Process planning can be defined as an act of preparing, processing documentation for the manufacturing of a piece, part or an assembly is called Process Planning. In this article, I will be explaining about Process planning, Computer-Aided Process Planning (CAPP), Generative CAPP, Variant CAPP, Retrieval CAPP and all its features in a detailed manner.
In order to know about Computer Aided Process Planning, you must know about Process Planning First which was mentioned below.
Steps of Process Planning in Manufacturing:
- Analysis of part requirements
- Selection of raw workpiece
- Determining manufacturing operations and their sequences
- Selection of machine tools
- Selection of tools, work holding devices, and inspection equipment
- Determining machine conditions (cutting speed, feed, and depth of cut)
- Manufacturing times (setup time, lead time, and processing time).
Two important areas in the life cycle of a product are design and manufacturing. Process planning serves as an integral link between design and manufacturing. i.e.
- Process Planning in Design
- Process Planning in Manufacturing
Process planning consists of preparing a set of instructions that describe how to fabricate a part or build an assembly which will satisfy engineering design specifications.
The resulting set of instructions may include any or all of the following:
- Operation sequence
- Cutting parameters
- Processes (such as how to heat-treat)
- Time standards
- Setup details
- Inspection criteria
- Graphical representations of the part in various stages of completion.
Process Planning in Different Environments:
- In tool-room type manufacturing, “make a part as per drawing” is sufficient
- In a metal-forming type of operations, the process planning requirements are embedded directly into the die.
- Process planning is fairly trivial
- Job-shop type manufacturing requires most detailed process planning
- Design of tools, jigs, fixtures and manufacturing sequence are dictated directly by the process plan.
Requirements for Process Planner:
- Must be able to analyze and understand part requirements
- Have extensive knowledge of machine tools, cutting tools, and their capabilities
This is the detailed explanation of Process Planning. Now, let’s discuss Computer-Aided Process Planning.
Computer-Aided Process Planning (CAPP):
It can be defined as an act of preparing processing documentation for the manufacturing of a piece, part or an assembly etc.is called as process planning. If process planning was done by using a computer it is called Computer-Aided Process Planning(CAPP). This post mainly focuses on, the structure of Computer-Aided Process Planning(CAPP) in a detailed manner.
COMPUTER-AIDED PROCESS PLANNING(CAPP) METHOD:
- It can systematically produce accurate and consistent process plans
- It can reduce the cost and lead time of process planning
- Less skilled process planners may be employed
- It increases the productivity of process planners
- Manufacturing cost, manufacturing lead time and work standards can easily be interfaced with the CAPP system.
Why Computer Aided Process Planning(CAPP)?
- Understand the interactions between the part, manufacturing, quality, and cost
- Systematically produce accurate and consistent process plans
- Reduce the cost and lead time of process planning
- Skill requirements of process planners are reduced
- Increased productivity of process planner
- Easily interface with other application programs for further analysis
This is the detailed explanation of Computer-Aided Process Planning. Now, let’s discuss the parts of it. They are:
- Generative Computer Aided Process Planning (G CAPP)
- Variant Computer Aided Process Planning (Variant CAPP)
- Retrieval Computer Aided Process Planning (Retrieval CAPP)
The detailed explanation of all these process planning is as follows:
1. Generative Computer Aided Process Planning(G CAPP):
A system which automatically synthesizes a process plan for a new component is called Generative Computer Aided Process Planning. It synthesizes the process information to create a process plan for a new part automatically without human intervention. This post mainly focuses on what is the Structure and Advantages of Generative Generative Computer Aided Process Planning(G CAPP) in a detailed manner.
Characteristics of Generative Computer Aided Process Planning(G CAPP):
- No existing standard plans
- Able to generate process plans for both new and existing parts
- Process plans are generated by means of
- Decision logic
- Technology algorithms
- Geometry based data
- Geometry-based coding scheme
- Process knowledge in the form of decision logic and data to perform uniquely the main decisions for converting apart from raw materials to a finished state.
A requirement of Generative Computer Aided Process Planning:
- Part to be produced must be clearly and precisely defined in a computer compatible format (OPITZ, AUTAP)
- The logic of manufacturing must be identified and captured
- The captured logic must be incorporated in a unified manufacturing database
Decision making logic and algorithms:
- Decision trees
- Expert Systems: AI-based approaches
Decision Tables in Generative CAPP:
- A decision table program structuring tool provides readable documentation as an automatic by product
- A decision table is portioned into conditions and actions
- Can be used with pre-processor to eliminate some program coding to provide automatic checks for completeness, contradiction, and redundancy.
Techniques for Generative Computer Aided Process Planning (G CAPP)
- Identify the machinable volume and attach necessary technological details relevant for mfg.
- Do a preliminary sorting of pockets in order of levels that clearly indicate the likely sequence in the final process plan
- Examine the pocket for any possibility of combining so that the machining operations could be reduced
- Select the machine tools that can be used for each of the identified pockets
- Identify the process sequence required for the machining of the pocket based on the technological requirements
- For each of the pocket and the operation decided, select the cutting tool required.
- Sort the operations on the basis of the machine tools and cutting tools.
- Sequence the operations on the basis of the machine tools and cutting tools by making use of heuristic rules
- Evaluate the machining time and idle time and select the final process plan based on the lowest cost and machining time
- Present the final results in a suitable form.
2. Variant CAPP:
A process plan for a new part is created by recalling, identifying and retrieving the existing plan for a similar part and making necessary modifications for the new part. In this article, I am going to discuss Advantages and limitations of VARIANT CAPP (VCAPP) in a detailed manner.
Steps involved in VARIANT CAPP are as follows:
- Define the coding system
- Group the parts into part families
- Develop a standard process plan
- Retrieve and modify the standard plan
3. Retrieval CAPP:
- Based on the principles of GT
- Also called as VARIANT Computer Aided Process Planning(Variant CAPP)
- GT: Group Technology
- The concept of grouping parts together depending upon their similarities in operation sequence or geometry is called Group technology.
- Experts’ knowledge and standard process plans as per GT are needed as database
- Considerable work is required to collect and organize data.
Salient points of VARIANT CAPP:
- Easy to build, learn and use
- Experienced process planners are still required to edit the process plan
- Cannot be used in an entirely automated manufacturing system without additional process planning
Problems Associated with Variant PP:
- The components to be planned are limited to similar components previously planned.
- Experienced process planners are still required to modify the standard plan for the specific component.
- Variant planning cannot be used in an entirely automated manufacturing system, without additional process planning
- These are the Advantages and Limitations of VARIANT CAPP.
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- Computer Aided Process Planning – IGNOU
- Computer-aided process planning (CAPP)-archives.njit.edu
- (PDF) Computer Aided Process Planning (CAPP) Approach