TPM Don't Overlook The Sporadic or "Small" Losses like Setup-Downtime

Enrique Mora

Setups of Equipment and 
Isolated or Sporadic Losses  

The capacity of the equipment is limited by isolated or sporadic losses that can be controlled, reduced and even eliminated: 

»     Taking preventive action against malfunctions that cause losses of time and losses of productivity. Prevention is obtained through listening about small anomalies that the users report. 

»     Reducing the necessary times for preparation or setup of the equipment, tooling changes, when we change according to requirements in the process of the different products. We should also avoid the losses for faulty products at the beginning of a new lot. There is a traditional tendency of accepting this situation and this doesn't always have justification. 

»     Reducing smaller stoppages: they are difficult to quantify but they are generally easy to solve. These time losses have a great impact on the effectiveness and they are usually due to malfunctioning, obstructions and lack of coordination. Again the operators can be the key element of the information that will facilitate this task. 

»     Reducing losses caused by low speed: production loss caused by the difference between the design speed of the equipment and the real speed of operation. We must know the capacity and determine why it is not being used to the maximum. Many cases are caused by lack of training of the operators. It can also be due to ergonomic failures that in most cases can be corrected easily by listening to the operator. 

»     Reducing chronic quality defects: they are losses caused when producing products with small defects that have been accepted as normal. There is not a defect that should be accepted as normal.

Taking Action Against Breakdowns

Most people recognize that breakdowns are a form of loss in the factory. To take this problem seriously, it requires first a different form of thinking. In Japanese, a breakdown means “damage caused by human actions”. 

A failure or breakdown is the loss of a specific function in certain object (machine, system, or part). We can divide these in two categories: 

»      Breakdown with function loss in which the equipment stops completely.  

»      Breakdown with reduction in the functions. They are considered less serious, and they are problems related with the deterioration in specific parts of the equipment. It is possible that they cause defects in the product or compromise the reliability of the equipment or the safety of the users.  

A poor administration of the equipment promotes chronic breakdowns. There are many reasons for the response to be ineffective to the problems of chronic breakdowns. For example: division of the work without good communication, inadequate training or absence of it, contractors' dependence, the unreliable design, too few maintenance personnel, absence of the necessary technology, overloaded equipment, ineffective inspection, inaction against deterioration, etc. These problems happen when the administration is not careful about the importance of maintenance. When it becomes evident, it produces a decline in the personnel's morale and this increases the chronic breakdowns. 

Basic Principles To Achieve Zero Breakdowns

The defects of the equipment are disorders that cause breakdowns. We will analyze the necessary actions to discover the hidden defects. 

Maintenance or conservation of the basic specifications of the equipment: 

These three points are critical 

»     Cleaning:

»      Remove and prevent the dust and polluting particles that cause friction or faulty breathing – ventilation

»      Eliminate the obstacles that impede a good inspection

»      Correct the leaks of cooling or lubrication fluids

»      Examine the nuts or screws

»      Discover hidden defects such as abrasion, scratches, vibration, over-heating, abnormal sounds

»      Determine the origin of the pollutants and eliminate them at the origin if possible. 

»     Lubrication: 

In many cases, we can see empty lubrication deposits and the level indicators are inaccessible or they are covered with dust, grim and even painted; clogged or leaking lubrication lines. This accelerates the deterioration, not only affecting the equipment but the whole area. Another common case is when the operator does not know the type of lubricant that the equipment needs. 

»     Inspection: 

In this phase we take care of possible loose pieces, broken parts, as well as missing screws or nuts that play an important role in the breakdowns. Include the verification of belts or transmission chains and couplings. If these details are neglected, the possibilities of vibration are increased and a series of consequent problems can happen. 

This is why we constantly insist that the operator should know the necessary principles to maintain the equipment. It should be clean, lubricated and daily inspected to assure the three previous points. It is essential that these tasks be considered as productive, because they are, and that the conditions in general allow for them to do it quickly and safely.  

Maintenance of the operation conditions: We should pay attention to the conditions for which the equipment was designed to operate at its best capacity. In hydraulic systems for example, the temperature, quantity, pressure, purity and chemical conditions of the oil should be controlled. The incorrect conditions will later turn into hidden defects. 

Restore all that has deteriorated: Frequently, when a piece of equipment breaks down, only the parts directly involved in the breakdown are restored or replaced. This can cause other problems. Even when the broken piece is replaced, in many cases the faulty operation persists. Other components of the equipment don't seem to have damage but in fact they were affected by the faulty piece, or those were that caused the defect. Just as we saw in the root cause analysis, it is important to determine which components are directly associated to the failure. Cause is effect and effect is cause. It is necessary to find the root. 

Correcting weaknesses of the design: In some cases, especially in custom machines, we find failures that may happen under normal operating conditions. This is because the designer or manufacturer didn't take into account the efforts that each part would be subjected to, or they skimped in the engineering, quality or quantity of the materials employed in its manufacturing. This is a situation that is fortunately being defeated by growing competition.  

An old (early 1900s) maintenance manual that suggested some measures to equipment re-engineering is still valid: 

»     Understand the occurrence of the defect, and the conditions before and after the breakdown. Confirm the design of the equipment structure and understand its function.  

»     Confirm the appropriate control of the basic operation, effort and load conditions. 

»     Assure the correct restoration of functions and calculate the real efforts to which each mechanism will be subjected. 

»     Plan, Implement and Evaluate the improvements that will allow a more reliable operation.    

Improving The Setup Times (SMED)

This is a Lean Manufacturing discipline that combines very well with TPM.  

The time of preparation of the equipment and adjustment (setup) begins when the production of a product is completed, and it finishes when the standard quality is achieved in the production of the following product. In other words, it is the time required to remove dies, molds, guides, etc. plus the time used to clean, to prepare the new dies, molds, guides, etc. for the following product, plus the time used to reassemble the equipment, to adjust it, to do test runs and make adjustments again, etc. until the new product reaches the specified quality. 

Shigeo Shingo, the brilliant Japanese engineer, wrote a well-known process called SMED (Single-Minute Exchange of Dies) that means a process where the tooling is changed for different product in one digit of minutes, that is less than ten minutes.  With such techniques and the growing reliability and advances of Industrial Engineering, the times of preparation and adjustment have been drastically reduced. A trained person continues finding opportunities for improvements in most of the cases. 

Most people complain about the time loss to prepare and to adjust the equipment, but few understand the opportunities and the relationship among the variables to make improvements. 

Internal AND External Operations of Preparation or Setup

The first step to improve the time of preparation is establishing the difference in the operations: 

»      External Operations are those that can be made when the equipment is running. 

»      Internal Operations can only be made when the equipment is stopped.  

The time is reduced by eliminating from the time of internal preparation all the operations that can be made while the equipment is still working. This it is the first step in the improvements. It is a line in which impressive improvements can be achieved. Example: bringing a setup of 4 hours to 21 minutes or less. 

The Small Problems And Their Bigger Costs

Reducing the small stoppages: In accordance with several Japanese authors, the small stoppages are a temporary process problem. They take time and they can be classified as losses by equipment. They have been defined as the natural enemies of the productivity. 

Let us see some cases: 

»      A problem is detected by an instrument and the equipment automatically stops.  

»     Detentions caused by overload are found in packing plants, assemblers, etc. when the pieces stop because a following station cannot receive them. 

»      Some quality problems cause machines with sensors to stop when an error is detected

»     Operation "in empty" is when the equipment keeps working but there is no material to process. It can be due to failures of equipment of previous processes or bad coordination.  

These are Some Characteristics of Small Stoppages. 

»     Easy to repair. They generally cause “minimum” losses.  

»     The occurrence conditions vary thoroughly. They can happen with certain products or parts and not with some others; or with all the products or parts, but under certain circumstances, weather, time of the day, operator.

»     They may only happen certain days, or only in certain machines. There are a variety of unavoidable conditions that makes them easy to ignore. They are taken as normal condition, especially for personnel at all levels who have seen them happen for years. 

»     Their localization constantly changes. The small stoppages rarely happen in the same place in the same machine. The problem can be chronic, or a sporadic problem can happen together with the chronic one, hiding each other.  

»     The effect of the loss is not clear. The loss caused by the smallest stoppages is difficult to quantify. It almost always passes unaware; a registry is hardly ever taken. It is part of the operation pattern. It is surprising to discover what those small losses can mean when they accumulate. 

Common problems. Typically the losses due to smaller stoppages are not appropriately treated, measured, or observed. 

»     The losses remain without being noticed and few are documented. A preliminary step is the measurement of the losses that they cause. This measurement can be achieved by means of the operator’s verification lists

»     The remedial actions are inadequate. The operators and maintenance personnel treat these failures superficially; therefore in many cases symptoms are corrected without attacking the real problem. Example: containers for leaks or not very professional repairs such as wire ties or adhesive tapes, instead of the appropriate fixture. 

»      The problem is not observed to detail. It will require some dedication to discover a simple and definitive solution.  

The outstanding American consultant and author Charles Latino attributes to this type of recurrent failures up to 80% of the maintenance costs and production losses. Imagine how a plant would benefit if we can reduce just half of them.  These strategies to reduce the small stoppages have already been established by diverse specialists through the 50+ years of TPM. 

»     Correct slight defects in parts, tools and facilities. Investigate and correct all the defects although they may seem simple.  

»     Realize that problems exist and it is the responsibility of all in the company to identify and to solve them.  

»     Discover the hidden problems, establishing the comparison between the existent conditions and what the optimal should be.  

»     Thoroughly investigate any condition or abnormal fact. Listen to the observations from the operators. They know their equipment. 

»    Assure that the basic conditions of the equipment are respected. These small problems are frequently caused when the basic maintenance of the equipment, (cleaning, lubrication, inspection) fails. So be careful of those details. 

»    Review the basic operations. Make sure that the preparation of the equipment, adjustments and setup operations are made correctly. A complete revision of the processes, with opinions of operators and technicians is good. Request that they write in their own words the most convenient process to fulfill that responsibility. 

»     Conduct a physical analysis of the problem. The three described strategies alter the occurrence, frequency and localization of the failures and small stoppages. Those improvements, by themselves, cannot eliminate the problems totally. To reduce the occurrence use an analysis under physical principles. 

»     Adopt and try to make the other people involved adopt an analytic attitude. Analyze each possible group of conditions in connection with the machines, tools, parts and materials without omitting any factor. When we do this in a systematic way, the actions taken will likely solve the problem. 

»     Determine the optimal conditions. The installation conditions include each factor related with the way the equipment was installed. The production conditions are the physical conditions related with the process. These conditions can always be improved by the experience and they can be optimized. 

»     Eliminates weaknesses in the design. In many cases we will be able to discover that the failures are due to an underestimation of the functions for which the equipment was designed. Example: suspension parts in cars that are deformed, gears that wear away even under good lubrication conditions, pipes that break for not withstanding a normal vibration of a hydraulic system, refrigeration condensers that are not able to cool and condense the gas in warm weather, etc. 

Confront all these problems with a positive attitude and with creativity and intelligent objectivity. Use the information, knowledge and collaboration of all the people involved.    

Reducing speed losses. A speed loss is the loss caused by the difference between the design speed of a machine and its real operation speed. Again, we should follow the equipment specifications. There is a mistaken idea that when running a machine at a reduced speed to that of design, we are protecting it. It is necessary to eradicate that myth. The losses can be due to: 

»     Uncertainty about equipment specifications. During the stages of the design, it can happen that specifications of speed and capacity are not clear and defined or are unrealistic. As a result, the equipment may be operated beyond the limits of speed, producing defects and breakdowns, or it is unnecessarily operated at low speed or load.  

»     The specified speed can be reached, but it is not utilized. Some machines cannot be operated to the specified speed because the quality or mechanic problems were never resolved. Such problems are neglected and no effort is made to pursue and to correct their causes. They accelerate the deterioration. The loss of speed can simply be eliminated correcting those errors at the root cause.  

»     An inadequate investigation of the problems that happen when speed is increased. When the speed is gradually increased from the present levels, the quality or mechanical problems appear immediately.  

»     This can also happen when the design speed is not appropriate with the ergonomic characteristics of the operation so it is humanly impossible or extremely difficult to operate the equipment at that pace. 

Some actions to increase the speed. A first vital step is to expose the hidden problems and to determine if they correspond to anyone of the following: 

»     Unsolved defects due to insufficient tests during the engineering stage 

»     Defects in the system or mechanisms of the equipment 

»     Inadequate daily maintenance or faulty operation  

»     Insufficient precision in adjustments and setups  

The operations to increase or to recover the speed should be organized with the same understanding, using the same methodology recommended to reduce the failures or smaller stoppages and other defects. 

Reducing the chronic quality defects. When a production system regularly produces total or partially faulty products in spite of several improvements and measurement controls, those faulty parts are called chronic quality defects. 

The irreparable faulty products are obvious losses. Less obvious are the losses generated by partially faulty products that require an additional investment in workmanship to repair or rework.  

General characteristics of the chronic quality defects. To progressively reduce the chronic defects, the improvement groups should learn how to recognize them and to avoid the most common traps: 

»     The improvement efforts have not been progressive. Even the biggest efforts rarely can take care of the causes of chronic quality defects. The quality assurance teams despair and they adopt Trial and Error measures, without knowing the causes. For that reason very often they don't have any effect. The members of the teams simply give up and the problems remain without solving.  

»     The problem is that many times we may take the mistaken perspective. The chronic quality defects are frequently caused by a combination of causes that is always changing. Each suspicious factor should be isolated, and the progress will come when several investigation paths are continued and resolved.  

»     The thought is some times limited to specific technical fields. The engineers of most companies are experts in certain technical fields. To solve the problem for chronic defects, they discard the solutions that would be outside of their field or ability. They sometimes favor complex solutions above the simple ones. As a result many problems remain unsolved.  

»    It is difficult to identify and investigate causes. The quality improvement teams often find two common problems: errors in the identification of the causes of chronic quality defects and an inadequate investigation after they have identified them correctly.  

These are some classic strategies to reduce chronic quality problems. To solve the chronic problems the ideas should involve the following strategies: 

»     Improvements that change the equipment status.  

»     Objectives established in agreement with the company’s improvement goals.  

»     The current standards reviewed.  

»     The current control points reviewed.  

»     The managers made responsible.  

Stabilize the current factors. To reduce the chronic quality problems all the variable factors should be stabilized, the significant differences among normal and abnormal conditions should be identified, and methods to prevent the defects that are generated in the first place should be studied. The causal factors are factors that can affect the results, and that directly or indirectly produce the problem. To stabilize something is to avoid its changes. Although the causal factors can seem stable in factories and shops, in fact the work is done under unstable conditions, in a mess of causal factors. The operations that take place while the factors are changing may fail. 

To reduce the chronic quality problems, these conditions should be stabilized one by one. The variability is caused by the lack of standard or for failures when selecting the standards. Stabilize each causal factor that logically can have an effect in the production: 

»     Process principles and steps.  

»     Mechanisms and tools.  

»     Operations or setup adjustments.  

»     Equipment precision, templates and tools.  

»     Work methods.  

In some cases, they simply cannot be stabilized because they have not been written. A process sheet is advisable in these cases. 

Comparative studies. In any program to reduce quality defects, the normal conditions (not defects) should be compared systematically with the abnormal conditions (defects) to identify significant differences.

Several methods can be used: 

»     Compare products (results). Compare the faulty and non-faulty products in form, dimensions and functions. Also investigate the variation in defects in the time and localization in the product.  

»    Compare processes. Compare the machines, templates, tools and dies that produce defects, with the equipment that doesn't produce them. Identify differences in form, dimensions, textures, etc. Make a special effort to develop new measurement methods for the factors that don't seem to be currently quantifiable.  

»     Compare the effect of changing parts. In the assembled products the study with the help of exchanging parts can establish relationships with the defects.  

»     Increase the analytic precision to detect more subtle differences. Use magnifying glasses, microscopes, and other apparatuses, as well as precision tools to detect differences that cannot be seen at first sight. Consider the differences in form, dimension, texture, brightness, etc.  

»     Review the causal factors. Review the control points and consider a new perspective for their selection and study. The best access is the root cause analysis.

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