Hardness Testers

Hardness is one of the most important properties which determine the suitability of any rubber component for its intended end use. Incorrect hardness may defeat the basic purpose for which the component is designed. Thus accurate and reliable determination of hardness is of extreme importance in rubber field.

The test specimen having flat and parallel top and bottom faces is placed on a horizontal platform located below the indenting tip. The platform can be raised up by rotating a screwed wheel. This upward movement of the platform causes the test specimen to come in contact first with the pressure foot and later with the indenting tip under the specified contact load.

Depth of penetration of the indenting tip into the test specimen is determined with the help of a dial indicator fitted at the top of the pressure foot assembly. The contact between the dial indicator and the top of the plunger rod is made through an electrical arrangement to ensure that the weight of the stem of the dial indicator does not act on the test specimen. An electric buzzer is provided to give low intensity vibrations to the plunger rod to eliminate friction. The dial indicator gives the depth of indentation in units of 0.01 mm, which can be converted into IRHD hardness values with the help of a standard table provided with the equipment.

The tester is finished in grey hammertone stoving painting and bright chrome plating to give it a corrosion resistant finish. Three models of the tester are available to cover different ranges of hardness.

The feel of softness of any flexible foam is quantitatively defined by its indentation hardness. Indentation hardness of foam is determined by pressing a circular indentor at a specified speed against a block of foam and finding the force needed to compress it to a specified percentage of its initial thickness.

The PROLIFIC Indentation Hardness Tester for polyurethane foam consists of a circular indentor which can be pressed against the foam block under test, a motorized arrangement to move the indentor, and a load indicating arrangement to indicate the load being exerted by the indentor on the foam block at any instant.

The indentor is in shape of a circular disc and is mounted on a self-aligning ball bearing to ensure that it sits parallel to the surface of the test specimen. It is mounted at the lower end of a screw, which can be raised or lowered at a specified speed with the help of a motor and worm reduction gearbox. An arrangement to stop the motor at extreme ends of travel of the indentor is provided.

The downwards movement of the indentor is measured with the help of a pre-set type digital displacement meter, which can be set at any desired value to stop the motor automatically at a desired displacement. A linear scale is provided to indicate the gap between the bottom face of the indentor and the loading platform. The indentor can also be moved by hand to apply the initial load.

The load platform is made of cast aluminium and has a large number of holes arranged in a grid for rapid escape of air during compression. It is mounted on shear beam type load cell. A digital load indicator is provided to indicate the load acting on the test specimen.

The equipment is finished in grey hammertone stoving painting and bright chrome / zinc plating to give it a corrosion resistant finish.