Study of Machining Processes & Inspection Techniques

A Project Report submitted to

 

MAHARISHI DAYANAND UNIVERSITY 

by

 

SHAILENDER SAHARAN

SPUN MICRO PROCESSING PVT. LTD. Spun Micro Processing Pvt. Ltd. was incorporated in 1991 for catering to complex machining

needs of automotive products. Taken over by a new management in the year 2000 Led by professionals with vast experience in top positions in the automotive field Three major multifold expansions in the last decade Direct on-line supply to renowned OEMs and Tier-1 companies Over 60% exports

Parts Manufactured:- Steering Shafts 2 Wheeler components and sub-assemblies:- Crank balancers, gear kick start, under-bracket and various sub

assemblies. Casting based products:- Case differential, clutch hubs, drive pulley etc.

Company Profile

Forging based products :-

Multiple products based on complex forging techniques and accurate machining. Gears and geared shafts :-

High precision gears- Helical/Spur and geared shafts from 100gms to 50kgs duly case hardened.

Bar and Aluminium products :-

Precision machined components like camshafts, yolks, insert etc.

Clients:- Maruti Suzuki Escorts Denso Sona Steering Valeo Wabco

Machining Processes means manufacturing a part using various machines and tools for using it making a product which is made by joining a number of parts. Machines which are mainly used for making parts are:- Drilling Milling Shapping Broaching Grinding Hobbing Shaving Rolling Surface Finishing Threading etc.

Introduction

1. CNC Machine:-CNC stands for computerized numerical control & it is used for machining and various machining operations are carried on cnc machine such as drilling , boring, milling, threading etc CNC machines can be used

continuously for long intervals

and only need to be switched

off for occasional maintenance. CNC machines can produce

several products, all similar and

dead accurate Less skilled/trained persons

can operate the CNC machines.

Machining Processes

2. VMC Machine:- A vertical machining center (VMC) is a machining center with its spindle in a vertical orientation. High-end VMCs are high-precision machines often used for tight-tolerance milling, such as fine die and mold work. Low-cost vertical machining centers are among the most basic CNC machine tools.

Operations which are carried on vertical machining center (VMC) are:-

Chamfer Drilling Tapping etc.

VMC machine is used to perform a

number of operations on a part such

as drilling, chamfering and it changes

the tool by rotory motion and perform

machining vertically.

3. Gear Hobbing:- Gear Hobbing is a process in which teeth of gear cut by hobbing process and both spur and helical gear can be cut using hobbing process . In gear hobbing , cutter moves in rotary motion and it cut teeth same as of its diameter. Gear Hobbing machine can be automatic or manual, on manual machine we have to change the speed , no. of teeth, feed etc.

Hobbing is used to make following types of finished goods:- Cycloid gears Helical gears Involute gears Ratchets Splines Sprockets Spur gears Worm gears

Gear Shapping:-Gear shaping is a machining process for creating teeth on a gear using a cutter. Gear shaping is a convenient and versatile method of gear cutting. It involves continuous, same-plane rotational cutting of gear. The types of cutters used for gear shaping can be grouped into four categories: disk, hub, shank, and helical cutters. The cutters are essentially gears that are used to form the teeth. This method of gear cutting is based on the principle that any two gears will mesh if they are of the same pitch, proper helix angle, and proper tooth depth and thickness. The machine used for gear shaping generally consists of a base, column spindle, and an arbor. The gear cutter is mounted on the spindle, and the gear blank is mounted on the arbor. The cutter reciprocates up and down while the workpiece is gradually fed into the cutter. At the end of each cutting rotation, the spindle is retracted slightly to discourage any more cutting into the new cut teeth of the gear. The process of gear shaping uses a toothed disk cutter which reciprocates in axial rotations.

4. Milling Process:- Milling Process is used to cut material using a cutter and material can be cut according to our requirement. Milling is the machining process of using rotary cutters to remove material from a workpiece advancing (or feeding) in a direction at an angle with the axis of the tool.It covers a wide variety of different operations and machines, on scales from small individual parts to large, heavy-duty gang milling operations. It is one of the most commonly used processes in industry and machine shops today for machining parts to precise sizes and shapes.

5. Tapping Process:-Tapping may either be achieved by hand tapping by using a set of taps first tap, second tap & final (finish) tap or using a machine to do the tapping, such as a lathe, radial drilling machine, bench type drill machine, pillar type drill machine, vertical milling machines, HMCs, VMCs. Machine tapping is faster, and generally more accurate because human error is eliminated. Final tapping is achieved with single tap.Although in general machine tapping is more accurate, tapping operations have traditionally been very tricky to execute due to frequent tap breakage and inconsistent quality of tapping.

6. Gear Rolling Process:- Gear rolling machine is used to cut teeth on gear. Part on which teeth to be cut is placed between two rollers which apply compressive force on part and give shape of teeths by using rolling action.

Inspection is most important process in an organization and Quality related in-process inspection/verification is an essential part of quality control in manufacturing .Inspection in manufacturing includes measuring, examining, testing, or gauging one or more characteristics of a product or process and comparing the results with specified requirements to determine whether is the requirements are met for each characteristic.

Machines used For Inspection:- Co-ordinate Measuring Machine (CMM) Counter Graphing Roughing Tester Profile Projector Lead & profile machine Gear Rolling Tester Hardness Tester

Inspection Techniques

1. Surface Roughness Tester:- Surface roughness often shortened to roughness, is a component of surface texture. It is quantified by the deviations in the direction of the normal vector of a real surface from its ideal form. If these deviations are large, the surface is rough; if they are small, the surface is smooth. Roughness is typically considered to be the high-frequency, short-wavelength component of a measured surface (see surface metrology). However, in practice it is often necessary to know both the amplitude and frequency to ensure that a surface is fit for a purpose.Roughness plays an important role in determining how a real object will interact with its environment. Rough surfaces usually wear more quickly and have higher friction coefficients than smooth surfaces (see tribology).

2. Gear Rolling Tester:-Composite testing of gears

consists in measuring the

variation in centre distance

when a gear is rolled in tight

mesh (double flank contact)

with a specified or master

gear. In composite gear

checking two types of checkings are made :(a) Total Composite

Variation, (6) Tooth to Tooth Composite Variation.Total composite variation is the centre distance variation in one complete revolution of the gear being inspected ; whereas tooth to tooth composite variation is the centre distance variation as the gear is rotated through any increment of 3607JV.

3. CMM:- Concerned with the measurement of the actual shape and dimensions of an object and

comparing these with the desired shape and dimensions specified on a part drawing Coordinate measuring machine (CMM) –

an electromechanical system designed to perform coordinate metrology

A CMM consists of a contact probe that can be positioned in 3-D space relative to workpart features, and the x-y-z coordinates can be displayed and recorded to obtain dimensional data about geometryProbe head and probe to contact workpart surfaces

Mechanical structure that provides motion of the probe in x-y-z axes, and displacement transducers to measure the coordinate values of each axis

Optional components (on many CMMs): Drive system and control unit to move each axis

Digital computer system with application software

4. Profile Projector Machine:-A profile projector is also referred to as an

optical comparator, or even known as a

shadowgraph, a profile projector is an optical

instrument utilized for measuring. It is a

valuable item in a small parts machine shop

or manufacturing line for the quality control

assessment staff. The projector magnifies the

profile of the specimen, and shows this on the

built-in projection screen. From this screen there

is usually a grid that could be rotated 360 degrees

therefore the X-Y axis of the screen could be aligned

correctly using a straight edge of the machined part

to analyze or measure.This projection screen shows the profile of the sample and is zoomed for better ease of computing linear dimensions.

5. Contour Graphing:-Contour Graphing is Used for the inspection of very small portions of a part , it measures corner chamfer, flatness, wedge,and etc.

Contour Graphing is used for measuring:-1. Chamfer2. Roughness3. Small round profile4. Flatness etc.

1. Vernier Calliper:-

The vernier, dial, and digital calipers give a direct reading of the distance measured with high accuracy and precision. They are functionally identical, with different ways of reading the result. These calipers comprise a calibrated scale with a fixed jaw, and another jaw, with a pointer, that slides along the scale. The distance between the jaws is then read in different ways for the three types

Inspection Instruments

2. Height Gauge:-A height gauge is a measuring device used

either for determining the height of objects

, or for marking of items to be worked on

.These measuring tools are used in metal

working or metrology to either set or measure

vertical distances; the pointer is sharpened

to allow it to act as a scriber and assist in

marking out work pieces.Devices similar

in concept, with lower resolutions, are

used in health care settings (health clinics,

surgeries) to find the height of people,

in which context they are called stadiometers.

3. Micrometer:-A micrometer sometimes known as a

micrometer screw gauge, is a device

incorporating a calibrated screw

widely used for precise measurement

of components in mechanical engineering

and machining as well as most

mechanical trades, along with other

metrological instruments such as dial, vernier

and digital calipers. Micrometers are usually,

but not always, in the form of calipers

(opposing ends joined by a frame), which

is why micrometer caliper is another

common name.

4. Go & NO Go Gauge:-A Go-No gauge (or Go/no go) refers to an inspection tool used to check a workpiece against its allowed tolerances. Its name derives from its use: the gauge has two tests; the check involves the workpiece having to pass one test (Go) and fail the other (No Go).It is an integral part of the quality process that is used in the manufacturing industry to ensure interchangeability of parts between processes, or even between different manufacturers.

A Go NoGo gauge is a measuring tool that does not return a size in the conventional sense, but instead returns a state. The state is either acceptable (the part is within tolerance and may be used) or it is unacceptable (and must be rejected).They are well suited for use in the production area of the factory as they require little skill or interpretation to use effectively and have few, if any, moving parts to be damaged in the often hostile production environment.