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International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),

ISSN 0976 – 6359(Online), Volume 5, Issue 9, September (2014), pp. 361-373 © IAEME

361

DESIGN OF COMPUTER AIDED PROCESS PLAN FOR A CASING COVER

PLATE

G Gopal, Dr L Suresh Kumar, Sriramadasu Sudheer Babu

1Department of Mechanical Engineering, Ramanandatirtha Engineering College

Nalgonda, Telangana, India. 2Principal, Ramanandatirtha Engineering College, Nalgonda, Telangana, India.

3Post Graduate Student, Mechanical Engineering, Nalgonda, Telangana, India.

ABSTRACT

This paper deals with the design of Computer Aided Process Planning (CAPP) for

manufacturing a Casing Cover Plate, which requires machining on inside and outside considering the

desired fit. CAPP is designed by using the Siemen’s developed NX 7.5 software. The design

considers the different aspects of the Process planning activities to convert the given 2 D drawing

into a final manufactured product. The factors include the following: Layered Manufacturing,

interpretation of product design data, selection of machining processes, selection of cutting tools,

selection of machine tools, determination of setup requirements, sequencing of operations,

determination of the production tolerances, determination of the cutting conditions, design of jigs

and fixtures, tool path planning & NC program generation and generation of process route sheets.

Keywords: CAPP, Casing Cover Plate, NX, Layered Manufacturing, Process Sheet, Concurrent

Engineering.

1. INTRODUCTION

Process planning is a production organization activity that transforms a product design into a

set of instructions (sequence, machine tool setup etc.) to manufacture machined part economically

and competitively. The information provided in design includes dimensional specification and

technical specification.

Computer Aided Process planning (CAPP) activities basically include the following:

interpretation of product design data, selection of machining processes, selection of cutting tools,

selection of machine tools, determination of setup requirements, sequencing of operations,

determination of the production tolerances, determination of the cutting conditions, design of jigs

INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING

AND TECHNOLOGY (IJMET)

ISSN 0976 – 6340 (Print)

ISSN 0976 – 6359 (Online)

Volume 5, Issue 9, September (2014), pp. 361-373

© IAEME: www.iaeme.com/IJMET.asp

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362

and fixtures, calculation of process times, tool path planning & NC program generation, generation

of process route sheets and optimization of manufacturing cost.

CAPP systems are designed as either Retrieval system or Generative systems.

A Retrieval CAPP system has a standard process plan and is stored in computer and is

retrieved for future use.

A Generative CAPP system uses the knowledge base to plan the Process for a new part.

An aiming and tracking device, for guided jet-propelled missiles, includes a periscope, and

both the aiming device and the periscope are mounted on a rotating ring and extend through a

common opening in an armor plate cover or top wall. The cover or top wall is circular, and the

opening is located eccentrically of the cover or top wall. Casing Cover plate is used to hold the

amplifiers, resistors and other circuit parts in electrical circuit box. It is clamped to entire circuit box

like cap.

A casing cover plate provides axial compression of the seal and stabilizes it in the housing

bore to achieve maximum seal performance. The cover plate must be dimensioned properly to obtain

the required fit.

CAD Application used for doing this project is NX 7.5. NX is an advanced CAD/CAM/CAE

software package developed by Siemens PLM Software.

It simplifies complex product designs, engineering analysis and manufacturing. Thus

speeding up the process of introducing products to the market.

The NX software integrates knowledge-based principles, industrial design, geometric

modeling, advanced analysis, graphic simulation, and concurrent engineering.

The software has powerful hybrid modeling capabilities by integrating constraint-based

feature modeling and explicit geometric modeling.

Increasing complexity of products, development processes and design teams is challenging

companies to find new tools and methods to deliver greater innovation and higher quality at lower

cost.

NX automates and simplifies design by leveraging the product and process knowledge that

companies gain from experience and from industry best practices. It includes tools that designers can

use to capture knowledge to automated repetitive tasks. The result is reduced cost and cycle time and

improved quality.

In Layered Manufacturing (LM), the CAD drawings are sent to an Automated Process

Planner in a data exchange format. In the Process Planner, the CAD model is “sliced”. Depending

upon the geometry of the slice, the Process Planner determines the motion control trajectories for

each slice. These trajectories are fed into a automated machine where the slice is traced or deposited

on a suitable substrate guided by the x-y motion of the build platform or that of the deposition head.

In short, a computerized solid model is converted into a physical solid model. The foremost

advantage of the LM is the ability to make a prototype rapidly. Hence this technology is also called

as Rapid Prototyping.

Concurrent Engineering approach is adopted wherein the functions of design engineering,

manufacturing engineering and other functions are integrated.

2. PROBLEM FORMULATION

Input for the project

The plate should be fastened with bolts, no more than 150 mm apart, on a bolt circle located

as close to the seal housing bore as practical. The cover plate should be flat and the housing bore

depth uniform.

Supplementary sealing is necessary by providing a seal cavity incorporated into a new plate

which is bolted into place.



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This model is having critical profiles; the component requires both inside and outside

machining. So it needs a special type of fixture to hold the component rigidly. For this, the

component is bottom clamped. Thus it calls for CNC machining.

A 2D drawing is used to design a 3D model for our component using Unigraphics NX 7.5

CAD software.

Manufacturing Process planning sequences

Step 1: 2D drafting sheet is taken as input for generating 3D model.

Step 2: 3D model is generated by using NX 7.5 CAD software. NC program is generated on this 3D

model

Step 3: NC program is generated by using NX 7.5 software. In NX CAM, NC program is generated

by specifying tools and cutting path in NX software.

Step 4: Specification of material for manufacturing of Casing Cover Plate. Material specification

places an important role in manufacturing.

Step 5: Specification of machine depends on complexity of the manufacturing component. Casing

cover plate is manufactured in CNC 5axis milling machine.

Step 6: Specification of tools.

Step 7: Manufacturing component on machine.

Fig. 1: Manufacturing Process Planning Sequences

2D INPUT

(DRAFTING)

3D MODELLING

CAD NX 7.5

NC PROGRAM CAM NX 7.5

SELECTION OF MATERIAL

SELECTION OF MACHINE

SELECTION OF TOOLS

MANUFACTURING COMPONENT ON MACHINE



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Step 1: 2D drawing Below shows the 2D drawings of the Casing Cover Plate in AUTO CAD SOFTWARE with

all the required dimensions.

Fig. 2: 2D Drawing of the Casing Cover Plate

Step 2: Generating 3D component of the Casing Cover Plate

Fig. 3: Complete 3D component of the Casing Cover Plate

Step 3: NC Program generation

In NX, the NC machining environment is referred to as the “Setup”. There are some standard

setups available in NX-CAM. The set up for the machining jobs should be decided by looking at all

the environmental information from four viewpoints: Program, Method, Geometry, and Tool.

Step 4: Selection of suitable material Cast Aluminum is used as raw material for the casing cover plate.



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Step 5: Selection of machine The complex series of steps needed to produce any part is highly automated and produces a

part that closely matches the original CAD design. For machining the Casing Cover a 5-axis milling

machine is used.

Fig. 4: 5-Axis Milling Machine

Step 6: Selection of tools

a) Slot drill Slot drills are centre-cutting end mills. Generally two- (sometimes three- or four-) fluted cutters that

are capable of drilling (plunge-cutting) straight down into the material and then moving laterally to

cut a slot is used.

b) Roughing end mill

Roughing end mills quickly remove large amounts of material. This kind of end mill utilizes a wavy

tooth form cut on the periphery. These wavy teeth form many successive cutting edges producing

many small chips, resulting in a relatively rough surface finish.

c) Ball nose cutter Ball nose cutters are similar to slot drills, but the ends of the cutters are hemispherical. They are ideal

for machining 3-dimensional contoured shapes in machining centers, for example

in moulds and dies. They are also used to add a radius between perpendicular faces to reduce stress

concentrations.

d) Slab mills Slab mills are used either by themselves or in gang milling operations on manual horizontal or

universal milling machines to machine large broad surfaces quickly.



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e) Side and Face cutter The side-and-face cutter is designed with cutting teeth on its side as well as its circumference.

They are made in varying diameters and widths depending on the application.

f) Involute gear cutter Number 4: 10 diametrical pitch cutter cuts gears from 26 through to 34 teeth

14.5 degree pressure angle is used.

g) Hob

Aluminum Chromium Titanium Nitride (AlCrTiN) coated Hobs are used.

Selection of tool holders

The devices which are used to hold different types of tools for carrying out different

operations such as drilling, boring, reaming, tapping, threading etc. are known as tool holders. Some

important types of tool holders are given below:

a) Tap holder Tap holder is used to hold the tool which performs the threading operations.

b) Face Mill

It is sophisticated tool holder and mainly used for facing operations of different components.

c) Taper Taper is used to hold the tool which is in conical shape.

d) Clamping nuts

These are used for fixing the tools in collets firmly.

e) Boring bar

Holder for rough boring with angular setting square bit to axis.

f) Milling chuck The highest accuracy reached by the tool is 0.005 mm. the design assures a powerful clamping force

capability, minimizing of vibrations and distortion.

g) Collets A collet is used for holding small semi-finished or finished parts so that additional

operations may be performed. It is practical device for quickly and accurately chucking symmetrical

work pieces.

h) Reducing sleeve In oil feed holder, positioning block and reducing sleeve are provided. The positioning block can be

mounted on to the spindle guide but it is mounted so as not to interfere with ATC arm etc of the

machine.

i) Oil feed holder By using this oil is allowed to pass through tool and work piece.

j) Slide cutter arbor

k) Rigid tap holder



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Setup1 tooling list 1 In the Project Manager, we can create and automatically assign new tools to tool stations in

the Tools view.

1) Drilling tools-

Table 1

2) Milling tools-

Table 2

Setup2 tooling list 2

Milling tools-

Table 3

Machine Setup operations

Setup1 – Face milling, Pocket milling, Angle milling, Contour milling, Center milling and Drilling.

Setup2- Face milling, Profile rough milling and Profile finish milling.



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Bench vice used as a fixture for casing cover

Fig. 5: Fixture for holding Casing Cover Plate

Step 7: Basic CAM setup

Operation creation

Fig. 6: Information for doing Operation

CAM Generation

Fig. 7: The 3D orientation of the Work piece Fig. 8: The Face milling Operation



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Fig.9: Profile Milling Operation Fig. 10: Cavity Milling Operation

Fig. 11: The Final Cavity Milling Operation Fig. 12: The Drilling Operation

CONVERT TO NC CODE

Using the post processor we have to convert CL file data into machine specified NC part

program.

Process Sheets for Setup1 and Setup2 are generated.

Tool failures and their remedies

a) Flank wear

Fig. 13: Tool Flank Wear Rate



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Table 4: Flank Wear – Causes and Remedies

Sl No. Causes Remedies

1 Cutting speed too high Reduce rpm

2 In feed depth too small Increase depth of cut

Modify flank in feed

3 Highly abrasive material Use coated grade

4

Inadequate coolant

supply Apply coolant

5 Wrong inclination anvil Reselect anvil

6

Wrong turned dia prior to

threading Check diameter

7 Insert is above centre line Check centre height

b) Deformation

Table 5: Deformation - Causes and Remedies


1 Excessive heat cutting

zone

Reduce rpm

Reduce depth of cut

2

Wrong grade

Check turned dia

Use coated grade

3

Inadequate coolant supply

Use harder grade

Apply more coolant

c) Chipping of tool

Table 6: Chipping - Causes and Remedies

Sl

No Causes Remedies

1

Cutting speed is too

high Reduce rpm

2 Depth of cut large

3

Wrong grade Reduce depth of cut

Use coated grade

4 Poor chip control Use tougher grade

5

In adequate coolant

supply Modify flank feed

Apply coolant

6 Center height incorrect Adjust center height



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d) Thermal Cracking

Table 7: Thermal Cracking - Causes and Remedies


1 Repeated Thermal shock

Reduce feed rate

Use tougher grade

Use stronger insert geometry

Reduce coolant completely or apply

coolant correctly

e) Mechanical Fracture

Table 8: Mechanical Fracture - Causes and Remedies


1 Cutting edge tool cold Increased rpm

2 Depth of cut too large

Reduce depth of cut

Increase number of infeed passes

3 Wrong grade Use tougher grade

4

Wrong turned dia prior to

threading Check turned dia

5 Corner height incorrect Adjust center height

6 Infeed depth too shallow Modify flank infeed

7 Wrong inclination of anvil Reselect anvil

8 Tool overhang too long Reduce tool overhang

f) Poor Chip Control

Table 9: Poor Chip Control – Causes and Remedies


1

Excessive heat in

cutting zone

Reduce rpm

Change depth of cut

Check turned dia

2 Wrong grade

Use coated grade

Check turned dia

Use m-type insert

3

Inadequate coolant

supply Apply coolant

4

Wrong turned dia prior

to threading Check turned dia



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Presetting of Tools The total length of tool travel depends on the length of work piece to be machined on the

length of tool or diameter of tool which should be known exactly.

Whenever a tool is replaced, it has to be calibrated again to determine its exact

length/diameter and this information is fed to tool card. Thus any difference between old and new

tool dimensions are recorded to calculate compensation offsets and new travel lengths are worked

out and program need not be rewritten. In this way the machine setup line is reduced considerably.

CONCLUSIONS

1) The given 2 D drawing is converted into 3 D model by NX 7.5 software.

2) Step by step manufacturing process planning is developed.

3) Casing cover plate is manufactured on CNC 5 axis DMG milling machine.

4) NC program is generated in NX 7.5 software. This generated NC program is given as input for

CNC 5-axis DMG milling machine.

5) Considerable savings in cost and time are observed.

Future scope

1) Optimization of manufacturing cost can be studied.

2) Calculations of process times can be observed.

Future trends

1) Digital manufacturing is a key emerging technology in Product Lifecycle Management (PLM)

and companies are trying to include Digital Manufacturing in their PLM.

2) In industry, the Internet promises to connect the enterprise with suppliers and vendors enabling

a new paradigm in manufacturing leading to Enterprise Production Management.

3) CAM software developers are introducing new NC programs tailored for optimal machining

known as "Knowledge-based machining".

4) Knowledge based machining has some systems emphasize providing knowledge about

machining while other systems emphasize capturing knowledge about machining. Most

systems offer a mixture of these two approaches.

5) Knowledge-based machining programmers store shop-proven processes and customize

databases. The benefits are realized throughout the shop. Operations become more consistent

and uniformly superior to past experience.

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