Dealing With Noise: Part 1

I worked on the machine to try to eliminate the horrible noise it was making when an axis moves at low speeds. The machine only makes the noise when the motor drives the lead screw and not when the lead screw is turned by hand so it’s defiantly to do with resonance from the stepper motor as said before. I worked with the x-axis adding some silicone pads between the motor and the acrylic in an attempt to deaden the vibration but no joy. I then added some felt padding between the nut assembly, again no joy. I then expected that it could be down to the coupling between the x-axis motor and lead-screw as the coupler was made of aluminium with slots cut into it. This allowed for slight variations in the alignment of the the motor and the lead-screw. If you flicked the coupler it rang like a bell so this raise my suspicion. I lightly grasped the coupler and told the controller to drive the x-axis, the noise reduced, I had found the cause but why and how do I solve it? The machine was vibrating due to the stepper motor and the connection point was the coupler. After some research I uncovered some interesting information relating to the subject

a) couplers especially of the slinky type (slits cut in them, which I have) are prone to transferring vibrations to the machine from the stepper. Use of a special type of coupler that has plastic dampeners within can help with the issue.

b) The nut itself if made of brass (which mine is) is prone to vibration and backlash. Use of an anti-backlash nut made out of plastic or nylon can help.

c) Use of a unsupported lead-screw (again, which mine is) can cause the lead-screw to vibrate. Either the use of a fully supported rail or stretching the lead-screw between the bearings can ease or eliminate the vibration.

I decided to go for a couple of solutions. Firstly I only had one side of the x-axis lead-screw supported by a bearing and the other directly coupled to the motor by a flexible coupler. To support the lead-screw I need to add a bearing in front of the coupler which would allow me to stretch the lead-screw between the two points.

Secondly I ordered yet another motor coupler this time of the leaf type variety with internal dampeners (well, a Chinese copy which will be hear by the end of January). In the mean time I discovered that sticking some tape around the coupler deadened the noise slightly.

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