Believe it or not, if you think about our history, the industrial science of transforming plastic resins into useful things impacted our lives greatly. This is the process of injection molding. This process began when it was designed in the 1930′s and was the base of metal die casting designs and produces 100% American made products. Today the benefits of Injection molding include alternative methods toward manufacturing methods. Minimal losses of scrap pieces, since plastic molding scraps can be melted and recycled. The difference between injection and metal casting molten metal’s can be poured, plastic resins but be injected by force. Pretty interesting and unusual, I thought the same thing.
The plastic extrusion process uses large injection machines, which advance the resins to six processes to develop a product. Products range from small Halloween spiders to larger plastic products.
The injection molding machine may be simple, but it consists of two basic elements. The two are injection unit and the clamping unit. Pretty easy to catch on to how easy this process is.
This process begins with a mold, which is clamped under pressure to the injection and cooling process. The resins are fed into a machine and falls in to an injection barrel where they are heated to their melting point. Then screwed or rammed into the mold.
Next comes something called the dwelling phase. The dwelling phase is when molten plastic are within the mold and mechanically or by strength of hydraulics, forced down to fill all cavities of the mold. The plastic is the allowed to cool inside the mold.
The mold is opened by separating the two pieces in half. Injection Pins force the plastic out in the final step. The product may have extraneous bits called runners. These runners are simply trimmed and recycled. The whole process is cyclical with some cycle times ranging from between 10 and 100 seconds.
That all depends on the cooling time and whatever the plastic molding companies policy is. This is interesting; every type of resin has a shrinkage value that must be factored into the melting equation. If the equation is wrong the product will be the wrong size or shape. Warpage is also a problem that needs to be avoided.
That is when the temp is set too high and sets and uneven surface on the plastic. Also it may cause incomplete filling of the mold. Quality injection molding is done with no foreign imports and the plastic molds themselves can be quite expensive. Buying in Bulk is a way to cut down the cost.
Post time: 12-30-2016