Speed restriction.. is it possible ?
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I hav a couple of printer, they have ballscrews on X and Y axis. The "propblem" is (already asked to the motor manufacturer) is if I run a 42/45 mm/s speed and in the middle of X position (printherad at the middle of the ballscrews lenght) you can hear a vibration starting to grow up till the vibration becomes an earthquake and only when moving on negative direction.
manufacturer says Im hitting the resonance point of the setup. This problem never happens with any other speed.
So my question is: is there any way from firmware to restrict this range of speed of being used? -
@Tinchus thats exactly what Input Shaping does
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@oliof But The vibration Im describing has no visible effect on the print, so how can I measure the vibration (I dont have special equipment for that)
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@Tinchus Download an audio frequency finder and use your phones mic as the input. alternatively you can put the phone against a surface that would "hear" the vibration as this is a quick engineering hack.
Then use the input shaper to try and cancel the frequencies being generated.
However this is unlikely to fix the issue as whipping of a ballscrew is not an impulse vibration but instead a constant generating frequency. the best bet is to either limit the speed via max speed limit, or add dampening to the ball screw.
(this could be adding a bit of slop to the screw, or another item to absorb the vibrating force before it can grow.
If you are using very high quality ball screws, you might be able to get away with constraining one end (if you are using a pillar block setup) and replace it with a compliant spring holder. enough to hold it in position, but also to flex absorbing the frequencies when its generated.) -
@Notepad Thanks for the feedback. Yes! I already tried the phone aprouch, not really sure yet how precise the app reading is but I have that data. I also found that input chaping ahs a grapgh where vibrations are shown, so Im in the process of getting an accelerometer in order to start test.
Yes, I have really high quality ballscrews. Im still not sure that resonance is born on the ballscrew itself and not on the stepper motor. The ballscrews are already included on the steppers, the re is no connector between them.
At the other end of the ballscrews since they are really straight, they are fixed into a a cnc with a bearing where the ballscrew tip fits. I was thinking on modify this and put some kind of rubber dumper and see (again: Im not sure if vibrations is being created by resonance on the ballscrew or in the stepper) -
@Tinchus From my experience most of the resonance when it is speed specific will be related to any mass that is not perfectly centred on the ball screw (i.e how much of a banana the screw is). The motor will have its own resonance, but its exceedingly hard to mitigate that without straight up changing the type of motor.
Your right to think about changing the tip of the screw from a hard clamp to some form of plastic dampening clamp. it can still hold up the tip and provide a little bit of dampening enough to remove the resonance.
You can see a similar system used on the Prusa XL or our Construct1 XL printers
(obviously these are threaded rods, but they work the same for ball screws)
