Y-axis slip on Ormerod v1. Upgrade or ????

Hi All,

I've been tweaking and teasing my Ormerod v1 to death (almost). To improve print precision and consistency. I have made a lot of progress which has been really satisfying.

But (there is always a but) ... there is one regular and persistent problem which is worse on longer prints. The Y-axis slips varying amounts, often about 5mm. It seems to me this must be mechanical, but I cannot pin it down. In the attached picture there are two examples, but the same part at different stages (height).

I had assumed this was the hot end catching, but perhaps not. More simple, or less wide prints (X & Y) seem to be fine.

I had thought the Z sensor was perhaps too close to the bed, resulting in Z drifting a little after calibration, so I offset the hot end with a couple of M3 washers effectively lowering the hot end slightly, in relation to the sensor. This worked for one print, but not another. So it's not the problem.

I considered that it could be bed levelling, so I replaced the MDF with an aluminium bed to remove warp/flexibility of the MDF, but this also has not worked.

The belts are tight enough, before during and after a failed print. Could they be too tight? Is that a potential issue? If so, how do I tell?

Can it be software? I'm on 1.09 ELECTRONICSuet (+ Extension) DATE:2015-04-21, and if I read correctly I should be able to update to the 1.18.1 on github, with the 1.18 web interface. However, are there any pin changes, or other issues?

I've been able to successfully print a fair few things (you can search for my username on thingiverse if you really want to), so I'm not a newbie, but I am way inexperienced compared to many.

Thanks to anyone who takes time to reply.

Regards,

Mr. Mess.

Edited 1 time(s). Last edit at 07/03/2017 05:39PM by HorrendousMess.

1. Have you modified the belt path at all? If so, check that the length of the belt path is constant regardless of the position on the Y axis. There was a mod described a long time ago that took the belt at an angle between the carriage and the idler, and that angle (hence also the path length) varied with position.

2. What Y motor current do you have set? Most people seem to use between 1000 and 1200mA instead of the original 800mA.

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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].

In terms of current, I have not modified anything. I am no electrical engineer and would not know where to begin so I have played it safe with that, taking the defaults rather than risk burning motors.

Yes, I modified the Y belt "grips". I will look at those more closely and see if I can determine anything.

In both cases, would the expected fault not lead to a steady slump, rather than a sudden slip?

Many thanks for your time dc42 :-)

Having a belt path whose length varies with position will make the belt tension vary with position, which could explain why you haven't had this or on small prints. Increasing motor current makes it more likely that the motor will not skip steps if the nozzle hits a blob.

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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].

I have attached a picture of each end of the belt paths. It looks OK to me, fairly level all along.

Unfortunately, in the process of moving it (slowly and carefully) to take the pictures, a previous crack in one of the Y end plates turned in to a full break. So I will have to completely rebuild the Y axis. At the same time, I will amend the current to 1000mA and perhaps replace the belt in case it has some wear/damage from time served.

When increasing the current, is that a global setting, or per motor? If per motor, would you suggest that I should make the change to X,Y&Z, or just Y?

Thanks again.

The current setting is per motor, in the M906 command in config.g. I don't think there is any need to increase the other motor currents, but other users may disagree.

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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].

Quote
HorrendousMess
.. The Y-axis slips varying amounts, often about 5mm. It seems to me this must be mechanical, but I cannot pin it down.

a loose grub screw on a flat sided motor axle will do just that

Erik

Thank you both for your suggestions and excellent advice. I am confident that you have helped me zoom in on the issue.

@Erik: I had checked the grub screws, as originally I also considered this to be fairly likely. Unfortunately, it was not that easy!

@dc42: I think you hit the nail on the head with the current. One of my "tweaks" was to the print bed to improve rigidity, resulting in a heavier than normal load on the motor. This would also explain why it was affecting the Y axis only. I will amend the config.g with the relevant command when I get back to printing. Thank you very much for giving me that hint (M906), it will save me a lot of time trawling the G-code sheets

• I have now corrected the broken Y-end plate.
  
  • My son is a polymechanik and he has created two replacements from 5mm aluminium sheet.
  • Miracle worker in such a short space of time!
• We have also reduced the weight of the print bed by asking the same son to cut holes in the new base plate.
• I have also replaced the y-ribs MDF with a more rigid ABS construct from thingiverse.

Obviously, with such a big re-arrangement/rebuild, I now have to do some fairly lengthy calibration runs, and get some sleep. However, when it's back to normal, I will report back the results.

If I update from 1.09 to the 1.18.1 firmware on github, with the 1.18 web interface, are there any pin changes, or other issues? Please, no need for detail, I would just like a heads up on things to watch for?

Thanks again. It's a real joy to see the community still buzzing along :-)

HM

Edited 1 time(s). Last edit at 07/06/2017 04:58AM by HorrendousMess.

With upgrading to 1.18.2 I suggest you keep your existing config.g file but watch out for these:

X axis running backwards. Fix it by reversing the X motor connector or changing S0 to S1 or vice versa in the M569 P0 command.

Heater tuning. Remove the M301 commands from config.g and tune the heaters as described in the duet3d wiki.

M305 commands. Make sure you have one for each heater and that the B, R and T values are all specified.

That's all I can think of at present. HTH David

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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].