1 Topic by sanguish

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Topic: Belt tensioning, utter frustration

After printing something last night (and still using the software to move the head around fine before shutting down) the belt tension on the Y motor has messed up completely.

it's only grinding part of the time, and only on the travel to home. I've been fiddling with it for hours now. I'm sure the issue must be that the belt is slipping in only one direction. I've moved the belt around on the pulley and it still does it, so I don't think the belt is messed up. I can tune the belt so that it only does it in certain places on the home travel. That's probably the most frustrating aspect.

I'm about at my wits end with this. Is there a trick I'm missing? Is slipping because of too much tension or not enough? And why only in a certain area of travel?


I can see where a thumbwheel and screw to very gently adjust the motor position could be really useful. has anyone tried this kind of modification?


And it really doesn't make me feel good that Solidoodle hasn't update the instructions for the Solidoodle 4 (which requires you to take the side off to move the motor). It feels like it isn't a product that is important.

2 Reply by jagowilson (edited by jagowilson 2015-01-11 04:22:14)

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Re: Belt tensioning, utter frustration

Have you followed this video to a T?
http://vimeo.com/55031028

If you are using an earlier SD4 with bolts on the left/right belts, you can follow this video exactly. Otherwise, the only thing that's really different is you adjust the belt tension at the front of the printer, and you have to be a little more careful checking the tension, because you can make the bolt go sideways if you adjust the front idlers incorrectly. You will also need a 2mm hex driver rather than a 2.5mm. For some reason they changed this and didn't tell anyone.

3 Reply by sanguish

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Re: Belt tensioning, utter frustration

I've tried to... :-) I think even to a U

The Y stepper motor is definitely being prevented from turning by something. I don't know if it is the right or left belt. Or the fact that the pulley on the other end of the Y stepper motor keeps moving because the rod it is on isn't actually prevented from sliding left and right (it might be when the side is on again, but you have to take it off to adjust the screws.

Thanks, I'll watch the video again and give it a try with fresh eyes in a bit.

I really think if you buy a SD you should either get a set of extra belts right away, or they should be included. That might be the same for any printer though. Although I dread the thought of having to replace that Y stepper motor belt though.

4 Reply by sanguish

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Re: Belt tensioning, utter frustration

So one thing of note is that video has different tensioning screws for the Y belts. The SD4 I have doesn't have them on the carriage, the only ones are at the front that move the front pulleys forward or back.

I think that might be the problem, so I'll have to go back and try it again.

Why are there not locking collars (the ones on one side of the pulleys on the rear rod) on both sides of the pulleys?

5 Reply by jagowilson (edited by jagowilson 2015-01-11 15:06:20)

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Re: Belt tensioning, utter frustration

sanguish wrote:

Why are there not locking collars (the ones on one side of the pulleys on the rear rod) on both sides of the pulleys?

The rod couldn't rotate if it had shaft collars on it...

Stopping the rod from sliding is a challenge and it is a bit of cat and mouse as they say in the video. Get it moving smoothly without sliding before attaching the Y motor belt, it will make it much easier. Make sure you don't let the front pulleys go sideways. You can check the equality of tension by plucking the belts like guitar string. If they don't resonate, they are too loose. If you can't pinch them together, they are too tight. Too tight will cause binding because there isn't a ball bearing anywhere in the stock system and it can't handle much drag.

6 Reply by sanguish

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Re: Belt tensioning, utter frustration

The collars are already on the rod though.. just on one side of a pulley. Doesn't that make it possible for the pulley to move in the other direction?

is there a bearing mod for the SD4 (fairly recent, no idea how to tell which extruder or carriage type I have)

7 Reply by jagowilson (edited by jagowilson 2015-01-11 15:15:16)

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Re: Belt tensioning, utter frustration

That's not a shaft collar on the back rod, it's a pillow bushing. The pulleys are in a constant position relative to the rod because they have set screws. Just to clarify, the ROD is shifting, not the pulleys. 

Yes there are mods. Check hacks/mods for the printable carriages that use linear bearings, and the back bushings are replaceable.

Have you made any progress? If it is binding up with the motor, but the Y axis moves freely by hand you may want to bump up VREF for Y In case that is the cause. (tons of info here just search).

8 Reply by sanguish

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Re: Belt tensioning, utter frustration

No progress yet. I'll check the VREF stuff. Because the carriage definitely moves just fine.

Thanks!

9 Reply by sanguish

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Re: Belt tensioning, utter frustration

So I approached this again tonight after a few days of leaving it alone. I followed the video instructions yet again...

And it seems to be good. :-)

I think I just needed to walk away and let it sit for a bit.

The prints are really good. Thanks for your help!