Kistler and STASA develop an automatic method for the prognosis of injection molded part quality

Swiss company Kistler Instrumente AG of Winterthur is the leading international supplier of sensors and systems for in-line cavity pressure-based quality monitoring of injection molding processes. German specialist Steinbeis Angewandte Systemanalyse GmbH (STASA) with headquarters in Stuttgart has many years of experience in the development of process models, online prognosis of quality features based on characteristic process values as well as the application of complex mathematical methods and models to industrial processes. This expertise is based on scientifically corroborated methods such as the design of experience (DoE) and the generation of models, and can be reliably applied to injection molding.

The implementation of approved Kistler systems into process-related quality monitoring of injection molding processes based on process profile characteristics such as the properties and tolerances of the cavity pressure curve is already widely established. Kistler and STASA have now joined forces to develop an enhanced quality monitoring method for injection molding processes that allows the direct quality monitoring and definite prognosis of the quality of the currently molded part by using the quality models of the STASA QC program. Based on the process models and measured process parameters, the final dimensions of the molded part can be predicted online, i.e. while the part is being produced. Immediately after injection molding, this approach provides information on whether the part will meet specified dimensional tolerances when it is used.

The new concept has many benefits for manufacturers and OEMs of injection molded products: they will receive information on the tolerance limits directly from the part specification and can use this criterion as a parameter of the process monitoring system. This technique significantly enhances in-line quality monitoring of injection molding processes: the limits of monitoring parameters such as pressure maxima, pressure integrals and other values need no longer be defined and evaluated. Instead, the relevant correlations between process profiles and quality criteria are acquired during mold sampling and are then used for process monitoring. The DoE used during mold sampling has beneficial side effects, because the injection molding process can be optimized automatically and ideal parameters for meeting the required quality criteria can be defined within the process latitude.

This combination of process and quality monitoring with quality prognosis has long been requested by molders of high-quality, extremely sensitive, hard-to-assemble moldings such as producers of medical parts and pharmaceutical components. This technology is integrated into Kistler CoMo Injection process monitoring systems as an optional module. Quality prognosis will become available as a high-end option for the CoMo Injection during the course of 2011.

Background: Quality Assurance with Mold Cavity Pressure

The cavity pressure curve is considered to represent a fingerprint of the injection molding process. It is the most informative characteristic for evaluating the quality of the part. Deviations from the optimum curve are clear indications of process fluctuations that lead to part defects ranging from incomplete mold filling to flashing or dimensional discrepancies.

As the supplier with the largest and widest range of sensors for all methods of injection molding, simple connection technology and intuitively easy to operate, networkable systems, Kistler is the only manufacturer to offer holistic monitoring of injection molding from a single source. Kistler is the world's leading manufacturer of pressure and temperature sensors for use in the plastics processing industry.

Kistler Group

Kistler’s core competence is the development, production and use of sensors for measuring pressure, force, torque and acceleration. Kistler’s know-how and electronic systems can be used to prepare measuring signals for use in analyzing physical processes, controlling and optimizing industrial processes, improving product quality in manufacturing and improving performance in sports and rehabilitation.

Kistler offers a comprehensive range of sensors and systems for engine development, automotive engineering, plastics and metal processing, installation technology and biomechanics.

A worldwide sales presence in the form of 25 group companies and 30 distributors ensures customer proximity, application support on an individual level and short lead times.

With a staff of about 1 000, the Kistler Group is one of the world’s leading providers of dynamic measuring instrumentation. The Kistler Group achieved turnover of 166 million Swiss Francs in the 2009 financial year.

STASA Steinbeis Angewandte Systemanalyse GmbH

STASA Steinbeis Angewandte Systemanalyse GmbH was founded by Prof. Dr. Günter Haag and is a member of the Steinbeis network. The specialist’s objective is the utiliza-tion of useful innovations on the leading edge of research and development in order to keep industrial customers abreast of the competition by leveraging their expertise. A selected team of highly qualified experts is providing solutions to complex tasks in the area of applied analysis, model development and simulation of technical systems. The integration of innovative statistics and physical methods is one the specialist’s core competencies. The STASA QC application won the do-it Software Award.