TPM - Total Productive Maintenance (more ») very rightly consider set-ups (or change-overs) one the 6 big losses related to equipment and machines.
Lean Manufacturing (more ») goes beyond that, and considers excessively long set-ups and change-overs a serious obstacle to its implementation.
In fact, only fast set-ups allow a flow style of production to take place. This is the heart of Lean Manufacturing.
What is a set-up?
It is whatever takes places in a machine, a line, or a productive operation, between the end of production of a certain type of product and the start of production of another type of product.
If, in order to produce the new product (or component, workpiece, sub-product, quasi-product....) a machine or a line or any productive facility needs to be re-set, then we talk of a set-up.
The main type of set-up and change-over operations in manufacturing are the following:
- EXCHANGING DIES & BLADES: dies, moulds, drill bits, saw-blades and other tools, silk-screening plates, etc. And also: cleaning and replacing filters (ex. in plastic extruders) and similar operations that cause a temporary stop to production.
- SWITCHOVER" or "RE-TOOLING". For instance:
- in assembly lines - includes exchanging supplies of components, materials, assembly jigs and tools, templates, etc.
- in certain machines - includes, for instance, new material feed to machine (new rolls of paper in winders, or new rolls of paper or material or plastic film in printers, etc.)
- CHANGING STANDARD PARAMETERS: in NC machines, dairy processes, chemical processes.....
- GENERAL PREPARATION before manufacturing starts: arranging the equipment, assigning tasks, checking drawings & work schedules, etc.
Under this class of set-ups fall also the general wind-down activities at the end of a day or a shift (cleaning, putting tools in order, switching-off equipment...).
Change-over time is defined as "that interval of time elapsed between production of last defect-free item (product, by-product, workpiece....) of previous lot, and first defect-free item of next lot"
The definition, valid for batch processing operations, needs to be adapted in other cases, such as in continuous processing, in general preparation and general wind-down situations, etc.
It is interesting to note that the concepts of set-up/change-over and set-up/change-over time apply also to many construction operations (like "exchanging the bucket of an excavator" or "preparing for casting concrete") as well as to service industry operations and general office work (like "getting a client's file to attend to a client's query" or "setting up photocopier for an A4 to A3 enlargement").
As set-ups and change-overs are non-value adding activities, in all three main industrial sectors (manufacturing, project, service) there is a processing discipline that attempts to reduce/minimise their entity and incidence: respectively, Lean Manufacturing - Lean Project Management - Process Engineering.
In conclusion, the Achieving Quick Change-Over methodology is a strong allied of all lean-based Processing disciplines.
Achieving Quick Change-Over (AQCO) is a modern and broad development of Shigeo Shingo's SMED - Single-Minute Exchange of Dies and kills once and forever two obsolete assumptions, typical of the manufacturing sector:
1 - Changing-over efficiently and effectively requires a high level of knowledge and ability, which are the result of long training and experience
2 - Producing in large lots mitigates the effects and counterbalances the costs of long change-over times
KNOWLEDGE AND ABILITY
AQCO methodology is very simple: transform change-over operations into such a simple issue that anybody with decent industrial skills (like a machine operator or a line attendant) can perform it easily and rapidly.
The focus, therefore, is on "simplification" and poka-yoke approaches.
Large, economic lots have been invented, in manufacturing, to compensate for long set-ups and change-overs.
AQCO approach is again very simple: minimise set-ups' duration to such a short time as to be able to discard the large lot concept once and forever.
The focus is on creative elimination of unnecessary/redundant set-up related activities and streamlining of the remaining, essential ones.
The final result is a productive system capable of producing wide-variety/small-lot outputs just as monster clients want.
The starting point in the AQCO methodology is in the "splitting" of the overall change-over time into two well distinct entities:
- the internal change-over time, and
- the external change-over time
INTERNAL CHANGE-OVER TIME
This is defined as that interval of time during which the productive process must stop, or no set-up could be made. This is the real and proper change-over time, that begins when the current lot process finishes, and ends when the next lot process produces the 1st defect-free item. Throughout this time no value is added to products.
EXTERNAL CHANGE-OVER TIME
This is defined as that interval of time during processing (of previous and next lot) during which change-over related activities (like transport, preparation, etc.) are implemented by various personnel (fitters, workers, operators....). Part of this time may elapse before Internal Change-Over Time, and part after it.
In traditional enterprises the two change-over times are not known and understood: many activities that could be done "externally" are wrongly done "internally", thus penalising the critical duration of the "internal change-over time". In certain extreme cases, the "internal change-over time" is the whole "overall change-over time" !
AQCO initial strategy is to make a clear distinction between the two times, and ensure that all change-over activities that could be done "externally" are removed from the "internal" zone.
Then AQCO looks for "wasteful" activities (unnecessary, redundant activities that need not to be there to begin with) and eliminates them.
The subsequent targets are:
- the drastic reduction in time-duration of the necessary internal activities
- the rationalisation/streamlining of the necessary external activities
With regard to time-reduction of the necessary internal activities (prime objective of AQCO) the analysis focuses on two main classes of activities:
- replacement activities
- adjustment activities
INTERNAL REPLACEMENT ACTIVITIES
In manufacturing, these include: stripping previous process ancillary tools (moulds, dies, plates, guides, rollers....) and fitting next lot's corresponding ones.
Generally, there is a lot of bolting and un-bolting operations to be done, rather time consuming, and a number of moving activities, such as lifting, lowering, removing....
AQCO strategy is to minimise these activities' duration by applying a number of dedicated techniques, addressed to: eliminating the need for bolts, nuts and other fasteners, or - replacing traditional fasteners with faster-action fasteners, or - streamlining as much as possible the un-fastening/fastening activities in order to cut drastically their duration, or - many other similar initiatives.
in AQCO bolts and nuts are public enemy N. 1....
The same approach is used to reduce radically the duration of any "moving" activity.
INTERNAL ADJUSTMENT ACTIVITIES
These include: centring, precision-positioning (for instance moulds and dies), measuring, calibrating, fine-tuning, and the like. This is done to ensure the correct quality standards of the output product.
Strictly associated, there is a number of trial activities, to verify that the adjustment/s made were actually correct.
All this is time consuming (also because of possible re-iterations) and may require knowledge, abilities and experience.
AQCO approach is very simple again: eliminate the need for any adjustment, by inventing ways of doing it once and forever with a permanent, poka-yoke solution.
This cuts to zero the need for any adjustment and for any particular knowledge/skill/experience. The target is to enable any operator with some decent industrial skill to "precision-replace" or "precision-set", without any need for measuring, calibrating and checking.
AQCO basic principles above, associated with a number of allied techniques (like "parallel change-over", for instance, and "workplace management for change-overs") allow, gradually, to reduce drastically all set-up/change-over times and to minimise the overall cost of "external activities".
Final results are astonishing: reduction in set-up times of up to 80% - 90% are well feasible. In many instances, it is possible to cut a 2 hour set-up to 2 minutes. One-touch change-overs are also possible to achieve.
There are a few key-words and related key-secrets in the AQCO approach:
- Gradually: best results that will last in time are obtained through a gradual, systematic, step-by-step approach, kaizen style.
This allows for the necessary "cultural" change to happen. AQCO is a revolution, in traditional enterprises. To make it go through smoothly and painlessly, it is important to prevent people (operators, but, most of all, technicians and set-up "engineers") reluctance, and even resistance to accept new methods and perform better.
- Involvement: best results are obtained with high involvement of those concerned (fitters, technicians, operators and their supervisors).
If people contribute, with their ideas, to improve change-overs, results will be achieved: being their own ideas, they won't make them fail....
When improvement ideas are "imposed" from the top (like in the case of "technological change-over improvements"), people might instead use their wildest creativity to make them fail.... what a waste of resources and opportunities !
- Poor man approach: money comes last in AQCO.
What comes first is brain, team work and simplicity. Whatever is creatively developed and is simple has many more chances to work well and indefinitely, better than sophisticated and expensive technology solutions.
Only if and only when good results are achieved with a kaizen style of improvement, time to spend money for some extra results through technology upgrades might come.
The final decision must, obviously, be economical.
- Measuring/documentation: like for any other performance improvement initiative, it is essential to "measure" the present, starting status, and to compare it with subsequent, improved ones.
This requires some basic documentation. The "score" must be known at all times, in real time.
...fast change-overs open wide the door to Lean Manufacturing and contribute substantially to Operational Performance improvement...
Under the Lean Thinking (more ») angle of view, the AQCO Discipline is today deployed to reduce/eliminate set-up times in any industrial and commercial sector/process