SMED and TPM

Standardization is not just for tooling or the element that is being exchanged. It applies to what is not being exchanged, the machine or permanent element. Adjustment becomes necessary if the exchanged element, or the permanent element, or both, have variation in performance. It is especially difficult to get right if both are varying from one run to the next.

Standardizing the tooling or exchanged element will not eliminate adjustment if the permanent element, a machine, system, or program, is not stable and standardized. There is thus a link between SMED and TPM, between setup reduction and maintenance. Wear, vibration, and other kinds of drift from the design condition all create problems that must be dealt with during setup. This kind of instability is particularly troublesome, because they cause the internal aspect of the changeover to take more time. If the condition is not known, or not dealt with during scheduled maintenance, then it must be dealt with, whether directly, or provisionally, during changeover. The second approach is, unfortunately, more common, because of the rush to get back up and running. Thus, the problem is faced again and again, with no chance for standardizing the internal setup procedure.

Careful observation is required to disentangle the sources of variation. Preventive maintenance and equipment improvement are necessary to eliminate variation in the permanent element of the production system.

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.