G W Owen

Rapid changeover - a pre-requisite for responsive manufacture

The ability to effect rapid changeover on a manufacturing line, from one product to another, is a key pre‐requisite for increased flexibility, lead time reduction and responsive manufacture. However it is a rarity for changeover times to be part of the design specification of a new machine tool or tooling system and even when it is, there are few design guidelines for translating the required changeover time into reality. This paper describes a set of “design for changeover” rules that have been derived from action research, carried out within a variety of companies. The rules address the design of machines, tooling, ancillary equipment and the products themselves and their use has been shown, through case studies, to lead to a significant reduction in changeover time and a leaner, more responsive manufacturing environment.

An assessment of the role of design in the improvement of changeover performance

Discusses the derivation of current changeover improvement methodologies from the work of the Japanese engineer/consultant Shigeo Shingo. Argues that under the interpretation and widespread adoption of the single minute exchange of dies (SMED) philosophy, substantive design‐based solutions are being overlooked in favour of incremental, low cost, team‐based approaches which emphasize organizational changes to the changeover. Identifies difficulties which can arise with existing approaches to changeover improvement and the relative merits of emphasis on design or organization are discussed. Pays particular attention to the problems which have been observed in sustaining levels of improvement.

Bone loss during long term space flight is prevented by the application of a short term impulsive mechanical stimulus

In long term space flight, the mechanical forces applied to the skeleton are substantially reduced and are altered in character. This reduced skeletal loading results in a reduction in bone mass. Exercise techniques currently used in space can maintain muscle mass but the mechanical stimulus provided by this exercise does not prevent bone loss. By applying an external impulsive load for a short period each day, which is intended to mimic the heel strike transient, to the lower limb of an astronaut during a long term space flight (5 months), this study tests the hypothesis that the bone cells can be activated by an appropriate external mechanical stimulus to maintain bone mass throughout prolonged periods of weightlessness. A mechanical loading device was developed to produce a loading of the os-calcis similar to that observed during the heel strike transient. The device is activated by the astronaut to provide a transient load to the heel of one leg whilst providing an equivalent exercising load to the other leg. During the EUROMIR95 mission on the MIR space station, an astronaut used this device for a short period daily throughout the duration of the mission. Pre- and post-flight measurements of bone mineral density (BMD) of the os-calcis and femoral neck of the astronaut were made to determine the efficacy of the device in preventing loss of bone mineral during the mission. On the os-calcis which received the mechanical stimulus, BMD was maintained throughout the period of the flight, while it was reduced by up to 7% on the os-calcis which received no stimulus. Post-flight, BMD in both the stimulated and non-stimulated os-calcis reduces, the extent of this reduction however is less in the stimulated os-calcis. For the femoral neck, the mechanical stimulation does not produce a positive effect.

Set-up reduction (SUR) beyond total productive maintenance (TPM)

Abstract There is a growing awareness of the importance of set-up performance in multiproduct manufacturing environments. This paper contrasts the potential business contribution of conducting set-up reduction (SUR) as an initiative in its own right with the contribution SUR will make as a component part of a rigorously conducted total productive maintenance (TPM) initiative. It is argued that under TPM a business can easily fail to recognize the global impact of SUR and fail to take the opportunities afforded by improved setup times. It is demonstrated that in the nature of TPM, and in the manner in which it is implemented and measured, there is pressure to move away from responsive, small-batch manufacture that SUR promotes. While there is a growing awareness of SUR benefits, there are relatively few reported cases in which sustained long-term improvements have been seen. One reason for this is that although faster changeovers are perceived as a ‘good thing’, there is little in-depth analysis of their impact on overall business performance. A classification is proposed against which the potential SUR benefits may be assessed and the commercial opportunities that can arise through having a more responsive manufacturing system are also highlighted.

Review of fast tool change systems

Abstract The key to success in many manufacturing businesses is a move toward a leaner, more flexible, more responsive manufacturing environment. The ability of a company to change over rapidly from one product to another is essential if this move is to be achieved. There is a significant amount of information in the literature on specific ideas that have been used to reduce changeover times, but in the vast majority of cases this rich source of data is ignored by companies undertaking changeover reduction programmes. Research has shown that, although some companies have a genuine desire to ‘reinvent the wheel’, the main reason why companies fail to tap the information source is that it lacks structure and focus. This review brings together information from research literature, journals, conferences, industrial collaborations and trade and technical literature. The information has been classified, and is presented here as an overview of the state of the art techniques for reducing changeover times.