CAD/CAM Concepts Mechanical Basics MECHANICAL THEORY

CAPP:Generative, Variant & Retrieval CAPP-Detailed

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.

What is the Structure & Advantages of Generative Computer Aided Process Planning(GCAPP)

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
 Formulas
 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 description
–Part to be produced must be clearly and precisely defined in a computer compatible format (OPITZ,AUTAP)
•Manufacturing databases
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.

VARIANT CAPP:  

Advantages and Limitations of 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.

Advantages and Limitations of VARIANT CAPP
Advantages and Limitations of VARIANT CAPP

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

Retrieval CAPP:

  • Based on the principles of GT
  • Also called asVARIANT 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.  

    Advantages and Limitations of VARIANT CAPP
    Advantages and Limitations of VARIANT CAPP

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:

This is the complete explanation of the Advantages and Limitations of VARIANT CAPP (VCAPP) which is shown in a detailed manner. If you have any doubts, feel free to ask from the comments section. Please Share and Like this blog with the whole world so that it can reach to many.

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