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Marking Parts in the Die

The most cost-effective method is to use a steel stamp that is built right into the tooling of the die.

In press working and stamping, it is vitally important to mark parts with part numbers, shift codes, machine ID, fixture ID or even operator ID. The most cost-effective method is to use steel bottoming markers that are built right into the tooling of the die. Today, companies like Columbia Marking Tools, Inc. can supply downloadable CAD files to die makers to make it easy to integrate the marking components into the die. It’s also important for the marking supplier to keep an ample supply of customer-specific stamps and retainers in stock to enhance delivery and help with emergency situations. In essence, stampers can get their marking done for free by putting the required fixed information right into the stamping die.

Bottoming markers for a single character or I.D. can have a threaded design that can be screwed directly into a bored and tapped hole in the die platen, or they can be mounted in a retainer that is located in a machined pocket in the platen.

Typical installation of bottoming marker.

When identification with multiple characters is required, the retainer design includes a backing plate and utilizes interchangeable L-shaped stamp inserts.  The L-shaped stamps are contained in the removable retainer/backing plate assembly with socket head screws. The assembly can be mounted in a machined pocket in the platen or it can be mounted on a flat surface. The L-shaped stamps have a flange on the bottom of the stamp that insures consistent stamp height by locating up against the bottom slot of the retainer stamp opening. These L-shaped stamps are .50-inches high, .31-inches wide, for character sizes that are 5/32, 1/8 and 3/16-inches. Any type of font can be produced on the stamp. For stamps to be long lasting and have the ability to consistently mark parts at consistent depths, they should be engraved and ground to size after heat treatment to ± .001-in.

Installation drawing for retainer, backing plate, stamps and socket head screws.

Stamps produced with an EDM process have a tendency to cause de-carburization on the cutting edges causing premature wear. Because the thin EDM surface layer is untempered, it brakes down where high impact or tensile stresses are encountered. Stamping inserts with high-speed double pass engraved characters with virgin sharp character cutting edges are needed Fig. 3.  Stamping inserts can also be engraved with any marking legend on custom die segments to be used in the stamping press or retainer system. 

Determining the Quantity of Type a Retainer Will Hold

  • Measure the gap width (A) of the stamp insert opening in the retainer.
  • Divide (¸) by the type width (this is determined by the character size)
  • The result is the number of stamp inserts the retainer will hold
Drawing of typical retainer with “
A”dimension showing the gap width for the quantity of type the retainer will hold.

There are four different retainer and backing plate sets that are typically available in single and double slot opening designs to accommodate a wide range of desired

identification. The simple shape of the retainers allow for easy plunge milling of the pocket in the die. The number of individual L-shaped stamps that will fit in each opening varies. Retainers and backing plate sets range in size from 2-inches to 2.94 inches in length and from 1.31 to 2.25-inches wide. Metric sizes are also available. Complete specifications and dimensions for these retainer sets and stamps are easily accessible on the Columbia Marking Tools web site, www.columbiamt.com.


Protective Coatings for Marking Stamps

Steel marking stamps are considered secondary operation tools. So it’s not uncommon to find stamps operating for up to six months without being replaced. Combine this situation with the increased use of more environmentally friendly water-soluble lubricants and release agents, and you’ll find compacted dirt in the character grooves and rust becomes a major tool life problem, especially with EDM style stamps.  This is deterioration is called character “blow out” and it creates chipping and ultimately loss of stamp integrity. Columbia Marking Tools has improved stamp life with their ACC™ “Auto Clean” chemically

Columbia stamps are high-speed double pass engraved not EDM’s. character cutting edges are vey sharp and do not have the disadvantages of thin EDM surfaces that wear fast.

applied electroless nickel coating that provides the lubricity of Teflon®, eliminating the effects of rust on the stamp characters and stamp retainers, while preventing dirt from compacting into the individual stamp characters. Tom Phipps, Columbia CEO, says,  “Our tests have shown that the nickel coating is the best rust inhibitor coating for steel stamps, compared with black oxide or chrome coatings, and it enhances the stamp’s’ shelf life.  As a result, we have standardized on the coating for all our standard and special stamps and retainers. And we’ve been able to add the ACC™ wear life benefits without additional cost to the customer.”

Pre-Packaged Sets

Because stamps are very small, they are hard to store and are often lost. To make it easier for the user to identify the stamps and retainers and to store them properly and protect them from being lost or mixed up with old stamps, Columbia Marking Tools has organized standard pre-packaged sets of press marking stamps and retainers.

Columbia Marking Tools is a leading designer, manufacturer and engineering source for metal and plastic marking equipment including stamps, roll marking dies, roll marking and impact marking machines, fully programmable laser, peen/scribe marking and UID/2D Square ◙ Dot® machines, numbering heads and special marking machines.

For more Information: www.columbiamt.com









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