X Axis Shift

Need help with a problem with X Axis shift (missing steps/thermo cutoff) not sure which. I am new to the world of 3D printing but I can’t get past this problem. It is a DIY printer and is printing great since I purchased a good hotend ( E3D-V6 ) except for this problem. Parts were purchased from Sain Smart as a kit. Attached are pictures showing the problem, only on the X Axis ( of all the prints trying to find the problem only once did it show up in the Y Axis). First place I looked was the driver, interchanged it with the Y axis and a spare, multiple settings of the driver current. No help. I have changed everything except the ramps 1.4 board, has anyone had problems with the ramps 1.4 board? Following is a list of things I have tried. This problem is somewhat intermittent put mostly there all the time, I have got some prints that were great (very very few).

Replaced driver board
Multi current driver settings
Fan directly on drivers
Replaced Arduino board
Replaced power supply
Replaced stepper motor
Checked pulleys and set screws
Printing large and small parts

I ordered a new ramps board today, will keep you posted but I would love to know is causing my problem

Edited 1 time(s). Last edit at 11/29/2014 07:01PM by Edward99.

Could it be that the printing speed is simply too high?

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http://www.marinusdebeer.nl/

Perimeters - Infill - Travel are 30 mm/s

Could be your pc if you are using it to control the printer. Try printing direct from an SD card.

I printed the same file from the SD card and had the same problem. I did order a new Ramps board, don't know what else to try short of getting my printer airborn.

Suggestions:-

- set the stepper voltages properly with a voltmeter.
- try reducing the acceleration on X.
- check your x carriage for any slight play in the belt drive, particularly the clamp, and make sure the belt is tensioned tightly.

I've just been through something similar on my new build (a Prusa i3 box variation, RAMPS 1.4 and cheap Chinese steppers), so I'll describe what I did to resolve it.

Symptom I had was occasional missed steps on X and Y axis (though not usually both in same print), usually happened after some minutes (not at the very start of a print), and some small prints were able to complete without problems. It was also noticeable that if I repeated the exact same print then the skip was at approximately the same point (within a layer or two) in the print, which is what pointed me towards a possible build up of heat. My motors weren't getting warm, but I could feel the heatsinks on the steppers getting hot so I first fitted a fan to blow on the steppers.

I still got the skips so I decided to fine tune the stepper voltages (I had originally just turned them up to stop binding, but in retrospect that was before I had adjusted acceleration and top speeds in Marlin, so I probably set them too high). The Chinese steppers don't have an endstop on the pots, so unless you want to risk exceeding your motors max current then that pretty much forces you to calibrate correctly using vRef. The Pololu website gives you the procedure, you measure vRef from the metal dial of the pot, and ground (I use ground from the RAMPS 12v input, just because it's easy to get my meter probe onto), using the formulae:

C (current limit) = Vref x 2.5

The A4988's can provide up to 2A (more than most motors we use can take), so the aim is to keep current high enough to stop the motors binding (more current equals more torque), but not so high that overheating becomes an issue, but here's the kicker, too much current, and not enough current, can both have the same symptom (missed steps in your print).

I decided the only way to make sense of this was to plot the effect of incremental Vref changes, so I started by plotting the workable range of Vrefs for my motor, like this:


C........Vref
1.0......0.4
1.1......0.44
1.2......0.48
1.3......0.52
1.4......0.56
1.5......0.6
1.6......0.64
1.7......0.68
(my motors have a max current rating of 1.7A)

Then as Y was causing the most problems (my Y carriage is much heavier than my X carriage) I set the Y stepper to a low voltage (0.323v) and worked progressively up (using the same "problem" print each time). You can see the attached spreadsheet if you're interested, but the resulting voltages have been stable (no skips) for the last 3 days:

X= 0.540v
Y= 0.622v
Z= 0.541v
E0= 0.584v

Probably way more detail than the OP wanted, but hopefully will help someone.

I adjusted Max-Acceleration and Default _Acceleration to 1200 and that corrected the problem. I was able to print the test file 3 times with no problem, before making the changes I could not get 5 minutes into a 45 minute print. Don't know if I need to do more fine tuning or not. I have know idea what are normal settings. Will have to do some research on the settings of Configuration H file.
Thanks for all the help with this, I think I can remove the wings from the printer.

My printer if working fine now that I have adjusted the Max-Acceleration and Default _Acceleration to 1200. Can anyone direct me to where I can get info on what the values in the configuration H file mean?

I switched from Marlin to Repetier v0.92 firmware. There is an online configuration website which really is a godsend.

[www.repetier.com]

Everthing is explained as you go along. You flash the Arduino the same way.