Monday, September 29, 2008

Elimination of Adjustment

Adjustment is a major source of downtime due to changeover. It is closely associated with conversion of internal to external – the adjustment is done externally. One of the basic ideas behind conversion from internal to external is elimination of assembly during downtime. By a simple exchange of preassembled components, setup is reduced.

To eliminate adjustment, the preassemble component is adjusted externally, or all assemblies are standardized, so that no adjustment is required. Examples of external adjustment are pre-heating of plastic injection molds, and shimming of dies in a trial press. Examples of standardization to eliminate adjustment is using a common die height for all tooling going into a specific stamping press or injection molding machine, and the use of keyways and locating pins to place tooling in a precise position without the need to measure off a datum point.

In most cases, it will require detailed study to determine the relationship between final settings and the conditions of the setup – what factors are influential, and how to measure and adjust for them prior to starting the setup. Keen observation, statistical analysis, and trial and error are all useful approaches. The key approach is to insist that it is possible to understand the relationship, and to make the necessary adjustments beforehand. Chemical processes can be particularly difficult to understand completely. In many cases, simple approaches, such as cleaning, and maintaining a constant environment, including temperature and humidity, will go a long way toward reducing and eliminating the amount of adjustment required as an internal activity.

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