Section 51. Total Productive Maintenance


51. Total Productive Maintenance

Overview

After determining the Overall Equipment Effectiveness (OEE) of a machine or process, clearly the next step is to determine why it isn't 100% and work towards the 100% goal. OEE is made up of three elements as per the equation:

OEE = %Uptime x %Pace x %Quality

After the level of each of Uptime, Pace, and Quality are known then focused Lean Sigma projects can be applied to each stream. This can have immediate breakthrough improvement in each area, but is sometimes difficult to sustain without embedding a fundamental change into the way that the process is maintained. To gain a lasting result it is highly recommended that a Total Productive Maintenance[88] initiative be undertaken.

[88] For more information, see Inspection and Training for TPM by Terry Wireman, published by Industrial Press Inc.

This is a large and complex subject area and is not dealt with in great detail here. However, there are some commonly held misconceptions, which hopefully can be dispelled. The biggest is that TPM stands for Total Preventative Maintenance and is just doing a bit of oiling and greasing of a machine like it says to in the handbook. TPM stands for Total Productive Maintenance and is much more.

To understand TPM better, it is useful to first consider the major causes of equipment breakdowns:

  • Failure to maintain fundamental machine requirements, such as housekeeping, oiling, tightening bolts, and so on

  • Failure to maintain correct machine operation conditions, such as temperature, vibration, pressure, speed, torque, and so on

  • Lack of operator skills causing incorrect machine operation

  • Lack of maintenance crew skills causing maintenance errors

  • Physical deterioration of bearings, gears, fixtures, and so on

  • Design deficiency of the equipment in terms of material construction (the machine just isn't strong enough to survive daily use), dimension (the machine works well within certain parameters, but is less robust outside certain settings), and so on

  • Misapplication of equipment, such as using light duty cycle equipment for a medium/heavy duty cycle task.

To be successful, TPM needs to address all these issues, which simple "Preventative Maintenance" certainly cannot.

Logistics

As stated in "Overview" in this section, TPM should be undertaken as an operations-wide initiative and should be resourced as such. It should have an Executive Champion, usually a Vice President of Operations or similar and an accountable hierarchy of resources to plan, structure, and implement change. Commonly multiple TPM Teams are active in a business at any one time working systematically through key equipment issues to raise the OEE of the facility.

Roadmap

The high-level steps in a TPM timeline for critical pieces of equipment are as follows:

Step 0.

It is the bare minimum responsibilities of any operators and maintenance crew to conduct cleaning, inspecting, and repairing the area and equipment. Items that are not fixed immediately should be Red Tagged. Create a log of who is responsible, what the action is, and when it is due.

Step 1.

Preventive Maintenance This is typically what the newcomer assumes TPM represents; preventing breakdowns from occurring through a regular maintenance program that fills fluid levels, replace filters, and so on. Create cleaning and lubrication standards and a schedule with identified responsibilities for operators and maintenance personnel.

Step 2.

Corrective Maintenance Making Preventive Maintenance easier and user-friendly by eliminating problem sources, such as leaks, and improving access to equipment to be able to clean, inspect, and repair it. Central lubrication systems are a common approach here.

Step 3.

Breakdown Maintenance Identifying the primary causes of machine down-time to be able to create recovery plans that reduce the amount of time it takes to repair a machine after a breakdown. It is often useful to use a Rapid Changeover (SMED) approach here. The assumption is that the equipment goes down at some point (for whatever reason), and so it makes sense to have a standard approach to rapidly bring it back on-line.

Step 4.

Maintenance Prevention Buying or designing equipment so that it needs minimal maintenance. Identifying the key maintenance risks and working to eliminate them with (typically) more advanced technology, such as replacing standard bearings with sealed bearings or traditional cutting heads with more exotic alloys or better still lasers.

Step 5.

Predictive Maintenance Identifying the key Xs that cause machine failure using the Lean Sigma Y = f(X1,X2,..., Xn) approach, then using technology to track those Xs to predict machine failure. Xs typically are one or more of heat analysis, vibration, electrical tests, measurements, and so on.

Step 6.

Scheduled Maintenance The previous steps give a detailed understanding of the Xs that drive failure and the systematic methods to bring equipment back online after failure or during routine maintenance. Thus, it is possible with this information to regularly schedule machine downtime with the production department.

To reiterate, TPM is certainly not a simple undertaking, but nonetheless is crucial to most Operational Excellence initiatives. The preceding roadmap is not nearly enough to commence such an initiative, but hopefully gives an indication of what is involved and hopefully the value of such an endeavor.




Lean Sigma(c) A Practitionaer's Guide
Lean Sigma: A Practitioners Guide
ISBN: 0132390787
EAN: 2147483647
Year: 2006
Pages: 138

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