CAD CAM Integration

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MEEM4403 Computer-Aided Design Methods

CAD/CAM Integration

Linking Design and Manufacturing!


CAD/CAM INTEGRATION

CAD : Computer Aided Design : Used for creating solid

models of the components to be designed. (Outputis a DESIGN.)

CAM: M stands for Manufacturing. Manufacturingincludes every step that is involved in creating thedesigned component, converting it from raw

material into final form. (Output is a manufacturedproduct.)


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Types of ManufacturingProcesses

There are two types of manufacturingprocesses:

Continuous

(e.g. oil refining, continuous cast rolling)

Discrete part

(e.g. drilling, milling)

We will only be dealing with discrete partmanufacturing.


Discrete Part ManufacturingProcess

Main phases of discrete part manufacturing:

Process Planning is the interface betweenthe design process and manufacturingprocess.

Figure from: K. Lee, Principles of CAD/CAM/CAE Systems, Addison-Wesley, 1999


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Process Planning

Input: Final Design

Output: Process Plan

A process planlists a sequence of manufacturingand assembly operations that will be used toproduce the part or assembly. For each operation,it describes details such as which material will be

used, which machine will be used, which settings,

etc.


Process PlanningSteps:

1. Select raw materials

2. Identify volumes of material to be removed

3. Identify the set of machining processes fromthe available standard machining processesthat can remove the required volumes.

4. Generate most effective/efficient sequenceof machining operations


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Example of a Process PlanThe part being manufactured:



Example of a Process PlanThe process plan:



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Process Planning Automation

There are three approaches to computer-aided process planning (CAPP):

Manual ApproachNot Computer-Aided.

Variant ApproachComputers store/match existing process plans.

Generative ApproachComputers generate a process plan from scratch.


Manual Approach

The process plan is developed by a skilled plannerwho is familiar with the companys manufacturingcapabilities.

The steps involved are:

1. Study the overall shape of the part.

2. Determine what stock material to use.

3. Identify datum surfaces for setups

4. Identify part features.


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Manual Approach

Typical machiningfeatures:



Manual Approach

Typical machiningsub-features:



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Manual Approach

Steps, contd:

5. Group features into setups.

6. Sequence the operations in the setup

7. Select tools for each operation

8. Determine fixtures for each setup

9. Final Check

10. Elaborate Plan (e.g. feeds and speeds)11. Prepare process plan document.


Variant ApproachIn the variant approach, parts that have similarfeatures are grouped into families. There is astandard plan for each family.

A process plan is found by:

1. Identify important features of part.

2. Identify which family a part belongs to.

3. Retrieve the standard plan.

4. Edit the standard plan if required.

Note: If the part does not belong to an existing family, anew standard plan needs to be developed.


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Variant Approach

It is an advanced manual approach to process planning.

Planners workbook is stored in the computer file.

Variant Approach requires a database of standardprocessing plans for each family of parts.


Variant Approach

Group Technology (GT) simplifies the problem offinding out which family a part belongs to. In GT a codeis assigned to a part based on which features it contains.

This code is compared to the codes for each family.

GT is a process of grouping parts sharing similar genericproperties under single family.


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Variant Approach

There are three types of GT coding systems:

1. Monocode (hierarchical)

Meaning of each digit depends on the value ofprevious digits.

2. Polycode

Meaning of each digit is independent of otherdigits.

3. Hybrid

Combination of Monocode and Polycode.


The part:

Figure from: K. Lee, Principles of

CAD/CAM/CAE Systems, Addison-Wesley,

1999

Example of

Monocode GT code.


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Thecodingscheme:

Table from: K. Lee,

Principles of

CAD/CAM/CAE

Systems, Addison-

Wesley, 1999

Example of Monocode GT code.


Table from: K. Lee,

Principles of

CAD/CAM/CAE

Systems, Addison-

Wesley, 1999



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Part GT code is 3321:


3 Rotational workpiece

3 D = 75 mm, L/D = 50/75 = 0.67

2 Holes not in axis

1 Plain steel


Generative ApproachThe Generative Approach requires thecomputer to perform these steps:

1. Enter design specification:- input/recognize stock material

- recognize machining features

2. Generate process plan

determine optimal setups determine optimal sequence of operations

determine optimal fixture types andlocations


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Generative Approach

The Generative Approach is not widely usedbecause:

- required information (such as tolerances) are notusually available in the CAD model

- a lot of knowledge must be added to the systemto make it capable of handling all the differenttypes of parts that occur.

- evaluating all the combinations of possibilities iscomputationally intense.


Studying for Final Exam

Textbook questions:

Ch. 10: 1, 7, 8, 9

Documents

CAD CAM Integration