from "below" the point the machine seems to move accurately.
I am perplexed. The machine is solid and square. Wondering if anyone else has had a similar problem or might propose a solution.
Thanks!
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Perhaps it is missing steps when moving.
You could try...
- slower movement
- greater stepper current
...to see if either made any difference
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@andymusser It also could be backlash.
Try different move lengths. If it's always short by 1.5mm it's backlash likely.
Also, try making a mark on the stepper motor output gear or pulley and see if THAT comes back to the same location as it started even though the spindle didn't. That's also an indication of backlash.
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You can share your config file and we can maybe tell if something is weird or out of normal range causing missed steps.
Also please post the results of M122 after doing a move that causes the positional errors in case it is a case of hiccups causing missed steps we'd see a large number of hiccups reported. Usually due to using high microstepping values and fast moves.
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@andymusser it sounds like severe backlash to me, perhaps caused by a loose pulley grub screw or a very loose belt.
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Configuration file for Duet
; executed by the firmware on start-up
; WorkBee Firmware Version 1.0.7; Configure Connection - ENABLE ONLY ONE OF THE BELOW THREE
M552 S1 ; Enable Wifi Network
;M552 S2 ; Enable Access Point Mode
;M552 S1 P192.168.2.12 ; Enable Ethernet - Change IP Address to suit; - - - - - - - - - - - - - - - - - - - -
; DO NOT CHANGE ANY OF SETTINGS BELOW
; TO MAKE A CHANGE, COPY THE LINE OF CODE, PASTE IT INTO customconfig.g. THE CHANGE CAN THEN BE MADE IN customconfig.g
; ANY ADDITIONAL SETTINGS SHOULD BE PUT IN customconfig.g; General preferences
M453 ; Put the machine into CNC Modes
M550 PWorkBee CNC Machine ; Set machine name
G90 ; Set absolute coordinates; Network
M586 P0 S1 ; Enable HTTP
M586 P1 S0 ; Disable FTP
M586 P2 S0 ; Disable Telnet; Configure Drives
M584 X0 Y1:3 Z2 U3 P3; Apply drive mapping to axes
M569 P0 S0 ; Drive 0 goes forwards
M569 P1 S0 ; Drive 1 goes forwards
M569 P2 S0 ; Drive 2 goes forwards
M569 P3 S1 ; Drive 3 goes forwards; Configure Axes
M92 X80.083 Y80.014 Z406.65 U80.014 ; Set steps per mm
M350 X16 Y16 Z8 U16 I1 ; Configure microstepping
M566 X500 Y500 Z500 U500 ; Set maximum instantaneous speed changes (mm/min)
M203 X6000 Y6000 Z2000 U6000 ; Set maximum speeds (mm/min)
M201 X100 Y100 Z100 U100 ; Set accelerations (mm/s^2)
M906 X2300 Y2300 Z1900 U2300 I100 ; Set motor currents (mA); Configure Axis Limits
M208 X0 Y0 Z0 U0 S1 ; Set axis minima
M208 X720 Y1260 Z120.5 U1260 S0 ; Set axis maxima; Configure Endstops
M574 X1 Y1 Z2 U1 S1 ; Set active low endstops; Other Settings
M140 H-1 ; Disable heated bed
M564 S1 H1 ; Disable jog commands when not homed
M911 S21.0 R23 P"G91 G1 Z3 F1000" ; Configure power loss resume
M501 ; Load Stored Parameters
;M98 Pcustomconfig.g ; Execute custom config settings
