Dampening

[Creech]

Hello, in a press shop I need to weigh very small parts (30-20 g) and need to read to +/- .5 g. I'm afraid the vibrations may cause incorrect readings. Is there any dampening materials or methods I can use to isolate the measuring equipment. Also how can I measure magnitude in the shop. Thanks

 

[tlee123]

I suppose you could build a platform, supported by springs and then use a dashpot to damp the resonant frequency of the spring-mass system.

But why do this because:

1) I would think most good electronic scales have built-in electronic damping. The one we use has it, and it makes +/- .5 gram readings easy in the shop. It's more difficult with .05 grams.

2)Many mechanical scales have built-in damping also. My guess is that they use eddy current dampers because they're frictionless.

Good luck.

Tom

 

[GregLocock]

Tom, ever worked in a press shop?

We do it by building a booth mounted on a rubber mat. The roof of the booth keeps the area clean. The rubber mat isolates the booth from the floor vibration. That may be overkill.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[GBor]

Well, it seemed too simple to suggest that tlee123 just place a rubber mat under the scale...I assumed I was missing something.

 

[wes616]

My vibrations professor at uni told me for vibration problems the simple solutions are always the best; either increase the mass, or add a mat, and see if it changes anything.

Wes C.

 

[mrMikee]

I agree that it's a good idea to try the simple and low cost solutions first, because sometimes they work. As wes616 says the parameters we could control are the mass and stiffness (of mat) of the system. A rubber mat will probably be effective for the higher frequencies an may well be adequate. If not the mass will have to be increased and/or the stiffness made less, in order to decrease the natural frequncy of the isolation system. It depends on magnitude of disturbances, site conditions, etc.

Regards,
-Mike

 

[MintJulep]

Just for the sake of discussion...

Any sort of spring scale is obviously susceptable to oscillation related inaccuracies.

However, in the "ideal" world that they taught us about in school, it would seem that a true balance would be less susceptable (I hesitate to say immune) to vibration of its base. Any forces are applied equally to both sides of the balance.

I'm sure that in the real world this doesn't hold fully true.

From a more practical perspective, would it be possible in your application to weigh 100 parts rather than 1?

 

[diamondjim]

Sorbane is touted as being especially
good for absorbing vibrations. Do not
know if they make mats or not. I know
they make foot inserts and heel cushions
for us weekend warriors.

 

[diamondjim]

Another dumb thought in the night season.
What about a floating system?
Can you float the scale in a small tub?

 

[tlee123]

I guess the point I was making above didn't come thru too clearly. My point was that Creech shouldn't have to do anything fancy if the damping is already built into the scale. He's only looking for +/- .5 gram accuracy on a 30 gram part.

I agree. Try the simplest solution, which would be to do nothing and see if it works.

 

[Leo01]

In our lab, we use a 30# slab of Granite under the scales to kill any vibrations. It works great down to .001 gram I know for sure.
Lee