1.2 Maintenance strategies
If there is one thing that should be avoided in the industrial production of cars, it is idle time – i.e., the time during which individual stations or even the entire production process is at a standstill. This is critical because in the automotive industry, due to the short cycle times, even a few minutes of idle time at the end of the day means that many fewer cars leave the factory than planned. This happens, for example, when machines are defective, or errors occur because individual work steps are not well coordinated. The term maintenance is therefore a very important one in the automotive industry. It is even regulated by its DIN standard, namely DIN 31051.
Maintenance can be divided into four basic measures:
- Maintenance: These are all activities that serve to ensure or extend the “life expectancy” of objects (for example, filling up operating materials, replacing, or readjusting wearing parts, but also cleaning).
- Inspection: These are all measures for recording and assessing the current condition of an object.
- Repair: These are all activities to restore the defined target state of a defective object.
- Improvement: This refers to all measures that serve to eliminate possible weak points or to generally increase the reliability of an object.
The goals of maintenance can be manifold. In the automotive industry, the following factors are particularly important:
- Optimization of the operating processes to be able to produce faster and more error-free
- Increasing plant availability to be able to produce more and longer
- Minimize breakdowns as well as disruptions to reduce standing and downtime
- Maintaining operational safety to prevent injuries and accidents
While the technologies and methods surrounding production processes are constantly becoming more modern and complex, the principles of maintenance described above have hardly changed over the past decades. However, the impending consequences of poor maintenance have become much more serious. Production downtime and the resulting overtime costs for personnel can quickly become very expensive.
To be able to implement the above-mentioned measures and goals in a meaningful way, there are various maintenance strategies. These can be divided into three different approaches:
- The damage-dependent maintenance strategy
Here the focus is on damage repair – that is, measures are only taken when there is already damage to the object, or it has failed. Such a strategy is pursued when no information is available about the condition or wear and tear of the object. The disadvantage is, of course, the unpredictability of the potential failure as well as the possible long waiting times if spare parts or replacement machines are missing. - The preventive maintenance strategy
Here, preventive maintenance is ensured with planned and regular measures already during the regular operation of the object. This makes downtimes easier to plan and reduces the risk of failure. A disadvantage here, however, is that work equipment is not necessarily fully utilized at fixed maintenance intervals (e.g. an oil change). This can be remedied by a condition-oriented approach, in which regular inspections are carried out, but the maintenance measure is only carried out when necessary.
- The predictive maintenance strategy
This is an extension of the two previous maintenance strategies. Based on various influencing factors, an attempt is made to predict the course of wear and to find the most efficient times for the necessary maintenance measures. In doing so, measures can also be bundled, and work resources can be used more efficiently.
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Unlike in the past, maintenance measures and strategies in most companies are no longer seen as a necessary evil or even a mere cost generator, but as an essential part and driver of corporate success. Due to the ever-increasing competition in terms of productivity and quality, downtimes must therefore be kept as low as possible, as they can have serious economic consequences for a company.
Due to the great economic importance, internal know-how about efficient maintenance is becoming increasingly important in companies. What counts here above all is an experience in daily use, because it is not uncommon for problems to arise in practice that were not yet recognized by the manufacturer of the machines.
An important point of maintenance here is the search for possible weak points in the production process – i.e. circumstances that lead to failures particularly often, but also make maintenance more inefficient. The most important are:
- Handling of spare parts: Spare parts are stored in an unsystematic or non-transparent manner.
- Incomplete documentation: The documentation of all current or past work is either not done at all or only on paper – an allocation or data selection, for example in the sense of the predictive maintenance strategy, is therefore not possible.
- Lack and transparency of key figures: Instead of determining precise key figures for maintenance measures, inaccurate or only makeshift data is used. This makes it difficult to plan preventive measures or their costs.
- Inaccurate strategy: No clear maintenance strategy is defined that is coordinated across the company.
- Isolation of the department concerned: technical staff act too autonomously instead of in close cooperation with production staff as well as maintenance staff.
- Too much external maintenance: If there is no internal maintenance know-how, the company becomes dependent on an external service provider, which makes it difficult to react quickly to failures.
