Inspection is defined as “the process of measuring, examining, testing,
gaging, or otherwise comparing the unit with the applicable
requirements”. This essential quality tool is used in every
organization to ensure that the quality of their product is acceptable
to the customer as well as the industry.
There are two primary purposes for inspection. These are to make
sure the product conforms to specifications and to determine whether a
non-conforming product is fit for use. In the following paragraphs, we
will discuss the uses, strategies, and tools of inspection.
Organizations may use different strategies for inspection depending upon
the type of process they use and the cost-effectiveness of using that
strategy. Types of inspection include operator inspection, in-process
inspection, tollgate inspection, automated inspection, 100 percent
on-line inspection, and computer-aided inspection. Firms in the U.S. and
Japan do not commonly use tollgate inspection because of the need to
inspect 100 percent of the product at every station before moving on.
Operator inspection involves a trained operator at one or more
workstations. This is the best position for inspecting a product given
there is enough time between workstations to complete the task and the
operator is sufficiently trained. The operator may also verify work done
at previous stations.
In-process inspection is when an inspector patrols from station to
station at given amounts of time to ensure that the inspection
procedures are properly executed.
This type of inspection is desired when the product has a low
defect rate, when operator inspection is not sufficient, or when there
are new employees on the job.
Tollgate inspection uses a sampling station at a fixed point
within the process to evaluate the quality level of products produced in
a given department before moving them on to the next. This type of
inspection is used when there is a high defect rate or when there is a
need to enforce quality levels between departments.
Automated inspection is used where human inspection would not be
possible or sufficient. Usually, automated inspection is used in
mechanical or electronic industries. It is also used when more precision
is needed in the process.
100 percent inspection is done in-process and involves separating
the good products from the bad. Contrary to its name, not all of the
defects are always caught since there may be multiple products flowing
through the system at any one time. Therefore, some companies may
inspect the product multiple times, in which case it is called 200 or
300 percent inspection.
Computer-aided inspection (CAI) is the most modern form of
inspection. It allows for 100 percent inspection at a relatively low
cost and there is less chance of damage to the products because the
products are not physically handled.
The type and frequency of inspection can vary from firm to firm.
A firm implements its desired degree of inspection until it meets
predetermined standard of quality or the standard of the industry. Also,
the best inspection strategy may change as new technologies are
introduced. The tools used for inspection include acceptance sampling
and control charts. Acceptance sampling occurs when a whole lot or
shipment is rejected from examining a percentage
of the lot. The exact percentage is up to the firm to decide. Control
charts called x-bar and R charts take samples from a lot to measure a
particular characteristic. If the samples fall within the upper and
lower control limits then the whole lot is determined to be acceptable.
These charts also help to determine if the firm should implement
more stringent standards for higher quality.
As you have seen, inspection is a very important part of the
manufacturing and production process. It is essential to the success and
productivity of an organization as well as cost-effective. Implementing
inspection into every stage of the production process will prevent
expensive costs from rework and returns. It can be used to inspect
damages caused in-transit from one location to another, in checking that
an order is correct and that it meets conformance specifications as well
as many other uses.
Article courtesy of Song Ling Chan
