Error Proofing to prevent Length Short - CNC Turning Process

E

ek911

#1
Dear All,

I always facing length short problem at our manufacturing cnc turning process. Any expert can give us some idea on error proofing method to prevent it, may be e.g. sensor detect in station.

Hope get you input.

Thanks.
Machining Automotive industry in Asia.
 
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#2
Additional information would be helpful. How short? What is the tolerance? What type of stock and how is the stock handled? What operations taken to finish the length?
 

Wes Bucey

Prophet of Profit
#3
Dear All,

I always facing length short problem at our manufacturing cnc turning process. Any expert can give us some idea on error proofing method to prevent it, may be e.g. sensor detect in station.

Hope get you input.

Thanks.
Machining Automotive industry in Asia.
I presume you are feeding bar stock from a hopper. The idea, of course, is to prevent wear and tear on cutting tools and save time by not cutting metal on a piece destined to be NC. We ran "lights out" part of every day. We added a sensor which detected presence of sufficient stock to chuck and complete the next workpiece. Insufficient stock triggered a cycle to load the next bar and push the short through. We did not invent or program this. It was recommended and installed by technicians from the factory which manufactured our CNC. It was more than 15 years ago.

Manufacturers of complex rotary transfer centers (Hydromat, for example) routinely solve such situations in the regular course of business.

Long ago (my great uncle's time during WWII), Browne & Sharpe lathe operators used a paint stick to mark where to stop on each bar they hand fed to the lathe.
 

apestate

Quite Involved in Discussions
#4
Usually I see this happening when the bar feeder pushes the stock up to the stop on the CNC turret, and then relaxes while the chuck is closing. Basically the stock bounces off the stop.

I would suggest adding more face-off stock, like .050" total face off allowance, but that won't really fix it if your bar feeder is acting as above.
 
E

ek911

#5
The length short mostly 0.5mm ~ 1.5mm is due to chips stuck at back stopper. We did use magnet to remove off but not effective.
Any idea on detect the length short more efficiency and effectively.
 
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