Every manufacturing process has periods where equipment is unavailable due to tooling changes, material changes, part changes, program changes, or any other changes to production that must be performed while the machine is stopped. Collectively, these events are referred to as “changeover times,” or alternately as “setup,” “make ready,” or “planned downtime”.

Strictly speaking, this planned downtime is the measurement of the cycle time from the moment the last good part of the previous process is produced to the moment the first good part of the subsequent process is produced. Reducing changeover time is a critical component of implementing a pull production system which operates with as little inventory as possible.

Why should changeover times be optimised

Reducing changeover time unlocks more productive (value-added) time for running production. Another benefit is that by reducing changeover time, you can minimize production batch sizes, work-in-process (WIP), and inventory. Consequently, sales teams can reduce quoted lead times on products and improve customer satisfaction.

Improving downtime with SMED

Far and away, the most commonly accepted best practice for reducing changeover time is Single-Minute Exchange of Die (SMED). Single-minute refers to reducing changeover times to less than 10 minutes, and the exchange of dies refers back to initial historical work performed by Shigeo Shingo, developing SMED and applying it to automotive presses. Shigeo Shingo was able to reduce the setup times by a factor of 20 or more across a wide range of companies.

In SMED, the changeover process is broken into a sequenced list of steps called elements. The objective of SMED is to remove as many portions from the changeover process as possible by separating or converting them and then streamlining any remaining elements (completing them faster, easier, or in parallel with other parts). The essence of the SMED system is to convert as many changeover steps as possible to “external” (performed while the equipment is running), and to simplify and streamline the remaining steps. The name Single-Minute Exchange of Dies comes from the goal of reducing the measured times to the “single” digits (i.e., less than 10 minutes).

A successful SMED program will have the following benefits:

  • Lower manufacturing cost (faster changeovers mean less equipment downtime);
  • Smaller lot sizes (faster changeovers enable more frequent product changes);
  • Improved responsiveness to customer demand (smaller lot sizes enable more flexible scheduling);
  • Lower inventory levels (smaller lot sizes result in lower inventory levels);
  • Smoother startups (standardized processes improve consistency and quality).

Improving changeover times with SOPs

The fastest path to improved changeover times is typically through non-technical improvements, such as creating standardised work instructions, marking down known settings on equipment, and displaying real-time metrics. Systems like REWO, that allow you to create video-based standard operation procedures (SOPs) are ideally suited to quickly document changeover procedures because they are more accessible, easy to use, and promote a continuous improvement culture. REWO is a plug & play end-to-end video SOP platform that transfers knowledge up to 12x faster than traditional documentation methods. REWO drastically improves capturing, visualizing and communicating knowledge to anyone within the company’s ecosystem.