0.05mm straight edge measurement method ?

[591996]

Hi,
I dont know if im in the right area but heres my problem
I need to accurately defining the profile of a sheared edge of a piece of sheet steel [pressing]. my sheared edges have to be within 0.05mm of straight (if you butted something perfectly straight up against it)
how would i measure this? I read something about optical shadowgraphing?

Has anyone got any tips?

Thanks

Dave

 

[unclesyd]

That's a pretty good edge for a shear.

If you have access to an optical comparator or shadow graph or maybe just a light box all may do the job. The comparator will measure the gap, the shadow graph is a Go::NoGo, the light box is a judgement call.

What is the size and shape of the part, especially the edge that needs to gauged?

Can you better explain your straightness requirement.
Is it the largest deviation to be measured form the standard?
Do you need a measurement or just a Go::NoGo assessment?

 

[NickE]

What thickness and hardness of steel are you stamping?

 

[591996]

Hi thanks your your reply. Maybe this diagram will help. I need to measure if the sheared edge is > or < 0.05mm off straight. What exactly is an optical comparator?

The average size of the parts are about 500 x 350 mm . Sheared edge should be as straight as possible. is high tensile 2.0mm material

thanks

 

[591996]

[obviously the diagram is greatly exagerated]

thanks

 

[NickE]

591996- More detail please. Hi-Tensile does not really describe the alloy. I know that Sandvik has a material called Hi Flex- but it is not usually supplied at 2mm.

2mm is very thick for getting a very perpendicular cut edge. At 10% clearance you need 0.020 between the punch and button. That eats almost half your tolerance.

You might try fineblanking, there is far less clearance on a fineblanked edge. I dont think high hardness materials lend themselves to fineblanking.

As for your inspection try googling a few of these resources:

Optical Gauging Products
Optical Comparator
etc... suggestions from above.

If you only need to do a few inspections you can prepare metallurgical mounts and polish them. It will then be simple to measure using a relfected light on a shadowgraph.


Nick
I love materials science!

 

[591996]

Thanks for replying, im unaware of the exact material properties. its classified! lol. the criteria is achievable as ive seen the quality reports. i just gota figure out how to measure some samples. i'll do some google research on optical guages thanks

thanks again

 

[ewh]

An optical comparator is basically a light table with zoom capability.

 

[NickE]

surface plate, 90degree block, feeler gauges?

(50um in 2mm is 1.43degrees. so the tolerance for perpendicularity is 88.57 to 91.43) <--is the following correct?

 

[591996]

Thanks all, feeler gauges have been used initially although his method is not acceptable for time reasons etc
Im still researching optical gauges

Thanks again

 

[BillPSU]

How long are your pieces? If the parts are short enough use a granite table with right angle blocks. Hold the part vertical Using a transfer stand and an indicator set both ends to the same height and measure the differences between the ends.

 

[591996]

Thanks Bill, ive been looking at the granite tables, some of the parts are quite big,so its an option at the minute

thanks

 

[tripleZ]

Granite block, toolmakers vice, and an indicator/stand in 0.0001" increments maybe? I'm assuming you have parallel surfaces to clamp off of. Set-up the part in the vise indicating both ends into a "0" point. Then it's a simple check to measure variation along the entire length. Just make sure to move your piece/vice combo and not the indicator. Standard Brown & Sharpe indicators with a 0.015" diameter ball-tip should work for what you need.

Optical comparators would work as well, but the length of the workpiece may be prohibitive if you're trying to check the entire length at one time.