Mould making
A competent mould designer must have a thorough knowledge of the principles of mould making as the design of the various parts of the mould depends on the technique adopted for its manufacture.
This chapter is included primarily for the beginner who does mot have background knowledge of the various machining and other mould making techniques. To cover the topic of mould making thoroughly would require a companion work equal in size to this monograph and therefore this inroduction to the subject must, of necessity, be superficial. However, we hope that very fact that it is included in a monograph on design, will emphasi the importance of mould making as a subject and will also encourage the beginner to a further and more complete study in this field.
The majority of moulds are manufactured by the u of conventional machine tools found in most modern toolroons. From the manufacturing viewpoint we classify the mould into two parts(i)the cavity and core, and (ii) the remainder of the mould . Thelatter parts is commonly
referred to as bolster work.
The work on the cavity and core is by far the most important as it is from the members that the plastics moulding takes its form .寂寞在唱什么歌
The work on the cavity and core can further be classified depending upon whether the form is of a simple or a complex nature . Fir example , the cavity and core for a circular or ectangular box-tupe moulding is far simpler to make than a cavity and core to produce ,say a telephone handt moulding . The mould parts for the simple form are produced on such machine
tools as the lathe ang the milling machine , whereas the more complex form requires the u of some kind of copying machine .
The bolster work is mot as critical as the manufacture of the cavity and core forms but nevertheless , accuracy in the manufacture of the various parts is necessary to ensure that the mold can be asmbled by the fitter without an undue amount of bench-work.
Now, while the bolster work is always produced on conventional machine tool , the cavity amd core, particularly the former , can be produced by one of a number of other techniques .The include investment casting, electro-deposition, cold hobbing, pressure casting and spark machining.
项目投资合作协议1. MACHINE TOOLS
The purpo of any machine tool is to remove metal .Each machine tool removes metal in a different way. For example, in one type (the lathe) another type (the milling machene ) a cutter is rotated and metal is removed as the work is peogresd geneath it .
羊侃Which machine tool is to be ud for a particular job depends to a large extent upon the type of machining required. There is , however , a certain amount of overlapping and some machine tools can be utilized for veral different operations. In the illustrations which follow, typical machining operations are illusurated but it must mot be assumed that the particular machinetool is restricted to the operation shown.
The machine tools which will be found in the modern toolroom are as follows:
i) Lathes for turning , boting and screwcutting, etc.
ii) Cylindrical grinding machines for the production of precision cylindrical surfaces .
落花生课文iii) Shaping and planning machines for the reduction of steel blocks and plates to the required thickness and for ‘与我同眠下载squauing up’ the plates .
iv) Surface grinding machines for the production of precision flat surfaces .
v) Milling machines for the rapid removal of metal, for machining slots , recess ,boring holes machining splines , etc.
vi) Tracer-controlled milling machines for the accurate reproduction of complex cavuty and core forms .
In addition to the above list of major machine tools there is , of cour , ancillary equipment without which no toolroom would be complete .This includes power saws , drilling machines ,toolpost grinders , hardening and polishing facilities , etc.
禁字组词2. CASTINGS
地板砖图片 The manufacture of cavities and cores in steel by the conventional casting method uding sand moulds is mot satisfactory owing to the poor finish obtained and to the porosity which
拧的组词occurs on , or just below , the surface of the casting . The expenditure involved in plugging ,machining and finishing the concentional castings makes this method of mould making uneconomic .
The shaw investment casting pricess does mot , however , share the disadvantages associated with sand casting and is therefore applicavle to the manufacture of cavities and cores .The process is carried out by specialists and the mouldmaker supplies the company with a pattern
of the required mould part . As the final casting will be an accurate reproduction of the pattern supplied , this must be manufactured to clo tolerances and have a good surfac
e finish . To allow for the contraction of the steel on cooling the pattern is made approximately 0.020mm/mm(in/in)oversize .
