November 2016 Roundtable on Inspection, Testing
Global Service Manager
Testing Machines Inc.
10 years with the company
Q: Talk about how your company is involved in inspection and testing. Why are these types of products important regarding flexible packaging?
Muchorski: Testing Machines Inc. manufactures, services and provides field calibration for a variety of critical flexible packaging measurements, including static and kinetic coefficient of friction, hot tack, surface energy, heat sealing, puncture resistance, thickness, seal strength and elmendorf tear. The above physical and surface property measurements play an important role in maximizing both material and packaging machine performance.
Q: Is there a particular product that has been the most popular to converters/printers when it comes to your company?
Muchorski: Consistent film quality is key to flexible packaging printers and converters. From a materials testing standpoint, one of the more popular and critical measurements to ensure material runability is static and kinetic coefficient of friction. COF is the force required to move a similar substrate or surface over another surface. The force is measured in grams and divided by the weight of a sled, which is typically 200 grams. The test result is a dimensionless value between zero and 1.
Too little or too much friction can cause line stoppages during the converting process. High-friction/low-slip conditions can cause the film to feed poorly over metal rollers or jam in chutes in the forming process. Low-friction/high-slip conditions result in packages sliding off the conveyor line. To complicate the measurement, the surface of the film changes or blooms over time, which can also change friction properties. Therefore, optimizing coefficient of friction to the specific application or machine requirement is important to control and eliminate problems in processing and transporting packaged products.
Q: In testing thickness/gauge of plastic packaging films, how do you know what specifications to use for foot pressure and diameter of the measuring foot?
Muchorski: This is not an easy question to answer.
Thickness measurement specifications for most compressible materials, such as paper, tissue paper, corrugated board, non-wovens and textiles, have well-defined specific dimensions and weight requirements for foot pressure weight and foot diameter. However, plastic film standards, such as ASTM D 6988, F 2251 and ISO 4593, suggest a range for the diameter and foot pressure based on the stiffness and thickness of the material.
When specifying foot diameter, ASTM D 6988 recommends a diameter range of 3.2-12.7 mm (0.125-0.5 inches). ISO 4593 recommends a foot diameter range of 2.5-10mm (0.098-0.393 inches).
When specifying foot pressure, ASTM D 6988 suggests a range of 5-70 kPa (0.73-10.1 PSI) for thin films and 160-185 kPa (23-27 PSI) for stiffer films. ISO 4593 recommends a pressure range of 0.5-1.0 N (51-102 gram) dead weight.
As a leading manufacturer of precision micrometers for measuring plastic film, it is necessary to carefully review customer requirements and make sure the recommendation we make for new equipment is based on existing instrumentation or customer requirements to insure we supply the exact specifications.