Dynamic stiffness of machine tool
Dynamic stiffness of machine tool
(OP)
I have just designed the fixturing and acquire the apparatus to perform a static stiffness test on our machine tool at work. I have not carried out the experiment however as I need to purchase a load cell which I am hesitant to do at the moment as I do not know whether I require an output from a load meter when I come to measure the dynamic stiffness of the machine.
I would appreciate any help you could offer in explaining how to calculate the dynamic stiffness of a lathe. I found a very informative website (below) however the steps to measure dynamic stiffness are missing.
http://www.engissol.com/Article2.htm
Specifically I don't understand how to acquire the vibration data if I use an unbalanced mass.
I would appreciate any help you could offer in explaining how to calculate the dynamic stiffness of a lathe. I found a very informative website (below) however the steps to measure dynamic stiffness are missing.
http://www.engissol.com/Article2.htm
Specifically I don't understand how to acquire the vibration data if I use an unbalanced mass.





RE: Dynamic stiffness of machine tool
I think searching rotating machinery or advanced books in vibration analysis would help you. I vaguely recall doing this in Vib classes, but that would be twenty (20) years ago.
Best of luck with it.
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
RE: Dynamic stiffness of machine tool
In other words, you are probably interested in a plot of Ftool/(Displacement of tool wrt workpiece) against frequency.
This is a tricky thing to calculate, and is also tricky to measure.
If it were a simple structure we would do an experimental modal analysis of the lathe, from which we could derive the dynamic stiffness. In practice the resemblance between values measured on a static lathe, and a running one, would be quite different.
Your static load cell can be used to some extent for dynamic work, look at its frequency response. But bear in mind that in practice we use special purpose low mass load cells.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Dynamic stiffness of machine tool
Having operated several different makes of CNC turning centers and machining centers, knowing the static stiffness can determine the metal removal capabilities of the machine. The dynamic stiffness will need to include the work piece, tooling, and cutting parameters. Kennametal has a system that listens to the cutting tool and adjusts the speeds and feeds to optimize the productivity of you machine and tooling.
This is what we did to test VMC stiffness. We have also done spindle torque tests, and a test of stiffness of KM, Capto, ABS and stick boring bars in a CNC turning center.
http:
RE: Dynamic stiffness of machine tool
RE: Dynamic stiffness of machine tool
RE: Dynamic stiffness of machine tool
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.