(a) Early Coordination Efforts. A typical engineering organization has a development group that is responsible for the design work involved in developing new products If the new product is tied in with a production contract, quality-assurance coordination must be factored into the design cycle as early as possible This can be accomplished by setting up a team of four or five key personnel to review periodically the progress of the design Normally the team would consist of representatives from Marketing, Design, Manufacturing, and Quality Assurance In this way indi­viduals from all the important engineering groups are keyed in to developments on new designs and are in a position to contribute from their special backgrounds They can feed back information to their respective organizations so that timely preparations can be made for manufacturing and testing the new design

Another approach is for the design engineer to hold one or more design reviews, depending on the complexity of the design The participants in the design review normally include the personnel noted above plus any other interested parties The review should be chaired by the design engineer So that the review will be successful, all parties involved must be given all the design particulars (drawings, specifications, prototype test results, design reports, etc ) before the actual review

(b) Design and Performance Specifications. Design and performance specifications must be forwarded to Manufacturing and Quality Assurance as soon as possible so that process development and design and construction of special manufacturing or test equipment may proceed well in advance of the release of the design to Manufacturing For the same reason, design reviews on new products should be held at critical stages of their development, and process reviews should be held on new processes as they are being developed The quality-control engineer should be involved in the development of new processes since it is often possible to integrate test and/or inspection equipment right into the processing equipment, thus ensuring auto matic feedback to keep the process within specification limits

(c) Process Development. The quality-control engi­neer is responsible for ensuring that all manufacturing processes are maintained under control throughout the manufacturing cycle He can best do this by being well informed about all these processes and by keeping in constant contact with the manufacturing engineer The controls he institutes must be consistent with product costs and must be compatible with the associated manufacturing equipment

Two basic types of process control are (1) operator, or open-loop, control, where the operator adjusts the process to keep it under control, and (2) automatic, or closed-loop, control, where the process is regulated by a feedback system. The objective of process control is to keep the process operating within predetermined operating limits

Mechanization of measurements and process control may be accomplished in one or more stages of the manufacturing process, depending on the quality require­ments placed on the product and the process itself For example,

1 Preprocess measurement and control may be required for monitoring or controlling the materials or parts entering the process

2 Measurement and control may be used during proces­sing to regulate the process in response to a measured variable

3 Postprocess measurement and control may be desir­able or necessary if it is difficult or impossible to measure or control the product during the manufacturing process

4 Features of two or more of the above techniques may be combined

(d) Prototype Construction and Testing. During prototype construction and testing, the quality-control engineer may have an opportunity to prove out inspection equipment and in-process testing equipment and proce­dures He should make every effort to have these developed in time to be used and evaluated during the phase

Although prototype testing is normally done by the design engineer, the quality control engineer can assist in these tests and thus gain (1) the product knowledge needed to develop a meaningful quality plan, (2) confidence in the special inspection and testing equipment that has been developed, and (3) the advance information needed to correct the quality information equipment if it does not work satisfactorily on the prototype Prototype testing should subject the prototype to essentially every environ mental extreme in which the unit is intended to operate This may entail use of expensive equipment that may be used for qualification testing alone Even if the test work has to be farmed out, a quality-control engineer should be involved in the prototype testing along with the design engineer so he can become familiar with the new product

Sensor Prototype Testing The major problem with nuclear sensors is that the operating environment of a nuclear reactor is very difficult and expensive to simulate This is particularly the situation for in-core sensors, where meaningful tests (e g, response, burnup rate, saturation level, and signal-to-noise ratio) require accurate simulation Test reactors are available where, by using specially built thimbles and specially designed instrumentation, meaning­ful tests can be performed These should be used whenever possible

Circuit Prototype Testing Circuit designs start with tests of breadboards and subassemblies Each individual module must function within the limits of the environ mental extremes for the complete assembly The design engineer must determine in advance at what stages in the development modules and subassemblies are to be tested to environmental extremes It may be that certain of these tests are only meaningful after the prototype instrument has been completed A test program must be carefully planned in advance so that all necessary tests are performed in a logical sequence and testing facilities are available when needed

System Prototype Testing More and more systems are being standardized, and it has become essential to perform environmental tests, such as temperature rise, on entire systems This can be accomplished by shrouding the entire operating system with a plastic hood and monitoring for hot spots with well-placed thermocouples Appropriate functional tests are performed on prototype systems

Peripheral Equipment Testing Peripheral equipment is normally mechanical and may be subject to wear and fatigue failures due to a hostile environment (heat and nuclear radiation) Life tests must be run to evaluate the reliability of the assembly before proceeding with produc­tion Weld integrity should be checked periodically in these tests

(e) Test Specifications. The results of prototype tests help the design engineer determine the test specifications for the product The test specification should be a formal communication to Quality Assurance which spells out the tests that Engineering believes are essential to prove out the product functionally and the limits of each test Test conditions need to be spelled out to preclude any mis­understanding A description of the test setup should be included

Although Quality Assurance must have the test specifi­cation, this document is not necessarily the only criterion for the determination of test limits on the quality-control test instruction The quality-control engineer may decide to tighten the limits set up by the test specifications if a particular manufacturing process is not as dependable as the quality-control engineer wants it to be or if the measuring capabilities of the test equipment are such that the credibility of the measurement is in doubt For example, as a rule of thumb, the measuring equipment should be capable of reading out to at least ten times the specification limits (This means that if a proportional counter is supposed to be capable of 106 counts/sec, then the count-rate meter must be capable of resolving to 10 7 sec or 100 nsec ) All test equipment, whether being used for engineering prototype tests or for quality control final acceptance tests, must be periodically calibrated to stan­dards that are traceable to the National Bureau of Stan­dards

(f) Engineering-Document Control Since the test specification is an official engineering document, it must be controlled in the same manner as other engineering docu­ments, such as engineering drawings The control of engineering drawings, often referred to as blueprint control, must be accomplished both at the place of origin (by Drafting or Engineering Services) and at the place of use (usually by the Production Control organization)

There are many techniques for maintaining blueprint control These will not be described here However, it should be pointed out that there are pitfalls that Quality Assurance personnel should be aware of Some of these are

1. Advanced manufacturing releases These drawings may or may not be identical with the final release, and any planning that is based on advanced releases must always be contingent on review of the final manufacturing release

2 Marked-up drawings Sometimes it is necessary for the engineer to mark up a drawing prior to the issuance of a formal engineering change There must be some system for maintaining control so that Quality Assurance can be certain the loop is closed One technique is to maintain a log with an open entry that can only be closed when a revised drawing, containing a change identical to that of the marked-up drawing, is issued

3 Engineering changes These should be reviewed by the cognizant quality-control engineer before issuance to ensure that any quality planning affected by the engineer­ing change can be revised accordingly The only effective way this can be handled is to keep the quality-control engineer in series with the engineering change, і e, if his signature is necessary for issuance of any change that may affect (1) health or safety, (2) functional performance, effective use, or operation, (3) interchangeability, reliabil­ity, or maintainability of the item or its repair parts, and (4) weight or appearance (where these are important factors)

(g) Process Instructions Manufacturing process in structions are as important as engineering drawings and must be controlled, і e, Manufacturing Engineering would be responsible for generating such documents, but Engi­neering and Quality Control Engineering must have ap proval authority Any changes to process instructions should be controlled in the same way as engineering changes and should have the same approvals In this way any process-instruction changes that may affect process limits are reviewed to ensure that no product degradation results and that quality checks are appropriately changed

(h) Quality Planning Quality planning is developed throughout the design phase of a new product It consists in determining all the quality checkpoints that are necessary to ensure, with a high degree of confidence, that any rational customer will be satisfied with the product for the duration of its expected lifetime and that the product satisfies all other special requirements, such as applicable standards and codes

Quality planning must take into account software as well as hardware requirements For example, the quality plan must specify the material certification requirements necessary for inspection of raw materials as they are received, the marking and identification of material through its machining and processing, and the in process inspection and tests and documentation thereof, as well as the final acceptance tests and all necessary paperwork required, both internally and for customer submission Thorough quality planning provides for each of the following

1 Determination of control points

2 Classification of characteristics

3 Determination of quality levels

4 Determination of process capabilities

5 Determination of control procedures

6 Appropriate record forms

7 Disposition routines

8 Routing and handling procedures

9 Quality information equipment development

10 QIE calibration

11 QIE maintenance

12 In-process test and inspection

13 Final-product test, inspection, and acceptance

14 In-process audit (both procedure and product)

15 Outgoing product audit

16 Shipping inspection

17 Quality data feedback

18 Quality measurements

A good overall quality system may provide for a general quality plan, an area quality plan, a product quality plan, a contract quality plan, and a vendor quality plan

A general quality plan takes into account quality- control procedures that are common throughout all seg­ments of the business and are followed regardless of what type product is being built or what manufacturing area is involved (e g, quality information equipment calibration)

An area quality plan integrates all the individual station control plans (A station control plan is the basic plan for each identifiable manufacturing station, such as a lathe or an electronic assembly bench This plan is usually an integral part of the manufacturing planning and should include provision for controlling all inputs to the station including direct and indirect materials, e g, stainless steel and cutting fluid or electronic components and solder, tooling, environment, and workmanship skills It should also include provisions for monitoring the station con­tinuously and checking the outgoing part or assembly as necessary ) It includes all controls and procedures that are common throughout a manufacturing area

In an area where there is a definite flow from one station to another, such as an assembly area (as opposed to a machine shop where each article is subject to a different sequence of operations), a flow chart should be constructed to indicate the relations of the various stations to each other and to show every important manufacturing process in its proper sequence with all quality checkpoints inserted Each manufacturing station and quality checkpoint (inspec­tion or test) should be identified by legend and references to the applicable operating instruction or general inspection procedure

In an area where there is no particular flow pattern, a schedule of stations should be established which describes each manufacturing operation or station and all the controls of inputs to such stations as well as specific quality checks applicable to these stations

The area quality plan should describe the environmental conditions required in the area (such as temperature and humidity extremes and cleanliness) and the controls for maintaining such conditions It should describe any special materials handling or in-process storage requirements peculiar to the area And it should describe all quality­measuring tools needed for direct support of production as well as the requirements of the test and inspection equipment for the quality checkpoints in the area Special maintenance work should be delineated for manufacturing tooling, such as stamping dies and cutting tools Calibration cycles on test and inspection equipment in the area should be reviewed and special exception made to the general quality plan whenever there is to be a deviation from standard practice

The quality-data feedback system should be described in the area quality plan and should include applicable quality cost data necessary for analysis, how it is to be obtained, and how it is to be fed back to Quality Control Engineering

A quality training and awareness program is an essential part of a good quality program for each manufacturing area and should provide for both operator training and con tinuous upgrading and verification of quality personnel Every quality plan must provide for an audit that ensures adherence to the quality plan in its entirety

A product quality plan is an integrating plan that ties together the individual quality plans for each of the various assemblies and subassemblies making up the final product and includes all the controls and procedures common throughout the manufacturing cycle of that particular product The product quality plan should reference all applicable area quality plans and workmanship standards as required

The number of individual quality plans for assemblies and subassemblies is dictated by the complexity of the final product, however, each quality plan must contain a flow chart indicating the relation between all lower-tier parts and subassemblies These flow charts should show each impor­tant manufacturing process with all necessary quality checkpoints Each manufacturing station and quality check point (inspection or test) should be identified by legend and referenced to the applicable method sheet or inspection or test procedure The manufacturing-operations sheets and inspection and test procedures should be an integral part of the product quality plan

A contract quality plan is an integrating plan that ties together all applicable area quality plans plus the product quality plan and all special customer requirements resulting from the contract It may modify standard quality plans to the extent necessary to meet all customer requirements The contract quality plan must contain a schedule spelling out in detail the data requirements and identifying who is responsible for them along with a schedule of target dates for each submittal

A vendor quality plan is a plan that describes in detail the requirements of the vendor’s quality system, including any and all requirements for data submittal The vendor quality plan should also spell out the special tests or receiving inspection steps that must be taken to ensure receipt of acceptable vendor material

(i) Process Capability Studies In addition to making certain that the test and inspection equipment is adequate during the prototype stage, the quality control engineer must know whether or not the production equipment is capable of meeting the engineering tolerances and, ac­cordingly, must determine the optimum sampling plan This information can be obtained by performing process capability studies

“Process capability” has been defined as “that which the process is capable of producing under normal, in­control conditions ” The key phrases in this definition are “the process” and “normal, in-control conditions ”

The process includes the entire manufacturing process and all that enters into it, such as the raw material, the machine or equipment, the measuring device, and the skill of the operator or inspector or both The process is a single combination of these factors One process is with a given raw material, a given machine, a certain operator, and the like, whereas another process may be different only in the raw material used Practically speaking, many of the processes made up by these various combinations of factors are similar in output and can be considered as one But only those combinations which will yield the same output under the second condition, “normal and in-control conditions,” can be so considered as one

Normal and in-control conditions are those which yield parts with measurements having a predictable and normal frequency distribution compatible with the target specified Since the process capability is a forecasted distribution of the variability for a given process, this distribution needs to be predictable not only in the spread but also in the shape Generally, most distributions that are not normal indicate a lack of control and nonnormal conditions

Quantitatively, the process capability is defined in terms of six standard deviation units (60) Within ±3a from the mean lie 99 73% of all the readings for a normal distribution For the majority of operations, this 6(7 interval includes practically all the readings and represents the capability of the process Thus, if the process capability is less than the drawing tolerances, a certain amount of sorting and scrap wnl result

The process capability study is a powerful tool Not only can it be computed easily but also its uses are many, including providing the following information

1 To facilitate the design of a product

2 For acceptance of a new or reconditioned piece of equipment

3 For scheduling work to machines

4 For setting up a machine for a production run

5 For establishing control limits for equipment that has a narrow process capability in comparison to the allowable tolerance band

6 For determining the economic nominal around which to operate when the process capability exceeds the toler­ance

The following points should be kept in mind when a process capability study is being performed

1 The study should be taken under normal conditions of operation

2 Factors in the manufacturing process that will introduce nonrandom variations should be held constant

3 Normally, at least 50 readings should be taken

4 The order of the readings should be preserved

5 The individual readings should be plotted over time

6 The measuring devices used should normally have an accuracy of at least 10 times the tolerance spread and 8 times the capability spread

Although computing the process capability from the range is usually the easiest and fastest method, it is also the one that is most affected by the requirement for a normal distribution The first step in computing the process capability through ranges is to compute the ranges, R, of subgroups of the total sample of 50 pieces If, for example, we assume a subgroup of 5, then the average range, R, is the arithmetic average of each of the 10 values of R Using the relation a = R/d2 (where d2 can be determined from the readings, see any standard text on statistical quality control3’4), then we find the process capability is simply 6(R/2 326) = 2 58R for subgroups of 5

Process capability studies can produce savings by identi fying losses due to inadequate processes, poor tool main tenance, unskilled operators, etc The process capability study can help ensure optimum programming of machines and operators in making the product to specification at a minimum cost