Manufacturing - Back to Basics
Posted : August 21, 2004 at 12:07 pm [IST]
Manufacturing Technology- Machining-1
Machining is a major manufacturing process in engineering industry. Performance of the product to a large extent is dependent on the accuracy and consistency of the machining processes used to produce the parts.
Machining constitutes, generally both cutting and abrasive processes that are mostly complimentary. Traditionally, metal cutting processes were used for bulk metal removal and were followed by abrasive machining processes for finishing. Again, for hardened parts abrasive machining processes were the only methods to machine to the specifications. Abrasive machining is still more precise process and normally applied for closer tolerance. However, with new cutting tool materials and better machine tools, hard turning/boring now is getting established as precision machining process eliminating grinding as finishing process.
Tolerance ranges for size, geometricity, surface finish, and surface integrity of various processes are different. Tighter tolerances require finish processes of better process capability. The tolerance range of some of the competing processes may overlap, as the capability of a machining process can be enhanced with special monitoring and slowing of speed of operation in number of cases. Relative cost increases, as tolerances become finer. Evaluation of all possible options of machining processes is necessary to reach at the optimum combination of the processing steps. Conventionally, abrasive machining are resorted to achieve the superior tolerances of size and surface finish, or to machine extra hard components not possible to be machined by cutting processes, or because some unique condition of the subject component e.g. shape or size does not make metal cutting feasible or economical. Process planning and tolerance at different stages have become critical to achieve the tighter tolerances demanded by the product designers during manufacturing.
Cutting parameters in machining-speed, feed and depth of cut (DOC) are to be the maximum to reduce the cycle time. Cutting parameters are dependent on machine tools, work-holding, cutting tool materials and their capability to withstand the heat generation and shock loading during the cutting, tool rigidity, and coolant. Tool size and tool holding methods determine the tool rigidity. Cutting fluid provides cooling of the interface of work-piece and cutting edge and facilitates flushing chips away from the work-piece. Tool life is another important consideration in machining that demands careful attention. Trend is to achieve a tool life that provides the minimum cost per part machined by the tool.
Some Updates on previous entries
1. Harsud does not exist any more. It is submerged in water of Indira Sagar Dam. But according to a news report, many of the inhabitants are fighting legal battle to share the compensation money that the family got. It is an anti-climax itself as against the complaints of Meda Patkar and Arundhati Roy, about which I wrote earlier.
2. An update on gold holding: Indians hold 13,000 tonnes of gold worth Rs 660,000 crore. Indians hold 7% of the global stock of 147,000 tonnes gold.
3. Atal Bihari Bajpai- the former Prime Minister got the number of his present residence of the Krishna Menon Marg bunglow got changed from 8 to 6A for making it numerologically auspicious.
- Indra
Category: Manufacturing |
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