What is Durometer: Durometer Scales & Considerations
Manufacturing components is not only about the chemical and physical properties of the materials. In fact, the role played by the hardness of the material is also very crucial. Different types of materials have varied hardness, and matching it with the required application is significant.
Therefore, to measure the hardness, a durometer is used. If you want to know what is durometer and how it works, read the guide below.
What is Durometer (Hardness)?
The durometer itself refers to the material hardness or its ability to resist deformation. It is mostly opted for measuring the hardness of polymers or non-metals. It is a tool which gives the measurement of material hardness. It doesn't have a unit but the values range between 0-100.
The materials that have a higher value are the ones that have more hardness, and the lower values refer to low hardness.
How Does a Durometer Tool Work?
The working mechanism of the durometer scale is very simple and has been featured below:
- The first step is when you have to identify the indenting foot which is appropriate and attach it to the durometer.
- Now, keep the test sample on a flat and hard surface.
- Test the material’s shore hardness by placing the durometer against the sample with its indenting foot and recording the value.
What is a Durometer Scale?
The durometer scale describes the level of hardness materials may have. Some scales are suitable for softer materials, and some for harder materials. There are different scales, and the value of each scale lies in the range of 0 to 100.
Types of Durometer Scales
There are different types of durometer scales, and each scale is meant for a different type of material. The section below features a detailed insight into these scales.
1. A
Type A, also called Shore A, is a scale which is suitable for measuring the hardness of materials that are flexible and soft. It includes natural rubber, leather, polyacrylics and TPEs. The hardness of rubber bands is around 20A, whereas the thread of a tire is 70A.
2. C
Type C durometer is used for rubbers, which are medium hard; it also includes certain plastics like TPEs. It is meant for measuring materials that have a hardness of more than 90B but lower than 20D.
3. D
Type D scale is used for materials that are hard, like polycarbonate and hard rubbers. You can consider an example of a skateboard wheel that has a hardness of 50D and a hard hat that has a hardness of 80D.
4. B
Type B is meant for measuring paper products, fibrous products, TPE, and rubbers with moderate hardness. This scale measures the materials which have hardness over 90A and less than 20D. The example of a caster on the shopping cart can be considered, which has a hardness of 76B.
5. M
Type M scale is used for measuring materials like plastic, rubber, and TPEs that have irregular shapes. It may include gaskets and o-rings that have a shore A hardness between the range of 20 to 85.
6. E
Durometer Type E is opted for measuring foamed elastomers, soft rubbers and medium-density windings of textiles like yarns and wound threads.
7. O
Type O includes plastics, soft rubbers and TPEs. It is suitable for measuring materials which have a hardness level of less than 20 DO.
8. OO
The type OO scale is for the soft rubbers that have animal tissues, foams, sponges, and textile winding, which have low density. It is suitable for materials having a hardness of less than 20OO.
9. DO
DO type is used for measuring hardness more than 90 and has dense textile windings, rubbers with moderate hardness, and TPEs.
10. OOO
OOO type measures materials which are extremely soft like suit foams and open and closed cell foams.
11. OOO-S
Type OOO-S is a durometer scale which measures the hardness of viscoelastic polymers. It includes items like gel mattresses, bicycle seats, and cushions for chairs.
12. R
The R scale doesn't measure Shore hardness; rather, it is a Rockwell scale. It is the same as Shore hardness scale but is used for measuring hardness of metals and not plastics. It, however, measures hard thermoplastics and TPEs.
Durometer and Material Selection
The commonly selected materials for measuring hardness using a durometer are as follows:
1. Vulcanized Rubber
Vulcanized rubbers are hardened through chemicals and heating. It is a process which makes rubbers highly elastic and hard compared to traditional ones. The hardness of such rubbers is measured using a durometer.
It helps assess materials so that engineers can decide if they are compatible with an application or not. Vulcanized rubbers have a hardness ranging between 30A to 70A.
2. Thermoplastic Elastomers
TPEs are used in scuba flippers, soles of shoes, and shock absorbers. They have their hardness measured ranging between 20 shore OO to 90A. They are used in highly abrasive environments and hence need sufficient flexibility.
3. Elastomeric Materials
Elastomeric materials include sponges, foams, and rubbers. They have elastic-like properties and are used in many industries. They are opted-in seals and adhesives and have a range of durometer hardness between 20A to 90A.
4. 3D-Printed Materials
3D printed polymers are used for printing components, and it is important to see their hardness or a successful design. The hardness of these materials is more than elastomers and TPEs, ranging between 70A to 100A.
5. Cellular Materials
Cellular materials are materials that are porous and have either open cells or closed cells. It includes cork, sponges, and foam. These are commonly used in applications requiring noise control, crash energy absorption and lightweight construction. They have a shore hardness ranging between 30-70 OO.
6. Gel-Like Materials
Gel-like materials are a combination of liquids and solids and are composed of gel insoles, silica gel, and hydrogels. The shore OO tests are conducted for measuring their hardness and their values are between 10 and 40 Shore OO.
Durometer Considerations for Injection Molds
Durometer also measures the hardness of materials used in injection molding. It ensures to consider the flow of material and part performance. The materials are flexible and easy to flow, which makes them suitable for grips and seals.
Harder materials, on the other hand, are rigid but need high injection pressure and strong molds. The selection of appropriate durometers ensures the manufacturing of accurate components with flexibility and strength.
Durometer Considerations for Additive Manufacturing
Durometer hardness is related to additive manufacturing, also known as 3D printing. The property of hardness is important for determining the right materials for 3D printing and their compatibility with a given application.
The hardness of the material opted for 3D printing impacts the optimal results for the part. Durometer impacts the layer of adhesion as soft materials need slow-speed printing and controlled temperature to avoid warping.
Conclusion
Understanding what is a durometer is one of the crucial considerations when manufacturing plastic parts. It helps achieve optimal results, improving efficiency and performance in the application. As you have gone through the guide above, you must have learned everything about durometer hardness and the different measuring scales.
We at DEK provide you with high-quality plastic components manufactured, ensuring the accuracy of durometer hardness. So, get in touch with us to get your components manufactured under highly precise methods.
