For industrial and manufacturing businesses, the cost of assembly and installation errors may be as much as 30% of reported failure and associated repair costs. For many this could mean millions of lost profit dollars each year! The problem as we all know is that it is not just the cost of repair but also; unscheduled production down time, poor product quality, a reduced reliability (OEE), diminished life cycle performance with an increase in parasitical/frictional forces that consume energy.
The Impact of Infant Mortality …
From the work that was accomplished by Nowlan, Heap, Moubray and others, the identification and realization of pattern “F” (see diagram), has been proven to be a great opportunity for us all. In simple terms, because of what we do in the repair of and how we operate machinery, the probability of this type of failure (as measured by the aircraft industry), is such that no less than 68% of the probability of failure is due from “infant mortality”. In relationship to “improvement”, what are the areas where we can have the largest and fastest impact in the reduction of this failure type?
Infant mortalities major sources include the following:
- Assembly & Installation,
- Unnecessary and/or over servicing of machinery
The Need for Reliability in Design …
While we are not going to go out and build new manufacturing facilities, we must realize that including reliability and life cycle performance in the design of new machinery can reduce the associated maintenance costs over the machine life by 50%. In most cases, the upfront cost added to the project is less than 3%. Not a bad return for a different and precise approach. But, let’s now pay attention to what we are addressing in this short note.
Understanding Mechanical Assembly Failures …
When we discuss mechanical failures, do not think that we are talking about “mechanics”. Mechanical failures happen in the electrical, instrumentation and production ranks as well. Wherever there is a “mechanical” device, the potential for this failure exists. As can be readily seen, approximately 30% of this type of failure is from how we “Assemble” machine systems “mechanically”. The old adages of “close or good enough” just doesn’t cut it in today’s manufacturing requirements. Profit margins and the need to produce first pass product are so tight that unrecognized failures can no longer be allowed.
A Simple Example …
The summation of eccentricities is where the “art” of assembly begins. When assembling “fitments” to shafts, there is always an accepted allowable roundness, clearance and eccentricity tolerance. How many times, do we just place parts together without thinking that the final position of these parts may change the way that the machine was intended to run? Most of us have been taught to think “arithmetically”. There is a need today to reintroduce the importance of “vectorial” thinking on the floor. Fitments in their final assembled position actually create vectors of force. The resulting mechanical force, measured vibration amplitude, machine performance and life cycle depends on how these systems are assembled. The diagram below clearly indicates the difference in correct assembly.
Therefore: “assembled” eccentricity can be added negatively. The net result is that a TRUER center can be determined and applied for all system components.[endif]–
Without going into detail, how many parts are assembled in a machine and then in connected machine systems? If we do not consider the statements above, we begin to quickly realize the number of failures and the resulting costs from assembly errors. We refer to and include these important techniques within a Precision Maintenance® and Reliability Roadmap process.
Where to Begin …
It is our experience that this topic is not just a basic technique but essential in the manufacturing requirements of today and tomorrow. This type of work needs to be introduced with hands on exercises. In this manner, the performance of a machine is measured before and after technique application so that the value of work is experienced. Correct skill set improvement with continuous and sustainable performance is an acquired behavior. Assembly and installation are just one important segment of this work. The need for a specific plan for hard skills training with management involvement and field application is paramount to success. Through correct “assembly” application pattern “F” can be; eliminated, mitigated and controlled to an acceptable minimum. Where are you today in reducing your costs? Where are you going to be tomorrow? Call us and let’s partner today to “Build the Workforce of the Future”!
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