## 4

Average

### Best of best OEE and potential benefit

The best of best OEE can now be calculated. In addition, if the hourly rate of added value is taken to be £100, the annual benefit (45-week year) of moving from the current average OEE of 39.4 per cent to the best of best can be found.

Best of best OEE = availability x performance x quality

At 39.4% OEE, value added per year = 0.394 x 5130 x £100 = £202 122 At 51.2% OEE, value added per year = 0.512 x 5130 x £100 = £262 656

Therefore, a benefit of £60 534 is possible by consistently achieving best of best through tackling the six losses using the nine-step TPM improvement plan.

### Step 3 Assessment of the six big losses

The importance of understanding and tackling the six big losses cannot be over-emphasized! They were listed in Chapter 3 and illustrated by the iceberg analogy in Figure 3.14, repeated here as Figure 5.5. The six losses are as follows:

• Breakdowns

• Idling and minor stoppages

• Running at reduced speed

• Quality defect and rework

These are elaborated in Figures 5.7-5.12 in terms of the relationship of these losses to the OEE.

Figure 5.6 shows the losses as a fishbone cause and effect diagram. This formula is used by the TPM core team as a brainstorming tool to list all possible causes and reasons for each of the six loss categories.

We will develop a detailed definition in later chapters regarding the four levels of control referred to under each of the six losses in Figures 5.7-5.12. However, in order to give an early indication a definition is as follows:

Figure 5.6 Factors in overall equipment effectiveness

• Level 1 Milestone 1 after pnot/roll-out activity: 12-18 months

• Level 2 Refine best practice and standardize: 6-12 months later (P-M

prize level)

• Level 3 Build capability: 12-18 months later

• Level 4 Strive for zero: 3-5 years from roll-out launch

Level 1

1 Combination of sporadic and chronic breakdowns

2 Significant breakdown losses

4 No operator asset care

5 Unstable lifespans

6 Equipment weaknesses not recognized

Level 3

1 Time-based maintenance

2 PM>BM

3 Breakdown losses less than 1%

4 Autonomous maintenance activities well established

5 Parts lifespans lengthened

6 Designers and engineers involved in higher-level improvements

I^evel 2 Chronic breakdowns

Breakdown losses still significant PM = BM

Operator asset care implemented Parts lifespans estimated Equipment weaknesses well acknowledged Maintainability improvement applied on above points

Level 4

Condition-based maintenance established PM only

Breakdown losses from 0.1% to zero Autonomous maintenance activities stable and refined

Parts lifespans predicted

Reliable and maintainable design developed

BM Breakdown Maintenance

PM Predictive Maintenance

Figure b.7 OEE assessment: breakdown losses l^evel 1

No control: minimum involvement by operators

Work procedures disorganized: set-up and adjustment time varies widely and randomly

Level 3

Internal set-up operations moved into external set-up time Adjustment mechanisms identified and well understood Error-proofing introduced

### Level 2

Work procedures organized, e.g. internal and external set-up distinguished Set-up and adjustment time still unstable Problems to be improved are identified

Level 4

1 Set-up time less than 10 minutes

2 Immediate product changeover by eliminating adjustment

Figure 5.8 OEE assessment: set-up and adjustment losses

The improvement cycle in TPM starts from an appreciation of what the six big losses are and proceeds through problem solving to the establishment of best practice routines. Eliminating the root causes of the six losses is tackled in Step 9 of the TPM improvement plan.

Finally, Figure 5.13 shows a summary of the loss categories with improvement strategy examples.

Level 1

1 Losses from minor stoppages unrecognized and unrecorded

2 Unstable operating conditions due to fluctuation in frequency and location of losses

Level 3

1 All causes of minor stoppages are analysed; all solutions implemented

Level 2

1 Minor stoppage losses analysed quantitatively by: frequency and location of occurrence; volume lost

2 Losses categorized and analysed; preventive measures taken on trial and error basis

Level 4

1 Zero minor stoppages (unmanned operation possible)

Figure 5.9 OEE assessment: idling and minor stoppage losses

Level 1

1 Equipment specifications not well understood 1

2 No speed standards (by product and 2 machinery)

3 Wide speed variations across shifts/operators 3

Level 3

1 Necessary improvements being implemented 1

2 Speed is set by the product. Cause and 2 effect relationship between the problem and the precision of the equipment 3

3 Small speed losses

### Level 2

Problems related to speed losses analysed: mechanical problems, quality problems Tentative speed standards set and maintained by product Speeds vary slightly

Level 4

Operation speed increased to design speed or beyond through equipment improvement Final speed standards set and maintained by product

Zero speed losses

Figure 5.10 OEE assessment: speed losses

Level 1

1 Chronic quality defect problems are neglected

2 Many reactive and unsuccessful remedial actions have been taken

Level 3

All causes of chronic quality defects analysed; aU solutions implemented, conditions favourable Automatic in-process detection of defects under study

Level 2

1 Chronic quality problems quantified by: details of defect, frequency; volume lost

2 Losses categorized and reasons explained; preventive measures taken on trial and error basis

Level 4

1 Quality losses from 0.1% to zero

Figure 5.11 OEE assessment: quality defect and rework losses

Level 1

1 Start-up losses not recognized, understood or recorded

Level 3

1 Process stabilization dynamics understood and improvements implemented

2 Causes due to minor stops aligned with start-up losses

Level 2

Start-up losses understood in terms of breakdowns and changeovers Start-up losses quantified and measured

Level 4

Start-up losses minimized through process control

Remedial actions on breakdowns, set-ups, minor stops and idling minimize start-up losses

Figure 5.12 OEE assessment: start-up losses

Loss Category Improvement strategy examples

Breakdowns Set-up losses

Minor stops

Reduced speed

Quality losses

Start-up losses

Improve detection of conditions contributing to this, spot problems early.

Identify in/outside work and organize/standardize. Identify unnecessary adjustments and eliminate.

Use P-M analysis. Cleaning will probably be a key factor.

Identify speed, capability/capacity through experimentation. Speed up process to magnify design weaknesses. Use P-M analysis to identify contributory factors.

Classify causes and develop countermeasures, including standard methods to reduce human error.

Establish key control parameters, minimize number of variables, define standard settings.

Figure 5.13 Reducing/eliminating the six losses

0 0