February 1, 2008
By Darren Dolcemascolo
Changeover reduction is one of the key concepts of the Toyota Production System. In this article, I will describe a case study based on an actual kaizen event that EMS facilitated. The event dealt with a company in the plastic injection molding business. The company assembled its own final products for the consumer market; thus, the injection molding operation was an internal supplier to the downstream final assembly process.
The tools/principles utilized in this event were as follows:
1. SMED (Single Minute Exchange of Die). Recall that the three major stages of SMED are:
Separate internal steps from external steps
Convert internal steps to external steps
Streamline both the internal and external processing steps.
2. The 5-S System: Sort, Set-in-Order, Shine, Standardize, and Sustain, which 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:
Average part-to-part changeover: 60 minutes
Average number of changeovers/week = 48
The process was video-taped prior to the event. The kaizen team identified the following items as key issues observed:
No pre-staging of tools and materials
Lots of time spent looking for tools and materials while machines are down
Items do not have designated storage locations
Poor communication – identified as the number one changeover/downtime issue.
People are often looking for other people to find information.
Machines often sit idle (before and after setup process)
Pre-staging is impossible because techs are not aware of next required changeover.
Each tech has his own way of performing a setup – setups are performed differently each time
Lots of Waste (walking, wasted motions, etc) - drew spaghetti diagram to illustrate.
Using the principles of standardized work, 5S, and SMED, the team instituted the following changes:
The team developed standardized work sheets that identified each job step and the sequence and time associated with each step. This significantly reduced the variation between setup technicians. The standard work identified work to be done externally (while machine is running) versus internally.
The team developed a status board that was used to alert technicians of the next changeover to facilitate pre-staging.
The team created tool carts that included all of the standard tools needed to perform a changeover.
The team also recommended and later implemented modifications to molds that further reduced the internal setup time.
Based on the above improvements, the team was able to reduce changeover time from 60 minutes to 15 minutes. This allowed for a significant reduction in inventory: the company was now able to convert storage space to production space for new products.
Click here to subscribe to our free e-newsletter Learning to Lean and receive three articles like this one each month.