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Author Topic: Need help with basic understanding  (Read 16140 times)

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Re: Need help with basic understanding
« Reply #40 on: February 21, 2011, 08:31:47 AM »
Yes, I still have the steppers as idlers. I'll see if I can remove some of the magnetic structure so they spin freely and see if it makes any difference.

If those gaps were skipped steps, it'd take about 20 skipped steps to make a gap that size.

Multitasking PC: I think that'd be a more random occurrence, and I dont think it'd happen at exactly the same time, every time.

Belt jumping a tooth, possible, though not exactly sure how I can test that. Are my belts better off tight enough that they don't sag much, but not stupid tight, or stupid tight?

Cheers,
Dan
Re: Need help with basic understanding
« Reply #41 on: February 21, 2011, 08:52:59 AM »
OK, I think I've found my problem. I set my original shape pattern on F60, and watched the belts move over the pulleys. I notices that sometimes the teeth of the belt actually ride ON the ridges in the pulley, and not the grooves like they are supposed to.

Now, why it's doing this has lost me. The pulleys and belt are the same pitch, so I'm thinking maybe my belts arent tight enough?

EDIT: I just took a pulley off, and wrapped the belt around it. I could get 1 full rev, but after that, the teeth started riding on the ridges. Maybe the machine was very slightly off when these pulleys were machined?

Cheers,
Dan

« Last Edit: February 21, 2011, 09:00:42 AM by Things »

Offline Tweakie.CNC

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Re: Need help with basic understanding
« Reply #42 on: February 21, 2011, 09:11:58 AM »
It's more likely that the belts are innacurate. (almost the same pitch is different to exactly the same pitch)

Tweakie.
KEEP SAFE !
Re: Need help with basic understanding
« Reply #43 on: February 21, 2011, 09:17:39 AM »
Here is a pic of the belt , the left side, the teeth are riding in the grooves as they should, but as you can see, they start riding up onto the teeth in the pulley.

If I pull on the belt VERY tightly, I think it manages to fit, but that kind of tension would rip my machine to shreds.



I'll email the place I got the belts and pulleys from and see what they say.

Cheers,
Dan
Re: Need help with basic understanding
« Reply #44 on: February 21, 2011, 09:34:16 AM »
It seems as if I may just need more belt tension. However, it's going to require a fair bit of cross bracing on the machine. Gotta do what you gotta do I guess!
Re: Need help with basic understanding
« Reply #45 on: February 21, 2011, 09:36:37 AM »
DraftSight is a nice, free CAD program.  It is offered by the company that puts out SolidWorks.

http://www.3ds.com/products/draftsight/download-draftsight/?xtor=SEC-6-GOO-[]-[]-S-[draftsight]
Re: Need help with basic understanding
« Reply #46 on: February 22, 2011, 01:30:03 AM »
OK, I tightened my belts this afternoon about as tight as I'd want to take them on my current setup, and the results are MUCH better:



Does still seem to be a little variation there though, which I'm not sure on.

Cheers,
Dan

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Re: Need help with basic understanding
« Reply #47 on: February 22, 2011, 02:06:49 AM »
The results are not really any better, OK the mis-allignment may be less but overall it is still a poor result.
IMO the reduction in the amount of error does tend to indicate that it is the belts/pulleys which are the main cause of the problem though.

Tweakie.
KEEP SAFE !
Re: Need help with basic understanding
« Reply #48 on: February 22, 2011, 02:29:29 AM »
Its not going to be perfect, as the laser can not turn on and off (thus the dark spots in places its been over more than once, or stopped at.

What is odd is that square at the top is pretty much perfect, however now the quadrant on the lower right is off.

Not really sure what else I can test now? the belt does not appear to ride on the teeth anymore, however sometimes it clunks, and the gap seems just under the width of a single tooth.

Cheers,
Dan
« Last Edit: February 22, 2011, 02:33:37 AM by Things »
Re: Need help with basic understanding
« Reply #49 on: February 22, 2011, 03:30:05 AM »
I've tightened the belts even more, and still have the problem. I am pretty sure my belts are not riding on the teeh at all now.

I think the problem may be the teeeny offset on the pulleys, meaning they very slightly loosen and tension the belt. Seem like it could be the issue?

Maybe I'll see about taking a stepper and a pulley to my local alu place, and see if they can make me 6 sleeves that'll keep them perfectly centered.

Cheers,
Dan