Delta part size is off.

Gilly

So I have a generic China Delta printer. (pictured at bottom) With a Duet 0.6, Piezo Z-probe, and aftermarket metal rods.

what seems to be happening is that the side facing my Z town will be near on perfect at 19.99 or dead on 20 cm for a test cube but the other side will be 19.45 or 19.6, anything but the same. (picture included for example)

Relevant code is

[[language]]
Config-override.g:   
M665 L226.328 R104.218 H271.924 B93.0 X0.346 Y1.042 Z0.000
M666 X-0.009 Y1.245 Z-1.236 A0.32 B-0.76

Config.g:     
M556 S79 Y-0.25 X1.5 Z0.5

I have made fairly sure the rods are the same length with no play in them what so ever. I've done a M556 test peace and I'm not sure with one is if my printer was switching X and Y or if S3D with Flip Y plan enabled so I have swapped X and Y around and printed in both circumstances with the same results. it's always one perfect and one not. I was thinking it could do with a stepper driver being slightly different but I thought I would as first as I have no clue how to fix that.

Other options are to get metal corners and kind of rebuild the delta again to make sure everything is level and perfect.

All help appreciated as it's bloody annoying and my tolerances are difficult to work out.

dc42

You probably have a geometrical inaccuracy that is causing the effector to tilt as i moves in the XY plane. See https://duet3d.com/wiki/Calibrating_a_delta_printer#Make_sure_your_build_is_accurate.

Gilly

I have spent half the day going over everything.

Measured the towers at the bottom and the top and corrected them.
Measured the top frame on all 3 towers and corrected it so they were all the same.
Made sure that the Carriages are the same width as the effector.
Printed out 4x 8mm spacers for the bed so I knew it was flat on the frame
Tightened all of the bolts. 99% were ok.
I also lowered the radius of the auto call.

All of that has risen it to about 19.76mm
apart from buying metal corner off Aliexpress, what else can I do? I've put my Config.g just in case there is something in there that I have missed but I'm pretty sure I've gone through it all.

[[language]]
; Configuration file for Duet 0.6 (firmware version 1.17)
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool on Thu Apr 06 2017 22:47:04 GMT+0100 (BST)

; General preferences
M111 S0 ; Debugging off
G21 ; Work in millimetres
G90 ; Send absolute coordinates...
M83 ; ...but relative extruder moves
M555 P2 ; Set firmware compatibility to look like Marlin

; Delta parameters
M665 L225.978 R105 H272.809 B93.0 X0.039 Y-0.031 Z0.000
M666 X-0.756 Y1.770 Z-1.014 A0 B0
;M556 S79 Y1.5 X-0.25 Z0.5 (settings changed, print another)

; Endstops
M574 X2 Y2 Z2 S1 ; Define active high microswitches
M558 P1 F500 T2000 I0 X0 Y0 Z0 H1 ;analogue piezo sensor output falls on contact, probing speed 500 mm/min
G31 X0 Y0 Z0 P500 ;sensor is nozzle, offsets for probe (nozzle) and trigger value.
M557 R85 S17 ; Define mesh grid

; Drives
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
M572 D0 S0.1 ; extruder pressure advance
M92 X100 Y100 Z100 E476 ; Set steps per mm
M566 X1200 Y1200 Z1200 E1200 ; Set maximum instantaneous speed changes (mm/min)
M203 X18000 Y18000 Z18000 E18000 ; Set maximum speeds (mm/min)
M201 X1000 Y1000 Z1000 E1000 ; Set accelerations (mm/s^2)
M906 X1200 Y1200 Z1200 E1200 I30 ; Set motor currents (mA) and motor idle factor in per cent
M84 S30 ; Set idle timeout

; Heaters
M143 S260 ; Set maximum heater temperature to 260C
M301 H0 S1.00 P10 I0.1 D200 T0.4 W180 B30 ; Use PID on bed heater (may require further tuning)
M305 P0 T100000 B3950 C0 R4700   ; Set thermistor + ADC parameters for heater 0
M305 P1 T100000 B4138 C0 R4700 ; Set thermistor + ADC parameters for heater 1

; Tools
M563 P0 D0 H1 ; 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

; Network
M550 PPrinty McPrint Face ; Set machine name
M540 PBE:EF:DE:AD:FE:A9 ; Set MAC address
M552 P192.168.1.122 

; Fans
M106 P0 S1 I0 F500 H1 T45 ; Set fan 0 value, PWM signal inversion and frequency. Thermostatic control is turned on

; Custom settings are not configured
M501

dc42

Two suggestions:

1. Put a bulls-eye spririt level on the effector so that you can observe any tilt.

2. You can use the M579 command https://duet3d.com/wiki/G-code#M579:_Scale_Cartesian_axes to adjust the scaling. But first I suggest you print a large nought-and-crosses/tic-tac-toe grid covering the whole bed, to check that straight lines really are straight.

Gilly

OK Spirit level ordered and just done a Grid pint

S3D slicer and settings

For some reason it's wonkie on my print. No idea why that is but lines look straight.