Duet 0.8.5 - Delta Kossel - XYZ Calibration

Hello fellow RepRap(ers?)!

I have upgraded from a RAMPS 1.4 board that I had been using for a long time and had calibrated to be extremely accurate (10mm cubes perfect all the way up to 40mm cubes). I then decided to take the plunge and buy myself some new upgrades - pretty much all from Think3DPrint3D including the Duet 0.8.5 board and new Carbon fibre rods with Traxxas ends.

I have been running through my fine tuning now but have come across a weird scenario on my X and Y axis. Basically I noticed that my prints were not being printed in the correct dimensions - so the first place I looked was the axis steps/mm and noticed that I had accidently left the original value of 80 untouched. I updated this with the value I required based on GT2 belt with 2mm pitch, 16 tooth pulley, 1.8' motor step angle and 1/16 micro-stepping giving me a value of 100 steps/mm (confirmed with the RepRapCalculator).

Now when I print a 10mmx10mmx10mm calibration cube I get lengths of 10.25mm on both X and Y axis however my Z axis is absolutely perfect at 10mm? Could anyone point me in the right direction of what I should look at calibrating next please?

Other notes:

I did notice that my diagonal rod length was out by 0.5mm so I corrected this by updating the value in my configuration - All rods were pre-assembled by the folks at Think3DPrint3D on their Jig and they are all the same length from centre hole to centre hole.

This is the first time that I have ever used the M666 end stops for levelling configuration as I would usually have gone through the more painful process of manually tuning the bed levelling with my Allen key - to be honest it was pretty close to spot on before I started with the M666 calibration.

For reference here is a copy of my configuration file as it is right now.

Thank you for reading!

; Configuration file for Mini Kossel kit from Think3DPrint3D
;
; Communication and general
M111 S0                             ; Debug off
M550 PMiniKossel		        	; Machine name and Netbios name (can be anything you like)
M551 Preprap                        ; Machine password (used for FTP)
M540 P0xBE:0xEF:0xDE:0xAD:0xFE:0xED ; MAC Address
;*** Adjust the IP address and gateway in the following 2 lines to suit your network
;***M552 P0.0.0.0						; IP address (0 = use DHCP)
M552 P192.168.1.115	; Static IP address for home network
M554 P192.168.1.1                   ; Gateway
M553 P255.255.255.0                 ; Netmask
M555 P2                             ; Set output to look like Marlin
M575 P1 B57600 S1					; Comms parameters for PanelDue

G21                                 ; Work in millimetres
G90                                 ; Send absolute coordinates...
M83                                 ; ...but relative extruder moves

; Axis and motor configuration
M569 P0 S1							; Drive 0 goes forwards
M569 P1 S1							; Drive 1 goes forwards
M569 P2 S1							; Drive 2 goes forwards
M569 P3 S0							; Drive 3 goes forwards
M569 P4 S0							; Drive 4 goes backwards (not forwards)
M574 X2 Y2 Z2 S1					; set endstop configuration (all endstops at high end, active high)
;*** The homed height is deliberately set too high in the following - you will adjust it during calibration - OLD 320.15
M665 R123.83 L215.5 B80 H256.61			; set delta radius, diagonal rod length, printable radius and homed height
M666 X-3.65 Y-2.80 Z-1.85						; put your endstop adjustments here, or let auto calibration find them
M92 X100 Y100 Z100						; Set axis steps/mm
M906 X1000 Y1000 Z1000 E600 I60		; Set motor currents (mA) and increase idle current to 60%
M201 X1000 Y1000 Z1000 E1000		; Accelerations (mm/s^2)
M203 X20000 Y20000 Z20000 E3600		; Maximum speeds (mm/min)
M566 X1200 Y1200 Z1200 E1200		; Maximum instant speed changes mm/minute

; Thermistors
;*** If you have a Duet board stickered "4.7K", change R1000 to R4700 to the following M305 commands
M305 P0 T100000 B3950 R4700 H30 L0	; Put your own H and/or L values here to set the bed thermistor ADC correction
M305 P1 T100000 B3974 R4700 H30 L0	; Put your own H and/or L values here to set the first nozzle thermistor ADC correction
M305 P2 T100000 B3974 R4700 H30 L0	; Put your own H and/or L values here to set the second nozzle thermistor ADC correction
M570 S180							; Hot end may be a little slow to heat up so allow it 180 seconds

; Tool definitions
M563 P0 D0 H1                       ; Define tool 0
G10 P0 S0 R0                        ; Set tool 0 operating and standby temperatures
;*** If you have a dual-nozzle build, un-comment the next 2 lines
;M563 P1 D1 H2                      ; Define tool 1
;G10 P1 S0 R0                       ; Set tool 1 operating and standby temperatures
M92 E152:152                       	; Set extruder steps per mm

; Z probe and compensation definition
;*** If you have an IR zprobe instead of a switch, change P4 to P1 in the following M558 command
M558 P4 X0 Y0 Z0					; Z probe is a switch and is not used for homing any axes
G31 X0 Y0 Z4.80 P500				; Set the zprobe height and threshold (put your own values here)

;*** If you are using axis compensation, put the figures in the following command
M556 S78 X0 Y0 Z0                   ; Axis compensation here

M208 S1 Z-0.2						; set minimum Z
;
T0									; select first hot end

A few things to check:

1. Make sure that the diagonal rod length, measured between the bearing centres, is configured accurately in the firmware (M665 L parameter).

2. Make sure the spacing between bearings is the same on the carriages as on the effector. A difference will cause the effector to tilt as it translates, which will affect the scaling.

3. To test the scaling accurately, you need to use a cube much larger than 10mm so that under/over extrusion has less effect.

4. If all else fails, you can use the M579 command to adjust the XY scaling, see [reprap.org]. But it is better to fix your machine geometry, otherwise you may find the scaling varies depending on where on the bed you print your cube.

---

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 quick response dc42! Here are the results:

Quote
dc42
A few things to check:

1. Make sure that the diagonal rod length, measured between the bearing centres, is configured accurately in the firmware (M665 L parameter). I can confirm that this is correct

2. Make sure the spacing between bearings is the same on the carriages as on the effector. A difference will cause the effector to tilt as it translates, which will affect the scaling. I can confirm that both the spacing on the carriages and effector are at 40mm

3. To test the scaling accurately, you need to use a cube much larger than 10mm so that under/over extrusion has less effect.Good suggestion - I will print a new 40mm cube now and report back on the results

4. If all else fails, you can use the M579 command to adjust the XY scaling, see [reprap.org]. But it is better to fix your machine geometry, otherwise you may find the scaling varies depending on where on the bed you print your cube.

Let hope it doesn't come to this - I will do everything to make sure that this is mechanically correct!


Thank you for your suggestions and assistance.

After racking my brain as to why this may be occurring I went back to basics and re-ran all of the calibration steps from your fantastic article Mini Kossel Calibration.

It's worth stating that this is the original article that I had followed - however it must have been late in the day as my new M665 values are as follows - you can see a significant difference in the delta radius settings and my updated diagonal rod measurements here:

Old M665 setting:

M665 R123.83 L215.5 B80 H256.61			; set delta radius, diagonal rod length, printable radius and homed height

New M665 setting:

M665 R110.95 L215.5 B80 H259.80			; set delta radius, diagonal rod length, printable radius and homed height

Just look at the difference in the delta radius setting! This must have impacted the scaling somewhat?

Now I am going to move onto the next piece of calibration - my extruder. Looks like its skipping (luckily not chewing the filament as I have the current low). Are these the correct 3 areas to be looking at calibrating:

1. Recalibrate Extruder Steps per mm based on Triffid Hunters Cal Guide
2. Ensure the current setting on M906 is sufficient - fine tune until just before grinding
3. Fine tune temp for E3Dv6 hotend (smaller heat chamber = higher temp required @ higher speeds)

Thank you for reading!

Results from new 40mmx40mmx40mm calibration cube as promised

X and Y axis are now measuring at 39.99mm and the Z axis is measuring at 40mm! I think that will be sufficiently accurate! Off to print some awesome things that I probably don't even need

Thank you dc42