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RE: Reduce cycle time


Mike is right.  Sulfur reacts to form silver sulfide.  Another alternative to VCI is the use of activated carbon.  You can test it out by getting some at a local pet store (its the stuff used for fish filters).  Place it in a cloth sack and throw the sack in with the parts.  It will only last so long, so it will need to be replace over time.  If the experiment works, you can find a cheaper source of carbon. 

One firm makes a bag made of activated Copper into the plastic matrix.  According to thier web site, "This reactive Copper then forms a tortuous path for these corrosive gases -- it is impossible for these gases to migrate through the Intercept material without hitting a piece of highly active Copper where the gases react and are permanently neutralized and stopped, thus protecting the metals stored inside. Likewise the material cleanses the air trapped inside of the package with your metal part - the surface area of the Copper on the surface of the bag is far greater than the metal being protected, so the gases will go to where it is easiest to react, the surface of the bag, protecting your valuables."

You can find out more at:  http://omega-intercept.com/    The nice thing about this product is that the bag changes color as it becomes less effective (from copper color to black).  That would be a ready signal for operators to use a new bag.  The bags could also be a replacement for the current zip lock bags..

Lacquers are often used to prevent tarnishing, but that would require stripping the lacquer off.......


At 03:23 PM 9/16/02 -0700, Callahan, Mike wrote:

Hi Judith,

Nice to get a detailed description regarding the process but I don't quite see the long delay time to unwrap the parts.  You don't want to ship and store the connectors in bulk because they can get damaged from impact.  Contact with the cardboard containers also leads to tarnish (due to sulfur in the paper). While you could reduce contact tarnish by shipping the parts in bulk in a wax coated box, you still have the problem of tarnish due to contact with air and mechanical damage due to impact.

I'm guessing that these parts are stored in more than a simple zip lock bag.  They are probably heavily wrapped and taped to prevent contact with air and to provide cushioning. The long delay time is due to the need to remove the part from the bag, cut through this tape, and clean the parts (I'm still guessing).

Perhaps the need for wrapping and taping can be reduced by first wrapping the connector in a layer of VCI (volatile corrosion inhibitor) paper.  This paper gives off a vapor that reacts with moisture in the air and maintains a dry environment for the wrapped part.  It often has a wax coating to provide a moisture barrier inside the box. The military was once a big user of this method for parts protection.  I have no other information as to product availability or potential environmental impact.

Another option might be to dip the plated connectors in a bath of peelable coating.  The coating provides protection from air exposure and some mechanical impact.  The use of this option will depend on the shape and complexity of the connector.  This may work fine for handling the outer shell but not for an assemble item with its pins and sockets.  As before, availability and impacts are unknown.

Hope this helps.

Mike Callahan, PE
Principal Chemical Engineer
Jacobs Engineering Group Inc.
1111 S. Arroyo Parkway
Pasadena CA 91105
(626) 568-7005

-----Original Message-----
From: Judith Wlodarczyk [mailto:jwlodarc@connstep.org]
Sent: Monday, September 16, 2002 1:53 PM
To: questions@mep.nist.gov; p2tech@great-lakes.net; clean@mep.nist.gov
Subject: Reduce cycle time

Hi!  I have a client that makes RF (radio frequency) connectors for  the cell
tower industry.  The connectors are 1/2" - 3" in diameter and are silver plated
at an outside vendor.  A brief description of the process for handling silver
plated parts is as follows:

1) Components are machined in our in house machine shop.
2) They are sent out to a plating vendor in divided corrugated cartons.
3) The components are plated by the vendor, packed individually in zip lock
plastic bags, put back into the corrugated cartons and returned to RFS.
4) The components are received and go to stock.
5) Components are pulled from stock to manufacturing orders.
6) The silver plated parts are brought to Easter Seals people who are
located in house to be removed from the bags.
7) The parts are brought to assembly.

 Question:  Does anyone have any ideas on how to possibly package these
differently to decrease the cycle and lead time but still protect the silver
plated parts from tarnishing? It takes a long time to individually unwrap the
silver connectors.  If we can find a different way to pack, we can lower the
cycle time.  The silver  tarnishes very quickly, and while the tarnishing
doesn't often the affect quality, it is unacceptable to the industry.   The
parts can't come back in direct contact with corrugated because this speeds up
the tarnishing process, and they can't be packaged so that they bang into one
another for quality reasons.  We would appreciate any ideas.

Judy Wlodarczyk
Environmental Management Specialist

1090 Elm St.
Suite 202
Rocky Hill, CT  06067

Phone:  860-644-9718
Fax:       860-529-5001
Email:    jwlodarc@connstep.org

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