In-process Monitoring of Micromoulding – Assessment of Process Variation

Abstract

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Characterization of the microinjection molding process

“…Plunger stroke at 0.2 s packing had the highest COV at around 15%. This was probably due to the small absolute values of the plunger stroke at the 0.2 s. The COVs of other CPPs were comparable to the results reported for peak cavity pressure and cavity pressure curve integral by Whiteside et al [5] for a 23-mg product. The COVs of the average plunger velocity, ranging from 2.43 to 11.2%, indicated the validity of both Eq.…”

“…The cavity pressure was not measured in this study, because of the restricted space available for such measurement. However, both Whiteside et al [5] and Kuek and Angstadt [12] found that, for similar gate dimensions at lower mold temperature, the cavity pressure increased for $100 ms before starting to decrease due to gate freezing. In this study, the CPPs for the packing stage are defined at 0.2 s, when packing was still in effect.…”

“…Whiteside et al [5][6][7] monitored the dynamics of both the injection pressure and cavity pressure and studied the flow behavior by visualizing the polymer flow through a transparent cavity and using sol-gel film ultrasonic sensors. It has been reported that cavity pressure measurements offer the most sensitive indicators of process variation.…”

Morphological evolution of HDPE parts in the microinjection molding: Comparison with conventional injection molding

“…Many micro and microfeatured products, such as micro sampling cells, micro heat exchangers, micro pumps, biochips, and optical grating elements have been successfully injection molded 4, 5. Parts manufactured by microinjection molding fall in one of the following three categories: Type A is parts with microweights in the milligram range; Type B is parts with microstructured regions which are characterized by local microfeatures on the order of microns, such as microholes and slots; Type C is parts exhibiting dimensional tolerances in the micrometer range but without dimension limit 6–8…”

“…Specific conditions should be chosen for a good replication of microparts 7. Lots of studies have investigated the effects of the main process parameters on the micro molding process, including mold temperature, injection speed and pressure, holding time, and holding pressure 8–11. However, the current knowledge regarding the influence of microinjection molding on polymers is not yet clearly defined, and only a few researches on the morphology and properties of the polymer microparts molded by microinjection are available 7.…”