Design limitations imposed by processing method

Before product design can commence in earnest, the designer must have considered which processing method to employ, since this has a direct bearing on the design. 

GRP hand lay-up methods are suitable for simple open design shapes (chair shells, covers, etc.) which can be easily removed from the wooden or metal 

Blow moulding is used to manufacture enclosed shapes (bottles, barrels, containers, etc.) where the shape is simple. Screw threads can be formed on the top, corrugated sections can be used to stiffen the product, and handles can be incorporated. Thinning will occur on the corners of the base and also on the corners in the sides of square bottles, but can be reduced by blowing a profiled parison. Some orientation is created in the blowing the parison, and is largely retained in the finished product (e.g. at a maximum in the vertical walls of a bottle). 

Extruded parts are normally one-dimensional and of a simple cross-sectional shape (curtain rail, rainwater gutters, pipe, or films which are produced from a very wide die and hauled off at a faster rate to produce orientation). In the extrusion of sections, the part thickness will affect distortion, and may lead to sinking and voiding. The polymer chains are extended in the direction of extrusion and the properties are correspondingly anisotropic. 

Thermoplastic injection moulding is by far the most common moulding process in use, as well as being amongst the most complex. Normally, injection moulded parts have features which are formed parallel to mould opening (two-dimensional features). Features perpendicular to mould opening are possible 

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