Process Planning
In companies, planning processes can result in increased output, higher
precision, and faster turnaround for vital business tasks. A process is described
as a set of steps that result in a specific outcome. It converts input into output.
Process planning is also called manufacturing planning, material processing,
process engineering, and machine routing. It is the act of preparing detailed work
instructions to produce a part. It is a complete description of specific stages in the
production process. Process planning determines how the product will be
produced or service will be provided. Process planning converts design
information into the process steps and instructions to powerfully and effectively
manufacture products. As the design process is supported by many computer-
aided tools, computer-aided process planning (CAPP) has evolved to make
simpler and improve process planning and realize more effectual use of
manufacturing resources.
Process
Planning
It has been documented that process planning is required for new product and
services. It is the base for designing factory buildings, facility layout and selecting
production equipment. It also affects the job design and quality control.
Objective of Process Planning: The chief of process planning is to augment
and modernize the business methods of a company. Process planning is planned
to renovate design specification into manufacturing instructions and to make
products within the function and quality specification at the least possible costs.
This will result in reduced costs, due to fewer staff required to complete the same
process, higher competence, by eradicating process steps such as loops and
bottlenecks, greater precision, by including checkpoints and success measures
to make sure process steps are completed precisely, better understanding by all
employees to fulfil their department objectives. Process planning deals with the
selection of the processes and the determination of conditions of the processes.
The particular operations and conditions have to be realised in order to change
raw material into a specified shape. All the specifications and conditions of
operations are included in the process plan. The process plan is a certificate
such as engineering drawing. Both the engineering drawing and the process plan
present the fundamental document for the manufacturing of products. Process
planning influences time to market and productions cost. Consequently the
planning activities have immense importance for competitive advantage.
Effect of process planning on competitive
advantage:
Principles of Process Planning
General principles for evaluating or enhancing processes are as follows:
1. First define the outputs, and then look toward the inputs needed to
achieve those outputs.
2. Describe the goals of the process, and assess them frequently to make
sure they are still appropriate. This would include specific measures like
quality scores and turnaround times.
3. When mapped, the process should appear as a logical flow, without
loops back to earlier steps or departments.
4. Any step executed needs to be included in the documentation. If not, it
should be eliminated or documented, depending on whether or not it's
necessary to the process.
5. People involved in the process should be consulted, as they often have
the most current information.
Process planning includes the activities and functions to develop a
comprehensive plans and instructions to produce a part. The planning starts with
engineering drawings, specifications, parts or material lists and a forecast of
demand. The results of the planning are routings which specify operations,
operation sequences, work centres, standards, tooling and fixtures. This routing
becomes a major input to the manufacturing resource planning system to define
operations for production activity control purposes and define required resources
for capacity requirements planning purposes.
Process plans which characteristically offer more detailed, step-by-step work
instructions including dimensions linked to individual operations, machining
parameters, set-up instructions, and quality assurance checkpoints. Process
plans results in fabrication and assembly drawings to support manufacture and
annual process planning is based on a manufacturing engineer's experience and
knowledge of production facilities, equipment, their capabilities, processes, and
tooling. But process planning is very lengthy and the results differ based on the
person doing the planning.
Major steps in process planning: Process planning has numerous steps to
complete the project that include the definition, documentation, review and
improvement of steps in business processes used in a company.
Definition: The first step is to describe what the process should accomplish. It
includes queries like, what is the output of this process? Who receives the
output, and how do they define success?, What are the inputs for the process?,
Are there defined success measures in place - such as turnaround time or quality
scores? And Are there specific checkpoints in the process that need to be
addressed?
Documentation: During the documentation stage, interviews are conducted with
company personnel to determine the steps and actions they take as part of a
specific business process. The results of these interviews is written down,
generally in the form of a flow chart, with copies of any forms used or attached.
These flow charts are given to the involved departments to review, to make sure
information has been correctly captured in the chart.
Review: Next, the flow charts are reviewed for potential problem areas.
Process planning in manufacturing may include the following activities:
1. Selection of raw-stock,
2. Determination of machining methods,
3. Selection of machine tools,
4. Selection of cutting tools,
5. Selection or design of fixtures and jigs,
6. Determination of set-up,
7. Determination of machining sequences,
8. Calculations or determination of cutting conditions,
9. Calculation and planning of tool paths,
10. Processing the process plan
Computer Aided Process Planning
Manufacturers have been following an evolutionary step to improve and
computerize process planning in the following five stages:
Stage I - Manual classification; standardized process plans
Stage II - Computer maintained process plans
Stage III - Variant CAPP
Stage IV - Generative CAPP
Stage V - Dynamic, generative CAPP
Earlier to CAPP, producers attempted to triumph over the issues of manual
process planning by basic categorization of parts into families and developing
standardized process plans for parts families that is called
Stage I. When a new part is initiated, the process plan for that family would be
manually recovered, marked-up and retyped. While this improved output but it
did not enhance the quality of the planning of processes.
Computer-aided process planning originally developed as a device to
electronically store a process plan once it was shaped, recover it, amend it for a
new part and print the plan. It is called
Stage II. Other ability of this stage is table-driven cost and standard estimating
systems.
Stage III: Computer-aided approach of variant CAPP is based on a Group
Technology coding and classification approach to recognize huge number of part
attributes or parameters. These attributes permit the system to choose a baseline
process plan for the part family and achieve about ninety percent of the planning
work. The schemer will add the remaining ten percent of the effort modifying or
fine-tuning the process plan. The baseline process plans stored in the computer
are manually entered using a super planner concept that is, developing
standardized plans based on the accumulated experience and knowledge of
multiple planners and manufacturing engineers.
Stage IV: It is generative CAPP. In this stage, process planning decision rules
are developed into the system. These decision rules will work based on a part's
group technology or features technology coding to produce a process plan that
will require minimal manual interaction and modification.
While CAPP systems move towards being generative, a pure generative system
that can create a complete process plan from part classification and other design
data is a goal of the future. These types of generative system will utilize artificial
intelligence type capabilities to produce process plans as well as be fully
integrated in a CIM environment. An additional step in this stage is dynamic,
generative CAPP which would consider plant and machine capacities, tooling
availability, work center and equipment loads, and equipment status in
developing process plans.
The process plan developed with a CAPP system at Stage V would differ in due
course depending on the resources and workload in the factory. Dynamic,
generative CAPP also entails the need for online display of the process plan on a
work order oriented basis to cover that the appropriate process plan was
provided to the floor.
There are numerous advantages of this type of process planning. It can decrease
the skill required of a planner. It can reduce the process planning time. It can
reduce both process planning and manufacturing cost. It can create more
consistent plans. It can produce more accurate plans. It can increase
productivity. Automated process planning is done for shortening the lead-time,
manufacturability feedback, lowering the production cost and consistent process
plans. Advantages of Computer-aided Process Planning include reduced
demand on the skilled planner, reduced process planning time, reduced process
planning and manufacturing cost, created more consistent plans, produced
accurate plans, increased productivity, increased high flexibility, attained high
efficiency, attained adequate high product quality and possibility of integration
with the other automated functions and systems.
Manufacturing Process Planning delivers essential process planning potential for
all manufacturing industries. Using Manufacturing Process Planning, process
planners can powerfully create and authenticate the original process plan using
the product structure from product engineering, modify the plan to specific
requirements, and link products and resources to the steps of the plan.
To summarize, Process Planning is important action in a production enterprise
that verifies which processes, materials, and instructions will be used to produce
a product. Process planning describes a manufacturing facility, processes and
parameters which are to be used to change materials from a primary form to a
predetermined final stage.
