SCIENTIFIC MOLDING

This should provide a clear understanding of “Scientific Molding”. A term that has been coined to describe the logic steps to successful and optimal injection molding process.

The molding process needs to be based on the plastic variables, not machine performance variations. A common sense approach dictates that it is fundamental for the machine performance to be stable and allow for easy and rapid identification when variation occurs or adverse trends develop. These variations can and will adversely effect the plastic variables thus resulting in poor product performance in both quality and productivity.

The acquisition of data from the key performance parameters of the machine will also parallel with the basic and key parameters for the plastic products. This information provides early warning of mechanical component deterioration, as well as changes in the plastic material (resin). When analyzed with an unbiased, third-party, measuring method that utilizes highly accurate, repeatable, and standards traceable equipment a preemptive capability is introduced and poor part performance can be avoided.

Additional benefits are that scientific and statistical confirmation is available in real-time for solutions the molder implements at the process as it applies to the plastic process variables. With the results being readily available engineers and technicians are by nature more inclined to use it routinely.

A list of basic items should always be looked at in order to keep the method of processing to a logical science rather than the “art form” it is often referred and sometimes believed to be. This starts with the basics of the mold or tool. The cavity(s) should be in good repair in respect to surface, parting line, and venting where applicable and in multiple cavity applications the fill should be balanced evenly. All water lines must be clear of obstruction and provide adequate cooling/heating for the tool/ mold. In the case of new tools/molds the aforementioned process should be qualified prior to releasing it to the production floor.

This basic checklist, when followed routinely, will often eliminate potential problems that are the root cause of defects in the molded product or at the very least induce added variation into the already existing plastic variables.

In general terms “scientific molding” uses two or three stage molding based on the control capability of the machine. The initial or boost stage of injection (1) is used to fill the mold cavity(s) with plastic (approximately 95%). Next, if so equipped, is the pack stage (2) and completing the overall injection portion of the process with the holding pressure stage (3). When this is accomplished with a highly accurate and repeatable velocity based closed-loop controller immense improvements are realized in quality and throughput.

Acquisition of performance data from Cycle, Inject, Hold, and Plasticate times along with pressure performance data for peak injection, hold, and back pressure allows for identification of changes in both machine performance and plastic material property changes as they begin to occur and prior to poor part quality production. Once the process stabilizes to an acceptable level of performance and quality additional parameter data can be utilized as needed or desired for processing “refinement” such as cavity and melt pressure, mold, barrel, and oil temperature to mention some popular options with the addition of the appropriate sensors.

This balanced and scientific approach to molding delivers a logical and the highest yield results for the plastic processor with out requiring lengthy training or difficult to use equipment.