Home > Articles > The Five Commandments Of Extending The Usable Life of a Rotary Die


article printed 11-99

"None of us are as smart as all of us"
By Ron Brenwall
President, MaxiM International Consulting

The Five Commandments Of Extending The Usable Life of a Rotary Die

As a consultant to the rotary die-cutting industry, I sometimes work with companies that have made the decision to move into rotary die cutting and they are looking to purchase machinery and tooling. Invariably, at some time during my stay with a company, someone will ask what they can expect the average usable life of a rotary die to be. I must first explain that there is no such thing as an "average" anything. My definition of "average" is that if you have your head in a freezer and your feet in an oven, then on "average" you're comfortable. I believe that if you had five different companies cutting the same product/material on the same brand of equipment with tooling manufactured by the same die maker, from the same steel, the quantity of parts produced before the die is no longer usable, would vary tremendously between the five companies. The differences in die life then, must come from the different ways the tooling and machinery are handled and maintained by the company. The reasons for these differences in quantity are the basis for my column this month.

Commandment #1: Know Thy Die Maker Well.
Actually, improving the length of die life begins with providing your die maker with all the information you can. Concerning quantities to be run, material to be cut, speed that you expect to run, will the product be sheeted or cut against a release liner, will the parts be used on an automatic applicator, etc. If the product is a short run, once or twice a year, you may not require a special hardness or coating on the die. If the material is a thin polyester or urethane, the die may require a higher Rockwell hardness with a different edge profile and higher degree of sharpness. These are the kinds of information that a die maker should be asking for. If your die maker is only asking you to send a print and a sample of the material to be cut along with the purchase order, you should be looking for another die maker. I think most rotary die makers would be happy to give a short seminar on ordering dies, tool handling and maintenance.

Commandment #2: Thou Shalt Never Use More Die Pressure Than Is Required
As a general rule, never use more pressure on the die than you can get by turning the pressure screws with one hand. Anyone that has been involved with rotary dies for any length of time has seen many clever ways to apply 2000 pounds of pressure to the die bearers to cut the last few pieces to complete an order. Usually this is something as gentle as a pipe wrench with a handle extension. Then, when the die is finally sent back to the diemaker for resharpening, it will probably require grinding off more of the cutting edge before the sharpening process can begin because of the excessive wear caused by applying too much pressure. Every .001 of metal that must be ground off of the cutting edge can be directly translated into less parts produced. You can expect to get two resharpenings, perhaps three, if they don't have to grind off too much metal to get the cutting edge flat. I would highly recommend using pressure load cells between the pressure screws and the die and have the pressure limits set as part of the training program and set-up procedure.

Commandment #3: Thou Shalt Document Everything
If you have read any of my articles in the past, you know that I advocate documenting all pertinent information in the interest of continuous improvement. This especially applies to rotary dies. You must maintain a record of each die from the time it is first received until it is no longer usable. This record should consist of the following information:
  1. Die maker
  2. Die number
  3. Any specific information (ie) special steel, hardness, coatings, etc.
  4. Date, job number, number of pieces produced, operator, machine number
  5. Total number of parts produced between each sharpening
  6. Misc, information
Armed with this information you will be able to compare the die life between die makers, Rockwell hardness of steel, operators, materials cut, etc.

Commandment #4: Thou Shalt Handle Dies With Much TLC
In my many years of being involved with rotary tooling, I can state that without question the number one cause of shortened die life is the way dies are handled before and after they are put in the machine. When you are investing thousands of dollars each year in rotary tooling, it is wise to handle your rotary tooling as if it were an egg that rather than a chunk of cold steel. I've seen dies handled while the operator was wearing a ring. I've seen dies that were gently removed from storage and set down on a shop towel only to discover that an Allen wrench is under the towel and the cutting edge now has a nick in it and will require resharpening. Or have two dies roll together because they were set down on a piece of corrugated cardboard and someone bumps one of the dies. An inexpensive remedy is a rack made from a couple of 2X4's with a "V" sawn in them at 6" inch intervals and the die journals set in the "V". To state it as simply as possible, the cutting edge should not come in contact with anything except the material that is to be cut. How often have you seen an operator struggle alone to install a die that is too heavy for one person to be handling? Hopefully not resulting in a smashed finger or the die crashing to the concrete floor. A web sling with proper handles can help prevent this from occurring. There are also thick covers that wrap around the die and are attached with Velcro and are removed only after the die has been properly installed in the machine. No one comes to work (I hope) with the intention to dull the cutting edge of a die. It almost always happens because we're in a hurry or haven't been trained properly or haven't been given the responsibility for proper handling. Sometimes something as simple as letting the people that handle the tooling know what the cost of the die is, can help them be more aware of their responsibility concerning protection during handling.

Commandment #5: Thou Shalt Refer To #1 through #4 On A Regular Basis
This information may seem rather simple and trite to people that have been in the rotary die cutting business for many years, but I think we can all agree that if we can increase the die life by 10% it would result in savings of thousands of dollars per year.

I would be interested in hearing what your company does in improving the usable die life of rotary dies. Please contact me at the phone number below with any suggestions.



If you have any comments on this article or questions about the narrow-web converting process, please give me a call at (1-800) 660-3696, fax (920) 894-4003 or e-mail info@maximinternational.net

Ron Brenwall has over 30 years of experience in production and operations management in the Rotary Diecutting, Rotary Diemaking, Converting and Packaging Industry and has been an independent Consultant and Project Manager for the past five years. If your company is thinking of entering into or expanding within the Rotary Die Cutting and Converting industry, give Ron a call and discuss the cost effective benefits of retaining his services as a Consultant or Project Manager or visit their web site at www.maximinternational.net