Spring Rate measurement error

[kkg123]

our Spring Rate tester readings & suppliers readings are not matching. hence we asked third party readings through NABL accredited lab. these readings also are not matching with earier both the readings. all the tester have been calibrated.

in this case how to go ahead?
are master springs (having defined values) available?

Kedar

 

[MikeHalloran]

There may well exist testers that can directly display a spring rate, but I have never seen one. Every tester I have used displays or allows measurement of a force and a corresponding length, from which you take a set of samples at different lengths and then compute a rate.

Since you have provided no useful information, you cannot reasonably expect a useful answer.

You might start by providing the detailed spring dimensions, and the make and model numbers of the testing machines which appear to disagree.



Mike Halloran
Pembroke Pines, FL, USA

 

[GregLocock]

Also, how much do the rates differ? Are the different labs using the same profile for the end plates? Are they measuring the same springs, or just springs made to the same drawing?

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[BrianPetersen]

Make the measurements on all of the testers using the same spring. Not just the same part number, but the SAME spring. Carry it with you to personally verify, if needed.

Once upon a time, I got a supplier off our backs for building parts that were allegedly out of tolerance by demonstrating that they couldn't measure the dimensions with sufficient repeatability. "How can you tell us that our holes are out of position, when you can't even measure them that accurately?" Same part, measured twice on the same fixture, same hole somehow magically moved by half a millimetre ...

 

[GregLocock]

Oh, and are they using the same test procedure?

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[BrianPetersen]

That's a darn good question to ask after you demonstrate that the SAME spring measured in three supposedly calibrated instruments gives (allegedly) different results.