X-axis slip

Initial issue was the x-axis slipped a few mm during print.

Several attempts resulted in different amounts of slippage, but all at about 3/4 inch on the Z.

I am trying to find where the printer (Mendel) is losing it's position.

I have the extruder offset @ x-45 y-8.
If I send gcode G28 X the carriage moves to here:

If I send code G1 X1 F3000 the carriage moves here:

If I send gcode G1 X200 F3000 then G28 X the carriage moves to here:

which is neither the home position nor the corner of the bed.
If I repeat the last steps the carriage homes to a new position to the right of its last 'home' position.
If I continued it eventually judders at the furthest point away from home. This, in my thinking, would effectively move the extruder carriage some distance towards home, which is the effect I am seeing in the print, although I am not sure if running out of range of the bed is actually happening.

Can anyone explain this behaviour, and whether it is correct or not.

Have you checked for loose pulleys? I had a similar problem in the Y axis, turned out to be a loose pulley.

Thanks Rich,
I used a Sharpie to park the pulley position. Does not move.

Using the 'get pos' I get the following results:
G28 X; G28 Y = X:-45.00Y:-8.00Z:0.00E:0.00 Count X:-45.00Y:-8.00Z:0.00
g1 x100 f3000 = X:100.00Y:-8.00Z:0.00E:0.00 Count X:100.00Y:0.00Z:0.00 It moved on both the X axis and the Y axis, but the Y value has not changed

If I home X I get X:-45.00Y:-8.00Z:0.00E:0.00 Count X:-45.00Y:-8.00Z:0.00
If repeat the G1 X100 F3000 I get X:100.00Y:-8.00Z:0.00E:0.00 Count X:100.00Y:0.00Z:0.00. Again the Y moved, by what I assume is 8. Now the Y is 16mm out of its reported position.

A similar thing happens if I switch the X and Y movements with the X being out of position by 90mm.

I installed the latest version of Pronterface/Printrun and I now have creep in the other direction, AND the pulley has not moved on the motor shaft.

I am starting to think it is a motor problem I will check the factory set motor drive current.

I moved this to "General Mendel Topics" as it is clearly not a Mendel90. What machine have you got?

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[www.hydraraptor.blogspot.com]

Tricolour Mendel 3 from Reprappro.com, purchased end of last year, built over the passed few weeks. Only using 1 extruder, as recommended, until I get it working well and have the warranty parts available.

I switched back to the original Pronterface and tried another print, to see where all the adjustments etc. had got me.

Now it is slipping both ways on the X and 1 way on the Y. Still have to check the motor voltages. I am thinking the problem may be with non-solid sides, i.e. extra material sticking up that 'stops' the motor. Higher voltage/power may 'force' it on, but may also unstick the print from the bed.
The issue with homing a single axis is probably a red herring, either needs a s/w fix or a work-around.

If vref on the stepper drivers is set too low, you may not be giving the steppers enough oomph and they may be missing steps at one or more points in the print. Either adjust the vref or slow down the print speed.

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[3DKarma.com] - suppliers of quality, affordable 3D printer kits and filament for the UK market.

I think that may have cracked it.
Reprappro set the vref to 0.6. I measured them all @ 0.588, but could be my meter.
Instructions (http://reprap.org/wiki/RepRapPro_Setting_Motor_Currents) for Melzi V2 suggest 0.6 upto 0.8
I have set them somewhere between 0.65 and 0.7 (not easy to get them the same)

I may fine tune them later to 0.7

Print looks much better, not perfect yet, but this time I could hear the head clunking over the hardened PLA, and it did not pull the piece off of the bed.

Thanks to 3DKarma, nophead and Rich K.

Over-extrusion and/or not enough retraction (hence blobbing) can be causes of nodules of PLA on the print surface. I'd play with these to try and minimise the issue.

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[3DKarma.com] - suppliers of quality, affordable 3D printer kits and filament for the UK market.

Reprappro.com suggested installing cooling fans as I was squirting vertical holes. Makes sense, you want the filament solid up to the nozzle, fluid through the nozzle, and then solidifying asap after, hence cooling fans.

Iphone stand

Barrel

Reel adapter


Looks pretty good now.
Thanks all