A polyethylene terephthalate (PET) manufacturing plant was struggling with high variation in the metrics of their plastic sheet. They reached out to Precision Roll Grinders (PRG), a roll service provider with proven value in the rubber and plastics industries. The rolls from the facility’s four-roll L calender were sent in for grinding for roll profile, roundness, and journal concentricity to roll face.

In plastics manufacturing, calendering is a process where heated rollers apply pressure to opposite sides of a forming plastic film. The plastic material is extruded at the nip of the first rolls with the product then flattened and compacted under load and temperature as it is squeezed through the gap between the rolls, resulting in compression and finishing of the sheet. Calendering is known to be linked to process optimization and production outcomes, affecting thickness variation, smoothness, printability, and gloss. Gloss is metric of plastic films that describes a sheet’s optical properties and ability to reflect light at different locations on the material surface.

Upon install of the precision ground calender rolls, the maximum-minimum gloss value representing the variation in the material gloss across the plastic sheet immediately improved. Gloss variation dropped by 30% at the time the rolls went into the machine, an indication of the improved consistency of the sheet in smoothness and optical properties including the ability to reflect light in a repeatable way. Sheet uniformity reduces customer returns and rejects.

Contact Precision Roll Grinders for more information about improving consistency in your product and process through precision roll grinding solutions.