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Why Buehler and Instron Improved the Vickers Hardness Testers

ITW, the parent company of Buehler recently recognized two outstanding engineers Rudolf Mayer, Buehler and Steve McMahon, Instron for their contributions to the design of the VH3100 /3300 micro-hardness products.

A Vickers hardness tester presses a pyramidal diamond indenter into the surface of the test specimen. The resulting permanent deformation of the test specimen is then measured with a microscope/filar system and that measurement (plus the force used) are used to calculate the hardness of the test specimen.

For decades, the users of Wilson’s own legacy Vickers testers and Buehler competitor’s testers and have simply tolerated the shortcomings of available machines. Rudolf Mayer and Steve McMahon made improvements that were incorporated into the following patented design improvements were incorporated into the Wilson VH3100 hardness testers to address the shortcomings:

1. No More Costly Microscope Collisions

Users have been known to ram the microscope objective into the test specimen while manually jogging the microscope downward in an attempt to bring the indent image into focus. This type of collision can destroy the objective, the turret and the XY stage.

The VH3100 uses a unique demountable kinematic connection of the objectives that senses any collision and responds by retreating the actuator before any components are damaged, saving the customer five-thousand dollars in repairs and days of downtime.

2. No More Rotating Turret

All other Vickers testers use a multi-position rotatable turret to hold and select the microscope objectives and the indenters. These turret systems are rather complex (with motors & controllers and drive systems) and may be prone to needing service.

The VH3100 was designed with a unique two-objective microscope system that uses one camera, a few half-mirrors and two light sources to create a “virtual turret” that switches between objectives by simply switching which light is on. Our thinking was’ “fewer moving parts means fewer service calls”; indeed, this system has proven to be very reliable.

3. No More Compromising on indenter Angle Adjustment

Previous Wilson Vickers testers required elaborate shimming of the XY stage to obtain symmetric indents from one of the indenters and we would hope that the second indenters would also be sufficiently aligned.

The VH3100 was designed with an easy-to-use, adjustable three degree-of-freedom mounting between each load cell and its indenter; ensuring alignment of BOTH indenters.

4. Repeatable X-Y Stage Mounting

Previous Wilson Vickers testers had a threaded-post XY stage mounting that had poor repeatability in positioning. That is, if you moved it (for service or system install), all alignment would be lost and only re-obtained through a tedious hit-or-miss try-and-retry method.

The VH3100 was designed with a push-and-lock mounting plate that exactly-constrains the X and Y positions. This mounting also has an easily adjusted and lockable Z axis rotation mechanism that ensures, after removal and reinstallation, repeatability of all stage positions.

The renowned Wilson brand of hardness testers, manufactured by Buehler, have been advanced and automated with the DiaMet Software.  DiaMet also helps maximize sample throughput with a four or six fold leveling vise. The latest Rockwell, Vickers / Knoop and Universal hardness testers along with the Wilson hardness blocks and calibration services assist customers with NADCAP audits.

The Wilson Hardness Calibration Laboratory manufactures the hardness reference blocks. This lab is recognized globally and is accredited to ISO/IEC 17025 by A2LA. The testers used in the calibration process undergo a stringent monitoring process using NIST traceable devices. Test blocks ship worldwide on a daily basis, after undergoing 100% inspection and passing all ASTM and ISO requirements.



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