TPM for the lean factory, or Lean TPM, means TPM directed at maintaining — at managing — the machines so that they support the elimination of waste, in the sense Lean gives that word, within the production process.
The seven TPM wastes, and why Lean TPM
- Machine stoppages — minor, moderate and long
- Set-up or changeover that takes a long time
- Rework, defects, unusable product, and a low rate of material utilisation
- Machine stoppages arising from planning (or from management)
- Incomplete application of the first two S
- Producing more than is needed because the machine is large
- Trial and adjustment at start-up, where that is troublesome
The new 5S
This is 5S that puts the weight on the result — an improvement in the production line — not 5S that puts the weight on appearance: painting, marking out lines, looking handsome. Formal 5S generally has these characteristics.
- Employees come to feel that 5S is of no use
- It becomes 5S in which everyone must do the same as everyone else, following the example
- It becomes 5S that is awake only during the campaign period
- Employees resist it
Instant maintenance, prepared in advance
Zero breakdowns is the dream of every organisation, but it is not easy, and it takes solving problems on several fronts at once, technical and behavioural. So to keep pace with machine problems as they press in on you, waiting for the success of zero breakdowns would take far too long. “Instant maintenance, prepared in advance” is one tool for making a breakdown have the least effect it can, or for getting the machine back quickly.
- Study the present conditions and constraints
- Summarise the problems of each machine and each line
- Analyse the mechanism by which minor stoppages arise, and their causes
- Draw the relation between the phenomenon, the mechanism and the cause so that it can be seen clearly
- Install the system of instant maintenance prepared in advance
- Promote the production department’s autonomous maintenance activity
- Produce the manual for instant maintenance prepared in advance
Set-up and changeover improvement (SMED)
Lean, seen from one angle, is small-lot production with high variety. Setting up or changing over many times is therefore unavoidable. But making each set-up or changeover take little time is something that can be done, and the highest aim of that improvement is SMED — single-minute exchange of die.
- Study the losses from set-up and changeover as they stand
- Form the team to promote set-up and changeover improvement
- Go down to the line and analyse how the work is done — this step is the SMED process itself
- Apply the thinking of loss elimination
- Communicate the improvement plan
- Carry the improvement out
- Assess it and extend the result to other areas
Process razing, re-design and re-layout
A machine stopped by planning or by management is a stoppage in the production process that prevents the fullest use of the machine — though it is done to guard against losses that might otherwise be greater still, such as a breakdown, or overproduction.
Analysing the effectiveness of the plant layout and redesigning it rests on the principle of the product family using one set of machines — process layout — so as to get the fullest use from the machines without creating waste, and above all without creating overproduction and planned downtime.
- Consider the loss hidden in the midst of everything that is proceeding to plan, using the P-Q analysis chart · process path analysis · the flowchart · the assembly process chart
- Gather the losses that are plainly visible and find the way to eliminate them
- Find the cause: why, when everything goes to plan, does loss like this arise
- Consider all seven wastes, and which of them makes managing production difficult
- Carry out the correction and the improvement
- Draw up the standard work
- Measure the result of the improvement and carry out the correction
Standard work
Once we have the new line, we must always keep in mind that whenever we want full value out of people, full value out of tools, full value out of machines — in the form of never letting them stand idle from production — you will meet a line filled with loss. To avoid it, you must make these things standard: the work steps, the cycle time, and the quantity that must not be exceeded, meaning the inventory. All of that together we call “standard work”.
And for standard work to be complete, these four are needed.
- The table of process capacity
- The standard work combination sheet, setting out the standard times for people and machines
- The standard work sheet, setting out the steps and the standard quantity
- The standard work instruction sheet, for teaching everyone to follow the standard work
Minimising variation in the process
A great many problems of machine breakdown and of product quality are bound up with the abnormalities that arise in the process and in the method of production. This is because working conditions differ enormously with the variety of the product, and it is unavoidable that our machines will meet difficulty in holding to a standard.
Conversely, if our process were fixed to one material only, working under conditions well defined and never changing — the whole of this is what is meant by variation arising in the process. So if variation in the process can be reduced, breakdowns and defects will fall. One technique brought to bear on it is finding the optimum conditions for the process — process optimisation — through design of experiment.
Effective daily maintenance
Machines today have grown faster and more automatic, and that is a large part of why their availability has risen too. Yet one still meets the fact, again and again, of a modern machine under automatic control whose availability is nonetheless low — because a minor stoppage arises and spreads into a moderate one and then a long one in turn, while we were never able to detect the warning signs beforehand. “Effective daily maintenance” is the best thing there is for catching an abnormality early.
- Summarise the problems arising at each work station
- Analyse the mechanism by which the damage arises
- Act on the method you believe can eliminate the true cause
- Fix a label on the equipment itself marking the daily check
- Divide the parts and spares into three groups — ABC analysis
- Manage the spare-parts inventory
- Improve the procedure for checking or replacing a part
- Find the true cause of a part fracturing, failing or wearing out before its time
- Train every employee thoroughly in daily maintenance