Mechanism of statistical product quality control
The mechanism of statistical product quality control is a superstructure over Taylor the mechanisms focused on quality management of separate products and allows to pass to process approach in management of technological processes.
The concepts "deficiency" "deficiency levels" are key for statistical quality management. The purpose of the offered mechanism - management of decrease in levels of deficiency. The mechanism assumes a certain economic independence of shops (sites, crews) of manufacturers of their relationship with other shops (participants, crews) as with consumers. In general the mechanism of statistical product quality control at the internal levels of the enterprise is shown on the scheme 1. Its basis is acceptance procedures on the stated methods, pricing taking into account progressive dependence of the price on decrease in the deficiency level guaranteed by the supplier, creation of stocks of quantity on quality, penalties for failure of deliveries on quality, quantity, terms.
On the scheme relationship of divisions of manufacturers and consumers with the central services and administration of the enterprise, including with accounts department, Quality Department, production management, the management of the chief designer (MCD) of the management of the chief technologist (MCT) is shown. Three last managements define the program of production of production (terms, quantity) and requirements to quality of separate products. Requirements to party as it was already told, the manufacturer defines.
Functions of the accountant and according to plan - economic services (central) organic the statement of the price of products depending on the guaranteed deficiency level, the size of sanctions and their collecting, and also determination of the amount of compensations of the damage caused to the consumer by the supplier at raw materials of deliveries on terms, quantity and quality.
The size of the penalties collected from the supplier will be defined by the damage caused to the consumer irrespective of the price of products.
Let's notice that within this scheme it is realized to the principles administratively - economic management, i.e. management in which it is combined economic, legal and administrative methods. The mechanism of management combines the centralized and decentralized methods. In particular, questions of pricing, rationing of requirements to quality of products and programs of production of products, collecting penalties and payments of compensations are solved centrally, leaning the administrative power.
Questions of rationing of requirements to quality of parties, drawing up plans of statistical quality control (acceptance) production, development of norms of quotations are solved on separate operations, managements of records of quantity of products on quality divisions, i.e. is decentralized. Behind them also the right to demand application of sanctions and compensation of damage, but decisions on imposing of sanctions is accepted centrally.
It is necessary to emphasize that application of statistical control in these mechanisms has basic character.
At application of continuous control there is as if a transfer of responsibility for quality of the manufacturer to the controller: the manufacturer is interested "to push" production through the controller and if further it is found defects, responsibility for them is born by control. At selective statistical control on this method responsibility remains for the manufacturer important movement of an initiative is - now not control "hunts" for performers, and the last offers his statement that the actual level of deficiency is no more, than norm.
Representation to the manufacturer of the right to normalize the level of deficiency and at the same time assignment of a duty (burden) on it proves by methods of statistical control compliance of quality of party to the established norms creates steady as in the organizational, and psychological relation the mechanism of management. In other words, to the parties becomes to carry out favorably correctly and accurately the functions, and it excludes a reason for the conflicts and psychological tension.
The technology of statistical management relies on the automated collecting, processing, accumulation of information on deficiency of production, the statistical analysis of deficiency, including detection of the most often arising and expensive defects, the reasons and responsible for their emergence. The technology includes statistical regulation, to the technician of histograms, the chart Pareto, discriminate and regression analyses and other modern statistical methods.
If a problem of the mechanism of management - to create conditions under which it is favorable to manufacturer to increase quality of production, to observe discipline, a problem of technology of statistical management - to arm persons interested to lift quality of production the corresponding receptions, by methods and equipment.
The technology of statistical management is calculated on modern personal computers. These packages can become (at the corresponding completion and development of additional software) a basis of technology of statistical quality management.
In the conditions of market the relation quality of the made production becomes the major economic category and a decisive factor in competitive fight. Long ago it is proved that quality production is economic, and defective production is empty expenses of time, productive forces, material resources.
Application of statistical methods on production allows to calculate authentically parameters of stability of technological process, criteria of effective management of quality, a share of defective production - the main indicator of a level of quality, and also to predict its probable decrease and increase on result of selective control of production.
Questions of the organization of process on which statistical methods can give help, can be formulated as follows;
1. With what probability the demanded field of admissions in the studied parameter is maintained, or
2. Whether as far as process is identical to earlier option, in other words, there were no such changes owing to which the operated properties of process became unpredictable.
Compliance (suitability of processes)
Before investigating quality, it needs to be created. In order that the product conformed to qualifying standards, such state and such accuracy of control of the equipment that production of separate details with implementation of the requirements of quality stated in normative documents was provided is necessary (standards, design documentation, etc.). Have to the ways of processing which are not allowing marriage will be applied.
For this purpose it is necessary to estimate the factors making impact on quality of production which is let out on technological processes. Estimating limits of opportunities and the most effective ways of improvement of quality it is possible to achieve the objectives stated above.
4.2 Statistical methods used in the process
In technological processes it is important to consider that:
- operations and process in general have to provide and guarantee functionally demanded qualitative characteristics;
- necessary control can be provided, having only reached visibility of process;
- it is necessary to introduce effective ways of intervention, change, management that at opportunity change conditions it was possible to hold quality indicators at the constant level;
- the above-stated objectives need to be achieved with the minimum expenses.
For technological parameters of productions and qualitative parameters of the made products some dispersion is always characteristic. Fluctuation of quantitative indices of products round any set size is defined by the sum of the casual and determined deviations. Part of the determined deviations it is usually possible to compensate. Casual deviations of the sizes of the made details can be determined by mathematical methods (dispersion, scope, etc.).
As the main requirement establish that dispersion in parameters of a product and in parameters of process has to be in the set limits. On the bases of fluctuations of essential parameters it is possible to judge compliance of process. Apply ways of statistical management of processes to implementation of this requirement.
In the course of the analysis of compliance of process of conditions of ensuring quality we will consider two important factors:
- limits of opportunities (processing accuracy) of the equipment that is usually known before process start-up;
- and shows settings (controllability) of the equipment or process which is criterion of "attentiveness", whether controlled parameter near the set size fluctuates. For its objective definition usually set differences between the "central" characteristics of the studied sizes (for example, arithmetic-mean, a median) and the set (nominal) limit values.
Characteristics of production call corresponding if the applied means and process during the long period of time are able to provide release of the products conforming to requirements. Compliance of characteristics of process should be expected in case possibilities of the equipment and process meets necessary requirements and controllability of the equipment and process.
It is necessary to apply such equipment and such technologies which with big reliability are able to provide implementation of requirements. For control of it the party of the made products should be put on trials compliances which are specially projected and developed for this purpose. Test of suitability and adjustability of the equipment can be carried out at a purchase stage, before production and systematically in the course of production.
Usually include the majority of working conditions in concept of process. Processes are perceived as joint influence of the equipment, raw materials, materials, the service personnel, ways and working conditions. They include the changes happening during longer period of time which can be caused by the production equipment, by the worker or external circumstances (temperature, climatic conditions), and often contain the fluctuations following from properties of raw materials and materials, different opportunities of the production equipment. Constancy of parameters of processes reflects degree influence of long influences in time.
The purpose of statistical methods applied in process consists in providing the demanded level of quality.
Means of achievement of the purpose - the statistical methods applied to characteristics (change and the analysis) of process. If the scope - technological process, the purpose of statistical methods applied in process consists in specification of its parameters, usually on the basis of results of research of selections of products.
The most important problems of statistical methods applied in process are as follows:
- assessment of the formulated or formulated requirements;
- identification of the factors having impact on quality, an assessment of degree of their importance;
- definition of the expected level of quality on given means of production;
- decrease in costs of quality by decrease in expenses marriage and control;
- decrease in costs of production by optimization of processes of transition by results of the statistical methods applied in process.
The system of the organization, documentation, the developed techniques the corresponding education of participants is necessary for introduction of statistical methods.
Stages of introduction of statistical methods in process get partially on a design stage and the organizations, partially to production process. In essence in both cases it is necessary to work the following questions:
- definition is more whole than process;
- definition of the moments, steps of working process;
- decomposition of requirements to the level of the making operations;
- modeling of definition of requirements.
On the basis of it all achievable parameters can be collected for the making operations.
After allocation of critical operations and parameters there comes development of strategy of improvement for the allocated operations and the studied parameters. It, in particular, consists of the causal analysis of possible influences. And it, in turn, is necessary because it is expedient to investigate only such parameters on which there is an opportunity to make impact.
Statistical methods - allow to facilitate a problem of control of the proceeding processes and to provide various a sort the facts for the analysis, adjustments and improvements of quality of processes.
Thus, statistical methods can find application in any productions. In particular, they can give real help in development of systems of analogical control of production and quality management of the made production.