unit 1 process planning

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UNIT I PROCESS PLANNINGIntroduction

In traditional process planning systems the process plan is prepared manually. The task involves

examining and interpreting engineering drawings, making decisions on machining processes selection, equipment

selection, operations sequence, and shop practices. Therefore, the manual process plan is very much dependent

on the skill, judgment and experience of the process planner. That's why, if different planners were asked to

develop a process plan for the same part, they would probably come up with different plans.

Process planning is the activity of developing such a plan (manufacturing) is called. Process planning consists of preparing set of instructions that describe how to manufacture the product and

its parts.

The task of the process planning consists of determining the manufacturing operations required to transforma part from a rough (raw material) to the finished state specified on the engineering drawing

It also known as operation planning is the systematic determination of the engineering processes and systemsto manufacture a product competitively and economically.

Process planning is a detailed specification which lists the operations, tools and facilities.Definition

It can be defined as an act ofpreparing a detailed processing documentation for the manufacture of apiece part or assembly.

According to American society of Tool and manufacturing Engineers Process planning is the systematic determination of methods by which a product is to be manufactured

economically and competitively.

Importance of process planningProcess planning establishes the link between engineering design and shop flow manufacturing. Since

process planning determines how a part/product will be manufactured, it becomes the important determinant of

production costs and profitability.

Also production process plans should be based on in-depth knowledge of process and equipment

capabilities, tooling availability, material processing characteristics, related costs, and shop practices.

The economic future of the industry demands that, process planning that are developed should be feasible,

low cost, and consistent with plans for similar parts. In addition, process planning facilitates the feedback fromthe shop floor to design engineering regarding the manufacturability to alternative.

SCOPE OF PROCESS PLANNING

A process is defined as any group of actions instrumental to the achievement of the output of an operations

system in accordance with specified measure of effectiveness. When the product designed, certain specifications

are established; physical dimensions, tolerance, standards and quality are set forth.

Then it becomes a matter of deciding over the specific details of how to achieve the desired output. This

decision is the essence of process planning. The production function essentially is a transformation process that

accepts the inputs and gives the outputs after adding value to the inputs. Process selection is a major strategic

decision as it involves allocation of men and material resources as well as financial commitments for a long

period.Operation planning is a responsibility of the manufacturing organization. A number of functional staff

arrangements are possible. This process leads to the same output despite organizational differences.

The following are business objectives for operations planning:

1. New product manufacture

A new design may have not been produced before or, alternatively, new manufacturing operations may

be introduced for the product. Unless there is planning, the product introduction will be helter-skelter.

2. Sales


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Opportunity for greater saleability of an existing or new product can develop from different colours,

materials, finish, or functional and non-functional features. Sales and marketing departments provide advice to

help manufacturing planning.

3. Quantity

Changes in quantity require different sequences, tools, and equipment. The OP planner differentiates

for these fluctuations. If volume increases, the chance is for lower cost.

In contrast, if volume decreases, the cost should not increase out of reason. There may be a fortuitous

opportunity for red-uced cost, if economics and technology will allow substitution of new process, training, and

resources even if quantities are reduced. If quantity reduces too much, however, it is appropriate for the OPplanner to recommend that production may no longer be economical; perhaps, a supplier may be the appropriate

lower cost alternative.

4. Ef fective use of f acil iti es

Operation planning often can find alternate opportunities for the plants production facilities to take up

any slack that may develop. Seasonal products, which might be popular in the summer, need an alternative product

for the winter season. For example, companies that produce sporting equipment may use the same facilities to

produce tennis rackets and skis.

5. Cost reducti on

Various opportunities become available if the company has an ongoing cost reduction effort.

Suggestion plans, value analysis, design for manufacturing (DFM), and directed and systematic

efforts involve operations planning.

Concept of process planning:The concept of process planning is to determine

1. The operations involved in the manufacture of each product.2. The machines on which operations are to be done.3. The tools, jigs and fixtures required.

4. The material requirements including scrap.5. The speeds and feeds that are to be used.6. The type of labour required.7. The time required for each operation.

The above information is made available on process sheet. The main objective of process planning is to find the most

economic method of performing an activity.

The following information is necessary to carry out this function effectively:1. Product data.2. Volume of production.3. Quality requirements.4. Equipments and personnel available.5. Time available to perform the work or delivery date.

Preparing Operation Planning Sheet

The following informations are required to do the process planning effectively:

1. Quantity of work to be done along with product specifications.2. Quality of work to be completed.

3. Availability of equipment, tools and personnel.

4. Sequence in which operations will be performed on the raw material.

5. Names of equipments on which the operations will be performed.

6. Standard time for each operation.

7. When the operations will be performed?

8. Cutting speed9. Feed

10. Material specification.

11. Job rating of labours.


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Process Planning Procedure

1. Preparation of working drawings.2. Deciding t

o make or buy.3. Selecting manufacturing process.4. Machine capacity and machine selection.5. Selection of material and bill of materials.

6. Selection of jigs, fixtures and other attachments.7. Operation planning and tooling requirement.8. Preparation of documents such as operation sheet and route sheet etc.(a) Make or buy decision

Recommendations should be made whether to make or buy the material, part or assembly informations should besufficiently detailed to take intelligent decisions. Cost and availability of the production capacity are the two importantfactors in arriving to make or buy decision.

Make

It requires appropriate production equipment, suitable personnel, material, adequate space,supervisions, designstandards and overheads maintenance, taxes, insurances, management attention and other indirect and hidden costs.

Buy

It permits lower investments, small labour force, less handling, lower plant cost for building and up keep, lessoverhead or taxes, insurance and supervision and less problems of man-management relations.

A company has a choice of three alternatives before starting for a new product.

1. Purchase the product from a contracted manufacturer.2. Purchase some components and materials and manufacture and assemble the balance in its own plant.3. Manufacture the product completely, starting with the extraction of basic raw materials.

(b) Determination of material requirements

The materials required are worked out and arrangements to procure them are made. The procedure

for examining the material requirements are given below.1. Existing requirements for works on hand.

2. The new or extra material required. It is to be calculated from bill of materials.3. Total material required.4. Existing stock of materials.5. Additional materials to be produced.

(c) Selection of material , jigs, fixtures etc.

The selection of material has become complicated by the great increase not only in the kinds of materials but also

in the various forms. The material should be of right quality and chemical composition as per the product specifications.The shape and size of material should restrict the scrap.


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Machines generally, represent long terms capital commitments. But process may be designed for relatively shortduration. The following factors must be taken into account while selecting correct equipment: The size and shape of the workpiece. The work material.

The accuracy and surface quality required. The quantity of parts. The sizes of lots required and, Personal preferences.

1. If a number of surfaces are to be machines on a part, the choice is offered of machining them separately, all together orin various combinations. If surfaces on a part are similar in shape and size, they are better suited to being treated in one

operation than if they are different from one another.2. More powerful machines may be needed to work hard material than soft material.3. Work piece size and dimensions may dictate particular features that a machine tool must have.4. Small work pieces are handled on equipment different from that used for large parts. As an example, small and mediumsize parts are turned on horizontal lathes, but short pieces of large diameters are commonly machines on vertical lathes.5. Small tolerance call for certain types of machine, whereas large tolerance does not call for specific machine.

In general, very large parts must be produced by slower methods. As a result, they must be produced on the largerand slower machines, mainly on a tool room basis. Smaller parts whose shape is contributing to ease of handling can be

produced on faster machines. They are more readily adapted to mass production. They are exceptions in the pressed metaindustry.

The size and shape of the workpiece associates itself closely with the size and type of machine required to produceit. Choice may be made between general purpose machines (centre lathes, planners, shapers, drill pressers etc.) and special

purpose machines.

The general purpose machines have the following characteristics:1. Usually less initial investment in machines.2. Greater machine flexibility.3. Fewer machines may be required.4. Less maintenance cost.5. Less set up and debugging time.6. Less danger of obsolescence.

The special purpose machines have the following characteristics:1. Uniform product flow.2. Reduced in process inventory.3. Reduced man power requirements.4. Reduced factory floor space.5. Higher output.6. Higher product quality.7. Reduced inspection cost.

8. Reduced operator skill requirements.The machines and equipment that will do a job at the lowest total cost are the ones that should be selected. Direct

overhead and fixed costs should be considered. Generally, more items put into one operation. The lesser the handling time

the more the chance for simulation and the lower the direct costs. But the operation is likely to become more complex

calling for more expensive machine.As a rule; a high rate of production justifies a largest investment in machine to reducedirect costs.

To select machine tools, an investigation must be made to ascertain the aptitude, range and capacity required for

the job. Each type of machine is best suited for certain kind of work. Lathes for turning, drilling machines for holes. Amachine must have adequate range and capacity for the work it is to do.

The factors determining the range and capacity may be the size of the work piece, the working area, length of strokespeeds, feed, forces and power required.

Personal preference or specific conditions may influence the selection of a machine tool. A particular type of makeof machine may be favored, because a person in the past found it dependable, easy to operate, safe and accurate. Often anew machine is not purchased if one almost as good is already in the plant and not fully loaded.(e) Operation planni ng sheet


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A process plan is a complete concept of a process. It is recorded and transmitted in a number of ways to suit variousconditions. In a small plant or where skilled workers may be relied upon to perform without detailed instructions, process

plans may be recorded quite incompletely. In a large organization with a complex product and highly refined proceduresprocess plans may be recorded in minute details.

A process planning medium almost universally used is the routing also known as route sheet, process sheet andoperation planning sheet. It lists and describes the operations of a process. Routings are written as briefly as possible to save

time. They completely designate departments, machines, tools, etc. The operation sheet form will vary for differentcompanies. However, thedescription of the operation special instructions is usually similar.

A process sheet is a manufacturing engineering document. It should be sufficiently explicit so that operationalpersonnel (example: workers) can perform every operation/function necessary to produce the finished component and thaoperations can establish staffing and piece cost from which to judge operation efficiency during and after physicallylaunching the operation.

The process sheet contains columns for recording operations, tools, types of machine used, speed, feed, times etc.Shop floor personnels i.e., supervisors and workers will follow the informations/instructions given in the process

sheet to carry out the necessary operations to make a finished part. The process sheet gives an estimate of time required tomanufacture the finished part and the requirements men, machines, materials and tools required for the said purpose. It alsoindicates through whichdepartments and machines, the raw material has to route before being converted into finished goods.

A process sheet is required to be made for every component to be manufacturer.A process sheet is necessary in order to

(i) Check the progress of component parts through the cycle of production operations.(ii) Make sure that the delivery dates (of the finished goods) will be met.(iii) Control and expedite the work if required.

Overall development of process planning plans

Process planning is an intermediate stage between designing the product and manufacturing

it.


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Responsibility of process planning Engineer

Various responsibilities of process engineer are given below

1. Interpreting part print analysis and symbols.2. Gathering the fundamental details of product design such as

(i) type of rough stock

Sales forecastsHow many to make

Work place andtool designs

Design Specification and requirements

Functional design

Production design, basic decisionssetting minimum possible costs

Drawing and specifications of what to

Product analysisassemblycharts and flow charts

Make / Buy decisions

Process decisionsselection fromalternative processes

Route sheet and operation sheets;specification of how to manufacture

Modifications of process plans due to

layout, quality preference and machine

BU

Pro

duct

Design

Proce

Planni


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(ii) dimensional tolerances(iii) type of finish(iv) production rate(v) production volume(vi) scrap losses(vii) down time(viii) design changes etc

3. Selecting the machining process.

4. Selecting proper machining with allied tooling based on(i) Required machine capability

(ii) Setup time

(iii) Practical lot size(iv) Quality of parts

(v) Cost of tooling, and

(vi) Type of tooling

5. Sequencing the operations.

6. Deciding on the inspection equipment in order to meet the desired quality.

7. Determining proper cutting tools and cutting conditions.

8. Calculating the overall times using work measurement techniques.

Factors affecting process planning Volume of productionThe skill and expertise of manpowerDelivery dates for parts or productsMaterial specificationsAccuracy and process capability of machinesAccuracy requirements of parts or products.

Process planning activities

Analysis of the finished part requirements as specified in the engineering design. Determining the sequence of operations required. Selecting the proper equipment to accomplish the required operations. Calculating the specific operation setup times and cycle times on each machine. Documenting the established process plans. Communicating the manufacturing knowledge to the hop floor.


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Process planning activities

Finished Part Requirements

First step in the process planning is to analyze the finished part requirements as specified in theengineering design. The engineering design may be shown either on an engineering drawing or in a CAD

model format.

The component drawings should be analyzed in detail to identify its features, dimensions, and tolerancespecifications.

The parts requirement defined by its feature, dimensions, and tolerance specifications will determine thecorresponding processing requirements (such as operations encompassing part shape generation

inspections, testing, heat treatment, surface coating, packaging, etc)

Information required to do process planning

COMMUNICATE

Manufacturing

Engineer Shop

ANALYSE

Part requirements

DETERMINEOperation Sequence

SELECT

Equipment

CALCULATE

Processing times

DOCUMENTProcess plan

PROCESS PLANNING


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Quantity of work to be done along with product specifications. Quality of work to be completed. Availability of equipments tools and personnel. Sequence in which operations will be performed on the raw material. Names of equipments on which the operations will be performed. Standard time for each operation. When the operations will be performed?

Process planning procedure

The different steps involved in process planning are:

Preparation of working drawings. Deciding to make or buy. Selection of manufacturing process. Machine capacity and machine/equipment selection. Selection of material and bill of material. Selection of jigs, fixtures and other attachments. Operation planning and tooling requirements. Preparation of documents such as operation and route sheets etc.

Process planning activities (details)

Step-I: Analyse finished part requirements

The first step in the process planning is to analyse the finished part requirements as specified in theengineering design. The engineering design may be shown either on an engineering drawing or in a CAD

model format.

The component drawings should be analysed in detail to identify its features, dimensions, and tolerancesspecifications.

The parts requirement defined by its features, dimensions, and tolerances specifications will determine thecorresponding processing requirements (such as operations encompassing part shape generationinspections, testing, heat treatment, surface coating, packaging etc)

Step-II: Determine operating sequence

To determine the sequence of operations required to transform the features, dimensions, and toleranceson the part from a rough (initial) to a finished state.

The basic aim of this step is to determine the type of processing operation that has the capability togenerate the various types of features, given the tolerance requirements.

There are two alternative ways of viewing the decision process in determining the sequence ofoperation.

1. The first view is to consider the processing evolution of the part from the rough (i.e., intial) state tothe finished final state. In this view, like in conventional production shop, material is removed or

modified on the rough part in stages in order to transform it to the finished part.

2. Second view is to consider part evolution from a finished state back to a rough/initial state. In thisview, in contrast to the first view, the operation processing is planned by adding material back onto

the part.

Machines selection


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4. Decision tables provide knowledge structure and readable documentation as a byproduct.

Expert system shells

Expert system is one of the latest system tools for the development and display ofmanufacturing knowledge.

Using an expert system shell, the knowledge engineers can collect the information todevelop a knowledge base within the predefined decision structure of the shell.

In figure, the basic format of a rule-based system shell is quite similar to the decision tablesformat.

Like decision tables format, in rule- based expert system, the knowledge base is formattedin structures of if this condition then this action, or if this condition then this action, or else this

action.

Approaches to process planning

The two general approaches to process planning are:1. Manual process planning and

2. Computer aided process planning (CAPP)

(i) Retrieval CAPP system.

(ii) Generative CAPP system.

Knowledge Engineer

Knowledge Base IF/THEN rules

Interference Engine forward or

backward logic chaining

Report Generator, conclusions,

interference explanation

Answer

Expert

Queries

User


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1. Manual process planning(Traditional

Process planning)

The duty involves examining and interpreting engineering drawings, making decision on processes

selection, equipment, operations sequence, and shop practices.

Therefore, the manual process plan is very much dependent on the skill, judgment and experience

of the process planner. Thats why, if different planners were asked to develop a process plan for the s ame

part, they would probably come up with different plans.

Advantages of Manual process planning

Manual process planning is very much suitable for small scale companies with few process plans togenerate.

This method is highly flexible. This required low investment costs.

Disadvantages of Manual process planning

Manual process planning is a very complex and time consuming job requiring a few process plans togenerate.

This method requires the skilled process planner. More possibilities for human error because this method depends on the planners skill, judgement and

experience.

It increases paper work. Inconsistent process plans result in reduced productivity.

Computer Aided Process Planning (CAPP)

In order to overcome the draw backs of manual process planning, the CAPP is used. With the use ofcomputers in the process planning, one can reduce the routine work of manufacturing engineers.

Also it provides the opportunity to generate rational, consistent and optimal plans. In

addition, CAPP provides the interface between CAD and CAM.

Benefits of CAPP

The benefits of implementing CAPP include the following:

1.Process rationalization and standardization :

CAPP leads to more logical and consistent process plans than manual process planning.

2. Productivity improvement:As a result of standard process plan, the productivity is improved (due to more efficient utilization

of resources such as machines, tooling, stock material and labour)

3. Product cost reduction:Standard plans tend to result in lower manufacturing costs and higher product quality.

4. Elimination of human error5. Reduction in time:

As a result of computerizing the work, a job that used to take several days, is now done in a few

minutes.

6. Reduced clerical effort and paper work.


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unit 1 process planning

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