Friday, March 6, 2015

Six Sigma in Machining Processes

Justifying Six Sigma Projects in   Manufacturing Management
Tapan P. Bagchi, Narsee Monjee Institute of Management Studies, Shirpur
NMIMS Review, 2012
The paper gives justification for investing reducing sigma of ball bearing outer race and inner race grinding operation.

Six-sigma Project on Coolant/Chip System Improvement – Batch 1
IMTMA organized a formal program focused at “performance of the coolant & swarf management on machine tools” through Six-sigma approach during May/ June 2011.

To upgrade machining process capability, Prof. Jerard is conducting research on the process capability of machine tools.

 Currently, CNC manufacturers are providing  two indicators of precision: positioning accuracy and repeatability. But what is the standard deviation of a machine tool?  For example, a machine tool with a standard deviation of 0.002 in. can achieve a six sigma quality level  only when the tolerance band of a part is 0.022 in. If the standard deviation doubles to 0.004 in.,  jump from six sigma quality level to 66,800 defects per million (three sigma).

If machine tools have be made with smaller standard deviations,  error sources such as machine axis squareness, encoder inaccuracy, tool and workpiece deflection, thermal expansion, tool runout and tool wear etc. have to be understood and their impact on standard deviation has to be found. Many of these factors change with time, environmental conditions and usage.

1 comment:

  1. Leaders within a company need to adopt a continuous improvement culture in order to promote it throughout the company.
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