automatic tool changer cnc

7/29/2019 automatic tool changer cnc

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DYNAMIC Industries Ltd.

Report on

Title

By

Shashank Singh

Roll no. 337, GR no. 71122100033

Submitted for

Technical internship programme

TrainingSupervisor and Guide

Prof. Ravi Terkar

Associate Professor, MPSTME

Mr. Anup Parikh

Chairman, Dynamic Industries Ltd.

MUKESH PATEL SCHOOL OF TECHNOLOGY MANAGEMENT & ENGINEERING

SVKM's

NARSEE MONJEE INSTITUTE OF MANAGEMENT STUDIES

(Declared as Deemed-to-be University Under Section 3 of the UGC Act. 1956)

Vile Parle(w), Mumbai-400 056.

Date:


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SVKMs Narsee Monjee Institute of

Management Studies(NMIMS)

Mukesh Patel School of Technology Management &

Engineering

A REPORT

on

Manufacturing of an injection moulded

component & reduction in the CNC machining time

using automatic tool changer.

ByShashank Singh

MBA(Tech)-Mechanical [337]



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ACKNOWLEDGMENT

It gives me immense pleasure to present this in-pant training report atDYNAMIC INDUSTRIES LTD. This training provided me a golden opportunity to

expose myself to the industrial environment.

I am very grateful to my training Guides, Mr. Anup Parikh & Prof. Ravi

Terker for their motivation and continuous support as well as guidance to pursue

and complete this research. Their wide knowledge and logical way of thinking

have been of great value for me. They were always there to meet and talk about

research ideas, to proof read and mark-up my papers, and to ask me good

questions to help me to think through my research. Without their encouragement

and constant guidance, I could not have finished this synopsis.

I would like to thank to Mr. Chandrakant Vichrolia, Mr. Chetan

Majithia & Mr. Amol Deshmukh for their valuable support and encouragement

during the research work.

Further I believe that the list of people would remain incomplete if I fail to

mention my supervisors & department colleagues; they were constant source of

encouragement and timely help.

Thanks


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Table of Contents:

ACKNOWLEDGMENT................................................................................................................................. 3

ABSTRACT .................................................................................................................................................. 1

1. INTRODUCTION TO THE COMPANY ........................................................................................................ 2

1.1. COMPANYS QUALITY POLICY......................................................................................................... 3

1.2. COMPANY SERVICES ....................................................................................................................... 3

1.3. LIST OF ESTEEMED CUSTOMERS ..................................................................................................... 4

1.4. COMPANY PRODUCTS .................................................................................................................... 5

2. PRODUCT DESIGN ................................................................................................................................. 13

3. PRE-MACHINING................................................................................................................................... 13

3.1. SHAPING: ...................................................................................................................................... 14

3.1.1.WORKING PRINCIPLE ............................................................................................................ 14

3.2. GRINDING: .................................................................................................................................... 15

3.3. CONVENTIONAL MILLING: ............................................................................................................ 16

3.3.1.METHODS OF MILLING: ........................................................................................................ 17

4. MOULD DESIGN .................................................................................................................................... 18

4.1. MOULD BASICS: ............................................................................................................................ 18

4.1.1.TYPES OF MOULDS: ............................................................................................................... 19

4.1.2.MOULD BASES & CAVITIES:................................................................................................... 20

4.1.3.MOLDING UNDERCUTS: ........................................................................................................ 21

4.1.4.PART EJECTION: .................................................................................................................... 22

4.1.5.MOULD METALS: .................................................................................................................. 22

4.1.6.MOULD COST AND QUALITY: ................................................................................................ 23

5. MACHINING & FINISHING ..................................................................................................................... 25

5.1. CNC MACHINING: ......................................................................................................................... 25

5.1.1.CNC LATHE: ........................................................................................................................... 30

5.1.2.WORKING OF CNC LATHE: .................................................................................................... 30

5.1.3.FEATURES OF CNC LATHE: .................................................................................................... 30

5.2. ELECTRIC DISCHARGE MACHING (EDM): ...................................................................................... 31

5.2.1.PRINCIPLES OF EDM-............................................................................................................. 31


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5.2.2.EDM PROCESS- ...................................................................................................................... 32

5.2.3.CHARACTERISTICS OF EDM- .................................................................................................. 33

5.2.4.DIELECTRIC- ........................................................................................................................... 34

5.2.5.ELECTRODE MATERIAL- ......................................................................................................... 34

5.2.6.ADVANTAGES OF EDM: ......................................................................................................... 37

5.2.7.DISADVANTAGES OF EDM .................................................................................................... 37

5.3. CLASSIFICATION OF EDM .............................................................................................................. 38

5.3.1.CONVENTIONAL EDM: .......................................................................................................... 38

5.3.2.WIRE-CUT EDM: .................................................................................................................... 39

5.3.3.CONVENTIONAL EDM- DIELECTRIC FLUIDS........................................................................... 39

5.3.4.WIRE EDM- DIELECTRIC FLUIDS ............................................................................................ 39

5.3.5.FLUSHING .............................................................................................................................. 39

6. FINAL COMPONENT .............................................................................................................................. 41

7. AUTOMATIC TOOL CHANGER ............................................................................................................... 43

7.1. AUTOMATIC MANUFACTURING SYSTEMS: .................................................................................. 43

7.2. REASONS FOR AUTOMATING: ...................................................................................................... 44

7.3. TOOLING FOR NUMERICAL CONTROL: ......................................................................................... 45

7.3.1.1. Tool Holders ...................................................................................................................... 45

7.3.2.2. Automatic tool selection ................................................................................................... 45

7.3.3.3. Automatic Tool Changer ................................................................................................... 46

7.4. AUTOMATIC TOOL CHANGER ....................................................................................................... 47

7.4.1.Why Tool Changer is needed? .............................................................................................. 47

7.4.2.Types of automatic tool changer .......................................................................................... 47


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Table of figures:

Figure 1: General CNC machines ................................................................................................................... 5

Figure 2: Electrical discharge machine(EDM) ............................................................................................... 6

Figure 3: Conventional Miling Machine ........................................................................................................ 7Figure 4: Under bonnet components - TANKS .............................................................................................. 8

Figure 5: Various Molded tanks .................................................................................................................... 9

Figure 6: Under bonnet components .......................................................................................................... 10

Figure 7: Major industrially accepted products .......................................................................................... 11

Figure 8: Mould process chart .................................................................................................................... 12

Figure 9: Shaping machine .......................................................................................................................... 14

Figure 10: Surface grinding machine .......................................................................................................... 15

Figure 11: Milling machine .......................................................................................................................... 16

Figure 12: Climb milling method ................................................................................................................. 17

Figure 13: Conventional milling method..................................................................................................... 18Figure 14: Basic components of NC system ................................................................................................ 26

Figure 15: Typical CNC machine .................................................................................................................. 27

Figure 16: Motion control system, (a) Open loop; (b) Closed loop ............................................................ 29
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ABSTRACT

The project is related to the production, design & manufacturing of an injectionmold component, called Shroud in this case, and also to reduce the machining

time in CNC milling by suggesting automated tool changing using automatic tool

changer(ATC) instead of changing the tools manually.

Presently the firm is using the method of manually changing the tool which

consumes time and thus affects overall productivity, so Ill be suggesting the

automated tool changing using an automated tool changer & a tool pre-setter.

In my training here, Ill be monitoring and studying the whole mold making

process starting from the product design to the final trial & correction, alongside

with the work on the automatic tool changer by observing & studying the

conditions and environment of and near the CNC machines so that ATC can be

successfully implemented thereby helping in increasing the overall productivity of

the firm.


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INTRODUCTION TO THE COMPANY

Dynamic Industries is originally a mould making and moulding company

specialized in Automobile, Air-conditioners, Water Purifier System, Thermoforming,

Television and House Hold Industries.

This company is a partnership firm professionally managed by Mr. Deepak Gandhi &

Mr. Anup Parikh and is executing enduring services to clients.

They have integrated product development, mould design and manufacturing facilities

along with injection moulding facilities to provide one-step service.

Following industries are covered in the services for this industry.

The companys services are available to the industries like-

AutomobilesWater

TreatmentConsumerAppliances

Electrical andElectronics

Bio-Medicals


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COMPANYS QUALITY POLICY

Company have a integrated product development, mould design and

manufacturing facilities along with injection moulding facilities to provide one-

step service. So that trial-testing can also be done at one go.

Quality policy is to achieve sustained, profitable growth by providing services

which consistently satisfy the needs and expectations of our customers.

To achieve and maintain a level of quality which enhances the companys

reputation with customers.

To provide a quality product that satisfies our customers requirement, deliver on

time. We are committed to continuously improve our processes to provide goods

and services at a better value to our customers.

COMPANY SERVICES

CAD-CAM Engineering

Reverse Engineering

In house mould design, part design consulting, assistance in project

development

EDM- Electrode manufacturing

On-time delivery at competitive price

Weekly process report


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LIST OF ESTEEMED CUSTOMERS

Mutual Industries Ltd.

Ronch Polymers Ltd.

TVS Motor Company Ltd.

Sundaram Auto-Components Ltd.

Tata Auto-Components Pvt. Ltd.

Banco Products (India) Ltd.

Alkraft Thermotechnologies Pvt. Ltd. Kabra Extrusiontechnik Pvt. Ltd.

Jyoti Plastic Works Pvt. Ltd.

Polysmart Technologies Pvt. Ltd.

Auro Plastic Injection Moulders Pvt. Ltd

Hitachi Home & Life Solution Ltd

Rajoo Engineers Ltd.

Tata Infotech Ltd. Sui Generics

Transpo International

Polyset Plastics

Transasia Bio Medicals

Kirti Industries Ltd.

Rita International

Harita Infoserve Ltd. Lear Corporation

Supreme Treaves Pvt. Ltd.

Vipul Plastocrafts


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COMPANY PRODUCTS

Figure 1


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Figure 2


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Figure 3


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Figure 4


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Figure 5


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Figure 6


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Figure 7


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Figure 8


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PRODUCT DESIGN

Product design is provided by the customer to the manufacturer, in order to get

the required mould.Product design is made on the 3D-CAD softwares like NX,

PRO-E etc by the customer itself then it is sent to the manufacturer and finally it is

checked for feasibility study.

PRE-MACHINING

Pre-machining the the process of machining the raw material before putting theminto CNC or EDM machining in


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SHAPING:

It is a simple and yet extremelyeffective machine. It is used to

remove material, usually metals

such as steel or aluminium, to

produce a flat surface. However, it

can also be used to manufacture

gears such as rack and pinion

systems and other complex shapes.

Inside its shell/casing is a crank andslider mechanism that pushes the

cutting tool forward and returns it

to its original position. This motion

is continuous.

WORKING PRINCIPLEThe job is rigidly fixed on the machine table. The single point cutting tool held properly

in the tool post is mounted on a reciprocating ram. The reciprocating motion of the ram

is obtained by a quick return motion mechanism. As the ram reciprocates, the tool cuts

the material during its forward stroke. During return, there is no cutting action and this

stroke is called the idle stroke. The forward and return strokes constitute one operating

cycle of the shaper.The main functions of shaping machines are to produce flat surfaces in different planes.The cutting motion provided by the linear forward motion of the reciprocating tool and

the intermittent feed motion provided by the slow transverse motion of the job along

with the bed result in producing a flat surface by gradual removal of excess material

layer by layer in the form of chips. The vertical infeed is given either by descending the

tool holder or raising the bed or both. Straight grooves of various curved sections are

Figure 9


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also made in shaping machines by using specific form tools. The single point straight or

form tool is clamped in the vertical slide which is mounted at the front face of the

reciprocating ram whereas the workpiece is directly or indirectly through a vice is

mounted on the bed.

GRINDING:

Grinding is a finishing process used

to improve surface finish, abrade

hard materials, and tighten the

tolerance on flat and cylindrical

surfaces by removing a small

amount of material. Information in

this section is organized accordingto the subcategory links in the

menu bar to the left. A

distinguishing feature of grinding

machines is the rotating abrasive

tool. Grinding machine is employed

Figure 10


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to obtain high accuracy along with very high class of surface.

In grinding, an abrasive material rubs against the metal part and removes tiny pieces of

material. The abrasive material is typically on the surface of a wheel or belt and abrades

material in a way similar to sanding. On a microscopic scale, the chip formation in

grinding is the same as that found in other machining processes. The abrasive action of

grinding generates excessive heat so that flooding of the cutting area with fluid is

necessary.

Reasons for grinding are:

The material is too hard to be machined economically. (The material may have

been hardened in order to produce a low-wear finish, such as that in a bearing

raceway)

Tolerances required preclude machining. Grinding can produce flatness

tolerances of less than 0.0025 mm (0.0001 in) on a 127 x 127 mm (5 x 5 in)

steel surface if the surface is adequately supported.

CONVENTIONAL

MILLING:

Milling machines are very versatile.

They are usually used to machine flat

surfaces on square or rectangular parts,

but can also produce many unique andirregular surfaces. They can also be

used to drill, bore, produce slots,

pockets and many other shapes. The

type of milling machine in the UCR

Mechanical Engineering Machine Shop

Figure 11


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is a variable speed vertical spindle, knee-mill with a swiveling head (also known as a

Bridgeport). Although there are several other types of milling machines, this document willfocus only on the vertical milling machine. A milling machine removes metal by rotating a multi-

toothed cutter that is fed into the moving workpiece.

METHODS OF MILLING:

Climb-milling:

Climb milling, is sometimesreferred to as Down milling, wherethe direction of the cutter rotationis the same as the feed direction.This method is probably the mostcommon option on the shop floorand will normally produce a bettersurface finish.

Figure 12


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Conventional-milling:

Conventional milling is alsosometimes referred to as Upmilling where the direction of the

cutter opposes the feeddirection.

MOULD DESIGN

MOULD BASICS:

At the most basic level, moulds consist of two main parts:

Cavity &

Core

The core forms the main internal surfaces of the part.

The cavity forms the major external surfaces.

Typically, the core and cavity separate as the mold opens,so that the part can be

removed. This mold separation occurs along the interface known as the parting

line. The parting line can lie in one plane corresponding to a major geometric

feature such as the part top, bottom or centerline, or it can be stepped or angledto accommodate irregular part feature.

Choose the parting-line location to minimize undercuts that would hinder Or

prevent easy part removal.

Undercuts that cannot be avoided via reasonable adjustments in the parting line

require mechanisms in the mold to disengage the undercut prior to ejection.

Figure 13


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TYPES OF MOULDS:

The two-plate mould, the most common mold configuration, consists of twomold halves that open along one parting line (see figure 7-1). Material can enter

the mold cavity directly via a sprue gate, or indirectly through a runner system

that delivers the material to the desired locations along the parting line. The

movable mold half usually contains a part-ejection mechanism linked to a

hydraulic cylinder operated from the main press controller.

The three-plate mold configuration opens at two major locations instead of one.

Figures 7-2A through 7-2C show the mold-opening sequence for a typical three-

plate mold. Typically, a linkage system between the three major mold plates

controls the mold-opening sequence. The mold first opens at the primary parting

line breaking the pinpoint gates and separating the parts from the cavity side of

the mold. Next, the mold separates at the runner plate to facilitate removal of the

runner system. Finally, a plate strips the runner from the retaining pins, and parts

and runner eject from the mold.

Unlike conventional two-plate molds, three-plate molds can gate directly into

inner surface areas away from the outer edge of parts: an advantage for center-

gated parts such as cups or for large parts that require multiple gates across

a surface. Disadvantages include added mold complexity and large runners that

can generate excessive regrind. Also, the small pinpoint gates required for clean

automatic degating can generate high shear and lead to material degrada- tion,

gate blemish, and packing problems. Because of the high shear rates generated

in the tapered runner drops


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and pinpoint gates, three-plate molds are not recommended for shear-sensitive

materials such as Cadon SMA and materials with shear-sensitive colorants or

flame retardants.

MOULD BASES & CAVITIES:

The mold base comprises the majority of the bulk of an injection mold. Standard

off-the-shelf mold bases are available for most molding needs. Typical mold bases

are outfitted with a locating ring and provisions for a sprue bushing in the

stationary or A half of the mold and an ejector assembly in the moving B half.

Both halves come with clamp slots to affix the mold in the press. The B half has

holes to accommodate bars that connect the press ejection mechanism to the

ejector plate in the mold.

Leader pins projecting from corners of the A half align the mold halves. Return

pins connected to the ejector plate corners project from the mold face when the

ejection mechanism is in the forward (eject) position. As the mold closes, the

return pins retract the ejector plate (if not retracted already) in preparation for

the next cycle.

Mold cavities, here meaning core and cavity sets, can be incorporated in the mold

three ways: they can be cut directly into the mold plates, inserted pieces into the

mold base, or inserted as complete cavity units. Cutting cavities directly into the

mold base can be the most economical approach for large parts and/or parts with

simple geometries. When doing so, select the mold base steel carefully. The

physical properties of standard mold base steels may be inadequate for heavy-wear areas or critical steel-to-steel contact points. Use inserts made of

appropriate materials in these areas.

Assembling the cavity in the mold base lets you select different metals for the

various cavity components, optimizing the molds durability and performance. It


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also simplifies and speeds repairs for worn or damaged cavity components,

especially if you maintain spare mold pieces for vulnerable components.

Additionally, assembling the cavities from pieces can simplify component

fabrication. Some of the drawbacks of mold-base cavity assemblies include high

initial mold cost, less-efficient mold cooling, and potential tolerance

accumulation problems with the cavity components.

MOLDING UNDERCUTS:

Undercuts, part features that prevent straight ejection at the parting line, tend to

increase mold complexity and lead to higher mold construction and

maintenance costs. Whenever feasible, redesign the part to avoid undercuts.

Minor part design changes can often eliminate problematic undercuts in the

mold. For example, adding through- holes can give access to the underside of

features that would otherwise be undercuts.

Likewise, simple modifications enable the mold to form a hole in the sidewall

with bypass steel rather than with a side action mechanism

Undercut features that cannot be avoided through redesign require mechanisms

in the mold to facilitate ejection. These types of mechanisms include side-action

slides, lifter rails, jiggler pins, collapsible cores and unscrewing mechanisms.

Side-action slides use cam pins or hydraulic (or pneumatic) cylinders to retract

portions of the mold prior to ejection. Cam-pin-driven slides retract as the

mold opens. As the mold closes, the cam pins return the slides to their original

position for the next injection cycle. Slides driven by hydraulic or pneumatic

cylinders can activate at any time during the molding cycle, an advantage in

applications requiring the slides to actuate prior to mold opening or closing.Shallow undercuts can often be formed by spring-loaded lifters (see figure 7-6) or

lifter rails attached to the ejector system. These lifters move with the part on an

angle during mold opening or ejection until the lifter clears the undercut in the

part. A variation on this idea


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PART EJECTION:

Typically, molds have ejector systems built into the moving B half. The ejection

unit of the molding press activates these systems. Rods linking the press-ejector

mechanism to an ejector plate in the mold enable the press controller to control

the timing, speed, and length of the ejection stroke. Reverse- injection molds

eject parts from the stationary side of the mold via independent ejection

mechanisms operated by springs or hydraulic cylinders. This configuration

facilitates direct injection onto the inside or back surface of cosmetic parts. The

added complexity of reverse- injection molds adds to the mold cost.

Specialized ejection components, such as knockout (KO) pins, KO sleeves, or

stripper plates, project from the mold ejector plate to the part surface where

they push the part out of the mold (see figures 7-9 through 7-11). These topics

are discussed in this section.

MOULD METALS:

Mold designers consider a variety of factors when selecting the mold metal

including, machining ease, weldability, abrasion resistance, hardness, corrosion

resistance, and durability. Metals can range from the soft, low-melt-temperature

alloys used in inexpensive, cast-metal, prototype molds to the porous metal used

in vent inserts. Metals are chosen based not only on the cost, manufacturing, and

performance requirements of the mold or component, but also on the experience

and comfort level of the mold design and construction shop.Aluminum, long a popular choice for prototype molds, is gaining acceptance in

moderate-run production molds. Improved aluminum alloys, such as

QC-7, exhibit greater strength and hardness than standard aircraft-grade

aluminum, and sufficient durability for some production molds. Hard coatings can

raise the surface hardness of aluminum molds to more than 50 Rockwell C (HRC)


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for improved wear resistance. Steel inserts and mechanical components are

usually used in high wear areas within the aluminum mold to extend mold life.

Aluminum offers easier machining and faster cycle times than conventional mold

steels at the expense of wear resistance and mold durability.

Most high production injection molds designed for engineering plastics are

fabricated from high-quality tool steel. Mold bases are usually made of P-20

prehardened to 30 35 HRC and are often plated to resist corrosion.

Specifications for high-quality molds, especially for medical parts, often specify

420 stainless steel to eliminate corrosion concerns.

Cavity and cores steels vary based on the production requirements, machining

complexity, mold size, mechanical needs, and the abrasive or corrosive nature of

the molding resin. . P-20 steel (30-36 HRC) provides a good mix of properties for

most molds running non-abrasive materials such as unfilled PC or ABS.

Prehardened 420 stainless (30-35 HRC) can also be used when corrosion

resistance is needed. For longer mold life and increased durability, many medicalmolders select 420 stain less hardened to 50-52 HRC for their molds running

unfilled resin grades. This highly polishable stainless steel resists corrosion and

staining but provides less efficient cooling than most other mold steels.

MOULD COST AND QUALITY:

The true cost of a mold includes not only the costs of design and construction,

but also mold-maintenance costs and the mold-related costs associated withscrap, cycle time, part quality problems, and press down time. In the long run, the

least-expensive mold option seldom produces the most economical, high-quality

parts. Extra engineering and expense up front can improve molding efficiency and

increase the number of good parts the mold can produce. When developing the

mold specifications, consider the following:


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Hardened steel molds last longer and require less maintenance and rework than

soft steel molds.

Money spent on enhanced mold cooling can pay back many times over in

reduced cycle time and improved part qual0ity.

Hardened mold interlocks and alignment features ensure proper mold

alignment and prevent wear or damage due to misalignment.

Spare parts for items prone to wear or breakage are usually cheaper to

manufacture during mold construction than after the mold is in production. Spare

parts reduce costly down time.

In the long run, it is usually more economical to adjust the mold steel to

produce parts in the middle of the tolerance range at optimum processing

conditions than to adjust dimensions by processing within a narrow processing

window at less- than-optimum conditions.

When obtaining quotations for new mold construction, make sure that every mold

maker works from the specific set of mold specifications. Also consult processing,mold-maintenance, and inspection personnel at the molding facility for mold

design input based on experience with similar molds


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.

MACHINING & FINISHING

Machining stage includes mainly two processes, one is the CNC machining &

secondly is the Electrical discharge machining (EDM).

CNC MACHINING:

It is a process used in the manufacturing sector that involves the use ofcomputers to control machine tools. Tools that can be controlled in this manner

include lathes, mills, routers and grinders. The CNC in CNC Machining stands for

Computer Numerical Control.

On the surface, it may look like a normal PC controls the machines, but the

computer's unique software and control console are what really sets the system

apart for use in CNC machining.

Under CNC Machining, machine tools function through numerical control. Acomputer program is customized for an object and the machines are

programmed with CNC machining language (called G-code) that essentially

controls all features like feed rate, coordination, location and speeds. With CNC

machining, the computer can control exact positioning and velocity. CNC

machining is used in manufacturing both metal and plastic parts.


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Figure 14

First a CAD drawing is created (either 2D or 3D), and then a code is created

that the CNC machine will understand. The program is loaded and finally an

operator runs a test of the program to ensure there are no problems. This trial

run is referred to as "cutting air" and it is an important step because any mistake

with speed and tool position could result in a scraped part or a damaged

machine.


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Figure 15

Computer numerical control is the process of manufacturing m/c parts using

computerized controller to command motors which drive each machine axis.

In order to achieve high precision machining, many efforts have been made

to develop more accurate computerized numerical control (CNC) systems.

CNC systems are commonly used in industrial and commercial applications for

its compact size, high power-to-weight ratio, reliability, and low maintenance.

CNC System includes a PC, motion board, servo motor drive and motors,

spindle drive and motor, automatic tool-changer and general I/O card. A tool

magazine is an indexable storage used on a machining center to store tools not in

use.

These machines are designed to perform a number of operations in a

single setting of the job. A number of tools may be required for making a

complex part.

Modern CNC milling machines differ little in concept from the originally


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developed NC machines. Mills typically consist of a table that moves in the X and

Y axes, and a tool spindle that moves in the Z (depth). The position of the tool is

driven by motors through a series of step-down gears in order to provide highly

accurate movements, or in modern designs, direct-drive stepper motor or servo

motors. Open-loop control works as long as the forces are kept small enoughand speeds are not too great. On commercial metalworking machines closed

loop controls are standard and required in order to provide the accuracy, speed,

and repeatability demanded.

As the controller hardware evolved, the mills themselves also evolved. One

change has been to enclose the entire mechanism in a large box as a safety

measure, often with additional safety interlocks to ensure the operator is far

enough from the working piece for safe operation. Most new CNC systems built

today are completely electronically controlled.

CNC-like systems are now used for any process that can be described as a

series of movements and operations. These include laser cutting, welding,

friction stir welding, ultrasonic welding, flame and plasma cutting, bending,

spinning, pinning, gluing, fabric cutting, sewing, tape and fiber placement,

routing, picking and placing (PnP), and sawing.


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Figure 16

There are many advantages to using CNC

Machining:

(a). The process is more precise than manual machining, and

(b). It can be repeated in exactly the same manner over and over again.

(c). It can produce complex shape would be almost impossible to achieve

with manual machining

(d). It is used in jobs that need a high level of precision or very repetitive tasks.


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CNC LATHE:

Automated version of a manual lathe is known as CNC lathe. Programmed to

change tools automatically, it is used for turning and boring metals etc.

WORKING OF CNC LATHE:

Controlled G and M codes.

These are number values and co-ordinates.

Each number or code is assigned to a particular operation.

Typed in manually to CAD/CAM

G and M are automatically generated by the computer software

FEATURES OF CNC LATHE:

The tool or material moves

Tool can operate in 5-10 axes.

Larger machines have a machine control unit which manages operations.

Movement is controlled by motors.

Feedback is provided by sensors.

Tool magazines are used to change tool automatically.


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ELECTRIC DISCHARGE MACHING (EDM):

PRINCIPLES OF EDM-

Electrical Discharge Machining (EDM) is a controlled metal-removal process that isused to remove metal by means of electric spark erosion. In this process an

electric spark is used as the cutting tool to cut (erode) the workpiece to produce

the finished part to the desired shape. The metal-removal process is performed

by applying a pulsating (ON/OFF) electrical charge of high-frequency current

through the electrode to the workpiece. This removes (erodes) very tiny pieces of

metal from the workpiece at a controlled rate.

Fig. A rough diagram showing the EDM process


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EDM PROCESS-

In EDM, a potential difference is applied between the tool and workpiece. Both

the tool and the work material are to be conductors of electricity. The tool andthe work material are immersed in a dielectric medium. Generally kerosene or

deionised water is used as the dielectric medium. A gap is maintained between

the tool and the workpiece. Depending upon the applied potential difference and

the gap between the tool and workpiece, an electric field would be established.

Generally the tool is connected to the negative terminal of the generator and the

workpiece is connected to positive terminal. As the electric field is established

between the tool and the job, the free electrons on the tool are subjected to

electrostatic forces.

The high speed electrons then impinge on the job and ions on the tool. The kineticenergy of the electrons and ions on impact with the surface of the job and tool

respectively would be converted into thermal energy or heat flux. uch intense

localised heat flux leads to extreme instantaneous confined rise in temperature

which would be in excess of 10,000oC.

Such localised extreme rise in temperature leads to material removal. Material

removal occurs due to instant vapourisation of the material as well as due to

melting. The molten metal is not removed completely but only partially.

Generally the workpiece is made positive and the tool negative. Hence, the

electrons strike the job leading to crater formation due to high temperature andmelting and material removal. Similarly, the positive ions impinge on the tool

leading to tool wear.

In EDM, the generator is used to apply voltage pulses between the tool and the

job. A constant voltage is not applied. Only sparking is desired in EDM rather than

arcing. Arcing leads to localised material removal at a particular point whereas

sparks get distributed all over the tool surface leading to uniformly distributed

material removal under the tool.


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CHARACTERISTICS OF EDM-

The process can be used to machine any work material if it is electrically

conductive

Material removal depends on mainly thermal properties of the work

material rather than its strength, hardness etc

In EDM there is a physical tool and geometry of the tool is the positive

impression of the hole or geometric feature machined

The tool has to be electrically conductive as well. The tool wear once again

depends on the thermal properties of the tool material

Though the local temperature rise is rather high, still due to very small

pulse on time, there is not enough time for the heat to diffuse and thus

almost no increase in bulk temperature takes place. However rapid heating

and cooling and local high temperature leads to surface hardening which

may be desirable in some applications

Though there is a possibility of taper cut and overcut in EDM, they can be

controlled and compensated.

EDM is a thermal process; material is removed by heat. Heat is introduced by the

flow of electricity between the electrode and workpiece in the form of a spark.

Material at the closest points between the electrode and workpiece, where thespark originates and terminates, are heated to the point where the material

vaporizes. While the electrode and workpiece should never feel more than warm

to the touch during EDM, the area where each spark occurs is very hot. The area

heated by each spark is very small so the dielectric fluid quickly cools the

vaporized material and the electrode and workpiece surfaces. However, it is

possible for metallurgical changes to occur from the spark heating the workpiece

surface. A dielectric material is required to maintain the sparking gap between

the electrode and workpiece. This dielectric material is normally a fluid. Die-sinker

type EDM machines usually use hydrocarbon oil, while wire-cut EDM machinesnormally use deionized water.


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DIELECTRIC-

In EDM, as has been discussed earlier, material removal mainly occurs due to

thermal evaporation and melting. As thermal processing is required to be carried

out in absence of oxygen so that the process can be controlled and oxidation

avoided. Oxidation often leads to poor surface conductivity (electrical) of the

workpiece hindering further machining. Hence, dielectric fluid should provide an

oxygen free machining environment. Further it should have enough strong

dielectric resistance so that it does not breakdown electrically too easily but at

the same time ionise when electrons collide with its molecule. Moreover, during

sparking it should be thermally resistant as well.

Generally kerosene and deionised water is used as dielectric fluid in EDM. Tap

water cannot be used as it ionises too early and thus breakdown due to presence

of salts as impurities occur. Dielectric medium is generally flushed around the

spark zone. It is also applied through the tool to achieve efficient removal of

molten material.

ELECTRODE MATERIAL-

Electrode material should be such that it would not undergo much tool wear

when it is impinged by positive ions. Thus the localised temperature rise has to be

less by tailoring or properly choosing its properties or even when temperatureincreases, there would be less melting. Further, the tool should be easily workable

as intricate shaped geometric features are machined in EDM. Thus the basic

characteristics of electrode materials are:

High electrical conductivity - electrons are cold emitted more easily and

there is less bulk electrical heating

High thermal conductivity - for the same heat load, the local temperature

rise would be less due to faster heat conducted to the bulk of the tool and

thus less tool wear

Higher density - for the same heat load and same tool wear by weight therewould be less volume removal or tool wear and thus less dimensional loss

or inaccuracy

High melting point - high melting point leads to less tool wear due to less

tool material melting for the same heat load

Easy manufacturability - should be easy to manufacture


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The followings are the different electrode materials which are used commonly in

the industry:

Graphite

Electrolytic oxygen free copper Tellurium copper 99% Cu + 0.5% tellurium

Brass

Fig. Sparking occurs at closest points between the electrode and workpiece.

In EDM, the spark occurs between the two nearest point on the tool and

workpiece. Thus machining may occur on the side surface as well leading to

overcut and tapercut as depicted in Fig.

Taper cut can be prevented by suitable insulation of the tool. Overcut cannot be

prevented as it is inherent to the EDM process. But the tool design can be done insuch a way so that same gets compensated.


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Fig. Tapercut & Overcut Fig. Tapercut prevention

The EDM process can be used in two different ways:

1. A pre-shaped or formed electrode (tool), usually made from graphite or copper,

is shaped to the form of the cavity it is to reproduce. The formed electrode is fed

vertically down and the reverse shape of the electrode is eroded (burned) into the

solid workpiece.

2. A continuous-travelling vertical-wire electrode, the diameter of a small needle

or less, is controlled by the computer to follow a programmed path to erode orcut a narrow slot through the workpiece to produce the required shape.


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ADVANTAGES OF EDM:

Complex shapes that would otherwise be difficult to produce with

conventional cutting tools.

Extremely hard material to very close tolerances. Very small work pieces where conventional cutting tools may damage the

part from excess cutting tool pressure.

Any material that is electrically conductive can be cut using the EDM

process.

Hardened work pieces can be machined eliminating the deformation

caused by heat treatment.

X, Y, and Z axes movements allow for the programming of complex profiles

using simple electrodes.

Complex dies sections and molds can be produced accurately, faster, and atlower costs.

The EDM process is burr-free.

Thin fragile sections such as webs or fins can be easily machined without

deforming the part.

DISADVANTAGES OF EDM:

The slow rate of material removal. Potential fire hazard associated with use of combustible oil based

dielectrics.

The additional time and cost used for creating electrodes for ram/sinker

EDM.

Reproducing sharp corners on the workpiece is difficult due to electrode

wear.

Power consumption is high.

Excessive tool wear occurs during machining.

Electrically non-conductive materials can be machined only with specificset-up of the process


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CLASSIFICATION OF EDM

CONVENTIONAL EDM:

In the EDM process an electric

spark is used to cut the workpiece,

which takes the shape opposite to

that of the cutting tool or

electrode. The electrode and the

workpiece are both submerged in a

dielectric fluid, which is generally

light lubricating oil. A servo-

mechanism maintains a space of

about the thickness of a human

hair between the electrode and the

work, preventing them from

contacting each other. In EDM ram

or sinker machining, a relatively

soft graphite or metallic electrode

can be used to cut hardened steel,

or even carbide. The EDM process

produces a cavity slightly larger

than the electrode because of the

overcut.


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WIRE-CUT EDM:

The wire-cut EDM is a discharge

machine that uses CNC movement

to produce the desired contour orshape. It does not require a special

shaped electrode, instead it uses a

continuous traveling vertical wire

under tension as the electrode.

The electrode in wire-cut EDM is

about as thick as a small diameter

needle whose path is controlled by

the machine computer to produce

the shape required.

CONVENTIONAL EDM- DIELECTRIC FLUIDS

During the EDM process the workpiece and the electrode are submerged in the

dielectric oil, which is an electrical insulator that helps to control the arc

discharge. The dielectric oil, that provides a means of flushing, is pumped through

the arc gap. This removes suspended particles of workpiece material and

electrode from the work cavity.

WIRE EDM- DIELECTRIC FLUIDS

The dielectric fluid must be circulated under constant pressure to flush (wash)

away the metal particles and assist in the machining or erosion process. If red

sparks occur during the cutting operation, the water supply is inadequate. To

overcome this problem, increase the flow of water until blue sparks appear.

FLUSHING


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Flushing is the most important function in any electrical discharge machining

operation. Flushing is the process of introducing clean filtered dielectric fluid into

the spark gap. Flushing applied incorrectly can result in erratic cutting and poor

machining conditions. There are a number of flushing methods used to remove

the metal particles efficiently while assisting in the machining process. Too muchfluid pressure will remove the chips before they can assist in the cutting action,

resulting in slower metal removal. Too little pressure will not remove the chips

quickly enough and may result in short-circuiting the erosion process


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FINAL COMPONENT

Fan shroud to be used by Ashok Leyland-Nissan with a joint venture in

commercial vehicles.


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AUTOMATIC TOOL CHANGER

A CNC tool changer fulfils the requirement of multiple tooling for a wide variety of machine

tools. A CNC machine tool raises the productivity by automatically translating designs into

instructions for a computer controller on a machine tool. The spindle axis of a CNC machine

tool fixes the chucks which is integral to the lathes functioning. A CNC tool storage system is an

organized, efficient, and secure method of storing tools at all stages and time. The main

component of a CNC tool storage system is a CNC tool holder. A CNC tool holder is suitable for

vertically storing all types of preset tools.

AUTOMATIC MANUFACTURING SYSTEMS:

Automated manufacturing systems operate in the factory on the physical product. They

perform operations such as processing, assembly, inspection, or material handling in somecases accomplishing more than one of these operations in the same system. They are called

automated because they perform their operations with a reduced level of human participation

compared with the corresponding manual process. In some highly automated systems, there is

virtually no human participation.

Examples of automated manufacturing systems include:

Automated machine tools that process machine parts

Transfer lines that perform a series of machining operations

Automated assembly systems

Manufacturing systems that use industrial robots to perform processing or assembly

operations.

Automatic material handling and storage systems to integrate manufacturing operations

Automatic inspection system for quality control


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REASONS FOR AUTOMATING:

Increase labour productivity to get better output.

Reduce labour cost and to mitigate the effects of labour shortages

Reduce or eliminate routine manual and clerical tasks

Improve worker safety

Improve product quality by confronting with quality specifications & uniformity.

Reduce the time between customer order & product delivery thus providing competitive

advantage.

Improved accuracies with consistency of quality parameters.

Suitable for mass production with better material handling and reduced WIP (Work-In-

Process).

Automatic data acquisition for computer aided quality control and inspection.

Flexible with zero set-up change over time.


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TOOLING FOR NUMERICAL CONTROL:Since NC machines are in general, more expensive than general purpose man-operated

machine tools, special attention is given to the design of the NC machines and production

tooling in order to reduce the time spent in both work and machine set up.

Tooling systems for NC are designed to eliminate operator error and maximize productive

machine hours. They do this in one or more of the following ways:

1. Using quick change tool holders

2. Automatic tool selection

3. Automatic tool Changer

4. Presetting of tool

5. Facilitating tool selection and tool changing through the numerical control program

While tooling for NC machines might appear to be specialized, the actual components and

principles involved have much in common with what would be considered proper practice for

conventional machine tools.

1. Tool Holders

Quick change tool holders are designed so that cutting tools can be readily positioned with

respect to the spindle axis of the machine. This requires that tolerances on length and/or

diameter be held on all tools used in the machine. Arbor type cutters such as face mills and

shell end mills are held in arbor type tool holders. Shank type mills are held in positive lock

holder. Drills, reamers and boring tools are held in a straight shank collet type holder. Taps are

held in a tension and compression collet type holders.

2. Automatic tool selection

Automatic tool selectors in NC make all the tool changes required to complete a predetermined

sequence of machining operations on a part.

There are two basic approaches to automatic tool selection:

When relatively small number of different tools is required, automatic tool selector is

the turret type. The turret is rotated under program control to bring the proper tool intoposition. The tools are held in preset tool holder adapters which are mounted into

turret spindles.


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An automatic tool changer and magazine of tools is frequently used in preference to the

turret approach, when the number of tools to be used is large. Each tool is inserted in a

common spindle as required. The tools which are mounted in uniform holders, are

automatically picked up, placed into the spindle and locked in place. When the

operations using that tool are completed it is returned to the tool storage magazine. Forchanging tools rapidly it is better to place tool in magazine or turret in the order in

which they will be used.

3. Automatic Tool Changer

For three axis machines which perform a wide variety of operations tool changes a

programmed into the tape for fully automatic selection and replacement.

The automatic tool change system may consist of following elements:

Rotary tool storage magazine for numerous tools.

Automatic tool changer to remove tool holders from the machine spindle and replace

them with tape programmed tools.

Basic tool holders adaptable to a multiplicity of cutting tool types and work

specifications.

Tool coding rings and system for selection of proper tools in accordance with tape

signals. In operation, the automatic tool change is accomplished in four steps:

By tape command (and from any location the magazine) the tool magazine rotates to

proper position to bring the pre-selected tool into place for particular operation. One

end of the tool change your arm then grasps the tool while the opposite end grasps the

tool to be replaced in the spindle.

The tool changer arm moves out away from the spindle removing one tool from the

magazine and other tool from the spindle


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AUTOMATIC TOOL CHANGERAn Automatic Tool Changer is equipment that reduces cycle times by automatically changing

tools between cuts. Automatic tool changers are differentiated by tool-to-tool time and thenumber of tools they can hold. CNC tool changers allow a machine to perform more than one

function without requiring an operator to change the tooling. A CNC tool changer can quickly

change the end effectors without the requirement of multiple robots. Tool changers can be a

manual tool changers or automatic tool changers. A CNC tool changer fulfills the requirement of

multiple tooling for a wide variety of machine tools.

Why Tool Changer is needed?

Tool changer is equipment which is used in CNC machines to reduce the cycle time. The term

applies to a wide variety of tooling, from indexable insert, single point tools to coded, preset

tool holders for use in automatic tool changers. It includes power-actuated, cross-slide tooling

and turret tool holders for single spindle chuckers, interchangeable-block boring tools. A

number of basic types of tool holders are available that accommodate most face mills, end

mills, drills, reamers, taps, boring tools, counterbores, countersinks, and spot facers. Arbor type

cutters such as face mills and shell end mills are held in an arbor type tool holders. Shank type

mills are held in positive lock holder. Drills, reamers and boring tools are held in a straight shank

collet type holder. Taps are held in a tension and compression collet type holders.

Types of automatic tool changer

There are mainly three kinds of tool changers available in market according to the toolmagazine arrangements provided.

1. Tool change system with gripper arm

2. Tool change system with chain magazine

3. Tool change system with disc magazine

1. Tool Change system with gripper Arm

In this system, there are mainly two elements

Disc with magazine

Gripper arm

In this system, a disc is provided with magazine, in which different types of tools are loaded. It

can hold maximum 32 tools. In magazines, all the tools which are required are fixed in the

magazines. The tool which is programmed in controller according to the program will

be indexed in front of the gripper arm and then the gripper arm grips the tool and performs the

operation. After completion of the operation by each tool, the gripper arm places the tool back

in to the magazine.


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Description of the gripper arm

The tool changer gripper arm consists of a central aluminum structure with terminal tool

grippers of hardened steel. Tool gripping and release are obtained by means of a spring-

operated mechanism actuated by the rotation of the arm. The latter, in turning, engages or

disengages the grippers from the tools when these are in exchange position.

2. Tool Change system with chain magazine

In this kind of system, a chain is

provided with magazines for tool

holding. This chain can hold

numerous tools so it is used in

heavy machineries. Starting from

32 it can hold more than 100

tools. These chain is indexed in

front of the head stock directly as

per the tool. In this kind of

system there is no arrangement

like gripper arm. The chain itself

is indexed and the machining is

done while keeping the tool in

the chain only.

Fig: Tool Change system with chain magazine


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3. Tool change system with Disc magazine

In this system, the tools are held in a

big disc. This disc is not similar to the

disc provided in gripper arm

mechanism. In this disc, there are

tool grippers provided separately for

each magazine these grippers holds

the tool and performs machining

operation as well.

This system disc can hold 32 to

maximum of 64 tools. These type of

tool changers are used in medium

capacity machineries.

Fig: Tool change with disc magazine


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CONCLUSION:

After the successful implementation of the automatic tool changer along with

tool a pre-setter, following will be some of the major advantages:

It would save 6-8 seconds of time per cycle, on an average, which is very

good in terms of time-reduction.

It can perform multiple operations in a single set up.

It can re-tool quickly in order to accommodate product designs that are

changing in timely response to market demands

It is able to replace quickly a worn out or broken part

REFERENCES:


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Reintjes, J. Francis (1991), Numerical Control: Making a

New Technology, Oxford University Press.

Design and Simulation of Microcontroller Based Automatic

Tool Changing System in CNC Machine, La Pyae Lynn,

Theingi and Win Khaing Moe.

Malloy, Robert A. (1994). Plastic Part Design for Injection

Molding. Munich Vienna New York.

Hanser.Todd, Robert H.; Allen, Dell K.; Alting, Leo

(1994). Manufacturing Processes Reference Guide. Industrial

Press, Inc.

automatic tool changer cnc

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