ISO 9001:2008 recommends taking PROCESS APPROACH to quality Management.In an Industrial Injection molding plastic set up which parameters one should watch to improve the repeatability of Molding.

Bhaskar,

Assuming you have already developed a molding process that yields an acceptable part, you're halfway to your answer. The Big 8 key process input variables (KPIV's) include injection pressure and speed, transfer position, melt temperature, cooling time, mold temperature, holding pressure and holding time. Monitor these regularly. Use your molding machine's SPC capabilities (hopefully it is so equipped) . The more stable these outputs are the more consistent your process is. And assuming again that you properly developed the process, you can be more confident that your product will consistently meet specification.

Thanks Mr. Robert,
First part of your comment is perfectly understood. Now a days machines have PLCs and the parametres like temp. stroke & time can be stored in memory and can be recalled every time we reload the mold. Your suggestion of SPC ,we have choce of parameters to be monitor during the production such as Injection(Fill) time, switch over position, cushion, refill time , peak pressure etc.These are not set but achieved due to combined effect of mold temp. melt temp. machine repeatability etc. Which of these you will suggest to monitor so that one can judge the process quality and also it will suggest us about quality of our parameter setting. I hope I am clear in my explanation.

In our mouldshop we continuously monitor the injection time, cushion, loading time, and cycle time with tight tolerances. Every type of problems will reflect on these parameters. If the parameters out of tolerance you can. pit the parts to the scrap with robot, or stop the machines immediately when the scrap rates going too high.

From my experience with electrical connectors there are very few if any machine provided variables that correlate well to product quality. That is why some people use cavity pressure transducers. You can however establish alarms around those variables mentioned above and they will at least tell you if the machine did what it was supposed to do. With that said, I always recommend you consider part weight when establishing and monitoring your process. Suggest to do a DOE and use part weight along with critical dimensions as outputs. Find your process window and determine the range of weights at which acceptable parts are produced. Include that in your process documentation and at a minimum check the weight prior to doing each in-process dimensional check. A good process variable to monitor is injection pressure since it gives you a good indication of your normal thermal variation and also, if nothing else changed, will tell you when melt viscosity is varying. If injection pressure starts to trend out of limits it is time to check to see what has changed (for example a new lot of resin, improper blend of virgin and regrind or the dryer not working properly). Happy Molding!!

Well said Matt, it is your Guidance and Involvement, we developed complex connectors.
Edaran and GCP will always remember you. We do applied cavity pressure Transducers for
One of North American Project; however in my experience it is just a Measuring Device.
Feedback device/ Method, which fine tunes the molding Process is, statistical Process control.