First Shot Samples Polished before the Buyer Ever Sees Them
Doctored T1 samples hide draft and thermal flaws through hand polishing; enforce raw steel T0 audits with continuous cavity telemetry before sign-off.
Shear Thinning Viscosity Curves
Meaning
Mathematical curves illustrate the relationship between the shear rate and the viscosity of a polymer melt, showing how the material becomes thinner as it flows faster. Analyzing shear thinning viscosity curves is a fundamental part of the mold design process, as it helps engineers understand how a resin will behave as it moves through the gates and into the cavities. This property is what allows plastics to be molded into thin-walled parts with complex details.
Viscosity Reduction
Alignment of the long polymer chains in the direction of the flow reduces the resistance between the molecules and lowers the viscosity. This effect is most pronounced at high shear rates, which are typically found in the narrow gates of a mold. Because the material becomes easier to push as it goes faster, designers can use smaller gates and thinner runners without requiring excessive injection pressure.
Process Application
Curves for different materials are used to select the best resin for a specific part geometry. A material with a very steep curve may be difficult to control because a small change in speed will result in a large change in viscosity. Conversely, a material with a flatter curve is more forgiving and easier to process on a wider range of equipment.
Model Accuracy
Rheological data used to build these curves are typically generated in a laboratory using a capillary rheometer. While these models are very useful, they may not perfectly capture the behavior of the material in a real-world moulding machine where the temperature and pressure can vary. The accuracy of the curve is most reliable in the middle of the shear rate range and becomes less certain at the very low or very high extremes.