Skewness

[mkmarizani]

I have recently joined this spring manufacturer, but it seems has got a problem when it comes to spring squareness.

There is too much resetting of springs(which i would call rework) due to springs being skewed(not square). I will explain the process now. The springs during manufacture a passed through a moving quenching oven, where they are heated to a temperature that will make them ready for quenching and then are tempered after quenching and then ground and Tested for squareness. When testing for squareness a higher percentage is skewed. The process will go back then to try and eliminate the skewness i.e. reworking, whereby we have to heat them again and re-temper them again.

The spring has the following specs: wired diameter d = 14mm, Free Length 243mm, ID 50mm, end grinding is 270-340 degrees.

For those that have encountered the problem of squareness, how did u solve such a problem...Thanks.

 

[israelkk]

What is the squareness requirements?

 

[israelkk]

Sorry, What are the squareness requirements?

 

[mkmarizani]

its 0.015mm per mm of Nominal free length, which is 3.6 from my calculations..

 

[israelkk]

I would use a jig with a vertical tube protruded from a plate. The spring is placed around the tube that support the spring when grinding on a horizontal grinding machine table. If you have many springs to grind the jig can have many vertical tubes protrude from the plate, then the springs are placed over the tubes and are grinded together while the inner tubes hold the springs straight and vertical to the grinding machine table.

 

[mkmarizani]

thank you israelkk

I suppose you mean for crush grinding like, but we use water vertical grinders and we have fixtures to hold the springs in position whilst grinding. At first i thought it was the quenching oven, where we heat the springs before quenching that was causing the problem, but it has minimum contribution. Maybe i should look at the dynamics that goes on during grinding.