Table of Contents

S.No. Topic Covered Page No.

1. Need for Study 3

2. Introduction 3

3. Types of process planning 5

4. Using Pro/PROCESS for MFG 7

5. 16

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1. Need for study

Once the design of a product has been evolved from customer’s views, its manufacturing necessitates careful planning and scheduling of the various processes of manufacture. So that, the product is made to right specifications and delivered at the right time at a minimal cost. The cycle from concept to design, planning, production, quality control and feedback to design goes on highlights the crucial role of planning.

Moreover, nowadays process planning is gaining limelight because of the increased role of Artificial Intelligence (AI) in process planning. This is because of the growing complexity of industrial manufacturing and the need for higher efficiency, greater flexibility and better product quality.

2. Introduction

2.1 Process Planning

Process planning is concerned with determining the sequence of individual manufacturing operations needed to produce a given part or product. The resulting operation sequence is documented on a form typically referred to as a route sheet (also called as process sheet/method sheet) containing a listing of the production operations and associated machine tools for a work part or assembly. Process planning in manufacturing also refers to the planning of use of blanks, spare parts, packaging material, user instructions (manuals) etc.

Process planning encompasses the activities and functions to prepare a detailed set of plans and instructions to produce a part. The planning begins 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 typically provide more detailed, step-by-step work instructions including dimensions related to individual operations, machining parameters, set-up instructions, and quality assurance checkpoints.

Fabrication and assembly drawings to support manufacture (as opposed to engineering drawings to define the part).

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2.2 Work holding device

Work holding refers to any device that is used to a secure a work piece and hold it in place against the forces of machining. The most basic work holding device is a simple clamp that is screwed into place on a machining centre’s table, but work holding can also involve complex fixtures that are custom-built for particular parts. Other common work holding devices include vises and chucks, as well as indexers or rotary tables that are able to change the part’s position while it is held, so the machine can reach various features of the part without the setup having to be changed. In most machining applications, work holding also locates the part. In turning, for example, a chuck not only holds the part securely but also holds it precisely on the centreline of the spindle. On a machining center, the vise or fixture that holds the part may also hold it in the precise position and orientation where the machining program expects to find it. For this reason, components such as locating pins and work stops that make it easy to place piece after piece in the same location are also common work holding components. The essential requirements for work holding devices are:

It should be possible for the work to be located precisely and secured quickly such that the datum edges are in the correct relationship.

The work has to be well supported.

The work has to be held securely to resist the cutting forces generated during machining.

The work must not be deformed by clamping forces.

The work should be released quickly without any danger to the operator.

The work holding method as simple as practicable without creating any hazard.

The work holder should be capable of being adapted to hold different components without major changes.

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3. Types of process planning

3.1 Manual process planning: This involves the following steps which are done by a skilled person with adequate knowledge of process planning. The steps include:

Study overall shape of part and identify features, all critical dimensions.

Thoroughly study the drawing; try to identify all manufacturing features and notes.

Determine best raw material shape to use if raw stock not given.

Identify datum surfaces; Use information on datum surfaces to determine the setups.

Select machines for each setup.

Determine rough sequence of operations necessary to create all the features for each setup.

3.2 Computer-aided process planning (CAPP)

CAPP determines a set of instructions and machining parameters required to manufacture a part and prepares data for production planning and scheduling activities. CAPP is the application of computer to assist the human process planner in the process planning function. In its lowest form it will reduce the time and effort required to prepare process plans and provide more consistent process plan. In its most advanced state, it will provide the automated interface between CAD and CAM and in the process achieve the complete integration with in CAD/CAM.

Fig.1. Framework for computer aided process planning

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A number of computer aided process planning approaches are as follows:

3.2.1 Variant Computer Aided Process Planning

Variant process planning approach is sometimes referred as a data retrieval method. In this approach, process plan for a new part is generated by recalling, identifying and retrieving an existing plan for a similar part and making necessary modifications for new part. As name suggests a set of standard plans is established and maintained for each part family in a preparatory stage. Such parts are called master part. The similarity in design attributes and manufacturing methods are exploited for the purpose of formation of part families. Using coding and classification schemes of group technology (GT), a number of methods such as coefficient based algorithm and mathematical programming models have been developed for part family formation and plan retrieval. After identifying a new part with a family, the task of developing process plan is simple. It involves retrieving and modifying the process plan of master part of the family.

3.2.2 Generative Computer Aided Process Planning

In generative process planning, process plans are generated by means of decision logic, formulas, technology algorithms, and geometry based data to perform uniquely processing decisions. Main aim is to convert a part form raw material to finished state. Hence, generative process plan may be defined as a system that synthesizes process information in order to create a process plan for a new component automatically.

3.2.3 Knowledge based Process Planning

The main forces behind to apply knowledge-based (KB) techniques for CAPP is the requirement of large amount of human expertise in CAPP. Based on the previous discussion, one realizes that a productive CAPP system must contain tremendous amount of knowledge - facts about the machine and shop environment as well as rules about sequencing machining operations must be included. A traditional CAPP program cannot learn new knowledge without a programmer explicitly rewriting it. The rigidity of traditional methodology endangers the implementation of CAPP systems. A KB system stores knowledge in a special manner so that it is possible to add, delete and modify facts and rules in the knowledge base without rewriting the program, i.e. it learns new things according to embedded learning procedures.

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4. Using Pro/PROCESS for MFG

The following procedure outlines a typical session in Pro/PROCESS for MFG.

1. Click File > New to create a new process assembly, or click File > Open to open an existing assembly.

2. Select Manufacturing as the Type.

3. Select Process Plan as the Sub-type.

4. Type a name for the process assembly

5. Now go to Applications > Manufacture, to switch to manufacturing module from process planning module.

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6. Click on Mfg model > Assemble > Workpiece, to insert previously created work piece part file

7. Click on Mfg setup > Work cell > NC machine to set the operation, machine zero and retract surface.

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8. Go to Mfg setup > Tooling, to setup the tool accordingly.

9. Again switch back to process mode by clicking on Applications > Process

10. Go to Mfg sequence > Step, to add a new step

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11. If no operation has been created, the operation creation user interface appears.

12. If an operation already exists, the STEP TYPE menu appears. Click one of the commands:

Fixture—Create a typical setup [place part A in fixture B]

Mfg Model—Assemble Workpieces, Ref Models, General Assemblies and Mfg Assemblies.

Machine—Create milling, hole making, turning, and WEDM step types which can be performed at this workstation type.

General—Create all of the step types which can be performed at any workstation type. These steps include inspect, paint, debur, edge break, and so on.

13. Select Mfg sequence > Step > Machine to plan out the required machining process (Here we have performed holemaking process)

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14. Fill up the machine step parameters such as Name, Comments, Tools Cost estimate, Time estimate etc.

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15. After everything is complete click ok

16. If done correctly then automatically Material removal tab will open, go to create > construct > done.

17. Continue by selecting solid > hole.

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18. Construct the hole accordingly. After it is finished click on done

19. To view step info go to Mfg sequence > Play Step > Set step and then after selecting the

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required step, go to Step info.

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