SUND Knowledge: Testing the limits - the Dartdrop

28 Oktober 2021


The series "SUND Knowledge" takes you through the laboratory: Quality assurance is a fundamental part of the SUND Group. For this purpose, various machines are used with which the products can be accurately tested. Lab manager Gabi Krügel explains the test equipment. Part 2: the Dartdrop.

"With the Dartdrop, we test the puncture resistance of the film in several passes," explains Gabi Krügel as she clamps a strip of trash bag into the device. The so-called dart, a metal bolt with a round base, is loaded with weights to test puncture resistance in accordance with the norm. "The film is clamped in place, so it's kind of like a shock-type test." At the push of a button, the dart falls from a height of about 60 centimeters onto the test sample and punctures a hole.

"We are looking for a weight at which the foil will hold 50 percent of the test, so to speak. For example, we now have a weight of 92 grams where three out of ten drop tests show cracks. So now I'm going down with the weight to the point where the foil can withstand the load ten times. I do the same thing in the other direction, so I look for a weight in which the dart will strike through the foil ten times. The weight level must always be the same. Using an analysis program, a physical compensation line is formed with these determined values and thus the F50 value is calculated. According to the norm, this is the value at which the film just about holds or just about tears," explains Krügel. 

The individual results can be viewed with an analysis program. “The results differ not only according to the material, but also according to the sample selected," she continues. Therefore, several puncture tests must be performed. The specimens are prepared exclusively in the transverse direction.

In the future, Gabi Krügel would like to run the test at the SUND Group completely digitally, so that the values are directly available on the test computer. "Currently, we still transfer the values by hand. In the new building, that will probably change," she says.

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