Control (industry)

See also: Control

A industrial control , is the checking of the conformity of a product or a service to preestablished specifications and including a decision of acceptance, rejection or final improvement.

Definition

Old the standard ISO 8402 (now cancelled) gave the following definition of it:

“Control: activities such as measuring to examine, test or pass to the gauge one or more characteristics of an entity and to compare the results with the requirements specified in order to determine if conformity is obtained for each characteristic. ” (ISO8402: 1994, § 2.15.).

Control is a technical act making it possible to determine the conformity of a product. To carry out a control on a product, it is necessary as a preliminary to determine the characteristics and to choose of them the limits (the machinists would say the tolerances) inside whose the product is in conformity. It is necessary that these limits are known by the “controller” who will carry out control.

It also implies that with resulting from the technical act of control, a decision is made with regard to conformity:

* produced conforms
* produced not-in conformity which must be rejected
* produced not conforms being able to be improved
*produit not-in conformity being able to be accepted in exemption.

Characteristics of a control

A control is defined by certain a number of parameters:

*La frequency of control: systematic, by
taking away * characteristics of the products which must be controlled.
*le standard of control: nondestructive, destructive (sometimes called “test”).
*la control method: by measurement, comparison (Défauthèque), by appreciation (visual monitoring for example).
*les average of control to be used: measuring device, reference frame
*l' entity which carries out control: personnel of manufacture (self-checking), specialized, staff personnel supervisory, machine (automation of control).

To choose the characteristics of a control, it is necessary to take account of the technical constraints (criticality of the characteristic to be controlled, precision necessary of the measuring device, qualification of the personnel carrying out control etc) but also economic constraints. The economic aspect exploits the nature of control, the means to engage and on the characteristics to be controlled. It is necessary to choose in priority, the characteristics having an influence on safety, the functionality of the product. The risk associated with nondetection must be taken into account. The client can limit this choice by forcing a certain number of characteristics to be controlled and/or controls to be carried out.

The frequency of control

If a control is carried out in a systematic way on totality (100%) of the parts, it makes it possible to carry out a sorting and to eliminate nonconformities directly. It is a method often long and expensive which cannot be chooses systematically.

Control by taking away aims rather to detect a drift of manufacture. The methods can be empirical. In this case one chooses a frequency and a size of taking away of the type “X parts every hour”, “all the manufacturing batches” etc the methods can be of statistical type by using methods MSP where standards specific to this type of control.

Type of control

Certain controls can be carried out without destroying the part or the unit which must be controlled: measurements dimensional, electric, of color etc same certain nondestructive control methods called (Ultrasonics inspection, Dye penetrant inspection etc) make it possible to control certain characteristics like health matter.

In certain cases, it is not possible to control a characteristic without destroying the product to be controlled. It is thus impossible to control all the parts. The destructive control of a limited number of product validates a batch. In this case control is accompanied or even sometimes is replaced by a control of the parameters of manufacture (Température, Pression, amperage etc) having an influence on obtaining the characteristic being able to be measured only by one destructive process.

Methods of control

So to carry out a control, the controller uses a measuring device, it must be adapted to measurement, give “the good” result and be maintained. There also, the technical choice must take account of the economic situation (cost of purchase, operation, maintenance). The problems of the means of measurement are to be brought closer to paragraph 7.6. (Control of the surveillance devices and measurement) of standard ISO9001: 2000.

The choice of the apparatus is a technical and economic decision: to measure a dimension, do I have to use a reglet, a Slide caliper, a Machine to measure three-dimensional? This choice is closely related to the question of the “good performance”. For that, it is necessary to raise the question of the capability of the means of measurement, of the Incertitude S of measurement. The good sense should not be neglected. Useless to use a reglet if one seeks a measurement with the Micromètre. Conversely, there are not few reasons to use a machine of three-dimensional measurement if I seek a measurement with some Millimètre.

It is necessary to take account of the conditions of use: is measurement taken in laboratory with a controlled temperature, in a workshop under difficult conditions, on a project exposed to the bad weather? In a workshop one will privilege an instrument of correct robustness, mono function and of an average precision. For a building site, where it is often difficult to have many apparatuses and where the conditions can be difficult, it will be rather multifunction and especially robust.

The maintenance of the apparatus is related to maintenance itself: the apparatus must be maintained in good state of operation and must be repaired or replaced in the event of breakdown. But, it is also related on the calibration or the checking of the apparatus. That fulfills the requirement of the ISO 9001: 2000: “… The measuring devices must be calibrated or checked with specified intervals or before their use, compared to measuring rods connected to international or national measuring rods…. ”.

The position of a control

The old versions of the standard ISO 9001 (version 1987 and 1994) envisaged three types of control: with the reception, under development (manufacture) and into final. If this classification is a little less explicit in the last version (2000) of this standard, it remains relevant. Each one of these three types of control has specificities.

Control with reception in the broad sense relates to the raw materials which will be used in manufacture. A good portion of these controls can be carried out by the supplier himself. This one being specialized in the production of this matter, it is qualified and equipped better generally more to carry out controls and tests on its product. This system rests on a contractualisation of the plan of control, a monitoring system often containing audit or of reception in the workshops of the supplier. Delivery being often then accompanied by a document (compliance certificate, test report…).

The processing control meets several aims: to eliminate nonconformity, to detect the drifts and thus to take part in the piloting of manufacture. The elimination of nonconformity in the course of manufacture answers an economic imperative: more the product nonin conformity is early rejected less the values added is important. But also certain characteristics are not accessible any more when the product is finished. It is thus necessary to carry out control before the characteristic is not masked. But the processing control is also an instrument of piloting. It makes it possible to detect the drifts and thus to bring the corrective actions. If this detection is well carried out, the correction can be carried out before nonconformity does not appear.

Final control is carried out when the product is completely finished. It is carried out in theory by specialized personnel, sometimes in the presence of an organization of control (standard NORISKO, Bureau Veritas, APAVE, SGS, SOCOTEC, Asiainspection…) or of the customer. He makes it possible to check the good performance of the product.

Control an element of the management of quality or environmental management

Sometimes, there exists a certain confusion between the general concept of quality and control (called the quality control sometimes). Control if it is an important device of a management system of quality is not all the quality system. Contrary, sometimes some blame the need for control because the device quality is supposed to prevent the drifts and not conformities. If the management system of quality aims to the reduction in the defects and the anomalies, there remains however necessary to check the conformity of the product.

Control is one of the four elements of the loop of continuous improvement PDCA at the base of the standards ISO 9001:2000 and ISO 14001: 2004. C of PDCA meaning C ontrôle ( check in English). It is thus one of the elements essential to the operation of a management system of quality or environmental management. This concept of control applying in these two standards not only to the control of a product but to the whole system of continuous improvement.

If one sticks to the control of a product, control is thus a share of the general device of management of the quality of a company. Upstream of the realization of a control, that implies that the provisions aiming at its realization are pre-established. These provisions specify the means, the methods and the limits of conformities. Concretely, that are presented in the form of plans of control, procedures, instructions, procedures, specifications etc They are elaborate when designing product. They are thus a share of the output data of the process of design. To be realized under good conditions, controls must be carried out by trained and qualified personnel. The requirements in qualification and formations elaborate and are managed by the human function resources of the company. They are output data of this process.

Downstream, to be fully integrated in a device of management of quality within the meaning of the ISO 9001:2000, the results of a control must be recorded and these recordings preserved in order to show the conformity of the controlled product. But control must also produce information which after treatment and analysis generates corrective actions or preventive. The goal of this treatment is to improve quality of the production from a point of view of continuous improvement. The processing control intended for piloting is the typical example (but nonsingle) of this loop of improvement. If one regards control as a process, the products and data

  • of entry are:
*le produces to control
*les pre-established provisions
*la qualification, the training of the people which carries out control
  • of exit are:
*le produced controlled
*les recordings of control
*les information intended for the improvement.

Note

  • : The standard ISO 8402 (§ 1.1.) give like example of entity, a process, a product, an organization (nobody or system) or a combination of the unit. If the article attempts to rather describe control on a product, the concept to apply little much more generally.
  • : satisfaction with the specified requirements. (ISO 8402, § 2.9.)
  • : Control by the executant himself of the work which it achieved, following of the specified rules. (ISO 8402, § 2.16.)
  • : the definition of a batch is extremely variable in function, of the type of industry of the product, the manufacturing method. The definition of a batch must guarantee a certain homogeneity of the entities belonging to this batch (even batch of raw material, even manufacture etc campaign).
  • : this concept is to be brought closer to the concept of “special Procédé” describes in the § 7.5.2 of the standard ISO 9001:2000: “The organization must validate any production process and of preparation of service whose elements of exit cannot be checked by a monitoring or measures carried out a posteriori”.
  • : ISO9001: 2000, § 7.6.
  • : The presence of the three types of control during a manufacture are not obligatorily present
  • control is not called any more besides “control” in the version 2000 of the ISO 9001 and the version 2004 of the ISO 14001 but “monitoring”.
  • : to see the standards ISO 9001:2000 § 7.3. : Design and development and ISO 14001:2004 § 4.3.3. : Objectives, targets and program (S).
  • : to see name them ISO 9001:2000 § 6.2. : Human resources, and ISO 14001:2004, § Compétence, formation and sensitizing)
  • : This determination can be made in way " informelle" by studying the system or by using structured methods standard AMDEC or analyzes functional which is adapted perfectly.

See also

control

Measuring devices

Destructive controls

Non destructive testings

Management of quality, environmental management

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