Flex Resistance Tester
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WORKING PRINCIPLE
This equipment is designed according to the specifications laid down in IS: 1741 of 1960 for Foam Rubber and IS : 8391 of 1977 for Rubberised Coir, Difference is only in the specifications of indentors and the size of the sample. The upper and the lower limits of the indentors can be adjusted as require in case of a sample of any thickness.
The flexes are given to the sample at the rate of 4/Sec. and continuously upto 2,50,000 flexes i.e. for more than 17 hours continuously.
There is, an electronic pre-set type counter attached to the movement which has a digital display of the number of strokes given. There is a thumb-wheel system to present the number of strokes to be given. When the pre-set strokes are over the electric motor is stopped by the counter and the hooter gives a continuous sound. Before each operation, a small reset button (Red) has to be pressed.
PROCEDURE TO TEST THE FLEX RESISTANCE OF THE FOAM RUBBER SAMPLE:
1) Take the sample and measure the thickness T, in mm. and the Indentation Hardness (H) by using the Equipment for Testing Indentation Hardness.
(2) Select the indentor circular for foam rubber and square for Rubberised Coir. For Foam Rubber fit the circular Indentor.
(3) Adjust the flex so that 40% thickness of the sample is pressed each times and the indentor also travels only this much height.
(4) Place the sample on the table below the indentor and clamp 1t on the table.
(5) Adjust the number of flexes at 2,50,000 by turning the thumb-wheels on the control panel. (System should be checked by putting the number of flexes at small numbers like 10 or 25 before the final operation).
(6) Press the small reset button (Red in colour)
(7) Now start the motor to give flexes to the sample continuously upto 2, 10,000.
(8) When 2,50,000 flexes are over the motor will stop and the hooter will sound.
(9) Take out the sample and allow it to recover for 30 minutes.
(10) Then measure the Thickness (T2) and Indentation Hardness (H2) by the same indentation hardness tester.
(11) Calculate (T1-T2)×100÷T1 =Rt
If Rt is more than 5%, the sample is rejected.
(12) Calculate (H1-H2)×100÷H1 =Rh
If Rh is more than 20%, the sample is rejected.
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