The Plastic Injection Molding Process

الخميس، 26 يناير 2017

By Ann Foster


Fundamentally, injection molding refers to manufacturing processes in which plastic granules are heated to melt and forced through some mold cavity. The process is commonly utilized in producing plastic parts. In addition, plastic injection molding enables the production of various products. Such products usually differ in size, application and complexity. The process nevertheless needs raw plastic materials, machines as well as molds.

The raw plastics are first melted in the machine and then injected into a mold where cooling and solidification takes place. In Cobourg, ON, this process produces thin-walled parts of plastics for many applications with the common one being plastic housings. These housings are normally used with many products such as consumer electronics, household appliances, automotive dashboards, and power tools. Other products produced are such as open containers like buckets.

Injection molding cycles normally are four-phase processes lasting a minimum of 2 seconds up to two minutes. The initial phase is termed as clamping. Normally, before materials are injected into casts, it is necessary to ascertain that all the 2 halves become securely shut with clamps.

During the injection stage, every half is attached to the machine and one half is made to slide. The clamping unit is normally hydraulically powered and pushes these mold halves together while exerting enough force to ensure the mold is closed securely while injecting the material.

The next phase entails infusion raw plastic pellet continuously into the molding apparatus. In this phase, raw materials are melted using continuous application of heat and pressure. The melted materials are then imparted into the casts where additional pressure build-up holds and compacts them. The quantity of imparted material is called a shot. The interval or time duration that the phase lasts is generally hard to ascertain. However, estimations are generally gained by relying on the injection power, injection pressure as well as quantity of shot.

The third phase is cooling. Here molten materials contained in molds are left to cool as they gain contact with the internal mold surfaces. They then solidify and take the desired shapes. Nonetheless, some shrinking can happen as the cooling takes place, although packing of materials at this point usually allows for addition of material into the molds that reduces any visible shrinkages.

Ejection is the final stage normally happening after adequate time passes to allow the cooled portions to be ejected. The ejection is done by an ejection system. Once a mold is unfastened, the parts are taken off the mold. Force is usually applied to eject parts because they may shrink and stick during cooling. To enable ejection, molds release agents are also utilized by spraying on mold-cavity shells prior to material injection.

Once this cycle elapses, post-processing procedures are undertaken. This is as the cast held materials usually become solid on cooling and stick onto the parts. Nonetheless, any extra materials as well as flashes that might have occured ought to be clipped off from the part.




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