Non Isothermal Tube Model Characterization for High Speed Thermoforming Stretch
Accurate non isothermal tube characterization reduces thermoforming wall variance to under six percent at hundred hertz stretch rates.
Thermoforming Stretch Characterization
Meaning
Analytical evaluation of plastic sheet deformation behavior under rapid heating and biaxial elongation defines the processing limits of thermoformable resins. Performing thermoforming stretch characterization allows manufacturers to predict how evenly a sheet will stretch when forced into deep-draw molds. This measurement provides the material data required to set accurate heat and pressure parameters on the production line.
Testing Methodology
Stretching tests are carried out on heated polymer sheet samples using specialized biaxial testing frames that mimic actual forming speeds. During thermoforming stretch characterization, the tensile force required to elongate the sheet is recorded across a range of temperatures and strain rates. This profile reveals the forming window of the material, which is the temperature range where the polymer stretches easily without tearing or thinning.
Thickness Optimization
Variable sheet thickness in the final tray is a common problem when processing materials with narrow forming windows. Using the data from thermoforming stretch characterization, process engineers can modify plug and vacuum sequences to improve material distribution in the mold corners. This optimization leads to parts with more uniform walls, which means that less plastic sheet is required to achieve the desired package stiffness.
By thinning the starting sheet without compromising part strength, companies can achieve substantial cost savings across high-volume production runs.
Material Comparison
Comparing different resin grades or recycled sheet materials allows processors to select the best formulation for high-speed runs. Since regrind material often stretches differently than virgin polymer, thermoforming stretch characterization helps compounders adjust additive levels to maintain consistent stretch performance. This control reduces the rate of part defects and prevents machine downtime when switching material batches on the factory floor.