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Barrel zinc plating 'fall out rate'
Our company specializes in large volume and small volume barrel plating. A large percentage of the work we produce is automotive specification. In barrel plating production, there is a "fall out rate" in which a small percentage of parts do not get plated or only partially plated. The automotive industry demands zero defect from all suppliers. However, the reality in a "job shop" is there is always a potential for some parts getting under coated or not coated because it got stuck somewhere in the barrel.
I have heard there are publications that address "fall out rates" especially for small parts like fasteners. I need to find such publication to show to customers.
Where can I find an article or publication that discusses this problem?
electroplating shop - TORONTO, ONTARIO, CANADA
2004
Dear Mr Kamal,
If you find it let me have a copy as well! My guess is you won't, because no one will agree to receiving bad parts as part of a contract! Please work on your barrel line and minimize rejects.
Khozem Vahaanwala
Saify Ind
Bengaluru, Karnataka, India
2004
Saify Saheb is 100% right . I am also surprised what you have wrote. Check your line and get advice from good consultant. Regards,
Qutub Saify- Ajman, UAE
2004
2004
Now wait a minute, fellas. :-)
Mr. Bhardwaj has implied, if not directly stated, that the parts move rather randomly in a plating barrel and that there is some statistical rule behind what portion of the parts will consequently be good (hopefully many 9s).
Plating barrel dynamics are complicated, so let's simplify and imagine that we have a "coin toss plating machine" that plates only the "up" side of a tossed coin, and that your customer has ordered coins with the "head" plated but he doesn't care about the tail side. Of the coins you toss onto this machine, half will be rejects. So you talk to the customer and he doesn't care how thick the plating is as long as he has coverage on the head of the coin. So, instead of dropping the coins into the machine once, you toss them again mid-cycle, and now only 25 percent remain with no plating at all.
To get down to an average of 1 bad part in a hundred thousand, you'd have to flip the coins 17 times if I've counted right, and 1 part would have 17 layers of plating, 2 parts would have 16 layers, 4 parts would have 15 layers, etc. Your plating thickness distribution would be preposterously bad.
The dynamics of a plating barrel are, as I said, complicated. But some statistical rules are inherent in barrel plating.
As a practical matter, Mr. Vahanwala is pithily accurate, but as a matter of scientific investigation, Mr. Bhardwaj should certainly not be criticized for asking an interesting question :-)
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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