Thickness Monitoring for Process and Quality Control

Accurately measuring layer thickness is critical to ensuring consistent quality, minimizing defects, and reducing material usage for products such as tubing, tires, plastic bottles, adhesives, and coatings. 

Terahertz technology provides a solution for thickness measurement that, unlike other traditional methods, is non-contact, works with both opaque and translucent materials, and works well for multilayer structures. 

Multilayer Web

Manufacturing a consistently flat sheet of multilayer material, whether it is Thermoplastic Olefin (TPO), rubber single ply roofing (EPDM), or ply balance in tire manufacture, can be challenging for traditional gauges. Terahertz sensors can measure multiple layers with a single sensor, allowing deployment with a single scanning frame over the product and no nuclear or ionizing radiation. Accurate measurement, coupled with automatic feedback to the extrusion die or calender, can provide substantial cost savings.  

Multilayer Thickness Monitoring for Plastic Packaging

Examination of multilayer, thin-wall packaging is a key application for terahertz sensing. Thermoformed plastic containers for food often include an EVOH vapor barrier layer to prevent flavor contamination or spoilage during storage. The plastic sheet may consist of two polyethylene layers separated by a thin EVOH layer. Traditional methods such as infrared gauges cannot distinguish between the top and bottom layers and only measure the total polyethylene present. Engineers often resort to examining the product edge under a microscope to measure layer thicknesses. In contrast, a single terahertz sensor can simultaneously measure all three of these co-extruded layers.

Tubing Wall Monitoring

Manufacturing precision tubing with single and multilayer walls requires monitoring wall thickness, concentricity, outside diameter, and inside diameter. Terahertz sensing provides a simple, universal solution for measuring all these critical parameters. Terahertz sensors are non-contact, completely safe, and can deliver the high measurement rates needed for real-time process control. Because terahertz pulses travel through the tubing walls, a single sensor can simultaneously measure the front and rear walls of a multilayer tube. 

Terahertz technology also monitors the thickness of many other products, including tire ply, roofing, coextruded plastics, insulation, foam products, shingles, etc.