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Hello Syazwan,
SMED was defined for a single mould or die generally CNC, press like machines by Shigeo Shingo. After technological improvement the single machines and processes became more complex. So today we use SMED term with the more complex processes and we use "Set-up" or "Changeover time".
The terms set-up and changeover are used interchangeably however this is incorrect!
Mostly we think a single machine when we use "Set-up" time. If it is more complex process we use "Changeover".
"Set-up" is clear so I will explain Changeover time. Think that there is an assembly line which has a belt conveyor. There are clenching, welding operations and also you have some air-pressure fixing gauges, screewing etc.. You can not talk about a single "Set-up" or a "Single SMED" you have to CONVERT the assemby line from one product or product familiy to other one! Those all SMEDs in the assembly line should be proceed in same time to get ready for another product in the assembly line. This is CHANGEOVER. Maybe you need to adjust the speed of conveyor with changing some moulds?! All of them are about changover which is converting whole process for another product family.
Changover generally has three steps:
1) Cleaning
2) Set-Up(s)
3) Start-up
For more complex changover issues we can use the term of "Sequence dependent Set-up(s)". In this case sequencing of each set-up requires some rules for timing.
Change over is not about cutting tools or blades or changing different part of the moulds/machines.
setup time is the time you take to set the machine to start production, the single minuet is about to reduce that time to single digit, while changeover time is the time between changing the machine from processing type to another
example : when you start panel saw you need to set the dimensions and the optimization (lot sizing) for hundred panels, this time is setup time where SMED is apply, changing some parts of the machine like blades to start different operation or for maintenance is the changeover time.
change-over' time; which is the time taken to stop production of a product and start production of the same, but it is an integral part of setup time for SMED operation, it occur due to part change over and tool change over in machine. change over time is an not always an essential constituents while running a machine. but setup time is an essential part of it.
