Belt tensioning

BigRez
Posts: 29
Joined: Thu Jan 08, 2015 2:11 am

Belt tensioning

Post by BigRez » Sun Jan 18, 2015 12:37 am

How tight should I have the drive belts? Should my Y-axis make any noise when I move it, or should it be relatively quiet? I also am getting some vibration on the Y-axis. I have the belts stretched pretty damn tight.
Shapeoko 2 Serial #7341. Relatively stock. Custom sound/dust enclosure. 24V 15 amp power supply.

WillAdams
Posts: 8608
Joined: Mon Apr 09, 2012 6:11 pm
Location: Pennsylvania --- south of the Turnpike, East of US-15
Contact:

Re: Belt tensioning

Post by WillAdams » Sun Jan 18, 2015 1:06 am

Shapeoko 3XL #0006 w/ Carbide Compact Router w/0.125″ and ¼″ Carbide 3D precision collets

BigRez
Posts: 29
Joined: Thu Jan 08, 2015 2:11 am

Re: Belt tensioning

Post by BigRez » Sun Jan 18, 2015 1:13 am

I read on another post that you should be able to slip a finger underneath the belt. Is this true? Mine are tight enough that I probably can't.
Shapeoko 2 Serial #7341. Relatively stock. Custom sound/dust enclosure. 24V 15 amp power supply.

WillAdams
Posts: 8608
Joined: Mon Apr 09, 2012 6:11 pm
Location: Pennsylvania --- south of the Turnpike, East of US-15
Contact:

Re: Belt tensioning

Post by WillAdams » Sun Jan 18, 2015 1:15 am

In theory, yes. In my experience, they have to be tighter so as not to slip.

The concern is too tight puts stress on the machine.
Shapeoko 3XL #0006 w/ Carbide Compact Router w/0.125″ and ¼″ Carbide 3D precision collets

BigRez
Posts: 29
Joined: Thu Jan 08, 2015 2:11 am

Re: Belt tensioning

Post by BigRez » Sun Jan 18, 2015 1:21 am

I tightened the rear end of the belt, adjusted the front end until the belt clip was ~3/16 inch from the end plate, and then stretched it until the clip touched, do you think that was too much?
Shapeoko 2 Serial #7341. Relatively stock. Custom sound/dust enclosure. 24V 15 amp power supply.

WillAdams
Posts: 8608
Joined: Mon Apr 09, 2012 6:11 pm
Location: Pennsylvania --- south of the Turnpike, East of US-15
Contact:

Re: Belt tensioning

Post by WillAdams » Sun Jan 18, 2015 1:19 pm

Downsides of stressing the machine w/ too tight belts:

- undue wear on motor bearings
- bending the Makerslide/ pulling the machine out of square.
- pulling out a bolt.

It probably makes a belt breaking more likely as well. Probably some other things.

I wonder if past a certain point it ceases to make skipping less likely and begins to lose ground on that.
Shapeoko 3XL #0006 w/ Carbide Compact Router w/0.125″ and ¼″ Carbide 3D precision collets

PGBcustoms
Posts: 2
Joined: Wed Jan 28, 2015 7:56 am

Re: Belt tensioning

Post by PGBcustoms » Wed Jan 28, 2015 9:25 pm

Did you solve your vibration issue? My Y axis vibrates on low feedrates/ slow moves. It slides fine without the belts but once i put the belts on I can feel it vibrate even when i move the axis by hand, particularly when i shift directions. I have tried various belt tensions to no success. I have tried to change the eccentric nuts too but it hasn't help me either. It also doesn't seem like the vibration is from skipping steps or slipping of the belt because i can program some moves and return it back to zero and it returns to the correct zero point.

khauser24
Posts: 30
Joined: Mon Dec 01, 2014 12:41 am

Re: Belt tensioning

Post by khauser24 » Wed Jan 28, 2015 10:36 pm

I wonder if you are mistaking the natural feedback a stepper motor introduces for vibration. if you take the belt off and turn the stepper axis by hand you're going to feel that it is 'bumpy', or whatever you want to call it, because of the way they are made. If that's what you are feeling with the belt on it, that isn't a 'vibration' having to do with belt tension at all...

clockit
Posts: 319
Joined: Sun Nov 16, 2014 11:05 pm
Location: California, MO

Re: Belt tensioning

Post by clockit » Thu Jan 29, 2015 3:26 am

@PGBcustom, I'd look at your v wheels and make sure that they are adjusted properly. I experienced a slight 'chatter' similar to what you are experiencing and found that one of my excentric nuts was a bit loose and another one the adjustment was just a bit off. When i pushed it without the stepper energized it would 'chatter'. corrected the aforementioned issues and it was smooth as silk....
Shapeoko 2, Full Kit #7071, Makita RT0701C Router, 1000 x 1000 upgrade, Acme Z Axis w/Nema 17 Belt Drive

PGBcustoms
Posts: 2
Joined: Wed Jan 28, 2015 7:56 am

Re: Belt tensioning

Post by PGBcustoms » Thu Jan 29, 2015 9:04 pm

@khauser24 The vibration was more similar to an impact driver than the vibrations induced from the x or z axis stepper motors. They were intense enough that running an air pass of a 10 min program I made, I would have to check all the screws and nuts I did not put thread lock on because some would become loose. I was worried the slow movements were exciting the natural frequency of vibration of my machine because G0 commands would not induce the vibrations.

@clockit I was adjusting my v-wheels a bunch because it seems like the obvious problem to no success so I came here. I wasn't sure if I was tightening my belts too much or too little so this thread caught my eye. I have eliminated the excess vibrations with v wheel adjustments and belt adjustments. I changed my adjustment method from using a combination wrench to turn the eccentric nuts until rolling the carriage would make all 4 v-wheels would roll together to using an 8mm socket head and turning it by hand so I could feel when the bottom v-wheels would engage the maker slide. With the combination wrench i would just use like 5 degree turns and check the carriage movement I think the wrench length gave me too much leverage to feel the appropriate position of the eccentric nuts.

To eliminate the excess vibrations I did really need to tighten my belts. I was varying my belt tension by stretching the belt .1" to .2" for very tight. Even with my v wheel adjustments when I would attach the belts I would still get the vibrations. I decided to try even more tension and used the method from the wiki "place one of the 13mm wrenches against the far side of the Allen wrench and use it as a handle to pull the Allen wrench to pull the belt anchor to tension the belt" to stretch the belts about .25" to .3" because I no longer could do it by hand. I am using nema 23 motors so the extra tension may have been needed. With the smoother motion and tight belts I was able to turn down the current potentiometer on my tinyG for my y axis . Only from 1 oclock to 12. At 11 oclock my motors stall out. The lower current also makes the motions seem a little smoother and quieter.

as a side note my belt on my right side would have some perpendicular motion along the length of travel, it would start on the right side of the pulley and end up on the left. It was only about 0.05" displacement over 6 inches of travel. My left belt would stay centered along the length of travel. I thought my makerslide had a twist or was angled a little and tried to adjust it. I wasn't able to change the perpendicular belt movement this way. Once I really tightened my y axis belts both belts stay centered on the pulleys.

Thanks for the quick replies @clockit and @khauser24

Post Reply