Sec 23 Inspection And Test

INSPECTION AND TEST

1

INTRODUCTION

gage, a nonvariable electronic or laser instrument, a nonvariable chemical or phy

Sec 23 INSPECTION AND TEST

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INTRODUCTION

hod that will display data generated by physically measuring the characteristic,

tance inspection and acceptance testing.

oductive operation appraisal. Within this movement of proactive product acceptanc

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PURPOSE OF INSPECTION AND TEST

: body to become involved in the details of so many decisions. Associated with the

nswer is obvious—the nonconformance is so severe as to make the product clearly

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PURPOSE OF INSPECTION AND TEST

departments to aid them in preventing a recurrence. In more elaborate data-collec

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PREPRODUCTION EVALUATION

the customer’s requirements, we expose the organization to uncontrolled, inefficie

ision on conformance to standard consists of a lot. The true lot is an aggregatio

form, the true lot emerges from one machine run by one operator processing one mat

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PREPRODUCTION EVALUATION

iner. In shop language, this mixture is a “lot,” but in more precise language it is

the batch. In continuous production, the lot is usually defined as an arbitrary am

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PREPRODUCTION EVALUATION

fferent from that presently used as the method of measurement. It also should inc

r, the planning is done by a quality assurance staff planner, an inspection or tes

be covered: inspection instructions, instrumentation, cost estimates, space and wo

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PREPRODUCTION EVALUATION

the planner lists the quality characteristics to be checked. To determine these,

ers ut may call for modifications parameters, such as

riteria for the checklist

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PREPRODUCTION EVALUATION

ys:

spection or testing appraisal using standard inspection and testing equipment. Ho

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PREPRODUCTION EVALUATION

departments, usually called process inspection or process testing As an integrati

ations may be sufficiently well in hand that no inspection stations are used betw

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INSPECTION AND TEST DOCUMENTED INFORMATION

It may, in addition, include the seriousness classification of characteristics, to

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INSPECTION AND TEST DOCUMENTED INFORMATION

odic reappraisal of the major forces in contention as well as analysis of the con

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INSPECTION AND TEST DOCUMENTED INFORMATION

pection plans is done extensively. New customer orders, new product designs, new pr issue inspection plans accordingly.

s. One technique is to do the planning by computer or by other means of mechanizi

-made planning by extending the use of inspection and test manuals that have broa

itself to the inspection supervisors and the

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INSPECTION AND TEST DOCUMENTED INFORMATION

o people or to systems. Machines are superior for doing deeds that can be clearly

of people, machines, and system masquerades under a variety of names: human factor

rocesses that collectively or sequentially turn out the final product. To prepare

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INSPECTION AND TEST DOCUMENTED INFORMATION

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INSPECTION AND TEST DOCUMENTED INFORMATION

procedure contents and should reflect the path the product takes and the types o

pecting and/or testing and should be detailed as to how to fill out an inspection

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CRITERIA FOR INSPECTION AND TEST DEVELOPMENT

product conformance decisions and in addition have accepted this very lot. In suc

y holes of correct size and in the correct locations. Such is the inherent nature

s who have not qualified. Suppliers who have established a record of good deliver

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CRITERIA FOR INSPECTION AND TEST DEVELOPMENT

of process capability). The presence of uniformity through fluidity greatly reduc

tivities and hence can be had for the procedural cost of retrieval. Other knowledg

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THE DEGREE OF INSPECTION AND TESTING NEEDED

check the lots in batches every so often is conducted. This skip lot will remain

ed “scientifically” once the tolerable level of defects in accepted product has be

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THE DEGREE OF INSPECTION AND TESTING NEEDED

o provide redundancy against the unreliability of 100 percent inspection. In thes

es, since the accepted lots are usually no better than the rejected lots.

sical arrangements and personnel procedures must be changed. In many cases, attitu

urce of evaluation is the check list type.

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OTHER TYPES OF CONFORMANCE INSPECTIONS

experimental or analytical approach .Examples of application:

ten time intervals, alleviate labor shortages, and avoid inspection monotony, among

g costs. The crux of justifying the investment lies in the amount of repetitive w

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OTHER TYPES OF CONFORMANCE INSPECTIONS

e vital few types are

identified. Estimates are then made of the personnel, costs

original design, construction, and prove-in, the machine must be set up specially

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OTHER TYPES OF CONFORMANCE INSPECTIONS

g the operator of the machine’s state of adjustment. Specification data stored in

reducing the volume of inspections necessary and making the inspector function m

to increased consistency and productivity; equally important, they will help to im

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OTHER TYPES OF CONFORMANCE INSPECTIONS

miautomated concept provides high-confidence repeatability and a faster analytical

or, and in microseconds each part passing under the “eye” or segment of a continu

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OTHER TYPES OF CONFORMANCE INSPECTIONS

Instead of having to physically transport the part to the inspection station, ce an existing machine.

rmance decision for almost any inspection situation, or both. The marriage of comp

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OTHER TYPES OF CONFORMANCE INSPECTIONS

and final inspection functions, as well as some testing operations. Yet, somewhat

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OTHER TYPES OF CONFORMANCE INSPECTIONS

quipped with an image-processing board, Moiré allows the operator to obtain a very

ning features with no sharp edges or lighting contrasts to define such shapes as

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OTHER TYPES OF CONFORMANCE INSPECTIONS

by counting the number of beams blocked by an object passing through the scanned

r includes a series of light-emitting diodes (LEDs) in a linear array. The control

d) so that each phototransistor only detects light from its corresponding LED in

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INSPECTION AND TESTING FUNCTIONS

niversal. Some final inspection or test functions are staffed by fulltime inspect

of product, entire shipments or just samples are brought to the inspection floor.

onsequently, the sampling plans involve random and (often) large samples, employing

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INSPECTION AND TESTING FUNCTIONS

ltaneously:

ct conform to specification? cess run or stop? ess inspection involves observation of process variables as well as inspection of

tup is correct, the entire lot will be correct, within certain limits of lot size.

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INSPECTION AND TESTING FUNCTIONS

is usual to provide for periodic sampling to be conducted during the progression

de. ed to a control chart. If the process remains in control, all product made since t is based on the sampling criteria. provided the process conforms to specification.

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INSPECTION AND TESTING FUNCTIONS

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INSPECTION AND TESTING FUNCTIONS

epartment has concluded its operations. Sometimes the product is moved physically

often automated, as are the data recordings. Testing may be done either at inspec

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INSPECTION AND TESTING FUNCTIONS

ons before enclosure into a container, a shipping inspection and/or test will prov

ts may be made daily, weekly, semiweekly, biweekly, etc. Whatever the frequency, it s, and many other requirement criteria.

atch destruction test on its components or assemblies is subject to a random dest

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QUALITY STANDARDS

use, are able to concentrate their efforts on the most important qualities. In mo

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QUALITY STANDARDS

plication to the entire progression of product from design through use: in quality

ries of tasks:

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QUALITY STANDARDS

administer. The actual plans in use consist of only several classes. While choice

ident that the classifications must simultaneously take into account multiple con

can see them as on whether the consumer can see them. It is found that some words

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QUALITY STANDARDS

ecifications. The classification may be in any of several alternatives:

d”) requirements, it is important to make clear which is which.

he jurisdiction over waivers.

fication of defects. (The contention is often raised that the tolerances on the s

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QUALITY STANDARDS

om the process capability of general use machines and tools. Once published, these

active review, and it also produces a better final result .However, some companie

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SENSORY QUALITIES

ents. In common with other qualities, sensory qualities require:

ry qualities. The qualities under test may be “desirable.” For example, if an expen

extent of the quality or deficiency under investigation. These samples are submit

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SENSORY QUALITIES

s principle may be subdivided as follows:

manufacturer should take action to make the quality to that level but not beyond

dom describe completely what is wanted, and often inspectors are left to make the

standard?

s. If a particular inspector lacks this knowledge, he or she is qualified to make

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SENSORY QUALITIES

a stake in the standard consumers, supervisors, engineers, and inspectors. Based o

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SENSORY QUALITIES

n exhibit of samples with varying degrees of defects intermingled with perfect un

different applications. Once limit samples have been agreed to, there remains a pr

ng distance, and so on. Standardizing these conditions is a long step in the direc

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SENSORY QUALITIES

of them quite complex. Some of the basic forms are described below.

mples. One sample is identified to each panelist as the standard or “control”; the

ree, two of which are alike. He or she also may be asked to estimate the degree of “control” to which she or he has been subjected previously in the order of concentration.

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SENSORY QUALITIES

ies formerly judged by human perception are now measured by instruments. This dev

hat permits, in theory, measurement by some inanimate instrument. limited number (10 to 50) of samples with each of the various measurement methods r of samples (100 to 1000) also chosen to reflect the entire range of quality vari

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SENSORY QUALITIES

es a high correlation.

the human test panel is to state preferences along the scale of measure. Hence th

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MEASUREMENT QUALITY : AN INTRODUCTION

of product and process characteristics. This quantification is done through a sys

permit conversion of abstractions (e.g., length, mass) into a form capable of being units of measure. which the product or process possesses the characteristic under study. This proce

ly

n the laboratory.” erances.”

etrology, i.e., the science of measurement. This science underlies the entire syste

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MEASUREMENT STANDARDS

for the kilogram, all units are defined in terms of natural phenomena. (The kilog

e construction and maintenance of primary reference standards. These standards con

measuring many hundreds of quality characteristics. These standard test methods de

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MEASUREMENT STANDARDS

ds the huge array of test equipment, i.e., instruments used by laboratory technicia

erarchy serves to “transfer” accuracy of measurement to the next lower level in t

ghly skilled metrologists, and their skills are a vital commitment to the high pr

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MEASUREMENT STANDARDS

t and process. Because of the wide variation in training, skills, and dedication am

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ERROR OF MEASUREMENT

surement error. The starting point is to understand the nature of accuracy and pre

ue value is called the error (also systematic error, bias, or inaccuracy) and is t

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ERROR OF MEASUREMENT

inge of doubt. Consequently, the expression of accuracy must show the extent of th

Instead, the measurements scatter about the average, as exemplified in Figure . The

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ERROR OF MEASUREMENT

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ERROR OF MEASUREMENT

readings.

ndard itself is consumable (e.g., hardness test blocks), so material variation affe

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ERROR OF MEASUREMENT

is subject to its own unique array of troubles. These instrument troubles are mu

and buyer laboratories may be at the root of a major quality problem.

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CALIBRATION CONTROL

continuing system of calibration control.

e tested to see if it is within its calibration limits. This test is often referr

mbination of checking the instrument and adjusting it to bring it within its tole

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CALIBRATION CONTROL

ional standards, new units of test equipment, and expendable materials. These elem

Control is based on the supplier’s calibration data and on his or her certificati pany unless the demonstrated performance of the supplier merits use of an audit o wever, it usually embodies measuring instruments of various sorts and may well inc reagents or photographic film.

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CALIBRATION CONTROL

he historical origin of the item, its assigned serial number, the checking schedul

lable on the results of checking, it becomes feasible to change the schedules in t

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CALIBRATION CONTROL

ccuracy. This deterioration takes place primarily though use and secondarily throu

identified and controlled within a traceability cone. Minimum TARs for each trace

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CALIBRATION CONTROL

oratories and a relatively few associated technicians. In contrast, the test equip

for each class of equipment are, but they cannot recall what the date of the last

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CALIBRATION CONTROL

ed to identify the grades of the standards themselves, whether primary, secondary,

m to be going smoothly. In these latter cases, interruptions for calibration can e

checked in the forthcoming week.

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CALIBRATION CONTROL

in hardware or software, carries these signatures, as do the labels on the equipm

anner, panels and drawers of test equipment are lock-wired, and the wires are lead

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CALIBRATION CONTROL

o keep a record of the results of checking calibration and of the extent of work

or

itive failure

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CALIBRATION CONTROL

The best inspector is only as good as his or her gages. If the gage is in error, t

ion of all of the above. The determining factor is usually based on master calibra

ctitioner must consult with the available experts: equipment manufacturers, resear

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HUMAN FACTORS IN INSPECTION

placed on it in inspection tasks. The effectiveness of the use of sight depends l

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HUMAN FACTORS IN INSPECTION

relatively simple triangulation and profiling to three dimensional object recogn

inspection costs.

recognition of an object or feature, to a quality decision, or to the control of a

tion, position analysis, character or bar-code

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HUMAN FACTORS IN INSPECTION

process and the model become disconnected, and the observer sees only what he or

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INSPECTION ERRORS

ibutes importantly to inspection errors. Inspection errors due to the inspector, c

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INSPECTION ERRORS

lack of knowledge due to insufficient education or job training; and lack of “ski

.

esulting data, when arrayed in a matrix (usually with defect type along one axis a

f his or her own prior results. The analysis of the resulting data discloses the

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INSPECTION ERRORS

ray is known by various names, including job sample. All units were previously car

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INSPECTION ERRORS

do differently from what I am doing now?” Unless the inspector is in a position t

the practice to require that the inspector be formally certified as qualified to

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INSPECTION ERRORS

e inspector wants not to make any errors. The term inadvertent or unavoidable is

ld find all the defects. Numerous unpublished and published studies have since de

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INSPECTION ERRORS

inspection work: redundancy, countdown, and fail-safe methods. that makes no inadvertent (or other) errors once the setup is correct and stable. devices to magnify the ability of the unaided human being to sense the defects. gainst their memories of the standard. When such inspectors are provided with a p template placed over terminal boards. Holes in the template mate with the projec

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INSPECTION ERRORS

responsible and concentrate attention on the real responsibility. lerance lines are drawn. The inspector’s task of judging the size or location of p hased all the items you originally planned to buy. At the other extreme, a checkli gue, due to inability to maintain concentration for long periods of time. Response

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INSPECTION ERRORS

lt or that needless burdens are placed on inspectors. In such cases, product redes e, i.e., critical to human safety and health. In such cases, the low tolerance for e

silently reads the copy while someone else reads the master aloud. aloud, performs a calculation, etc.

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INSPECTION ERRORS

ent errors in shipment of uninspected product or even shipment of rejected produc

ntity” to packers and shippers. Bar codes should be used where appropriate. her purpose. ally chosen personnel. to bear an inspector’s approval.

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INSPECTION ERRORS

be initiated by management, by the inspector, or by a combination of both. However these deeds rather than from the propaganda. management’s real interests are elsewhere.

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INSPECTION ERRORS

one perpetrate such a fraud. The manager requires confederates who submit themselv erstandings are a breeding ground for poor industrial relations.

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INSPECTION ERRORS

tor is exposed to suppliers who have a good deal at stake in the lot of product i

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INSPECTION ERRORS

especially when it is their own performance.

symptom (the unnatural pattern of reading) rather than the disease (recording fic

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INSPECTION ERRORS

y inspectors is actually management-initiated through manager pressures that seem s to the nearest scale division, Rounding off is easy to detect from analysis of

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INSPECTION ERRORS

tors. If this measurement is made only occasionally, use can be made of standard s

ng out of documents, etc.

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INSPECTION AND TESTING SOFTWARE

ween instructor and trainee and can provide alternate training schedules without

esses. Many manufacturers have integrated the measurement system directly onto the

These data can then be analyzed for trends or problem solving.

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INSPECTION AND TESTING SOFTWARE

ccuracy, reportability, and gage performance. Features include gage type, gage due

nd many other inspection and test interfaces into production processing.

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