By Darren Dolcemascolo, senior partner and co-founder, EMS Consulting Group
Over the last few editions of Thinking Lean, we have been talking about tools that support continuous flow and pull systems. In this edition, we will cover one of the most important lean tools for medical device manufacturers: quick changeover. Being able to quickly change from the manufacture of one product to the next enables continuous flow and pull systems.
What Is Quick Changeover?
Single Minute Exchange of Die (SMED), or Quick Changeover, is a method developed by industrial engineering consultant Shigeo Shingo to reduce changeover time on machines. Changeover time is defined as the time between the last good part produced from one run and the first good part produced from the next run. SMED is considered a key tool for implementing flow and pull systems within the Toyota Production System, because it both reduces and standardizes setup time. In the Toyota Production System house diagram, it is located in the “Just-In-Time” pillar (Fig. 1).
Shingo’s time studies proved that his quick changeover methodology will work on any machine. Application of the system reduces setup from hours to minutes. The goal is to utilize this flexibility to create continuous flow and leveled production.
Shingo broke up the operations that occur during a changeover into four categories. He estimated that 30 percent of a typical changeover consisted of preparation, after-process paperwork, and checking of materials, tools, and other items. This includes gathering all parts and tools needed for the changeover, returning all parts and tools from the previous run to where they belong, machine preparation and cleaning, and any other paperwork or transactional items.
Shingo estimated that only 5 percent of changeover time consisted of changing out parts, such as blades, dies, molds, or other tooling. About 15 percent of a typical changeover consists of the measurements and calibrations necessary to perform a production operation, such as centering, dimensioning, and measuring temperature or pressure. Finally, about 50 percent of changeover time consists of trial runs and adjustments. It has been my experience that, on particularly long changeovers — those taking many hours — trial runs and adjustments exceed 50 percent of changeover time. While not all changeovers are the same, all contain these elements.
Shingo’s SMED system includes three stages:
Example: Establishing Quick Changeover Of Injection Molding Machines At A Medical Device Manufacturer
A medical device manufacturer produces plastic products utilizing injection molding machines. The company put together a team to address changeover reduction on its machines. The tools/principles utilized by the team were as follows:
1. SMED. The team streamlined both the internal and external processing steps.
2. The 5-S System. The team followed Sort, Set-in-Order, Shine, Standardize, and Sustain. This system is used to "clear the clouds" and is considered a foundation for many other lean concepts.
3. Standardized Work. The “current condition” for this particular changeover process was as follows:
The process was videotaped prior to the event, and the kaizen team observed and identified the following items as key issues:
Using the principles of standardized work, 5S, and SMED, the team instituted the following changes:
Quick changeover, or SMED, generally can be applied to any changeover situation within a factory. By applying this methodology, a medical device manufacturer can be much more responsive to the customer. The ideal state is to provide customers with what they need, when they need it, and in the right quantity. The SMED system for quick changeover is a tool that moves us closer to this ideal state.