Low pressure structural foam injection molding is a gentle injection molding process which makes use of polyamide or polyolefin hot melt adhesives that is designed as a feasible solution for sealing printed circuit boards, batteries and connectors and provides relief for cables. Now the key to the process is the consideration of raw materials and the specialized molding equipment used. It is always wise to talk to the supplier before doing the low pressure molding process regarding in-depth specifications for the machine. Well! There are some other factors which are necessary for deciding for machines and are discussed in brief below.
The mold should be fitted in the clamping area and this is determined by the spacing on the machine restricting mold fitting and removal. The height and depth of the mold should be accommodated well in the stroke of the clamp and there should be a sufficient opening in the stroke for ejecting the plastic component. For free fall ejection, daylight between platens must be greater than mold height and twice the depth of the component to be ejected.
The clamping unit should supply locking force so that mold stays tight during low pressure structural foam injection molding process, otherwise, the mold will be broken into parts and the molten material will splash out along the mold split line. Most of the times thin wall sections and deep draw depths require 3-4 tons per square inch, whereas thick wall sections and shallow draw depths require 2 tons per square inch. For calculating the locking force during low pressure molding these values can be multiplied by the projected area of the component.
The injection unit is important in low pressure structural foam injection molding and must be capable of supplying component shot weight. The total shot weight should not go beyond the 90% of the injection capacity of the machine otherwise, there will be damage. Usually, the injection capacities are written in grams and whenever any other material needs to be processed, then that component shot weight should be recalculated using that material’s specific gravity.
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