Using optical metrology in injection moulding

Abstract

Quality control (QC) is integral to monitoring and controlling defective or poor-quality products from reaching the customer. Developments in optical metrology promise more accurate measurements and faster turnaround times to QC than current tactile measurements. With the rising demand and complexity of injection moulded products, manufacturers are pressured to produce quality products faster, notwithstanding that the current metrological methods may not meet the output demand. This study investigates the efficacy of optical metrological devices (3-D scanner) as a QC tool for injection moulding. The study followed a quantitative and experimental methodology. This study adopted a probability, simple random type of sampling technique. A sample size of four was used. Measurements of four different products (closures and tubs) were undertaken, including eight attributes of the closures and five different attributes of the tubs. Tests were conducted on two samples of each product, utilising a 3-D scanner and contact measuring devices. The statistical conclusion validity method was used to determine the validity of the data obtained. Repeatability and reproducibility methods were used to determine the reliability of the data obtained from the tests conducted in the study. The results indicated that optical metrology provided insufficient measurements for plastic injection-moulded products. The results also provided an understanding of optical measurements compared to tactile measurements. Based on the study conducted, it can be concluded that even though there are established and emerging optical metrological technologies, such as 3-D scanners, which are versatile and fit for industries such as automotive and aeronautical manufacturing, they are currently not effective or adequate for routine quality control testing in injection-moulded plastic products. Although the 3-D scanner proved to be an inappropriate quality control measuring device for plastic injection moulded products in this study, it is recommended that further investigation is required. The importance of considering aspects such as product size, material composition, and colour of the products in future studies cannot be overstated, as these factors could significantly impact the effectiveness of the 3-D scanner.