SMED
What is SMED?
SMED stands for Single Minute Exchange of Die. The SMED system is theory and set of techniques that make it possible to perform equipment set up and changeover operations in under 10 minutes – in others words, in the single minute range. SMED was originally developed to improve die press and machine tool set-ups, but its principles apply to changeovers in all types of process.
It is important to point out that if may not be possible to reach single minute range for all Set ups, but SMED does dramatically reduce Set up times in almost every case.
Why SMED is important for companies?
Customers today want a variety of products in just the quantities they need. They expect high quality, a good price, and speedy delivery SMED helps meet these customer needs with less waste by making it cost – effective to produce things in smaller quantities, or lots.
The trouble with large lot production:
Large lot production has several disadvantages:
· Inventory waste: storing what is not sold costs money and ties up company resources without adding any value to the product.
· Delay: Customers must wait for the company to produce entire lots rather than just the quantities a customer needs.
· Declining quality: Storing unsold inventory increase the chance that it will have to be scrapped or reworked, which adds cost to the product.
The Benefits of SMED:
SMED changes the assumption that set ups can be done quickly, they can be done as often as needed. This means companies can make products in smaller lots, which has many advantages:
· Flexibility: companies can meet changing customer needs without the expense excess inventory.
· Quicker delivery: small lot production means fewer customers waiting time.
· Better Quality: less inventory storage means fewer storage related defects. SMED also lowers defects by reducing Set up errors and eliminating trial runs of the new products.
· Higher productivity: Shorter changeovers reduce down time, which means a higher equipment productivity rate.
The benefits of SMED for you
SMED also benefit you and also company employee. First quicker set up support job security by strengthening the companies competitiveness. In addition SMED make daily production work go smoother because:
· Simpler set up results in safer change over with less physical strain or risk of injury.
· Less inventory means less clutter in the work place, which makes production easier and safer.
· Set up tools are standardise and combined which means fewer tools to keep track of.
Basic Steps In a Set up Operation
1-Preparation, after process adjustments, checking of material and tools
2-Mounting and removing tools and parts
3-Measurements, settings and calibrations
4-Trial runs and adjustments
1-Preparation, after process adjustments, checking of material and tools
This step ensures that all part and tools are where they should be and that they are functioning properly. Also included in this step is the period after processing when these items are removed and returned to storage, machinery clean and so forth.
In a traditional set up, parts of the preparation step are done after the machine is stopped. This step should be done as external set up, while the equipment is still running.
2-Mounting and removing tools and parts
This step includes the removal of parts and tools after one product is processed, and the attachment of the parts and tools for next product.
Generally the machine must be stopped to do this step, so it is internal set up. This internal set up step the actual changing over takes very little time compared to the other steps.
3-Measurements, settings and calibrations
This step refers to all the measurements and calibrations that must be made in order to perform a production operation, such as centring, dimensioning, measuring temperature or pressure and so forth.
Although the equipment must be stopped for this step, the SMED system teaches ways to do these tasks quickly by preparing the equipment is running.
4-Trial runs and adjustments
In the final steps of the traditional set up operation, adjustments are made after a test piece is machined. The more accurate your measurements and calibrations are in the previous step the easier these adjustment will be.
Correct adjustment of the equipment is one of the most difficult tasks in a set up operation. In traditional set up, the time needed for trial runs and adjustments depends on personal skill.
In a traditional set up the machine is not making good products until this step is finished, it is considered part of internal set up. SMED teaches ways to eliminate this step completely, so that the machine makes good products right after it is started up.
Steps in set up / Proportion of set up time before SMED improvements1-Preparation, after process adjustments, checking
of material and tools
2-Mounting and removing tools and parts
3-Measurements, settings and calibrations
4-Trial runs and adjustments / 30%
5%
15%
50%
Analysing your Set up operations
The main reason traditional Set up operations takes so long is that internal & external Set ups are confused. Many tasks that could be done while the machine is still running aren’t done until the machine is stopped.
The three stages of SMED are described & designed to simplify and shorten changeovers. But before you start applying SMED, you need a clear idea of how you currently perform Set up operations and how long each steps takes.
The preliminary step, called a Set up analysis, will help you how to implement SMED improvement on your equipment. Set up analysis has three main steps:
1-Videotape the entire Set up operation focusing on the hand, eye, and body movements of the person doing the Set up. Use the camera’s time and date function if there is one.
2-Show the video to the Set up person and other people involved with the equipment. Ask the Set up person to describe what he is shown doing. Have the group share their thoughts about the operation.
3-Study the video in detail, noting the time and motions involved in each step of the Set up. Use the video players pause and rewind functions as needed. Also use a stop watch if necessary.
The three stages of SMED:
Stage 1:separating internal & external Set up
The most important step in implementing SMED is distinguishing between internal and external Set up. By doing obvious things preparation and transport while the machine is running, the time needed for internal Set up, with the machine stopped, can usually cut by as much as 30 to 50 percent.
Stage 2:Converting internal set up to external Set up
Further reducing Set up times toward the single minuet range involves two important activities: 1) re-examining operations to see whether any steps are wrongly assumed to be internal Set up, and 2) finding ways to convert these steps to external Set up. Operation can often be converted to external Set up by looking at the true function.
Stage 3:Streemlining all aspects of the Set up operation
To further reduce Set up time, the basic elements of each Set up are analysed in detail. Specific principles are applied to shorten the time needed, especially for steps that must be done as internal Set up, with the machine stopped.
Description of stage 1:
There are three techniques help us separate internal external Set up tasks. These techniques are: using checklists, performing function checks, and improving transport of die and other parts.
Checklists:
A checklist lists everything required to set up and run the next operation. The list includes such items as:
· Tools, specifications, and workers required.
· Proper values for operating conditions such as temperature, pressure etc.
· Correct measurement and dimensions required for each operation
Checking item of the list before the m/c is stopped helps prevent mistakes that come up after internal set up begun.
Function checks:
Function checks should be done well before Set up begins so that repair can be made if something does not work right. If broken dies, moulds, or jigs are not discovered until test runs are done, a delay will occur in internal Set up. Making sure such items are in working order before they are mounted will cut down set up time a great deal.
Improved transport of parts and
Tools:
Dies, tools, jigs, gauges, and other items needed for an operation must be moved between storage areas and machines, then back to storage once a lot is finished. To shorten the time the machine is shut down, transport of these items should be done during external set up. In other words, new parts and tools should be transported to the machine before the machine is shutdown for changeover.
Stage 2: Converting internal set up to external Set up
I-Advance preparation of conditions:
Advance preparation of conditions means getting necessary parts tools and conditions ready before internal set up begins. Conditions like temperature, pressure, or position of material can be prepared externally while the machine is running.
(Ex. Pre-heating of Mould or Material)
II-Function standardisation: SMED uses a targeted approach call function standardisation. It would be expensive and wasteful to make external dimensions of every die, tool or part the same, regardless of the size or shape of the product it forms. Function standardisations avoid this waste by focusing on standardising only those elements whose functions are essential to the set up. Function standardisation might apply to dimensioning, centeing, securing, expelling, or gripping for instance.
Implementing Function standardisation: involves two steps:
1- Look closely at each individual function in your set up process and decide which functions if any can be standardise.
2- Look again at the functions and think about which can be made more efficient by replacing the fewest possible parts.
(Exp.clamping Function standardisation)
Streamlining external set up:
External set up improvement include streamlining the storage and transport of parts and tools. In dealing with small tools, dies, jigs, and gauges, it is vital to address issue of tool and die management. You need to ask yourself questions such as:
· What is the best way to organise these items?
· How can we keep these items maintained in perfect condition and ready for the next operation?
· How many of these items should we keep in stock?
Improving storage and transport:
Operation for storing and transporting dies can be very time consuming, especially when your company keeps a large no. of dies on hand. Storage and transport can be improved by marking the dies with colour codes, and the location numbers of the shelves where they are stored, the shelves are also marked.
Streamlining internal set up:
Through improvement in internal setup operations are next. These include implementing parallel operations, using functional clamps, eliminating adjustments, and mechanization.
I. Implementing parallel operations:
Machines such as plastic moulding machine, and die costing machines often require operation at both the front and back of the machine. One person changeovers of such machines mean wasted time and movement because the same person is constantly walking back and forth from one end of the machine to the other.
Parallel operations divide the set up operation between two people, one at each end of the machine.
When set up is done using parallel operations, it is important to maintain reliable and safe operations and minimize waiting time. To help streamline parallel operations, workers develop and follow procedural charts for each set up.