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X Axis Failure during print

Posted by dj_woff 
X Axis Failure during print
August 20, 2015 05:03PM
Hello All

I've run into a very weird fault with my Ormrod 2. To make life harder its sporadic rather than predicable. I have however been present when it happened this time.

During lagrer prints I've noticed had a couple of them fail with the X axis suddenly moving off position for no reason. When it first happened I though that the hot end wires might have caught, but I have since supported them out of the way.

Tonights occurance happened after about 2 hours of printing. There was a sudden grinding noise from the X motor during a fast move and the whole axis slipped 30+ mm. I hit the pause button on the web interface and clicked to re-home the X axis, which it appeared to do fine. This however caused the Y to become uncalibrated so I homed that as well. This spelt doom. The X motor turned on hard and started banging the hot end into the stop by the pillar and wouldn't relent. I had to power the unit down to prevent damage, costing me the print.

Has anyone else experianced this?

Can anyone suggest any faults that could cause this? Sadly, to my mind, the latter fault suggests the Duet rather than an intermittent cable.


Re: X Axis Failure during print
August 20, 2015 05:49PM
I've had the X axis slip when doing a fast travel move from one end of a print to another, over a lot of partially-printed holes aligned with the Y axis. The print had curled up slightly at the edges of the holes and the nozzle was catching on them. I reduced the travel speed for the next attempt, which was successful.

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].
Re: X Axis Failure during print
August 21, 2015 03:01AM
Hi DC42

Thanks for your reply. In the case of this move it was running over / near the top of what should have been a flat surfce, it was printing the top of a support structure generated by slic3r. This hadn't gone well, as slic3r had been a bit overambitious on the lower structurs spacing, and I'll admit that in the cold light of day it was asking for something to catch.

However this doesn't explain the odd behaviour after the y axis calibration.

Having spent a night mulling things over I'm wondering if the microstepping profile used by the controllers could cause movement if one of the phases went down? Thus after the y axis cal, when the X was returned to it's original position the microcontroller selected a slightly different position which used microstipping and.......... Knowing what I know now (i've been through the schematics and the motor controllers datasheet) if it happenes again I'll disconnect the motor and take a look at what's happening on the duet.

As a silly one in your post about new firmware I spotted a reference to an interrrput priorities bug. Could that cause problems like this, as I had the web interface running at the time.


Re: X Axis Failure during print
August 21, 2015 03:40AM
If the head hit the printed part some steps may be skipped and you get an offset.That is totally normal. I often suffer from this problem at the moment. It can be caused by warping, by blobs or by over extrusion. It also may happen that the printed parts get loose after hit and it ads at the nozzle. That looks funny on one side but the print is ruined of course. I mostly have this problem at the y-axis but by rotating the part it can differ and even affect both axes.

Slicer: Simplify3D 4.0; sometimes CraftWare 1.14 or Cura 2.7
Delta with Duet-WiFi, FW: 1.20.1RC2; mini-sensor board by dc42 for auto-leveling
Ormerod common modifications: Mini-sensor board by dc42, aluminum X-arm, 0.4 mm nozzle E3D like, 2nd fan, Z stepper nut M5 x 15, Herringbone gears, Z-axis bearing at top, spring loaded extruder with pneumatic fitting, Y belt axis tensioner
Ormerod 2: FW: 1.19-dc42 on Duet-WiFi. own build, modifications: GT2-belts, silicone heat-bed, different motors and so on. Printed parts: bed support, (PSU holder) and Y-feet.
Ormerod 1: FW: 1.15c-dc42 on 1k Duet-Board. Modifications: Aluminium bed-support, (nearly) all parts reprinted in PLA/ ABS, and so on.
Re: X Axis Failure during print
August 21, 2015 07:16AM
Make sure all your rods are oiled properly. When I got my Ormerod 1 originally, I had a problem where my prints would suddenly jump sideways like you explained. I eventually realised that my z-axis needed a drop of oil on the smooth rod. The issue was essentially that the printer was sticking ever so slightly on a particular height on the z-axis. This caused the head to be 0.05mm lower than expected. Imperceptible to the eye, but as explained the head caught on my print, and caused it to jump.
It took me ages to find, because I thought the issue was on the X or Y axis, since the print jumped sideways, so I kept investigating and tweaking those.
Re: X Axis Failure during print
August 22, 2015 03:53AM
Last two days I've experienced it twice as well. Last time I was printing four pieces of a small component. I realised it first when print was done so I haven't really seen it happening live. It slipped 6-8mm on x axis. In my case I think it was caused by the axises not being oiled enough. The print after that the whole nozzle part came loose from the x axis bearing. Since then I've lubricated the axis with silicone lubrication spray. Have only printed once since then but that was successful.
Re: X Axis Failure during print
August 22, 2015 09:02AM
I used some hot glue to keep the bearing in place( and its easy to remove later if you need to disasemble just peel it off) just run it on the backside of the X caridge and the bearing dont glue on the side thats closest to the Z extrusion( it will hit the extrusion when homing).
Re: X Axis Failure during print
August 22, 2015 10:22AM
I used some hot glue to keep the bearing in place...

also note zombiepantslol's cable tie mod:

..I modified the x-carriage a few weeks ago so I can add a cable tie to it, you can get that part from here if you have one of dc42's Z-probes



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