模具专业英语 作者 王浩钢 14456第20章.pptVIP

Lesson 20 Bench Fitting 　　Irrespective of the machine tool or technique used to manufacture the various parts of the mould, the final responsibility for the finishing of the individual parts and for fitting them together lies with the bench fitter. 　　The mould finishing and assembly procedure adopted by the bench fitter varies from toolroom to toolroom; it is therefore impossible to set down a standard pattern for the work. 　　In consequence, we intend only to indicate the general approach to this problem without going into details. 　　We will do this by considering the various stages in the bench fitting involved in the manufacture of a simple mould. The various stages are listed as follows. Stage1. Finishing the impression 　　When the mould plates are received from the machine tool section, the impression form (on both plates) is in the rough machined state. Cutter marks, burrs, etc., are very apparent on the surface. 　　The bench fitter’s first job is to produce a cavity and core free of machine marks and to the shape and dimensions specified on the mould detail drawing.① Stage2. Aligning cavity and core 　　This operation is to align the two parts with respect to each other so that the molding produced will have the correct wall section. This is achieved by using packing pieces between the cavity and core. 　　The two mould plates are clamped together and returned to the milling or jig boring machine to have guide holes bored through both plates. 　　When this operation is complete, the clamps are removed, the mould plates separated and the guide pillars and guide bushes fitted. 　　The two mould plates are again brought together and checked to ensure that the core is in alignment with the cavity. Stage3. Bedding down 　　This is the process of ‘marrying’ the two opposing mould halves together to prevent the plastic material escaping between the two surfaces when the material is injected into the impression.② 　　One surface (the core plate in our exam