26 Reply by op7ical

  • op7ical
  • Member
  • Offline
  • From: Orlando, FL
  • Registered: 2013-01-21
  • Posts: 136

Re: Another Shifty Y-Axis

At long last, I have fixed my Solidoodle!

The culprit turned out to be completely non-mechanical.  As jjcuff1 had suggested, there turned out to be a problem with the y-stepper driver. 

I suspected something might be overheating, since the defects tended to start occurring in long prints, in higher layers.  So I pointed a large CPU fan at the electronics board with no cover on and ran some test prints.  The skipping vanished totally - not a single error in hundreds of layers now.  The picture attached shows a before (left) and after (right) comparison.

So how can you recognize this sort of error?

-Small skip size - no bigger than maybe 2mm, usually much smaller.
-Occurs later in prints (need to be intensive - not just single walled cylinders and such)
-When the glitch occurs, the machine will quietly, and very briefly stop moving the y-axis, just long enough to cause the small skip. 
-It does not sound loud, like a skipped step would.

This is almost certainly a result of the high demands on the y-stepper, as it is already pushed to the limit of its capabilities.  I am not sure why so few users have encountered something like this.

Thanks again for the help, to everyone who contributed.  And to Kvirre, I will use some of those tips as I optimize my backlash now!

Post's attachments

20130320_232531.jpg
20130320_232531.jpg 1.77 mb, file has never been downloaded. 

You don't have the permssions to download the attachments of this post.

27 Reply by jjcuff1

  • jjcuff1
  • Member
  • Offline
  • Registered: 2012-10-18
  • Posts: 253

Re: Another Shifty Y-Axis

That is great. I ordered a new stepper driver 3 actually all over sized with heat sinks and I will print a small fan holder for the board as well. Once I hope I get it running. I will run prints without a fan,

As for the earlier comment about the rod alignment is so critical:
Once you dial in the alignment and tension the pulley location needs to remain fixed. because this is the main culprit of smooth carriage moment. So if you have the pullies set, that rod location needs to remain there (regardless of where the rod actually is a few mm left or right doesn't matter) but the location of the pullies on the rod does. If you shift that rod a few MM or knock the carriage could instantly bind.

I tried this dozens of times and it is repeatable.

Now with that said I found by having the rod flush with both sides minimize the risk of knock the rod side to since it is flush with the machine.

SD2 owner- Surestepr, filament holder,QUBD servo and heaters, glass bed
Print for fun and for parts for my sports cars
current car is 88 IROC

28 Reply by IanJohnson

  • IanJohnson
  • Moderator
  • Offline
  • Registered: 2012-08-07
  • Posts: 2,815

Re: Another Shifty Y-Axis

I have a cheap stepper driver on another project, and it has overheat protection.  This takes the form of short pauses, less than a second.  Something like that is probably what happens with the pololus.  During the summer I found that I would always have banding on my prints if I didn't keep a fan on the electronics.  My Z driver would run to0 hot and sometimes not advance the layer.

29 Reply by Kvirre (edited by Kvirre 2013-03-21 15:00:31)

  • Kvirre
  • Member
  • Offline
  • From: Malmö, Sweden
  • Registered: 2012-10-05
  • Posts: 81

Re: Another Shifty Y-Axis

jjcuff1 wrote:

That is great. I ordered a new stepper driver 3 actually all over sized with heat sinks and I will print a small fan holder for the board as well. Once I hope I get it running. I will run prints without a fan,

As for the earlier comment about the rod alignment is so critical:
Once you dial in the alignment and tension the pulley location needs to remain fixed. because this is the main culprit of smooth carriage moment. So if you have the pullies set, that rod location needs to remain there (regardless of where the rod actually is a few mm left or right doesn't matter) but the location of the pullies on the rod does. If you shift that rod a few MM or knock the carriage could instantly bind.

I tried this dozens of times and it is repeatable.

Now with that said I found by having the rod flush with both sides minimize the risk of knock the rod side to since it is flush with the machine.

I tried to remove the front pulley-holders that are mounted to the frame but was unsuccessful with a hex-driver.
After destroying the grip for one screw I avoided to go for the back pulley's since I now suspect that they are not hex but in fact something else. Please do tell (the screws are really tiny and I can't tell)

Kvirre's Website

30 Reply by jjcuff1

  • jjcuff1
  • Member
  • Offline
  • Registered: 2012-10-18
  • Posts: 253

Re: Another Shifty Y-Axis

They are metric I believe 1.5mm it is the 2nd smallest one in my set then the main ones are 2.5mm nuts

You might have to break those free eventually. I know departed on here bought Fel-loc pullies I believe that have a different mechanism for holding torque that doesn't marr the shaft or strip. I should order those now in advance LOL

SD2 owner- Surestepr, filament holder,QUBD servo and heaters, glass bed
Print for fun and for parts for my sports cars
current car is 88 IROC

31 Reply by jjcuff1

  • jjcuff1
  • Member
  • Offline
  • Registered: 2012-10-18
  • Posts: 253

Re: Another Shifty Y-Axis

Yes it is a 1.5mm but if stripped you might be able to get a 1/16" in there. And they are Fair-loc

see below
I removed the shaft above the Y motor (the shaft the Y motor turns and through that moves the axis).  However now that you mention it that stepper will be removed and a flat will be put in that output shaft as well before I am done.  I already (in another topic) ground a flat in my extruder stepper with excellent results (at least for me).

FairLoc(TM) hubs are designed to reduce the exact issue you pointed out earlier in this topic.  They are essentially a compression hub made out of aluminum but unlike the set screw they grab most of the shaft circumference.  SDP-SI sells them (this idea is patented) as alternatives for gears, pulleys and other applications where non-marring adjustment of that item will happen often.  There are other ways to do this, and FairLoc(TM) does require some regularity in the shaft dimensions, but in this case I can substitute these gear pulleys for the ones on the shaft without cutting a flat at all.  Effectively it is a drop in replacement.  As those 2 gear pulleys were obviously heavily tightened because without a flat they would otherwise slip.  My hope is with the FairLoc(TM) hubs I won't have that sort of issue.  Course as proprietary parts they cost a bunch more.

I bought 3 18 tooth FairLoc(TM) hub pulleys at basically $19 each.
I won't need one for the stepper because I will put a flat in that shaft, there is no rotational misalignment there that requires adjustment...just the need to stop it from slipping so the $5 existing stepper gear pulley is just fine.

SD2 owner- Surestepr, filament holder,QUBD servo and heaters, glass bed
Print for fun and for parts for my sports cars
current car is 88 IROC

32 Reply by ckirby

  • ckirby
  • Newbie
  • Offline
  • Registered: 2013-03-24
  • Posts: 1

Re: Another Shifty Y-Axis

I wonder if that's the problem I've recently started having. Simple test prints come out fine, but the last couple more involved prints I've tried have failed in similar ways. In both cases, after printing scores of layers without incident, the printed decides to shift everything 1-2mm towards the front of the printer.

33 Reply by shidhuroy

  • shidhuroy
  • Newbie
  • Offline
  • Registered: 2013-05-06
  • Posts: 2

Re: Another Shifty Y-Axis

Hi Mr Kvirre.

Thanks for your information

Brand  Manger
Events  Models
Promo Models

34 Reply by Briggs

  • Briggs
  • Member
  • Offline
  • From: Minnesota
  • Registered: 2013-03-20
  • Posts: 226

Re: Another Shifty Y-Axis

Maybe try putting a small fan directly on the controller and see if this helps. It did for me. If so, then you might want to add one or two 40mm fans to the controller for a more permanent solution.