Production Planning and Control (PPC)
Stages in
Production Planning and Control:
The basic phases of production planning
and control may be identified as (i) routing, (ii) loading, (iii) scheduling,
(iv) dispatching, (v) follow-up or expediting, and (vi) corrective action.
These functions are discussed below:
(i) Routing:
“Routing means determination of the route to
be followed by each part/component being transformed from input/raw material
into final product.”
Production routing involves the laying
down of path which work will follow and the order in which various operations
will be carried out. It consists of the determination of operations through
which the product must pass and the arrangement of operations in the sequence
that will require minimum of handling, transportations, storage and
deterioration through exposure. It is the job of routing personnel to determine
the production routes in the organisation.
Routing may be generalised or detailed,
depending upon the quality of product to be manufactured, production system in
use and other factors. Generalised routing may be established either by
building or by departments such as machine shop, assembly or others. Detailed
routing indicates the specific work station or machine to be used for each
operation.
Efficiently routing permits the best
utilisation of physical human resources employed in production. Routing is an
essential element of production control because other production control
functions are dependent on routing function. The persons who make out a list of
operations must be thoroughly familiar with all the operations and various
machines in the plant so that they are able to establish routes which will
ensure maximum utilisation of the plant and machinery.
(ii) Loading:
Loading deals
with the amount of work assigned to a machine or a worker. It deals with the
record of workload of different workshops. The total time required to perform
the operations is computed by multiplying the unit operation time given on the
standard process sheet by the number of parts to be processed. The total time
is then added to the work already planned for the work station.
The process
results in a tabulated list or chart showing the planned utilisation of
machines, work stations in the plant. From the chart, it is easy to assess the
spare capacity of the plant. If the loading charts indicate sufficient spare
capacity, efforts may be directed through the sales department to obtain more
orders for the utilisation of spare capacity.
Under load of
certain departments may also arise from ineffective planning. In such a case,
the remedy lies in proper planning.
But if, on the
other hand, there is an overload in any workshop, action on any one or more of
the following lines may be taken to relieve the bottleneck:
(a) Arranging for overtime work;
(b) Introducing an additional shift;
(c) Transferring operations to another
shop; and
(d) Sub-contracting of the excess load.
(iii) Scheduling:
Scheduling is the process of prescribing
“When” each operation in a production process is to be executed. According to
Kimball and Kimball, Scheduling is “The determination of time that
is required to perform each operation and also the time required to perform the
entire series of operations as routed.”
Thus, scheduling can be termed as:
(i) A detail of when and where each
operation in a manufacturing process is to be performed or executed.
(ii) Establishment of an activity time
table which gives at which time to start and/or finish each event or operation
comprising any procedure or process.
Scheduling being the last of the planning
functions consists of the assignment of starting and completion times for the
various operations to be performed. It is significant to point out that there
exists a considerable integration between routing and scheduling activities.
One cannot lay the route of an item
efficiently through a plant without consulting previously designed schedules
and scheduling is equally difficult without a knowledge of required routing.
Scheduling determines when an operation is to be performed, or when work is to
be completed; the difference lies in the detail of the scheduling procedure.
Where routing,
loading and scheduling are centralised, a production schedule will specify the
starting and finishing time for an operation. In other cases, it will simply
provide a budget of time required to complete a job of work..
Preliminary
information required in the construction of a production schedule is obtained
from the following three sources:
(i) The
planning department,
(ii) The date
of delivery specified by the customer in the order, and
(iii) The
minimum time, in terms of past experience, required for production.
Other factors
which must be taken into consideration for preparation of detailed schedules
are: availability of equipment, availability of specialised skill and
availability of required materials.
There may be two types of schedules:
(a) Plant schedule and
(b) Master schedule.
The first one is the schedule relating to
a particular plant, but the latter lists the production of a given product in
one or more divisions of the concern. Master schedule may cover a period of
twelve months or more. Two important guidelines for effective scheduling are
that they should be simple to follow and should be flexible.
A good schedule must make provision for
emergencies arising in normal operation, such as rush of orders for a
particular type of product, breakdown of machine or power, absence of workers,
etc.
(iv) Dispatching:
Dispatching may be defined as the setting
of productive activities in motion through release of orders and instructions,
in accordance with previously planned timings as embodied on operation sheet,
route card and loading schedules.
Dispatch
provides official authorisation and information for.
(i) Movement
of materials to different work stations,
(ii) Movement
of tools and fixtures necessary for each operation,
(iii)
Beginning of work on each operation,
(iv) Recording
of beginning and completion time,
(v) Movement
of work in accordance with a routing schedule, and
(vi) Control
of progress of all operations and making of necessary adjustments in the
release of operation.
Dispatching
requires coordination among all the departments concerned. This is obtained
through varied degrees of centralised control.
Under
centralised control, dispatch
clerks, centrally located, release all orders including the movement of
materials and tools necessary for the operations.
Under
decentralised control, this
responsibility is handled by each department. In continuous manufacturing,
under normal conditions, orders may be dispatched to departments a day or more
in advance of operations. Each department prepares its own instructions and
sends a duplicate copy to the central office.
Since
duplicate copies are received by the central office considerably in advance of
operations, there is sufficient time for the recommendation of changes. If it
is found that certain orders are being unduly delayed, a request may be made
for adjustments.
However, under
abnormal conditions, when a company is being pressed by impatient customers,
and the plant is loaded to capacity, emergency changes are more frequent. A
special rush order may require that operations start immediately and that other
orders originally scheduled may be held temporarily. Under these circumstances,
it is apparent that centralised control plays an important role in obtaining
speed and coordination.
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