VC300 belt tension?
Just ran for first time, didn’t realise was so out..
Is higher or lower better? I take it the higher up the graph the slacker the belt?
What’s good numbers?
13 Replies
xenial-black•2y ago
This graph can not provide u information about the absolute Tension of the belts. It can only provide Information about the belt tension relative to each other. It can provide Information about underlying Problems with your CoreXY-System too, e.g. loose bolts.
The belt-tension can be measured with the Help of the frequency. Looking at your Graphs the peaks are at the same frequencys, so the belt tension of both belts is similar. The peaks don't have to be the same, but should be at located at the same frequency.
Here is a good video about how to read and analyze input shaper graphs:
https://www.youtube.com/watch?v=M-yc_XM8sP4
3D Printers & a Whiteboard
YouTube
How to Read and Analyze Input Shaper Graphs Generated by Klipper
This video is supposed to be a brief overview on what the input shaper graphs can tell us. It is the first video of a series of videos which will give a more in depth view on the kinematic system and input shaping in Klipper.
As always: feel free to jump to those parts, that help you with your problems:
00:00 Intro
00:57 What we can learn from...
xenial-black•2y ago
If u want to know if u have the right belt tension, u can calculate the necessary frequency with mersenne's laws.
The formula for the fundamental frequency is:
xenial-black•2y ago
L is the free length of the belt (for my VC400 i moved the X-Gantry that the distance between the two pulies is 0.2m or 200 mm )
F is the belt tension force (I did my calibration with 13,3447 N or 3 lb, which is the minimum Force for a 9mm GT2 belt)
µ is a Material constant, the weight per length (Here i used 0,01245 kg/m)
With the given parameters the frequency is 82 Hz.
To measure the frequency of the belt i used the Spectoid app. U just need to deflect the belt and look at the frequency where the belt is swinging out.
If you are at a lower frequency you need to tighten the belts more, and loosen the belt if you measure a higher frequency than 82 Hz.
And you have to move the toolhead after adjusting the belt tension, before you measure the frequency again to make sure the tension is even in the whole belt.
constant-blue•2y ago
(Even though following no notification 😑) Many thanks for all that.. I’ll ponder over and see what I can make of it 😅 👌
One thing.. with the 82 Hz.. is that on the belt tension graph or on a frequency analyser?
xenial-black•2y ago
The 82 Hz are on the frequency analyser
xenial-black•2y ago
Here are my measurements for reference:
constant-blue•2y ago
Legend 👍
Just watched that vid, and I was always trying to get the power and freq the same 😅
xenial-black•2y ago
Glad i could help, if u have more questions just ask and i'll try my best to answer them ^^
constant-blue•2y ago
Thanks that would be awesome 👍
adverse-sapphire•2y ago
82hz on spectoid? That seems awfully far from the 120-130hz others recommend
xenial-black•2y ago
If you use a 6mm belt the frequency will be Higher since the Material constant is lower. The next Factor ist the free distance of the belt used for the measurement. The third Factor is the force in the belt system. The minimum is 3 lb for a 9mm GT2 belt. Others use a force of around 6 lb but this reduces the Lifetime of the bearings because of the higher loads.
So a higher force result in a higher frequency. 82 Hz is the minimum.
Do you know what the free belt length for the 120 to 130 Hz is?
adverse-sapphire•2y ago
I don't know off hand, but I did not consider that I was comparing it to 6mm belts (vzbot). 82hz seems super loose on my 9mm setup, but I'd be happy to give lower tension a try based on your info
xenial-black•2y ago
After looking through the Nema 17 datasheet there is a given value for the maximum radial force in N, 20 mm away from the Flange. This force is 28 N.
The belts on the VC have a warp angle of 180°. Because of this the load on the shaft is two times the belt tension force, therefore the maximum belt tension force is 14 N. You can apply a higher load, but this shortens the lifetime of the bearings in the stepper motor.
After some research i think 150 mm is often used as free belt length (I could be wrong there though). For a 6 mm GT2 belt the mass per length is around 0,0091 kg/m.
With a belt tension force of 13,3447 N i get a frequency of 127,6 Hz.