Analysis of cavity pressure and warpage of polyoxymethylene thin walled injection molded parts: Experiments and simulations

Abstract

Influence of mold surface temperature on polymer part warpage in rapid heat cycle molding AIP Conference Proceedings 1593, 189 (2014) Abstract. Process analysis and simulations on molding experiments of 3D thin shell parts have been conducted. Moldings were carried out with polyoxymethylene (POM). The moldings were performed with cavity pressure sensors in order to compare experimental process results with simulations. The warpage was characterized by measuring distances using a tactile coordinate measuring machine (CMM). Molding simulations have been executed taking into account actual processing conditions. Various aspects have been considered in the simulation: machine barrel geometry, injection speed profiles, cavity injection pressure, melt and mold temperatures, material rheological and pvT characterization. Factors investigated for comparisons were: injection pressure profile, short shots length, flow pattern, and warpage. A reliable molding experimental database was obtained, accurate simulations were conducted and a number of conclusions concerning improvements to simulation accuracy are presented regarding: pvT data, mesh, short shots, cavity pressure for process control validation as well as molding machine geometry modelling. Eventually, a methodology for improved molding simulations of cavity injection pressure, filling pattern and warpage was established.

Three-dimensional numerical modeling of an induction heated injection molding tool with flow visualization

“…The first verification of the timings without induction heating showed that both ram acceleration and using machine geometry as hot runner to get the effect of all the compressible material were needed to obtain such accurate results, as demonstrated in [41,42]. This was transferred to the flow simulation together with transient thermal results of the induction heating, and these showed the same trends as in the experiments.…”

Flow visualization and simulation of the filling process during injection molding

“…Pressure dependent viscosity has proved to have an effect on the filling pressure required, and the packing pressure levels. This is shown by Pantani et al [12] and Guerrier et al [14] to give a higher pressure drop through the melt, giving more realistic pressure predictions. The D3 coefficient from Eq.…”

“…This will be referred to as the reference simulation, and this was implemented with the mentioned ram speed, the temperatures and the different (packing, cooling) times specified in the experimental setup. The size and the geometry of the cushion in front of the sprue and up to the nozzle can have a significant impact on the filling simulation of the cavity and must be taken into account [12][13] [14]. This is of particular importance when the volume of the cushion is larger than the runner/cavity system to be molded.…”

Pengaruh Variasi Injection Velocity Dan Packing Pressure Terhadap Kualitas Part Produk Injection Molding

“…Tentunya diperlukan teknologi yang cukup baik dari segi mesin injeksi, injection molding, material, prosedur, dan personel agar dapat menghasilkan produk plastik sesuai dengan yang kita inginkan. Menggunakan pendorong, bahan termoplastik yang meleleh dipompa ke dalam cetakan berpendingin air selama proses pencetakan injeksi, menyebabkannya mengeras (Guerrier et al, 2015). Setting parameter pada mesin injection moulding merupakan salah satu elemen kunci diantara sekian banyak parameter tersebut.…”