Which belt tension gauge do I need?

2

1

I have a 3D printer that is going crazy with x-axis shift, and I need a tension gauge belt to measure the tension.

I've never used one before, and looking online, I can't tell which one would be the right fit.

Any ideas? What things should I look for?

Bashar Abdullah

Posted 2016-04-12T07:13:43.367

Reputation: 123

What kind of printer is it? Most Cartesian printers that experience X-axis shift are having problems with fatigued electrical wiring to the X stepper or X endstop. – Ryan Carlyle – 2016-04-12T14:35:37.590

@RyanCarlyle It's Cubicon. Not popular brand in West. Korean made. Supposed to be good. But soon after getting it, this started happening. Part of their troubleshooting suggested checking the belt – Bashar Abdullah – 2016-04-12T20:17:22.923

Looks like a cartesian XY gantry printer, from a quick googling. If you can pluck the belt like Tom mentioned and get a low note, but still get X axis shifting, my next guess would be bad X motor or X endstop wiring. – Ryan Carlyle – 2016-04-13T02:04:23.947

Answers

6

It's extremely unlikely that belt tension is actually your problem. I've never heard of anyone using a gauge to measure their belt tension. Typically you just pull your belt tight by hand so that it produces a low note when plucked. It's far more likely that you're experiencing shifts due to too high or too low stepper current.

Unless your belt is so loose that it easily skips over the pulley (which should be obvious without using a gauge) or so tight that it completely binds up (it would be impossible to get it that tight without some kind of superhuman force) it's definitely not the problem.

Tom van der Zanden

Posted 2016-04-12T07:13:43.367

Reputation: 14 003

1I've read of people using smartphone apps that calculate the belt tension by measuring the frequency of the plucked belt. If you (the TO) are completely lost and need any kind of confirmation this might be a way to get it easily. – kamuro – 2016-04-12T10:00:39.713

1I used a spring scale (meant for fishing). But it's really not critical. Just make sure it's not skipping teeth on the pulley and you should be fine. – TextGeek – 2016-04-12T17:34:17.600

1I tensioned the belts of my delta printer equally tight solely based on their note when plucked. If you have an ear for music, that should be fairly straightfoward. – Tormod Haugene – 2016-04-12T18:42:32.517

@kamuro thanks, will do if needed. Although now it seems not the issue. – Bashar Abdullah – 2016-04-12T20:18:44.693

@TormodHaugene alright. Although now it seems unlikely this is the issue. – Bashar Abdullah – 2016-04-12T20:19:59.357

@Tom van der Zanden Any tips how to know if this is stepper current problem?

I'll most likely end up opening separate thread for that. But it would be good to have more info. – Bashar Abdullah – 2016-04-12T20:24:21.600

1@BasharAbdullah your issue is one of possible signs of current problem :) #1. Check resistor on your SS (right next to black central chip. #2. There should be R200 or R100 so R=0.2 or 0.1 #3. Read current (I) value from motor label #4. V = I * R * 8 #5. this is max voltage which should be set on SS #6. set it and check if your printer works ok #7. if not - reduce it 10..15% and chceck if this helps. you can repeat #7. – darth pixel – 2016-04-13T08:54:29.730

@darthpixel thanks. I'm new to 3D printing really, so will try to tinker and see where I get :) – Bashar Abdullah – 2016-04-14T06:51:56.687

1

People are using this to tighten the belt but I would totally agree with @Tom - there is no need to use such devices or gauges and your problem lies in stepsticks current.

It would be also problem with endstops so PCB doesn;t know it's time to stop :)

darth pixel

Posted 2016-04-12T07:13:43.367

Reputation: 3 363

Can you explain how this belt tensioner (if that is a correct name for it) works? – kamuro – 2016-04-12T10:01:50.997

2@kamuro it's just a spring that you put on the belt. It isn't really a tensioner (you still have to pull the belt tight somehow) but it helps keep the tension consistent. – Tom van der Zanden – 2016-04-12T10:03:37.993

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In the meantime I found the idea by image searching 'belt tensioner', too: http://www.iheartrobotics.com/2009/11/timing-belt-tensioner.html The search also turned up lots of other interesting tensioning designs used in various other (industrial) sectors, too. Sweet inspiration ;)

– kamuro – 2016-04-12T10:05:32.667

1On another note, I would assume that the current of the stepsticks also is a less important effect. I would take a look at the axis motion friction first. Parallelity of rods first, if the strength of the effect is varying depending on the position. – kamuro – 2016-04-12T10:09:17.150

1Well - depending on drive train design - this effect can also apear because of low wrap angle. Which means that timing belt surrounds a pulley not enough. – darth pixel – 2016-04-12T11:32:55.023

1@kamuro as TvdZ said - it's not real tensioner it's more like laundry clip but it works fine so why not to give it a try :) But be careful it cost even $2 (as a "tensioner") but if you buy 10 laundry clips you will get 10 "tensioners" for half od dollar. – darth pixel – 2016-04-12T11:38:26.690

I didn't want to diminish the idea of using a belt tensioner at all, sorry if it came across like that. – kamuro – 2016-04-12T11:41:43.077

@kamuro not at all :) – darth pixel – 2016-04-12T11:48:44.807

I would advise AGAINST using that kind of belt tensioner. Springs anywhere in your drivetrain add ringing at corners. The last thing you want in a precision motion control device is stretchy belts. – Ryan Carlyle – 2016-04-12T14:35:00.617

@RyanCarlyle Are you sure about that? It seems these spring-type tensioners are used in "professional" printers (Ultimaker comes to mind) and even some mass-market 2D printers. In any case, this problem is likely not about belt tension. – Tom van der Zanden – 2016-04-12T14:44:04.870

@RyanCarlyle don't you think these tensioners are just compensate sudden de/acceleration. Belt itself is not stretchy, its dimension change during acceleration only then it gets back to normal so counting whole amount of the movement dimension doesn't change a bit. Timing belt itself is doing the same by its nature isn't it? – darth pixel – 2016-04-12T16:45:51.477

2Yes, I'm sure. A spring-tensioner is better than a loose belt, which is why some Ultimakers have them (particularly since getting even belt tension on a UM gantry is hard) but a rigid tensioner (adjust and lock) is superior to a spring tensioner. We use fiberglass-core and aramid-core timing belts in 3D printers for a reason, because they're as stiff as possible in tension. Spring tensioners makes the belt more stretchy. Specifically, when you turn a corner at positive velocity (jerk>0) any springiness in the drivetrain causes increased overshoot and therefore ringing. – Ryan Carlyle – 2016-04-12T17:01:19.850

Should add here that if the clothes-pin spring tensioner is nearly fully extended, it will be fairly stiff, because the geometry creates a force multiplier to make the spring apply a lot more tension. (EG see http://physicsbuzz.physicscentral.com/2015/04/physics-life-hack-number-3-getting-your.html) But if the spring tensioner is taking up a lot of slack and is not extended, it will add springiness to the belt.

– Ryan Carlyle – 2016-04-12T17:25:55.450

thanks all for the input. Lots of useful info and tips to consider. – Bashar Abdullah – 2016-04-13T08:41:32.023