Far away from precision

Hello,

my Ormerod 1 lost its precision. I do not have any clue where I can look for the fault. Can anybody give me a hint?
Circles look like ellipses. The x-dimension is to big. the 2nd layer does not fit the first layer in y-direction.
I am using the firmware from dc42 Version 1.04f.

X=0 is at the top of the picture.

Part of my config.g

; RepRapPro Ormerod
; Standard configuration G Codes
M111 S0; Debug off
M550 P****; Set the machine's name
M551 P****; Set the password
M540 P0xBE:0xEF:0xDE:0xAD:0xFE:0xED ; Set the MAC address
M552 P192.168.***.***; Set the IP address
M553 P255.255.255.0; Set netmask
M554 P192.168.***.***; Set the gateway
M555 P2; Emulate Marlin USB output
M563 P0 D0 H1                       ; Define tool 1
G10 P0 S0 R0                        ; Set tool 1 operating and standby temperatures
M92 E420; Set extruder steps/mm
G21 ; Work in mm
G90 ; Absolute positioning
M83 ; Extrusions relative
M574 X0 Y2 Z0 S1					; set endstop configuration (Y endstop only, at high end, active high)
M558 P1 ; Turn Z Probe on
M305 P0 H14 L-11					; set ADC correction
M305 P1 H14 L-11					; set ADC correction
G31 Z1.8 P600 ; Set Z probe height and threshold
M906 X800 Y800 Z800 E800 ; Motor currents (mA)
M201 X800 Y800 Z15 E1000; acceleration tweaks for improved finish
M203 X15000 Y15000 Z250 E3600; speed tweaks for improved finish
M569 P0 S0                          ; Reverse the X axis
M556 S78 X-0.63 Y1 Z-0.3
M566 X600 Y600 Z30 E20              ; Minimum speeds mm/minute
M208 X214 Y210						; set axis travel
M208 X-15 Y0 S1							; set axis minimum
T 0
;End of config

Looks like a classic Ormerod 1 slipping Y belt to me. Have you done anything to secure the Y belt more effectively to the carriage? I use these Y belt fasteners [www.thingiverse.com], and these shims [www.thingiverse.com] under them to adjust the belt tension.

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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].

Many thanks for your help.
That was my first thought, too that the Y belt could have been slipped. I only used cable ties and I was sure that this would be enough. Maybe it was too late, but I checked the Y belt and I assumed that the belt was weak, but strong enough that slipping was no risk. Maybe I should teach my mechanical knowledge more. I totally can understand how your approved Z probe is working.
Which one of the Ybelt fasteners do you use? The round one or the flat one? And I have no idea what to do with the shims. I have been seeing them often, but I thought that these pieces belong to the Ormerod 2.
Okay I will disassemble my Ormerod and report later, but I am afraid, that there is a second fault. Maybe the X belt?

I use v7 which is the flat one. The shims go between the belt fastener pieces and the plywood rib that they are attached to. The belt has a 2mm tooth spacing AFAIR, and this isn't fine enough to adjust the belt tension precisely, because you can only adjust the belt length by a whole number of teeth. By choosing which shims to put under the belt fasteners, you can get a finer adjustment.

There are also designs out there for modified Y idler pulley supports with belt tension adjustment built in.

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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].

Many thanks.

That was indeed the problem. I fixed it now for the moment. I will try to print the Y belt fasteners later. I think I should print them in ABS or HIPS. Lickily there were some photos how to mount them.

Also make sure the grub screws on the pulleys are tight and correctly aligned with the flats on the shaft. Loose pulleys are also a very common cause of your symptoms.

Dave

Thanks Dave. But in my case it was indeed the connection from the belt to the heated bed. I was astonished that the belt could get loose in that way.
As soon as my printer works again and I have enough time I will print the Y belt clamp either in ABS or HIPS.