Automating Manufacturing Systems - Process Control and ...

plc software - 32.22
ures to the total failures.
- To calculate the SFF
- do an FMEA for each system component in the system
- classify failure modes as safe or dangerous
- calculate the probabilities of safe/dangerous failures (S/D [0, 1])
- estimate the fraction of the failures that can be detected (F [0, 1])
- SFF = ....
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32.8 LEAN MANUFACTURING
- lean manufacturing has received attention lately, but it embodies many common
sense machine design concepts.
- In simple terms lean manufacturing involves eliminating waste from a system.
- Some general concepts to use when designing lean machines include,
- setups should be minimized or eliminated
- product changeovers should be minimized or eliminated
- make the tool fit the job, not the other way. If necessary, design a new tool
- design the machine be faster than the needed cycle time to allow flexibility
and excess capacity - this does seem contradictory, but it allows better
use of other resources. For example, if a worker takes a bathroom break,
the production can continue with fewer workers.
- allow batches with a minimum capacity of one.
- people are part of the process and should integrate smoothly - the motions
or workers are often described as dance like.
- eliminate wasted steps, all should go into making the part
- work should flow smoothly to avoid wasted motion
- do not waste motion by spacing out machines
- make-one, check-one
- design "decouplers" to allow operations to happen independantly.
- eliminate material waste that does not go into the product
- pull work through the cell
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