Lean manufacturing is highly acclaimed all across the manufacturing domain. And why would it not be? After all, businesses adopting lean manufacturing saw a significant increase in their stock turnover, productivity, and waste reduction.
Among all these invaluable lean approaches, one such approach is SMED or Single Minute Exchange of Die. SMED is a process that is entirely dedicated to reducing the changeover time of a machine. Before we get into what SMED is, let’s understand the ABCs of changeover time.
What is changeover time?
Changeover time is the duration that the machine takes between two successful batches of production. For example, the factory of a confectionery company transitions from manufacturing chocolate bars to gummy bears. In the process, they might have to change the ingredients, cast or mold, temperature, packaging, etc. Here, the span of time they consume to make changes in equipment for producing the next batch, is called changeover time.
Why is it essential to reduce changeover time?
A lengthy changeover time can result in two major implications:
1. Lost Capacity: When the changeover is time-consuming, the production capacity of a plant or equipment slowly shrinks away.
2. Overproduction: When the production targets are not met, you will have to produce more batches. Over-production will likely take a hit on overall manufacturing performance and efficiency.
Paying attention to changeover time is crucial for any manufacturing plant. Reduction in changeover time will help the company cut corners in manufacturing and increase the output. Hence, many companies adopt SMED to improve their changeover time.
What is SMED(Single Minute Exchange of Die)?
SMED or Single Minute Exchange of Die is a lean-production method that reduces the changeover to less than 10 minutes. SMED is a quick and effective way to switch the manufacturing process from the current product to the following product. This method reduces production lot sizes and output instability by streamlining the changeover process with specific steps to follow.
The SMED Process is the brainchild of Shigeo Shingo, a Japanese industrial engineer. He was one of the main contributors to TPS(Toyota Production System).
Five steps of changeover time reduction
1. Time study and identification of internal and external tasks
To conduct a time study, pick the equipment where you need to improve the changeover time. Use videography to capture the equipment’s current changeover time. Closely register each activity of all the operators. Before making a machine layout, divide the responsibilities amongst the team members(maintenance staff, supervisors, and quality assurance personnel). Observe the detailed process to figure out areas to cut time. Since it takes time to find defects, start with fewer sections at first and then target more equipment. Here are a few checklists to shortlist target areas for improvement:
- Changeover time is longer than usual
- There is a significant variance between two changeover times
- The team strongly feels the need for a reduction in changeover time.
- The reduction in changeover is inevitable and is otherwise causing delays in operations.
After conducting a thorough time study, the next thing to consider is the identification of internal and external tasks in changeover time.
- Internal tasks: Internal tasks can be done only when the equipment is not producing or working.
- External tasks: External tasks can be carried out even while the equipment is running.
2. Separate internal and external tasks
First things first. You need a checklist in order to ensure the availability of each item. You must arrange all the materials, tools, logistics, etc., before the next changeover. Analyze each component to see if the changeover can be done while the equipment is in its working status.
3. Convert internal tasks to external ones
Identify the internal activities that can be converted into external ones. The more you convert the activities, the quicker the changeover. Here are some key ideas for converting internal tasks to external ones:
- Pre-assembly of parts:
- Ensure availability of items like tools, parts, fasteners, etc
- Create a checklist and establish a table for each machine
- Pre-heating molds, casts or dies:
- Use induction for quick heating of parts
- Enable offline system for electrical & coolant connections and bring the component to run temperature
- Standardization
- Standardize outside dimensions, fittings, and settings.
- Decide other functions that can be standardized. For example, in the case of a die, the mechanical pressure can be standardized, but it’s forming stays unique.
While converting the internal activities to external, use the ECRS method — Eliminate, combine, rearrange and simplify. It helps remove the trivial steps from your changeover process, making it quicker and uncomplicated.
4. Reduce internal activity time
Internal tasks lengthen the changeover process. While you can convert most of them into external activities, some cannot be modified and hence, call for a reduction. Here are some ways for internal time reduction:
- Removing and fitting parts
- Adopt a boltless approach and use magnets wherever possible. During a dire necessity of bolts, use fewer and shorter bolts. Also, try to eliminate the need of removing the bolts completely.
- Use one-touch fasteners and quick couplings to save time
- Make use of pneumatic tools for portability
- Cleaning
- Keep a spare equipment to work as a two-bin system
- Use removable plastic sheets for quick cleaning
- Use cleaning agents and chemicals
- Reduce the material in hoppers before the changeover
- Settings and Adjustments
- Use numerical adjustments
- Visualize the settings on a machine to avoid errors
- Label the machine parts where the setting is done
- Implement auto-settings wherever possible
- Use similar settings for similar products with the same dimensions
- Create SOP(Standardized operating procedure) for each operator
5. Improve External Steps
Lastly, craft your changeover process to perfection by improving the external steps. Ensure that the material is available in sufficient quantity and is near the location of its usage. Use a preparation checklist for the changeover process to streamline it.
Benefits of SMED:
1. Reduces unproductive machine downtime
2. Smaller batch sizes
3. Improvement in client service
4. Lower manufacturing costs
5. Negligible Inventory costs
6. Reduces capital expenditure
7. Increases machine capacity
Complex and time-consuming changeovers limit the production capacity and create waste. The purpose of the SMED approach is to eliminate this waste and stimulate production efficiency. It is a cutting-edge procedure that saves you ample time. It also ensures that your production process is executed at a ‘just-in-time’ pace. Over and above that, you get effective cost reduction, higher quality, competitiveness and happy customers.
