Defective Bags, Sorting the Wheat from the Chaff with 30,000 Bags

Written by Paul Brooker – Consultant at TechRentals - September 2012
In the world of instrumentation rental we take a lot of pleasure in solving a customer's challenging problem in the simplest, quickest, and most economical ways. Perhaps half our rental enquiries are from clients who are very familiar with the measurements to be made and the function of the instruments that they hire. For others it is not quite so straightforward and in some instances it's a case of disaster recovery.

One such application involved defective products bags - 30,000 of them - discovered only after the product had been packed. These bags have a paper outer and a plastic liner but some were found to have the plastic liner missing.

What could we do to quickly separate the bags correctly lined with plastic and those lined only with paper. There was no obvious way to separate the bags using visual inspection. The following potentially distinguishing measurement parameters were explored and eliminated.

  1. Magnetic properties.
  2. Low voltage resistance.
  3. High voltage resistance.
  4. Moisture content of the bag outer.
  5. Weight variation.
  6. Thermal properties (using a thermal imaging camera).
  7. Thickness using an ultrasonic thickness gauge.
  8. Dust content of the bags content that might have been influenced by the packaging difference.

The solution finally found was to use a 6mm diameter endoscope and insert along the bag glue seam. The plastic was visible and an economical solution found to a potentially very expensive problem.

Whatever your problem we are always ready to offer advice and in most cases find a solution.