Letter 38041

Automatic process control: what is possible?  

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Hi,

We have a rather new plating shop with baths of about 200 liters each to deposit (copper, nickel, silver, gold) on decorative zinc pieces.

We would like to make the process more stable and so have better end products. We do daily analysis in laboratory, but is there more to make the baths steadier, closer to their optimum? What kind of apparatus exists to measure or even correct parameters online?

Thanks,

Marc
- Queretaro, Mexico

There are all sorts of things that can be done to reduce chemical parameter variation in plating line baths, but these have to be matched to individual situations. Without more information, about the only thing that can be suggested is the addition of plating additives based on amp-hour consumption and a long conversation with a consultant or your suppliers.

James Totter, CEF - Tallahassee, Florida

I also read about the automatic dosing equipement for brighteners from our provider.

We have temperature controlled heaters.

I guess it is impossible to check for concentrations on line (CuCN, NiSO4, boric acid, KCN or AgCN for example), as I see how complex the laboratory work is sometimes?

Marc
- Queretaro, Mexico

I wouldnt say its impossible to check the basics automattically in your line, but i would say its uncommon at least where I come from.

I remember recieving some junk mail advertising from some company in the UK once that had a process control unit that claimed to measure many of the basic components in plating solutions via voltammetry and this could be connected to auto dosing units that would correct and maintain the solutions. i dont recall what the name of the manufacturer was. searching on google for "online analysis of plating solutions" gave me a link to this website:
http://www.manufacturingtalk.com/news/moh/moh100.html
this site talks about the technique a bit.

however I think you should just go with a good plating suplier that is happy to analyse your solutions for free.
it will be cheaper and you will have someone to point the finger at when something goes wrong :)

Peter Van de Luecht
- Melbourne, Vic, Australia

By having both yourself and your suppliers analyze your plating bath at regular, scheduled intervals; keeping track of work load during those intervals (amp hours or mil/sq ft. processed) a correlation and averages can be drawn. These can be used to schedule regular standard addtions.

I have also seen automated equipment to control the solutions in all parameters but they are generally cost prohibitive. I would suggest the use of amp hour feeds for brightener additives.

Gene Packman
- Great Neck, NY

Decorative applications:
Your biggest issue will be color variations from batch to batch, piece to piece. You need some one that has a knack for color judgement and can make the necessary adjustment on line.

I tried colorimetric measurements, it worked with painted surfaces but not with the electroplated surface.

Good luck,

Hamilton

H Solidum
- Philadelphia, Pennsylvania