Understanding Plastics Engineering Calculations

Beschreibung

Resin Characterization by power law exponent Effect of shear rate Effect of temperature How to calculate power law exponent - Worked-out example Practical screw design Output Feed and metering depths Motor power Practical die design Step by step calculation of pressure drop in a tube die - Example Pressure drop in a flat die - Example Case studies of optimizing dies Pelletizer dies - Example Blow molding dies - Example Blown film dies - Example Extrusion coating dies - Example Optimizing melt quality Poor melt quality in a coating process - Example Improving melt quality in blown film - Example Air bubbles in a flat film - Example
The plastics engineer working on the shop floor in a plastics manufacturing plant often needs quick answers to questions such as why the extruder output is low or whether he can expect better quality product by changing the resin or if the die pressure can be lowered. Applying state-of-the art numerical software to address these issues is time-consuming and costly. Starting from practical design formulas which are easily applicable, and yet take the resin rheology into account, this guide provides answers to these questions quickly and effectively by guiding the user step by step through the computational procedures on the basis of illustrative technical examples. Problems related to melt fracture, homogeneity of the melt, effect of screw geometry on the quality of the melt and the effect of die pressure on the pellet surface and their troubleshooting are only few of the topics among many that are dealt with in detail. All the calculations involved can be handled by pocket calculators and hence can be performed right on the site where the machines are running. This guide is a valuable tool not only to troubleshoot but also to estimate the effect of design and process parameters on the product quality in plastics processing.
1 Use of easily applicable basic resin rheology as a tool for troubleshooting extrusion processes and machinery 2 Quick and easy calculation of screw and die geometry as a function of resin viscosity 3 Hands-on technical examples illustrating the optimization of blown film, blow molding, coating and pelletizing processes by a step by step procedure 4 All formulas used can be easily handled by pocket calculators , and hence can be quickly applied for on site process optimization and estimation of design parameters of screws and dies

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Natti S. Rao

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