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doa
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any guide to find proper belt tension?

Aug 13, 2018 7:27 am

Hi,

is there any way to measure the tension of the belts to show whether my tension is good or not? Belt Status does not refresh, I still have X276/Y319 and my belts are quite tense.

I thing everybody would welcome some guide, knowing that some instruments are needed.
for example I have seen somewhere:

- move the X axis to the right side
- prepare a 100g weight
- hang the weight to the upper belt (because the lower does not have a space to move vertically)
- belts should be 5mm from each other in the point where the weight is hanging


anybody from Prusa Teams to consider this as an optional standard? For people who don't have a ruler and 100g weight should be the assembly instructions sufficient. But I don't really have much time to try-fail, especially when the Belt Status numbers are not changing, whatever I do

thanks

Best Answer by Dreide » Aug 13, 2018 5:15 pm
mgx0 wrote:
Aug 13, 2018 4:07 pm
Just one thing, which belt part is tested? On X axis it's clear upper shorter part. But Y? Both can be plucked. What do you have and which part of the belt?
Yes, for X I use the upper part (after having pushed the motor all the way to the left), and I aim for 74Hz. Note that especially with high tension, the tension might depend on the Z position as the Z axes give in to the belt tension more easily at mid Z levels than close to MIN or MAX, but I actually never tested this systematically. Therefore, I suggest measuring X belt tension after Z homing, so when the X axis is close to the bed.

For Y it would be the lower part and I aim for 66Hz (motor position doesn't matter here).

It would be interesting to know what belt tension others use in terms of pluck frequencies under these measurement conditions.

Regarding Prusa's belt status values, I consider them useless. I think the values are even not consistent across firmware versions, and they have a poor resolution and accuracy. For actually adjusting the belt tension instead of just checking them, the frequency method is so much faster anyway - and kind of fun.

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RHDreambox
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Re: any guide to find proper belt tension?

Aug 13, 2018 7:39 am

You have to run a Self Test (Calibration / Self Test) to update the Belt Status.
Happy owner of a Prusa MK3

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doa
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Re: any guide to find proper belt tension?

Aug 13, 2018 8:03 am

tried that, numbers did not change. I tried an extreme: loosen the belts so that they don't skips any steps but they were visibly loose. other extreme was tighten the belts so that I could play a guitar. In both scenarios the Belt Status did not change at all

Dreide
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Re: any guide to find proper belt tension?

Aug 13, 2018 1:01 pm

You can use a smartphone for measuring the frequency while plucking the belt. This is a quick and accurate method. See also others-archive--f66/use-free-span-frequ ... tml#p73398.

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RHDreambox
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Re: any guide to find proper belt tension?

Aug 13, 2018 2:19 pm

mgx0 wrote:
Aug 13, 2018 8:03 am
tried that, numbers did not change. I tried an extreme: loosen the belts so that they don't skips any steps but they were visibly loose. other extreme was tighten the belts so that I could play a guitar. In both scenarios the Belt Status did not change at all
Perhaps you should reload the latest firmware again. There may be something that has hung up.
Happy owner of a Prusa MK3

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doa
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Re: any guide to find proper belt tension?

Aug 13, 2018 4:07 pm

Dreide wrote:
Aug 13, 2018 1:01 pm
You can use a smartphone for measuring the frequency while plucking the belt. This is a quick and accurate method. See also others-archive--f66/use-free-span-frequ ... tml#p73398.
That's exactly what could be provided!

Just one thing, which belt part is tested? On X axis it's clear upper shorter part. But Y? Both can be plucked. What do you have and which part of the belt?

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doa
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Re: any guide to find proper belt tension?

Aug 13, 2018 4:08 pm

RHDreambox wrote:
Aug 13, 2018 2:19 pm
mgx0 wrote:
Aug 13, 2018 8:03 am
tried that, numbers did not change. I tried an extreme: loosen the belts so that they don't skips any steps but they were visibly loose. other extreme was tighten the belts so that I could play a guitar. In both scenarios the Belt Status did not change at all
Perhaps you should reload the latest firmware again. There may be something that has hung up.
I would do a full reset, load the FW, reset again and calibrate. Will come up with results. Thanks

stephan.k
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Re: any guide to find proper belt tension?

Aug 13, 2018 5:06 pm

I gotta ditto the issue with belt status. It's pointless.. Between sloppy as heck and tight as I dared to tension it, the result after self-test remains stuck.

As so many of the "smart features", this, too, seems not quite working. :-(

Dreide
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Re: any guide to find proper belt tension?

Aug 13, 2018 5:15 pm

mgx0 wrote:
Aug 13, 2018 4:07 pm
Just one thing, which belt part is tested? On X axis it's clear upper shorter part. But Y? Both can be plucked. What do you have and which part of the belt?
Yes, for X I use the upper part (after having pushed the motor all the way to the left), and I aim for 74Hz. Note that especially with high tension, the tension might depend on the Z position as the Z axes give in to the belt tension more easily at mid Z levels than close to MIN or MAX, but I actually never tested this systematically. Therefore, I suggest measuring X belt tension after Z homing, so when the X axis is close to the bed.

For Y it would be the lower part and I aim for 66Hz (motor position doesn't matter here).

It would be interesting to know what belt tension others use in terms of pluck frequencies under these measurement conditions.

Regarding Prusa's belt status values, I consider them useless. I think the values are even not consistent across firmware versions, and they have a poor resolution and accuracy. For actually adjusting the belt tension instead of just checking them, the frequency method is so much faster anyway - and kind of fun.

User avatar
doa
Posts: 100
Joined: Jun 03, 2018 6:53 pm
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Re: any guide to find proper belt tension?

Aug 13, 2018 6:48 pm

Dreide wrote:
Aug 13, 2018 5:15 pm
Yes, for X I use the upper part (after having pushed the motor all the way to the left), and I aim for 74Hz. Note that especially with high tension, the tension might depend on the Z position as the Z axes give in to the belt tension more easily at mid Z levels than close to MIN or MAX, but I actually never tested this systematically. Therefore, I suggest measuring X belt tension after Z homing, so when the X axis is close to the bed.

For Y it would be the lower part and I aim for 66Hz (motor position doesn't matter here).

It would be interesting to know what belt tension others use in terms of pluck frequencies under these measurement conditions.

Regarding Prusa's belt status values, I consider them useless. I think the values are even not consistent across firmware versions, and they have a poor resolution and accuracy. For actually adjusting the belt tension instead of just checking them, the frequency method is so much faster anyway - and kind of fun.
perfect, thanks a lot. excellent idea, maybe we can share our settings here. I made it X75 and Y65 after XYZ homing. It's quite hard to measure the exact value because of the loudness (or quieteness?) of the sound, microphone sensitivity (50Hz is a pretty low value), but a measured range 70-80Hz would be enough. A lot more enough than the tensioning is described in the building manual.

Values are pretty much useless, I agree. Now I have done full reset of EEPROM, reload firmware 3.3.1 and Belt Status says X274 Y315, which is nonsense. It shows same values when my belt played 110Hz or 50Hz.

for iOS I recommend SpectrumView https://itunes.apple.com/us/app/spectru ... 62922?mt=8, alghough it's good to pay for pinch and zoom feature, it's needed for this. There are also other apps available, but I already own this, so I used.

thanks a lot. from now on all my prints will be amazing! :mrgreen: :mrgreen: :mrgreen:

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