SMED: An In-Depth Guide

What is SMED?

SMED, or Single-Minute Exchange of Die, is a Lean tool used in manufacturing to reduce equipment changeover time. The goal of SMED is to complete as many steps as possible while the equipment is running (or processing), to save time and quickly change over to processing the next product.

Each letter of this time-saving tool stands for a specific term, as follows:

• SM (Single-Minute) – ideally how long it should take to switch from making one product to another or “to exchange dies”

• E (Exchange) – switching from making one product to making another

• D (Die/s) – a specialized piece of equipment used to define the size and shape of a product

Do You Need this Tool?

Before going into the benefits of SMED or why manufacturers use it, it may be helpful to ask if SMED can be applied to your production process and if it’s the right Lean tool to use for making improvements.

To determine this, check if your current equipment changeover system satisfies the following factors:

1. Do you have a system in place to measure manufacturing performance data?

2. Does the system measure Overall Equipment Effectiveness (OEE)?

3. Do you have at least 2 weeks’ worth of manufacturing performance data collected from the system?

4. Based on the data, what percentage of lost productive time is from changeovers? IndustryWeek provides the formula for this as follows: Availability score = Available time ÷ Scheduled time

5. Is the percentage of lost productive time from changeovers 20% or above?

6. Do you have equipment that:

   1. employees are familiar with; and

   2. is a constraint?

7. Is the changeover of this equipment:

   1. performed more than once each week;

   2. take an hour or so to complete on average; but

   3. can sometimes take much longer to complete (such as 2 hours more)?

Benefits

The main benefit of implementing SMED is reduced equipment changeover time, which creates a positive domino effect on other aspects of production. The five key advantages are:

1. Increased capacity/machine work rates

2. More frequent completions of equipment changeovers

3. Reduced batch sizes / smaller lot sizes

   1. Reduced stock holdings / lower inventory levels

   2. Less space and handling required

   3. Less waste produced

4. Standardized changeover procedures

   1. Less room for errors / improved quality

   2. Fewer defects produced

   3. Improved safety and consistency

5. Lower production cost due to less planned downtime

3 Steps to the SMED Process

To help you get started with implementing SMED, here’s a quick 3-step guide on the SMED process:

Step 1: Separate

The first step in the SMED process is to separate changeover elements or group them according to their type (internal or external). Changeover elements are the steps taken to complete the equipment changeover. There are two types of changeover elements:

• Internal changeover elements – can only be done when the equipment is not processing anything

• External changeover elements – can be done while the equipment is running (or in the middle of processing something)

Identifying the type of changeover element is important because making as many steps (or changeover elements) external is how SMED reduces equipment changeover time.

Step 2: Convert

The second step in the SMED process is to convert internal changeover elements to external changeover elements. Once you’ve identified an internal changeover element that could be converted to external, ensure that the benefit (in terms of time saved) outweighs the cost of conversion (the resources needed to convert the changeover element to external).

A SMED technique for converting internal changeover elements to external ones is to use intermediate or duplicate jigs. The next product can be prepared using a jig (a kind of framework or mold) while the first product is being processed. The jig containing the prepared next product is then simply attached to the equipment.

Step 3: Streamline

The third step in the SMED process is to streamline the internal changeover elements that weren’t converted to external. The fundamental SMED technique for this step is to follow the Lean principle of “trimming the fat” by removing inefficiencies from internal changeover elements. Simple and effective SMED techniques for this include the following:

• Try the 5S Lean method

  • Organize the work area for maximum efficiency

• Use functional clamps

  • Reduce the number of actions to only what is necessary

• Standardize parts or features

  • Make performing internal changeover elements easier

• Eliminate adjustments

  • Calibrate equipment to transition quicker

  • Use standardized settings and fixed guides

SMED Examples

To give you a better idea of how the SMED process fits in your workplace or business, here are 2 SMED examples for manufacturing and restaurant settings:

SMED Example for Manufacturing:

SMED Example for Restaurants: