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Tuesday, April 8, 2008

What is Durometer?

When new products are being developed, one of the most difficult tasks is to determine the material. Materials are typically selected based on several criteria:
  • Association - use material that has been used with similar products.
  • Mechanical properties - Flex Modulus, Tensile strength, Impact, HDT, etc.
  • Color - Part needs to be clear – Knowing the color can help to narrow the search
  • Durometer - measure of hardness in polymers, elastomers and rubbers.
I would like to discuss durometer. Durometer can be a very fast way to narrow your search for a material. Durometer is a value that indicates the hardness of a material, defined as the material's resistance to permanent indentation.

There are several scales of durometer, used for materials with different properties. The two most common scales, using slightly different measurement systems, are the ASTM D2240 type A and type D scales.

The A scale is for softer materials

The D scale is for harder materials

Durometer works together with association.

The chart below relates Shore A and Shore D values with production grade and some common materials

Shore A

Shore D

Material

30


Art Gum Eraser

40


Pink Pearl Eraser

50

15

Rubber Stamp

60


Pencil Eraser

70

30

Rubber Heel

80


Rubber Sole

90

45

Typewriter roller

100

55

Low Density Polyethylene


70

Polypropylene PP


75

ABS


80

Polycarbonate PC


85

GF Nylon


90

Glass


In the Rapid Prototyping industry there are a number of resins that can simulate different production and common materials.

The chart below relates Shore A and Shore D values with Rapid Prototyping resins. The chart is only a guide to help direct you to a material that closely represents your final product.

Shore A

Shore D

Material

30


Tango Plus

Cast Polyurethane

40


Cast Polyurethane

50

15

Cast Polyurethane

60


Tango Black

Cast Polyurethane

70

30

Tango Gray

Cast Polyurethane

80


Cast Polyurethane

90

45

Cast Polyurethane

100

55

Cast Polyurethane


70

Cast Polyurethane


75

Cast Polyurethane


80

Accura 25

WaterClear Ultra 10122

Cast Polyurethane


85

Accura 60

ProtoGEN 18420

WaterClear Ultra 10122

Cast Polyurethane


90

ProtoGEN 18420

SL 5530

Cast Polyurethane


Durometer is a tool to use when selecting a material for a new product design. It’s one of many tools that can aid in the design and material selection process. Once a design is complete and a material has been selected – ProtoCAM will be glad to produce high quality prototypes.

Ed Graham
Engineering Manager
egraham@protocam.com
posted by ProtoCAM at

2 Comments:

Blogger L Chrzan said...

Interesting and informative post about this useful measurement. This should be helpful to people who need to describe the relative hardness / softness of the material they want to use in the product that is being prototyped.

Questions:
Is durometer an actual physical tool that is used? If so, what does it look like? Do you have a picture?

Thanks!

April 9, 2008 at 11:21 AM  
Anonymous RobK said...

Great post Ed. Thanks!

January 4, 2009 at 12:02 AM  

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