I am developing an imaging device, in which a negative pressure pump (KNF negative pressure pump) is used（Fig 1） .
The pump causes vibration to the imaging system. If I turn off the pump, the vibration disappears. I tried to fully isolate the pump with isolator, the isolator such as ordinary rubber, polyurethane shock pads, etc.(Fig 2), but not enogh. Is there a better way? thank you.
Hello Peng Zhang ,
You can try Sorbothane. Follow the below link for detailed explanation:
https://www.sorbothane.com/technical-data/articles/sorbothane-and-the-vibration-damper/
PFA of the product range avaialable for the same.
Haresh Bhanushali , Thanks for your reply. In fact, I have tried many shock pads, and the effect is very poor except for the insulation cotton
Dear Peng,
You can find in web repositories many encyclopedic papers on machinery vibration isolation; first of all you have to understand the difference between vibration decoupling (a rupture of structural impedance) and vibration damping (turning vibration into heat)! (sorbothane provides a higher damping compared to rubber but this does not make it better if decoupling is the primary issue...)
Introducing decoupling devices create at least 6 new resonance frequencies (and many more if the machine is not perfectly rigid) and they have to be carefully tuned off the excitation frequencies (of your pump). High performance vibration isolation CANNOT BE ACHIEVED BY CHANCE, you must implement a proper vibration control engineering process.
Good luck - or seek for expert support!
Bernard Garnier ，Thank you for your kind reply. I do consider a little about decopling. I try to adjust both elasticity and damping, but it is not OK.
I will try your suggestion, Thanks a lot.
Try to find out the natural frequency of the system, then choose operating rpm of the pump that are quite far from (much higher or much lower than) the system's natural frequency. This way, the vibration of the pump will be isolated in a natural manner.
Junaid Najmi ，thank you.
In fact, the operating frequency of the pump is 50HZ, and the natural frequency of the optical system is unknown. It seems that the frequency of the pump is not close to the optical system of interest.
I will consider your kind suggestion. Thank you.
In Fig 1 - it looks for me as if the pump is sitting on top af a rather fragile long "tower"? Is this the only possible way to use the pump?
Placing an active element (vibrator) at the end of a long extension is kind of asking for trouble.
As previous mentioned from Bernard Garnier - proper isolation demands to know a lot of input parameters and to make some calculations.
You could try to add a rather heavy mass (block) directly to the pump and then use the damper pads below. Assuming that the pump is generating only a certain amount of vibration energy - and the system is not in resonance.
Andre Pevestorf Thank you. ''the pump is sitting on top af a rather fragile long "tower"?'', you are right this must be not good. I will try to switch the positon
Dear Peng, is hard to give specific advice without knowing all the details. As Bernard Garnier rightfully notes, this requires a systematic approach. There is a recent book on precision vibration control, titled Vibration Control for Optomechanical Systems, World Scientific, 2022, ISBN 9789811237331 that attempts to provide just that.
Thank you for your kind suggestions。The problem is solved.First of all, as a temporary method, I chose a metal spring with a lower rigidity to damp the pump, and the effect is good. Then, I strengthened the optical structure, so that the optical shock resistance is improved, and it is not sensitive to the vibration of external sources such as pumps.
Thank you everyone.
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