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Functional Range Of Motion Chart & Percentage of Compression Calculator Functional range of motion & percentage of compression calculator
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Articles
EJECTION
RUBBER Dilemma

by David West
Ejection Rubber Dilemma by Dave
The History of MRP
The History of Monroe Rubber and Plastic

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Die Performance

Die performance is based on 3 things in regards to die ejection:

  1. Rubber Selection
  2. Rubber Location.
  3. Ejection balancing.

RUBBER SELECTION:
The only moving parts on a cutting die are the ejection materials. As with any moving mechanical or compressible part there is a maximum funtional range of motion. Once that range is exceeded the item no longer functions properly which will lead to failure.

Click on the link below and you will find a worksheet and chart to identify which type of rubber is best for your application. The chart shows the Maximum Range of Motion in green for each product. Once the functional range is exceeded it enters the yellow densification point where the rubber becomes a solid and can no longer compress. Go beyond this point and the rubber will fail and break apart. For the rubber to work properly it must remain in the green Functional Range of Motion. Enter the values for your job in the worksheet above the chart, and your compression percentage will automatically be determined for you. Then refer to the percentage columns on the chart to determine which type of rubber will perform best for your job.
Functional Range Of Motion Chart & Percentage of Compression Calculator.

RUBBER LOCATION:
On a flat die the rubber height should be 1/16 over the cutting edge of the rule. Rubber should be placed 1/16 away from the side of the rule. Some shapes such as Sidewave™ and Ejectoflex™ have built in spacers to keep the body of the rubber properly spaced away from the rule.

Sidewave die ejection rubber
Ejectoflex die ejection rubber
 

 

EJECTION BALANCING:
THIS IS WHAT SEPARATES A GOOD DIE FROM A GREAT DIE!

Balanced flat dieRarely should a die only have one type of rubber. It should almost always have at least 2 types of rubber per die. Think of a die cutting not just one job but rather many different sized pieces. Each sized piece should have the same amount of ejection force. This is what is meant by a balanced die. To do this the larger areas need softer rubber and the smaller areas need harder rubber. This way the ejection force of a large piece is close to the same ejection force of a smaller area. If the same rubber was used for both large and small areas the ejection force of the different pieces would all be different.