TPM – Total Productive Maintenance
Lean Maintenance is a relatively new term, surfacing around the last 10-20 years. However the foundations of this technique were already in place, as TPM (Total Productive Maintenance). Lean maintenance builds upon the TPM to reduce wastes (Muda) within a system or process.
In manufacturing there are three “laws” which govern maintenance:
- Correctly maintained machinery will produce more quality parts.
- Incorrectly maintained machinery creates more parts of questionable quality.
- Machines left to full degrade will produce no parts.
For a company wishing to implement a complete Lean philosophy it must have stable, reliable machinery. Without this, processes become unpredictable, waste is created, and Lean principles are difficult to apply. In Lean this instability or inconsistency is known as Mura. By definition Lean means the best quality and value, at the least cost. It stands to reason, that this is not possible if machinery is not running at maximum efficiency. This is why TPM is a foundation of the “House of Lean”.
Total: This includes everyone in the workplace, aiming to reduce accidents, defects and breakdowns.
Productive: Actions performed whilst production continues.
Maintenance: Keeping in good condition, repairing, cleaning, lubricating.
There are various types of maintenance:
- Planned (scheduled at intervals or pre-defined points)
- Unplanned (aka. run to failure)
- Corrective (returning a machine to correct running state)
- Emergency (implementing corrective procedures to avoid serious consequences)
When a machine is critical to the overall process, the cost of unplanned maintenance can be significant.
Unplanned maintenance is only suitable when; the unscheduled stoppages cause minimal disruption to the system, or that they are less costly unplanned. Due to the often random nature of machine failure, unplanned maintenance can’t be avoided, but can be reduced.
Planned maintenance is that which is carried out with forethought, control and the use of records to determine when maintenance is due.
There is also preventative maintenance, which as the name suggests is the application of maintenance at predetermined levels. This maintenance is intended to reduce the probability of machine failure, or the products being produced at a lower grade.
Often there is the option of opportunistic maintenance, where by machines which are non-operational, or currently broken down can have additional maintenance. To some extent this can offset the cost of the repair, as no supplementary costs are being incurred.
So what are the benefits of TPM?
- Increase equipment productivity
- Reduce downtime
- Lower costs in maintenance and running
- Increase plant capacity
- Reduce amount of machine caused defects
- Increased return on investment