MBot3D Dual - X Axis problems, print gets skewed.

[Thierry Baumann]

Hello to all fellow Tinkerers.

I have run into the following problem. After successfully printing dozens of objects using ABS of different colors, one day suddenly the print gets skewed badly along the X-Axis, pictures attached:

 

Strangely enough the skew is only in the middle part of this “V.I.N. Cent” figure, the topmost layers are fine.

Here you see how my machine used to print, right side, and now, left side.

I have tried just about everything recommended in this forum and then some. I have changed the X-Axis motor support, because it had a hairline fracture, but the problem persists. All Pulleys are as tight as they can be, all the belts are fine.

I do not know what else could be the problem. Any suggestions are welcome.

Thanks.

 

Thierry Baumann

[happyman]

Another possible issue is X stepper controller, you might want to switch it with Z axis stepper driver to confirm the issue - warning - be very carefully when you plug it - it need to be in the same direction as when it is unplugged.

[Thierry Baumann]

Nope did not work, as a matter of fact it seems worse than ever...

 

[Giga Faze]

That looks like the X-axis belt is slipping. It could also be your X cable bundle developing an open, if you haven't done the drape down mod yet. Seems like a lot of people had one or more pulleys come loose. The other possibility is you had some prior print that went bad and the malfunction was enough to make the belt slip.

[happyman]

Then I am quite sure that the problem is due to power cable that go to X-motor - it is a common issue for MB Rep clone especially on X-axis. You can try to swap with another Axis motor to test out.

[Tamrat Abishu]

Hi!

I have the same problem but in my case, the print gets skewed in the +Y-axis, as shown in the picture below. In the beginning the printing goes well for about 5 mm height but after that, sometimes, it skewed smoothly and another time step-wise like a stairs. I used ABS. First I thought there is slipping between the belt gears and the shafts but I checked that and there is no slipping. I need help on this!

[happyman]

First, you should check the Y-motor pulley if the screw get loose first or not before confirm the power cable. There are 2 screws in the pulley on the Y-motor belt, a small belt that you can see on the back of the printer, check that the 2 screws are tighten and not cause free rotate.

If it is tighten, then I guess your cable power to Y motor might fail. This happen if your extrudder hit the print job while you are not monitor the printer for a long period of time - especially when print with ABS when the print job like to get curl up and cause the nozzle to collide with it. If you come back to check the print job and found the messy blob of plastics lied around or your print work got knock off the bed, then it is a very good chance that you might damage the power cable.

Good luck

[Thierry Baumann]

Ok, happyman. I checked everything:

1:         I swapped two stepper motors - No change

2:         I swapped X and Y cables on both ends - No change

3:         I repeatedly reseted the Mainboard – One good print and then back to skew...

4:         I tightened all the belts and shafts and what not…

 

I’m starting to think it’s a Mainboard problem…

[b...@magicfirm.com]

you can try to choose "utilities"--"enable motor stepper" ,then use your hand push the extruder move along X axis .

if you can move it ,then you need to fix the synchronizing wheel 

在 2014年6月2日星期一UTC+8下午10时33分40秒，Thierry Baumann写道：

[Thierry Baumann]

Tried it and it does not budge, not even a little bit. Solid as a Rock.

[Giga Faze]

You said you reset the mainboard and got one good print. That is a clue. What do you mean you "reset the mainboard"?. Did you use the factory reset in ReplicatorG? This isn't a good thing to do unless you want to lose a lot of settings. So, first, are you using ReplicatorG? Are you using the Mbot driver and not a Replicator driver? When you look at the driver in the ReplicatorG menu, it should have this selected: The Mbot Cube (Replicator Compatible). If that is picked, then what slicer Profile are you using? I use the Replicator2 profile with my edited settings. Once tried the Replicator one and it did all kinds of strange things. The Replicator 2 has a rectangular build plate, and the Mbot has a square. If Replicator 2 dimensions are used, then the Mbot tries to fit something sliced for a square build area and try to print it to the rectangular ratio. One thing to do is go down the layers where X and Y should not be changing for awhile, like a straight side, then examine the Gcode values. If they are actually changing to a rectangular reference, then it is the slicer calculating those positions thinking it is going on a rectangular build plate. You should be using Skeinforge 50 as the slicer for ReplicatorG, the Slice3 is way old and doesn't work well, Skeinforge 47 had some bugs.

[Thierry Baumann]

Thank you for your recommendations, I will try to check all that at once.

System Specs;

  MBot Cube II

  Firmware 7.2 (Currently, recent downgrade from 7.5)

  ReplicatorG 0040r22 (I also tried with MakerWare, same error)

  Happens with USB print and SD Card print

  The so called good print had a very slight skew in the first 15 or so layers, see picture attached)

After that, the base plate, the print was as near perfect as it can get with my printer.

I'll get back to you on the results of my tests.

[Drugless]

Please try the following:

Remove the cable tidy from the X-Axis Stepper Motor loom and X-Axis Endstop cable.

Separate the X-Axis Stepper Motor loom from the X-Axis Endstop cable.

In other words make sure that the loose single wires from the X-Axis Stepper Motor are not braided around the X-Axis Endstop grey covered cables. 

Just leave the entire lengths separated dangling down the front of the Stepper Motor Mount. (basically like Giga Faze described)

Repeat printing one of the objects that you had the offset printing on and see if the problem goes away.

Your problem is typical of a short OR as in one case I had interference due to 'getting clever' and making up my own set of cables when I had a short. I used 8 core twisted pair cabling specifically designed for robotic use but didn't determine that the twisted pairs I used resulted in both sets of cables being braided into each other. I created two sets of cables with same result before stripping one set and just separating the sets and immediately problem went away. It makes perfect sense now but at the time I was rather stumped.

[Giga Faze]

I agree. If all those other things have been ruled out, and the original X-wire bundle hasn't been modified to let it dangle, then the wire in the X-bundle is starting to fray and will eventually fail. It starts with intermittent problems that get progressively worse. When it starts banging the head, then the wire is getting close to totally opening up. 

[Thierry Baumann]

Hello fellow Cuber’s :-)

 

It's been a while. I really got fed up with my machine so I got another one. It's not really mine yet, but I am working on it. Suffice to say that it was an MBot3D Kit with the spring loaded Extruder and, oh wonder, it worked right away after assembly. I have since printed almost 2 entire rolls of PLA, with minimal loss.

 

After a while of success with the new machine I had gotten past the frustration of the problems of the old one. So I took the machine back into my shop and disassembled it. I solved a few problems, like the bearings for the guides on the side of the z-axis. After a few prints, or tries, they would start to get dirty and the platform would sometimes fail to move smoothly up or down. So I got myself some bearings and I made flanges to fit them in. I uploaded the STL files for the flanges, but I have no pictures now. I will upload them later today.

 

After that I reassembled the MBot3D and started to make tests. Now to my surprise I suddenly discovered something very weird. Whenever I would use Jog Mode in the MBot ReplicatorG and would move the z-axis, either up or down, the print head would move one small but noticeable step on the z-axis (left, right). There is no way I can imagine why that is…

 

But it is very clear to me now that there is the reason for my skewed prints.

 

Now I now the how, I need to know the why.

 

Any suggestion would be fine.

Thanks

Thierry

[b...@magicfirm.com]

could you send a video about the problem you mentioned to my email b...@magicfirm.com  ?

that will help me figure out your problem 

在 2014年8月23日星期六UTC+8下午11时37分39秒，Thierry Baumann写道：

[Thierry Baumann]

Ok, will do.