The Roller Shear Machine determines the resistance to compression fatigue of flexible cellular polyurethane. It does this by using a dynamic roller compression test.
The Roller Shear Machine fatigues a specimen dynamically with a constant force. Moreover, it deflects the material both vertically and laterally. Majority of companies within the foam industry use this to test quality of foam. This is because the machine accurately determines the percentage loss in thickness.
The Roller Shear Machine has been specially designed and manufactured in accordance with international standards
. It is used to fatigue a specimen dynamically at a constant force, deflecting the material both vertically and laterally.
There are two procedures that can be used with the Roller Shear Machine. Both procedures are the same, and vary only in the number if cycles required to test the specimen. Procedure A uses 8000 cycles for testing, while Procedure B uses 20 000 cycles for testing.
The Roller Shear Machine is manufactured using the following components:
- Perforated-Base Platen: measuring 500mm x 500mm by 10mm. The centre section has 6.5mm holes covering a total area of 360mm x 360mm
- Roller: measuring 450mm in length with a diameter of 76.0 ± 1.3mm
- Counter: To set the counter to the predetermined test procedure: Procedure A: 8000 cycles & Procedure B: 20 000 cycles
- Limit Switches: installed in the Roller Shear Machine for added safety. If the doors of the machine are opened during a test, the test will automatically stop. To begin testing again, close the doors and press the START button.
Test specimens to be used on the Roller Shear Machine shall be 380mm long and 300mm wide. The specimen thickness shall be at least 25mm thick, but no greater than 125mm. However, it is preferred to be 50mm thick.
Specimens shall be prepared by saw. Condition the test specimen as per standard requirements. One specimen shall be tested at a time.
- Prepare your test specimen for testing
- Connect the power to the mains, and switch ON the machine
- Place the test specimen on the base platen ready for testing. Ensure the long dimension is parallel to the stroke of the Roller Shear Machine.
- Fasten the test specimen by means of tape and metal retainer
- Lower the roller down to the specimen, with the weights provided positioned to the top of the roller assembly so that a constant force of 130 ± 2N is obtained
- Set the Counter on the machine to desired number of cycles as per Procedure A or Procedure B (8000 cycles or 20 000 cycles)
- Press START on the machine to begin testing
- When testing is complete, remove the test specimen, and record the Thickness Loss within 60 ± 5 mins using the IRGL method (this can be done using an IDM Foam Compression Machine).