Thread measurement in light out manufacturing.

[Bruce Caulley]

Morning all,

I would like to know how any of you are going about thread checking on machines that run untended. I think it would be easier to trust repeatability if thread milling, but what about tapping? We could improve this of course by using only carbide drills and coated taps, but how can we be sure?? We could get a couple of thousand acceptable holes, but many of our customers demand that core size and PD are kept to ridiculous tolerances as well.

 

Our 3 year plan includes no manned operation between recieving raw material and having a robot deliver finished parts to dispatch. Since most of our work is flight critical and/or defence related our biggest challenge in lights out production is going to be QC.

 

What to do???

 

 

Bruce

[Psychomill]

Not sure that you really can short of checking some in the morning. If a part has "hundreds" of holes though, you could implement a backup tooling system if your machines are capable of that. That way, when the "time is up" for tool life, the machine can automatically use the backup tooling from that point on. Change the "worn out" tap for a fresh one, reset the tool life. Then when the 'other' tap times out, the machine can switch back to the original "tool" and the cycle just keeps going back and forth.

 

If you don't have that option on your machine, another way to control this is to program a macro that "changes tool" for you. I've done this in Makino cells. Basically, in the tap cycle, a macro will count holes. When a variable reaches a certain number, the program tool changes to a "back up" tool and runs that.

 

Doesn't solve the "how do you check" problem, but at least you know you're always running a "good tap".

[Bruce Caulley]

 

Anyone using measurement cameras? Is it realistic to think that we could drill and tap holes in a scrap block, machine half the hole away and then use a camera to measure core and pitch diameter? We could then do this after every couple of components if necessary?

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Bruce

[crazy^millman]

I would think that this is possible problem would getting a perfect half of the part of the camera. Where as if you did the standard go no go then you just need a low paid guy doing this type of checking is all. On the machine I would say do as recommend above. I know of time when 10,000 holes could be tapped by a tap and then others where 10 holes was lucky. You might look at torque or percentage readings on the machine and set the tap to what is 5 to 10% above average then when it reaches it do the auto change tool or alrm out and stop so you do not have a bunch of holes to retap or rework if reworks is more expensve then having the machine run.

 

HTH

[kinglouie V]

quote:

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Anyone using measurement cameras?

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Bruce, these are capable of location, but not the thread form usually. But you might ask these guys, been a while since I've even seen one in action. I can't remember if they'll check threads.

sciencescope.com

[Bruce Caulley]

Ok. I rang a local mob that make these cameras and they reckon measurement is not a problem. The challenge will be installing a camera in a tool holder in a similar fashion to a probe.

 

If the test piece is tapped and cut in half we could then run a deburring brush over it. Then call out the camera and locate a set distance away and do a measurement. The cameras work on pixel measurement, so repeatable distance from measured object is critical.

 

Bruce

[Bruce Caulley]

Stupid question time.

 

Can the spindle load meter be used to measure the resistance created by trying to screw in a no-go?

 

If it is a sensitivity issue, could a spindle be spec'd up to measure such fine loads?

 

I can think of a few mechanical/electronic torque devices that we could possibly interface with the machine to give an alarm, but it would be much easier to just put a no-go in a standard holder and press go.

 

Ideas?

 

Bruce

[Bruce Caulley]

667

[kinglouie V]

quote:

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Can the spindle load meter be used to measure the resistance created by trying to screw in a no-go?

 

If it is a sensitivity issue, could a spindle be spec'd up to measure such fine loads?

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I don't think so buddy. If you get any registerable load at all doing what I think you're thinking you'll just break off the thread gage.

 

this is a tough one.

 

Bruce, take a look at this gadget. very cool

[Bruce Caulley]

Thanks lou!

[El Scotthead]

Bruce,

I'd go with Psycho's or Lou's ideas. Lou's looks pretty cool. We use measurement cameras on some of our operator molds. Ours, at least, are not very accurate. The operators still manage to smash molds with cameras on them by putting core pins in backwards or in the wrong holes. IMHO, the camera should be able to tell when a core is in the wrong hole, for crying out loud.

 

We also use a measurement camera to measure steel tube length protruding from a medical molded part. The parts go by on a conveyor and the camera is supposed to watch the tube length. If if gets too far out of wack, the machine should stop and send an error message to our mechanic. Lets just say we still have to 100% inspect them. Camera = worthless.

 

scotty