Squareness of a spring
Squareness of a spring
(OP)
The spring in question is an extremebly high stress, very high cycle requirement, top of the line material, bee hive shaped spring. What I mean by that is both ends are smaller than the middle section.
For the past 15 years we have been measurign the squareness of the end by setting the part on a flat surface and laying a digital protractor on the top and taking the reading. I realize this is not correct, but that is what we have done for years without complaint. Well, now our customer is arguing with us about our parts, they say they are out of square and we say they are in.
They measure the part by setting round cylinders in the end coils with a shaft between themselves. The shaft then centers it self and pushes on an idicator that reads a degree of square. (sorry no pictures, only saw the device once myself). My issue with this is that the ends of the spring are not true circles, the ends are a varying pitch that forms a Spiral of Archamedies.
I can not accept their method of measurement, and they will not accept ours. Anyone have any ideas how we might check for squareness?
For the past 15 years we have been measurign the squareness of the end by setting the part on a flat surface and laying a digital protractor on the top and taking the reading. I realize this is not correct, but that is what we have done for years without complaint. Well, now our customer is arguing with us about our parts, they say they are out of square and we say they are in.
They measure the part by setting round cylinders in the end coils with a shaft between themselves. The shaft then centers it self and pushes on an idicator that reads a degree of square. (sorry no pictures, only saw the device once myself). My issue with this is that the ends of the spring are not true circles, the ends are a varying pitch that forms a Spiral of Archamedies.
I can not accept their method of measurement, and they will not accept ours. Anyone have any ideas how we might check for squareness?





RE: Squareness of a spring
-Tony Staples
www.tscombustion.com
RE: Squareness of a spring
http://w
The price is right at $9.50, and it says that it covers squareness and parallelism.
Regards,
Cory
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: Squareness of a spring
The problem is that the ends are an ever expanding spiral, so there is no good way to find a centerpoint to test off of. This is a sort of un-conventional spring in a manner of speaking.
RE: Squareness of a spring
What I'm really suggesting is to find a third way to make the measurement where you and the customer might reach common ground.
The hardball way to handle this (and bring it to resolution quickly) is to agree to test the springs with their test method and let them know what the price increase is going to be based on the new reject rate.
RE: Squareness of a spring
What tolerance on squareness are you working to?
We may be able to suggest better mearsuring technique's once we know the accuracy expected.
According to my associated spring design handbook a commercial tolerance on squareness is 3 degrees.
It also shows a method of measuring squareness by standing a spring on end on a horizontal flat surface and bringing it upto a straight edge vertically positioned off the horizontal flat surface, the spring is slowly rotated and the gap between the body of the spring and vertical straight edge is measured and recored as the spring is turned, the spring is then placed on its other end and the same procedure is repeated.
They also check parallelism by standing the spring on one end and recording the variation of the free length on top of the other end by taking measurements around the circumference of the top coil.
In your case with a barrel shaped spring you would need to bring the largest diameter coil in contact with the vertical
straight edge then rotate it and measure any gaps as they occur.
regards
desertfox
RE: Squareness of a spring
I actually have to laugh at your suggestion of how Associated spring guide tells you how to measure. We tried that, and it didn't work. Furthermore I have to laugh, because my boss, actually wrote that when he worked for Associated years ago. Between him and a few other, they wrote that design manual.
I think I agree with sreid, and use a CMM to generate the planes. I will just need to make sure the inspector understands that the part does not have true circular ends, so they need to adjust for the offset....
RE: Squareness of a spring
RE: Squareness of a spring
RE: Squareness of a spring
Yeah, it seems like everyone worked for Associated at one time. From what I hear, they were one of the best companies to work for back in the 70's....
Everything in that method didn't work, the way the springs arr manufactured, they have a slight lean and it skews that method of checking.
RE: Squareness of a spring
I didn't work for Associated springs (Barnes) but have great respect for their role and contribution to the spring design and analysis area. When the plate sits flat on the spring end it defines the end flatness (three points in space define a flat surface). Any other method like CMM prove to be false. I fail to see how it will determine the exact three points on the spring end that will touch the flat plate (however I may be mistaken).
RE: Squareness of a spring
"Any other method like CMM "MAY" prove to be false."
RE: Squareness of a spring
Your customer has a requirement for the geometry of the spring, in order for it to suit their end use. They've told you (or can tell you) what that requirement is, in the form of a gaging method. Regardless of terminology (squareness of a doubly-tapered helix?!), they want it their way, so cost it out and send them the updated pricing. They can decide whether to pay you or let you continue doing it your way.
RE: Squareness of a spring
I'm afraid if I were to reccomend that, I would be seeking employement in the very near future... Others in the company have warned me about that on this particular product line....
I have a meeting with them in December, at that time I am going to poke all sorts of holes in their gauge, and get them to see the light... (hopefully)...