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Assessing the Accuracy of Thickness-Measurement Tools

(April 2004) posted on Tue Apr 13, 2004

Discover what tools and procedures lead to the most accurate measurements for screen printing.

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By Fernando Zicarelli

Table 1 shows the results of this experiment. It verifies that using different probe shapes/sizes and different gauging forces does cause measurement variances, even with the same gauge. Assessing the Accuracy of Thickness-Measurement Tools

Figure 3 Measuring Thickness In the case studies discussed in this article, thickness measurements were conducted on groups of eight or 16 screens with identical thread counts, thread diameters, and tension levels. Multiple readings were taken for each screen.

Gauge type

For this portion of my study, I wanted to see if the brand and type of gauge had any impact on the measured results. I began by focusing on two spring-activated systems: the Mitutoyo model #543-252 and Heidenhain's model #1201. I then compared the results with these systems to values recorded previously for the Heidenhain model MT-60 motorized gauge.

I used the spring-activated thickness gauges to take eight readings from the 8 x 8-in. image area of 16 separate screens. The readings were again taken from NBC monofilament polyester mesh with a thread count of 380 threads/in. and a thread diameter of 33 microns that had been stretched to a tension level of 18 N/cm2. Four probe types were used with each device: round tip, domed tip, pin tip, and flat tip. Measurement values were recorded in an Excel spreadsheet for comparison.

Tables 2A and 2B show how the probe shape affects the thickness measurement, just as it did on the motor-activated unit. The tables also demonstrate how two different gauges from two different manufacturers can provide completely different readings if the gauging force is not the same. In this test, the Mitutoyo model #543-252 used a force of 1.2 N, while the Heidenhain model #1201 used a force between 0.6-0.85 N. Assessing the Accuracy of Thickness-Measurement Tools

Table 1 The Impact of Probe Type and Measuring Force This table shows how the use of different probe geometries/sizes and probe forces can alter the measurement results delivered by a thickness gauge. The gauge chosen for this experiment uses an electronic motor for probe deployment and supports several probe-force levels.


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