I said from the very beginning, I don’t want a big house, I don’t want big grounds, I don’t want the trouble with the maintenance and all of that.
—Nancy Reagan The TPM strategy includes zero defects, zero accidents, and zero break-downs, as shown in Figure 5.1.
Types of Maintenance Involved with TPM
There are different types of maintenance involved with TPM, which will be described in detail below:
1. Breakdown maintenance 2. Preventive maintenance
a. Periodic maintenance b. Predictive maintenance 3. Corrective maintenance 4. Maintenance prevention
Breakdown maintenance: You wait until the machine completely fails, and then you repair it to working order. Usually this type of main-tenance is assigned to machines with backups in place, or machines that are of low importance to production.
Preventive maintenance: You maintain the machine, while still in operation, to prolong or prevent the machine’s failure. This should be applied to machines of importance and high value when compared to production. This type of maintenance includes cleaning, oiling, retightening, and inspecting. Preventative maintenance is further divided into predictive maintenance and periodic maintenance.
Predictive maintenance: You predict when the machine may require maintenance based on analyzing past history, inspecting, and applying maintenance just before the machine has failed in the past,
extending its service life. Predictive maintenance is condition- based maintenance. It manages trend values by measuring and analyzing data about deterioration and employs a surveillance system designed to monitor conditions through an online system. This concept often is applied in conjunction with preventative maintenance.
Periodic maintenance: A set schedule of maintenance routines assigned to prolong the life of the machine. This is a time- based maintenance consisting of periodically inspecting, servicing, and cleaning equip-ment while also replacing parts to prevent unexpected failures and process issues. This concept is often applied in conjunction with pre-ventative maintenance.
Corrective maintenance: A form of system maintenance that is per-formed after a fault or problem emerges in a system, with the goal of restoring operability to the system. In some cases it can be impos-sible to predict or prevent a failure, making corrective maintenance the only option. Corrective maintenance improves the equipment and its components so that preventative maintenance can be car-ried out reliably. Any design weaknesses in the equipment must be redesigned in order to improve reliability and maintainability.
Maintenance prevention: Machine engineering and design that is based on preventing the need for maintenance or for ease of access to machine parts so that maintenance may be carried out easily—differ-ent than preveasily—differ-entative maintenance in that maintenance is performed
TPM Defects0
Breakdowns0 Accidents0
FIGURE 5.1 TPM methodology.
while a machine is still in working order to keep it from breaking down. Maintenance prevention indicates the design of new equip-ment. Any current machines operating inefficiently are studied and incorporated into the new design and commission of machinery.
Preventive maintenance includes lubricating, tightening, and replacing worn parts. Preventive maintenance is work that is done on a machine, often involving testing and the replacement of worn but still functioning parts, in order to prevent a failure (as against fixing something only when it breaks).
Maintenance prevention means stopping maintenance from taking place. If used in a positive context, it is steps taken perhaps in the design of a device to make it require less maintenance. The types of maintenance are shown in Figure 5.2.
Breakdown Maintenance
Breakdown maintenance is simply the repair of equipment after it has already deteriorated in performance or broken down (Figure 5.3). Breakdown main-tenance is used when failure does not significantly affect the operation and the financial losses are insignificant apart from the repair costs.
TPM TPM
Preventive Maintenance
Periodic
Maintenance Predictive
Maintenance Breakdown
Maintenance Corrective
Maintenance Maintenance Prevention
FIGURE 5.2
Types of TPM maintenance.
Breakdown maintenance can be broken down into two types:
1. Planned repairs: Maintenance performed when it is more feasible to deal with a problem after the machine has broken down rather than to prevent the failure from occurring.
2. Unplanned repairs: Maintenance performed when it would have been more feasible to prevent the problem but this type of mainte-nance could interfere with production scheduling.
Examples of breakdown maintenance include the following:
Extremely dirty pieces of equipment that stay that way Raw materials encrusted into parts of existing machinery Machinery needing oil or lubricant frequently but is out Tangled cords unable to be placed to the source
Equipment that you cannot see the parts inside
In order to increase the efficiency of breakdown maintenance, opera-tors should detect abnormalities when they perform their daily checks or routinely monitor their equipment. This is part of their planned mainte-nance program.
The steps involved in breakdown maintenance in a planned maintenance setting consist of the following:
Step 1: Evaluate the current equipment and understand the current conditions.
Step 2: Restore the deteriorated equipment and correct the weaknesses of the equipment.
Step 3: Build an information management system.
FIGURE 5.3
Figure of out- of- order machine.
Step 4: Build a periodic maintenance system.
Step 5: Build a predictive maintenance system.
Step 6: Evaluate the planned maintenance system.
Preventive Maintenance
Preventive maintenance helps sustain equipment from breaking down and becoming defective. Proper types of equipment should be installed in the first place for functionality purposes. Three main types of activities will be required for preventive maintenance to be rolled out properly (Cudney et al., 2013):
1. Daily maintenance: Cleaning, checking, lubricating, tightening to prevent equipment from breaking down and deteriorating.
2. Periodic inspections to check on equipment current status.
3. Restoration to correct and recover from equipment that is deteriorating.
Preventive maintenance will be broken down to predictive and peri-odic maintenance.
Periodic maintenance is also considered time- based maintenance. Tools such as standby units, spare parts, inspection equipment, lubricants, and technical information may be required in order to perform the work. The preparation of these tools will help in the rollout of periodic maintenance.
It is possible to overmaintain equipment by scheduling work at intervals that are not set appropriately. It is important to think through the work being scheduled to ensure it is in need of maintenance. The best way to sched-ule appropriate maintenance is to understand the root cause behind the last breakdown and revise the intervals and tasks before the next service.
Figure 5.4 depicts the proper periodic maintenance plan. Each step of the flowchart is briefly explained below (Agustiady and Badiru, 2012a).
Select appropriate equipment for periodic maintenance: Ensure that the equipment selected has the following standards:
Equipment by law that requires periodic maintenance.
Equipment that has proven intervals of maintenance determined by past experience.
Equipment that is critical to quality that requires regular checking because of its importance to the process.
Equipment that has proven intervals of maintenance determined by the serviceable life of its components.
Select appropriate equipment for
periodic maintenance Prepare tools and manuals including check sheets for
periodic maintenance
Determine appropriate maintenance intervals and work
to be performed
Prepare for periodic maintenance
Perform periodic maintenance
Determine if appropriate maintenance interval was
obtained No
Determine if No appropriate maintenance work
was obtained
Prepare final report and file
equipment history
Revise maintenance
work and intervals
FIGURE 5.4
Periodic maintenance flowchart.
Equipment whose life performance begins to deteriorate after known amounts of time.
Equipment that has abnormalities that make it difficult to detect or correct during operation.
Prepare tools and manuals including check sheets for periodic main-tenance: Maintenance plans should be based on basic short- term production plans normally spanning 5 years. The details for the shutdown of the maintenance of the equipment or the entire site should be mapped out. These plans should include annual, monthly, weekly, and daily plans. The plans for opportunities for mainte-nance should also be included. In order for preparation for these tools and manuals for the periodic maintenance, the following should be incorporated:
The setup or fabrication in advance of tools and manuals.
Cross- functional teams of skills and knowledge to minimize a short-age of skilled labor for the maintenance.
The preparation of all manuals, check sheets, tools, etc., to be done ahead of time.
The examination of previous plans and checks that took place and any operating conditions that should be noted.
Determine appropriate maintenance intervals and work to be performed:
Maintain standards for a solid base of periodic maintenance that should be performed.
Materials selection: Understand if the standards for existing parts and materials are still the same or need to be updated.
Work estimating: Utilize the use of the latest maintenance tech-niques, equipment, materials, and standards to establish the base work needed and costs for upgrades and maintenance. Look for replacement parts, leaks, testing, serviceability, and replacement.
Spare parts: Spare parts are an essential element for ensuring reli-able equipment while reducing downtime for equipment. It should be understood what the proper amount of spare parts should be to reduce stock and inventory of capital along with additional warehouse costs. The control on these spare parts must be performed. In order to control the spare parts, the main-tenance department should control standby units, general parts, and tools and testing equipment.
Lubricant standards: Personnel should understand the different types and uses of lubricants to suit the equipment being utilized while ensuring the limitation on multiple amounts of lubricants.
Safety standards: Safety standards should be drawn up and reviewed annually and revised as needed. These standards should include:
Employee and supervisor duties Pre- start- up duties
Activities to occur in the event of an accident Safety procedures during operation
Electrical safety Shutdown safety
Employees should be allowed to inspect the work site in advance of the operation to ensure safety compliance.
Prepare for periodic maintenance: This concept includes having the above ready for when the equipment is ready for the periodic maintenance.
Perform periodic maintenance: This concept should be rolled out when the equipment is ready for the periodic maintenance.
Prepare final report and file equipment history: At the conclusion of the periodic maintenance, a report should be generated that details the work accomplished, the progress that was made, the employ-ees involved, and the costs. All problems and conditions should be reported, especially regarding safety, number of employees involved, and costs.
Predictive Maintenance
Periodic maintenance will help minimize the amount of maintenance needed along with unexpected failures; failures will still occur, which will increase costs. Periodic maintenance is a time- based system that hypothe-sizes the deterioration of equipment without in- depth statistical measures (Cudney, 2009). It is difficult to find the optimal service interval without mea-suring the exact deterioration and failures of specific equipment at specific times. Measures that need to be taken for understanding failures of equip-ment include temperatures, vibrations, pressures, flow rates, lubrication lev-els, corrosion rates, defects on materials, and electrical resistances. Utilizing predictive maintenance, equipment can be diagnosed systematically, leaving the guess-work out. A simple table can be used to collect the data needed, as shown in Table 5.1.
A simple flowchart can be constructed after the data measurements have been taken. The flow should consist of the plan diagnosis, the equip-ment to diagnose, and the repairs and assessequip-ments to be made. It should
be understood if any thresholds are over the limit allowed and what work will be needed for successful repairs. An example flow diagram is shown in Figure 5.5.
Corrective Maintenance
Corrective maintenance can be defined as a maintenance task performed to identify, isolate, and rectify a fault so that the failed equipment, machine, or asset can be restored to an operational condition within the tolerances or limits established for in- service operations.
Corrective maintenance is carried out after failure detection and is aimed at restoring an asset to a condition in which it can perform its intended function.
Corrective maintenance helps improve equipment and its components so that preventive maintenance can be accomplished properly. Any equipment that has design weaknesses must be redesigned. Corrective maintenance is TABLE 5.1
Predictive Maintenance Data Recording Table Date and
Time Equipment Abnormality Cause Diagnostic Process
15-Jul-14 Die cutter Leak in
system Corrosion Visual inspection, wall thickness measurement 16-Jul-14 Vibration
meter Excess
vibration Rubbing of
metal belts Bad parts found, vibration measurements
Equipment Selected
Diagnosis Plan
Diagnostic Process
Threshold Value
Is Data Good or
Bad?
Perform Diagnosis
Is Repair Needed?
Plan Repair Work
Perform Repair
Reassess Deterioration and Equipment
Needs
Record Data Good
Bad
Yes
No
FIGURE 5.5
Predictive maintenance flowchart.
a form of maintenance that is performed after a fault or problem emerges in the system, with the goal of restoring operability. In some cases, it can be impossible to predict or prevent a failure, making this type of maintenance the only option.
Corrective maintenance can be subdivided into:
• Immediate corrective maintenance: Work that will begin immedi-ately after a failure.
• Deferred corrective maintenance: Work that is delayed in confor-mance to a given set of maintenance rules.
Corrective maintenance refers to action only taken when a system or component failure has occurred. It is important for the maintenance of repairs to begin as soon as possible. Costs associated with corrective main-tenance include:
• Repair costs
• Lost production
• Lost sales
• Corrosion maintenance costs, which represent a significant portion of operating budgets in most industrial sectors, particularly where aging equipment and facilities are involved
The process of corrective maintenance begins with a diagnosis of the fail-ure to determine why it occurred. The diagnostic process can include:
• Physical inspection of a system
• Use of a diagnostic computer to evaluate the system
• Interviews with users
• Numerous other steps that could potentially be thought about
It is important to determine what caused the problem in order to take appropriate action and to be aware of multiple component or system failures that may have occurred simultaneously.
The process behind redesign could use the DMADV approach from design for Six Sigma (DFSS). DMADV stands for the following:
Define Measure Analyze Design Verify
The difference between DMADV and DMAIC is the design and verifica-tion porverifica-tions. DMAIC is process improvement driven, whereas DMADV is for designing new products or services. Design stands for the designing of new processes required, including the implementation. Verify stands for the results being verified and the performance of the design to be maintained.
The purpose of DFSS is very similar to the regular DMAIC cycle, where it is a customer- driven design of processes with Six Sigma capabilities. DFSS does not only have to be manufacturing driven; the same methodologies can be used in service industries. The process is top- down with flow- down CTQs that match flow- up capabilities. DFSS is quality based, where predic-tions are made regarding first- pass quality. The quality measurements are driven through predictability in the early design phases. Process capabilities are utilized to make final design decisions.
Finally, process variances are monitored to verify that Six Sigma customer requirements are met.
The main tools utilized in DFSS are failure modes and effects analyses (FMEAs), quality function deployment (QFD), design of experiments (DOE), and simulations.
Quality Function Deployment
Dr. Yoji Akao developed quality function deployment (QFD) in 1966 in Japan. There was a combination of quality assurance and quality control that led to value engineering analyses. The method for QFD is simply to utilize consumer demands in designing quality functions and methods to achieve quality in subsystems and specific elements of processes. The basis for QFD is to take customer requirements from the voice of the customer and relay them in engineering terms to develop products or services.
Graphs and matrices are utilized for QFD. A house- type matrix is com-piled to ensure that the customer needs are being met in the transformation of the processes or services designed. See Figure 5.6.
The QFD house is a simple matrix where the legend is used to understand quality characteristics, customer requirements, and completion.
Design of Experiments
Design of experiments (DOE) is an experimental design that shows what is useful, what has negative connotations, and what has no effect. The majority of the time, 50% of the designs have no effect.
DOEs require a collection of data measurements, systematic manipulation of variables, also known as factors, placed in a prearranged way (experimen-tal designs), and control for all other variables. The basis behind DOEs is to test everything in a prearranged combination and measure the effects of each of the interactions.
фф ф ͍ ͍͍ y
Strong relationshipLegend Moderate relationship Weak relationship Strong positive correlation Positive correlation
Negative correlation Strong n
egative correlation Objective to minimize Objective to maximize Objective to hit target1Column
Title: Completed by: Date:
Row 1 2 3 4 5 6 7 8 9 10
Target Difficulty Relative WeightImportanceValue in ColumnMax Relationship
Max Relationship V alue in
Relativie Weight Impo rtance
Our Compan y
Company 1 Company 2 Company 3 Company 4 Company 5
Improvement Quality Characteristics Customer Requirements
Methodology (Minimize, Ma
ximize, or Hit Ta
rget)
23456789101112131415 Competitive Analysis 0 - Worst 5 - Best FIGURE 5.6 Quality function deployment.
The following DOE terms are used (Agustiady and Badiru, 2012b):
Factor: An independent variable that may affect a response.
Block: A factor used to account for variables that the experimenter wishes to avoid or separate out during analysis.
Treatment: Factor levels to be examined during experimentation.
Levels: Given treatment or setting for an input factor.
Response: The result of a single run of an experiment at a given set-ting (or given combination of setset-tings when more than one factor is involved).
Replication (replicate): Repeated run(s) of an experiment at a given set-ting (or given combination of setset-tings when more than one factor is involved).
There are two types of DOEs: full factorial design and fractional facto-rial design.
Full Factorial
DOEs determine the effect of the main factors and factor interactions by test-ing every factorial combination.
A full factorial DOE combines all factor levels with one another covering all interactions.
The effects from the full factorial DOE can then be calculated and sorted into main effects and effects generated by interactions.
Effect = Mean value of response when factor setting is at high level (YA+) – Mean value of response when factor setting is at low level (YA–) In a full factorial experiment, all of the possible combinations of factors and levels are created and tested.
A two- level design (where each factor has two levels) with k factors has 2k possible scenarios or treatments:
2 factors each with 2 levels, we have 22 = 4 treatments 3 factors each with 2 levels, we have 23 = 8 treatments k factors each with 2 levels, we have 2k treatments
The analysis behind the DOE consists of the following steps:
1. Analyze the data.
2. Determine factors and interactions.
3. Remove statistically insignificant effects from the model such as p- values of less than .1 and repeat the process.
4. Analyze residuals to ensure the model is set correctly.
5. Analyze the significant interactions and main effects on graphs while setting up a mathematical model.
6. Translate the model into common solutions and make sustainable improvements.
Fractional Factorial
A fractional factorial design locates the relationship between influencing fac-tors in a process and any resulting processes, while minimizing the number
A fractional factorial design locates the relationship between influencing fac-tors in a process and any resulting processes, while minimizing the number