The tool is manufactured in brass using conventional milling to perform the experiments. The overall size of the mould insert is 25 x 28 x 5 mm with four 3 mm holes for ejectors as shown in Fig. 1 (b). A single open gate design was used to reduce pressure and temperature that could affect the gating. Then, the tool halves were assembled and inspected using a primary mould tool for parallelism before the mating faces were shut off. The part design is made up of many features that could determine the mould accuracy. The influence of the process parameters in replication capabilities could be determined by comparing the dimensions of the tool and mouldings and the part weights.

Fig. 1. (a) Microfludic test part design (b) and it’s mould insert

3.3. Design of experiment

In this study, four process parameters at two levels given below were employed:

A - Barrel temperature (Tb); Level 1=240, Level 2 = 300 B - Mould temperature (Tm); Level 1 = 70, Level 2 = 130 C - Holding pressure (Ph); Level 1 = Off, Level 2 = On D - Injection speed (Vi); Level 1 = 200, Level 2 = 800

In order to investigate the level of process parameters that affect the replication process in micro injection moulding process, the demoulding force during the ejection process was focused as the measured response in this experiment. Because this experiment has multi factor effects it will not be easy   to

study the effects of so many factors since every factor can behave differently at certain point [15]. At the same time, it is essential to know which factors and their interactions are significant for a proper design of experiment. Therefore, it is necessary to use a factorial design to investigate several factors. In this study, the Taguchi method was used to reduce the number of experiments that needs to be conducted without compromising the outcome. Thus, for the four process parameters considered at two levels each a Taguchi L16 Orthogonal Array was selected (see Table 1). Then, the demoulding force was measured as the response for each set of control parameters. The trial was repeated ten times at the same parameter settings in order to measure process variation.

Table 1. The Taguchi L16 Orthogonal Array

Fig. 2. Battenfeld Microsystem 50 injection moulding machine

4. Experimental results and analysis

In studies of influencing factors that affect the replication capabilities in micro injection moulding, the demoulding force was used as a response variable to indicate the output of the process. As discussed before, the demoulding force of micro injection moulding is important as it affects the quality of the moulded part. The experiment was conducted by repeating each run 10 times and the average demoulding force was noted as given in Table 2. The test results were analysed using Signal to Noise (S/N) ratio and ANOVA. S/N ratio is very useful measure for improvement of quality through reduction of noise and improvement of measurement [Ranjit, 2001]. Table 2 presents two different set of results based on the measured responses where S/N ratio is considered to be nominal-the-best  and larger-the-better.

摘要：本文的重点调整微注射成型工艺参数。在这项研究中四个处理参数即，机筒温度，模具温度，保持压力和喷射速度进行了审议。为了捕获他们的行为L16正交阵列具有两个水平的每个参数被用来产生使用环烯烃共聚物（COC），公共聚合物有15毫米×20毫米×1毫米微流体平台的设计。微注射成型过程中，测定脱模力。十六个试验是重复10次以纳入实验过程工艺变化，系统性和随机噪声。使用田口实验法识别过程参数的在所述脱模力的影响以及它们对噪声的敏感度的结果进行分析。此外，该结果还表明无论存在或不存在这些过程参数之间的二级相互作用。这项研究对于理解他们的主要影响，相互作用，对噪声敏感的方面，这些工艺参数的特性，并调整他们贡献了他们的最佳性能。论文网