Influence of Injection and Cavity Pressure on the Demoulding Force in Micro-Injection Moulding

Abstract

The paper reports an experimental study that investigates part demoulding behavior in micro-injection moulding with a focus on the effects of pressure and temperature on the demoulding forces. In particular, the demoulding performance of a representative microfiuidics part was studied as a function of four process parameters, melt temperature, mould temperature, holding pressure, and injection speed, employing the design of experiment approach. In addition, the results obtained using different combinations of process parameters were analyzed to identify the best processing conditions in regards to demoulding behavior of microparts when utilizing a COC polymer to mould them.

Micro-nanostructured polymer surfaces using injection molding: A review

“…Consequently, to achieve a complete and preferable replication, a combination of different processing parameters is necessary. A design of experiments (DoE) method has been used in a number of studies 18,20,28,86,88 . Through a DoE method, experimental data is acquired in a controlled way; the significant and non-significant factors affecting a process are determined, and, finally, the behavior of injection molding of micro-nanostructures can be carefully monitored.…”

“…No matter how high the mold and melt temperatures are, a great pressure is needed to push the molten material into the structures. In addition to the role of holding pressure in pushing the polymer into the holes, it also could compensate for the trapped air pressure and polymer shrinkage 28,53 . It has been reported that pressure over 150 MPa is an appropriate holding pressure for a complete filling of micro-nanostructures, however too many processes work with lower pressures 53 .…”

“…Use of chemical demolding agents is restricted in the medical or some microfluidic applications due to probable harmful effects on human health 57 . Mechanical ejectors can lead to permanent deformation especially when the part geometry is complicated or the distribution of the ejector pins is not appropriate 28,109 . Therefore, a proper design of produced tool and the location of ejector pins is necessary to avoid damage and failure to the polymeric parts 20 .…”

“…As different polymers have various rheological, thermal, mechanical, electrical, and optical properties, polymers with the desired flow properties and a low viscosity at high temperatures are suitable as materials for microinjection molding 20 . A wide range of polymer materials have been studied 19,[21][22][23][24][25][26] including thermoplastic polymers such as polystyrene (PS) 18 , cyclic olefin copolymer (COC) 3,20,[27][28] , poly methyl methacrylate (PMMA) 19,27 , polypropylene (PP) 19 , polysulfone (PSU), polyoxymethylene (POM) 29 , polyethylene (PE) 19 , polyamide (PA) [30][31] , poly ether ether ketone (PEEK) [32][33] , polycarbonate (PC) [34][35] , liquid crystal polymer (LCP) 29 , polybutylene terephthalate (PBT) 36 , acrylonitrile butadiene styrene (ABS) 35 , polyphenyl ether (PPE) 37 , and liquid silicone rubber (LSR) as a crosslinking polymer material 38 . To the best of our knowledge, only a few studies have been carried out on rubber materials 38 , a research area that our research group is actively investigating.…”

Investigation of the Integrity of aC:H Coatings on Stainless Steel Micro-Moulds during Thermal Cycling

“…However, a coating with a lower level of surface friction than typical metals used for moulds, such as steel, can be added to the mould to decrease the ejection stress [5]. Griffiths et al [6] report how to monitor such forces during ejection of microsized parts as it is considered such an important factor but is not of high concern during conventional injection moulding. De Santis et al [7] developed a system whereby the mould surface temperature could be increased by some tenths of a Celsius degrees in a matter of a second.…”