guest lecture lecture on advanced manufacturing processes prepared by prof. shinde vishal vasant...

Guest Lecture

On

Advanced Manufacturing Processes

Prepared By

Prof. Shinde Vishal Vasant

Assistant Professor

Dept. of Mechanical Engg.

NDMVP’S Karmaveer Baburao Thakare

College of Engg. Nashik

Contact No- 8928461713

E mail:- [email protected]

Website:- www.vishalshindeblog.wordpress.com

PROF.V.V.SHINDE NDMVP'S KBTCOE NASHIK 03/10/2016 1

mailto:[email protected]





Grinding Process

• Grinding is a material removal and surface generation

process used to shape and finish components made of

metals and other materials.

• The precision and surface finish obtained through grinding

can be up to ten times better than with either turning or

milling.

03/10/2016 PROF.V.V.SHINDE NDMVP'S KBTCOE NASHIK 2

Grinding

• Grinding is a surface finishing operation where very thin

layer of material is removed in the form of dust particles.

• Thickness of material removed is in range of 0.25 to 0.50

mm.

• Tool used is a abrasive wheel.


Types Of Grinding Machine

• There are many forms of grinding, but the four major industrial grinding

• Surface grinding

• Cylindrical grinding

• Centerless grinding

• Internal grinding

• Electrochemical grinding

• Belt grinder

• Bench grinder

• Tool and cutter grinder

• Gear grinder


Major Advantages And Applications Of Grinding

Advantages

• Dimensional accuracy

• Good surface finish

• Good form and locational accuracy applicable to both hardened and

unhardened material

Applications

• Surface finishing

• Slitting and parting

• De-scaling , De-burring

• Stock removal (abrasive milling) finishing of flat as well as cylindrical

surface

• Grinding of tools and cutters and re-sharpening of the same.


Grinding Wheel Materials

• Most abrasives used in industry are synthetic. Aluminum oxide is used in three quarters of all grinding operations, and is primarily used to grind ferrous metals.

• Next is silicon carbide, which is used for grinding softer, non-ferrous metals and high density materials, such as cemented carbide or ceramics.

• Superabrasives, namely cubic boron nitride or "CBN" and diamond, are used in about five percent of grinding. Hard ferrous materials are ground with "CBN", while non-ferrous materials and non-metals are best ground with diamond.


Standard Shapes Of Grinding Wheels

• Straight wheel

• Cylinder

• Tapered

• Recessed one side

• Straight cup

• Recessed both sides

• Flaring cup

• Dish

• Saucer

• Mounted wheels


Selection Of Grinding Wheel

For grinding a job the right grinding wheel is to be selected. The selection of a grinding wheel will depend on the following factors.

• Material to be ground

• Amount of stock to be removed

• Finish required

• Area of contact

• Wheel speed

• Work speed

• Personal factor

• Method of cooling


Standard Marking System for Aluminum-Oxide

and Silicon-Carbide Bonded Abrasives


Standard Marking System for Cubic-Boron-

Nitride and Diamond Bonded Abrasives


Grinding Fluid The Grinding fluid serves three main functions :

• Reduces Wheel wear.

• Cools the w/p.

• Flushes away the chips.


Grinding Process

Grinding is an abrasive machining process that uses

a grinding wheel as the cutting tool.


Surface Grinding

Surface grinding uses a rotating abrasive wheel to remove

material, creating a flat surface.


Surface Grinding

• It is machine basically used to grind flat surface.

• Job is mounted to a table which moves

longitudinally as well as in transverse direction.

• Manual feed or power feed.

• Work piece is clamped to the table by operating

magnetic chuck.

• Required grade of grinding tool is fixed to spindle.

• Grinding operation is carried out be operating both

table traverse wheel and vertical feed hand wheel.


Types Of Surface Grinding Machine

Basically there are four different types of surface grinding

machines characterised by the movement of their tables and

the orientation of grinding wheel spindles as follows:

• Horizontal spindle and reciprocating table • Vertical spindle and reciprocating table • Horizontal spindle and rotary table • Vertical spindle and rotary table


Surface grinding

• In surface grinding, the spindle position is either horizontal or

vertical, and the relative motion of the work piece is achieved either

by reciprocating the work piece past the wheel or by rotating it. The

possible combinations of spindle orientations and work piece motions

yield four types of surface grinding processes illustrated in the figure


Horizontal And Vertical Grinding Machines

• This machine may be similar to a milling machine used mainly to grind flat surface.

However, some types of surface grinders are also capable of producing contour

surface with formed grinding wheel.

A: rotation of grinding wheel B: reciprocation of worktable C: transverse feed D: down feed 03/10/2016 PROF.V.V.SHINDE NDMVP'S KBTCOE NASHIK 19

Cylindrical Grinding

• It is a process of grinding curved surfaces.

• Surface may be straight or tapered.

• Work piece is mounted on two centers, one is tailstock

centre and the other is headstock centre.

• Head stock center may or may not revolve.



• In this operation, the external or internal cylindrical surface of a work piece

are ground. In external cylindrical grinding (also center-type grinding) the

work piece rotates and reciprocates along its axis, although for large and

long work parts the grinding wheel reciprocates.

• In internal cylindrical grinding, a small wheel grinds the inside diameter of

the part. The work piece is held in a rotating chuck in the headstock and the

wheel rotates at very high rotational speed. In this operation, the work piece

rotates and the grinding wheel reciprocates.


External Cylindrical Grinding


Internal Cylindrical Grinding

Internal grinding is used to grind the internal diameter of the workpiece.

Tapered holes can be ground with the use of internal grinders that can

swivel on the horizontal.


Plunge Cut Grinding

Infeed (Plunge) Grinding is used

to grind work pieces which have

projections or shoulders,

multiple diameters or other

irregular shapes which preclude

the use of through feed grinding.

For example :- Grinding of crank

shaft.


Centerless Grinding Machine

• It is used to grind curved surface work piece which are long and slender.

• Work piece rests on a work-rest blade and is backed by a second wheel called as regulating wheel.

• Grinding wheel pushes the work piece down the work-rest blade against the regulating wheel.

• Center less grinding differs from centered grinding operations in that no spindle or fixture is used to locate and secure the work piece.

• The work piece is secured between two rotary grinding wheels, and the speed of their rotation relative to each other determines the rate at which material is removed from the work piece.


Center less Grinding


Thread Grinding

Figure - Thread grinding by (a) traverse and (b) plunge grinding.


Electrochemical Grinding

• The wheels and work piece are electrically conductive.

• Wheels used last for many grindings - typically 90% of the

metal is removed by electrolysis and 10% from the abrasive

grinding wheel.

• Capable of producing smooth edges without the burrs caused

by mechanical grinding.

• Does not produce appreciable heat that would distort work

piece.

• Decomposes the work piece and deposits them into the

electrolyte solution. The most common electrolytes are sodium

chloride and sodium nitrate.


Applications

• Grinding turbine blades

• Grinding honeycomb metals for aerospace

application

• Sharpening hypodermic needles

• Machining carbide cutting-tool inserts

• ECG is used to remove surface defects from parts

where excessive material removal and residual

stresses are undesired, such as re-profiling

locomotive gears


Electrochemical Grinding


Specification Of Grinding Wheel

i. Abrasives

ii. Bond

iii. Grit/grain size

iv. Grade

v. Structure of wheels


Specification of Grinding wheel

• Specification of a grinding wheel ordinarily means compositional

specification. Conventional abrasive grinding wheels are specified

encompassing the following parameters.

– The type of grit material

– The grit size

– The bond strength of the wheel, commonly known as wheel

hardness

– The structure of the wheel denoting the porosity i.e. the amount

of inter grit spacing

– The type of bond material

– other than these parameters, the wheel manufacturer may add

their own identification code prefixing or suffixing (or both) the

standard code.


Dressing Of Grinding Wheel

• When the sharpness of grinding wheel becomes dull

because of glazing and loading, dulled grains and chips are

removed (crushed or fallen) with a proper dressing tool to

make sharp cutting edges and simultaneously, make

recesses for chips by properly extruding to grain cutting

edges. Thus, these operations are for the dressing.

• Dressing is the process of breaking away the glazed

surface so that sharp particles are again presented to the

work.


Grinding-Wheel Dressing

Figure (a) Forms of grinding-wheel dressing. (b) Shaping the grinding face of a

wheel by dressing it with computer control. Note that the diamond dressing tool is

normal to the surface at point of contact with the wheel. 03/10/2016 PROF.V.V.SHINDE NDMVP'S KBTCOE NASHIK 37

Truing And Dressing Of Grinding Wheel

• Truing is the act of regenerating the required geometry on the grinding

wheel, whether the geometry is a special form or flat profile. Therefore,

truing produces the macro-geometry of the grinding wheel.

• Truing and dressing are commonly combined into one operation for

conventional abrasive grinding wheels, but are usually two distinctly

separate operation for super abrasive wheel.


Difference Between Truing And Dressing


Balancing Of Grinding Wheel

• Due to high rpms, unbalanced grinding wheels may have

negative effects both on quality and productivity.

• It is essential to control the vibrations induced in the

machine as an effect of the imbalance of mechanical

parts and the rotating grinding wheel.

• To enable the full potential of modern tool grinding

machines and to produce efficiently according to today`s

standards, it is absolutely essential to use balanced tools.


Safety Precautions

• Wear goggles for all grinding machine operations.

• Check grinding wheels for cracks before mounting.

• Never operate grinding wheels at speeds in excess of the recommended speed.

• Never adjust the work piece or work mounting devices when the machine is operating.

• Do not exceed recommended depth of cut for the grinding wheel or machine.

• Remove work piece from grinding wheel before turning machine off.

• Use proper wheel guards on all grinding machines.

• On bench grinders, adjust tool rest 1/16 to 1/8 inch from the wheel.


Types Of Super Finishing Processes

Honing.

Burnishing.

Polishing Buffing.

Lapping.


Honing

• Honing is a finishing process, in which a tool called hone carries

out a combined rotary and reciprocating motion while the work

piece does not perform any working motion. Most honing is done

on internal cylindrical surface, such as automobile cylindrical

walls.

• Honing is an abrasive machining process that produces

a precision surface on a metal work piece by scrubbing

an abrasive stone against it along a controlled path.

• Honing uses a special tool, called a honing stone or a hone, to

achieve a precision surface. The hone is composed of abrasive

grains that are bound together with an adhesive. Generally,

honing grains are irregularly shaped and about 10 to 50

micrometers in diameter (300 to 1,500 mesh grit). Smaller grain

sizes produce a smoother surface on the workpiece.


Setup Work piece

(Pipe)

Coolant

Honning

Tool or

Hone

Machine

Bed


Honning Tool


Advantages And Disadvantages

ADVANTAGES

• Low cost simple fixturing

• Accuracy in thin walled parts

• Accuracy in long bores

• Honing maintains the original bore

centreline

• Bores are corrected with least

possible amount of material

removal

• Material removal in all materials

regardless of hardness.

• Any degree of surface finish in a

part.

• High stock removal rates ( up to 12

times faster than internal grinding)

DISADVANTAGES

• Honing is a slow process.

• Horizontal honing may

create oval holes unless the

work is rotated or supported.

• If the workpiece is thin,

even hand pressure may

cause a slightly oval hole.


Applications

• finishing of cylinders for internal combustion engines

• air bearing spindles

• Gears


Super finishing /Micro honing

• Super finishing is a micro finishing process that produces a controlled

surface condition on parts which is not obtainable by any other method. The

operation which is also called ‘micro stoning’ consist of scrubbing a stone

against a surface to produce a fine quality metal finish.

• The process consists of removing chatter marks and fragmented or smear

metal from the surface of dimensionally finished parts.

• As much as 0.03 to 0.05 mm of stock can be efficiently removed with some

production applications, the process becomes most economical if the metal

removal is limited to 0.005 mm


Super finishing

Figure:- Schematic illustrations of the super finishing process for a cylindrical part. (a) Cylindrical mircohoning, (b) Centerless microhoning.


Lapping

• In lapping, instead of a bonded abrasive tool, oil-based fluid suspension

of very small free abrasive grains (aluminum oxide and silicon carbide,

with typical grit sizes between 300 and 600) called a lapping compound

is applied between the work piece and the lapping tool.

• The lapping tool is called a lap, which is made of soft materials like

copper, lead or wood. The lap has the reverse of the desired shape of the

work part. To accomplish the process, the lap is pressed against the work

and moved back and forth over the surface.

• Lapping is sometimes performed by hand, but lapping machines

accomplish the process with greater consistency and efficiency.


Lapping

Figure (a) Schematic illustration of the lapping process. (b) Production lapping on

flat surfaces.(c) Production lapping on cylindrical surfaces.


Advantages:-

1.Increase wear life of part. 2.Improve accuracy and surface finish. 3.Improve surface flatness. 4.Provide better seals and eliminate need for gaskets.

Applications:- Lapping is used to produce optical lenses, metallic

bearing surfaces, gauges, and other parts requiring very good finishes and extreme accuracy.


Lapped Objects


Burnishing

• Burnishing is the plastic deformation of a surface

due to sliding contact with another object. Visually,

burnishing smears the texture of a rough surface and

makes it shinier. Burnishing may occur on any sliding

surface if the contact stress locally exceeds the yield

strength of the material.

• Burnishing is a Super-finishing process.


SETUP


Advantages

• Mirror Finish in One Pass, Accurate Sizing, Close

Tolerances, Eliminates Lapping & Honing

• Improved Metallurgical Properties - Work Hardened

Surface, Increase in fatigue strength,

• No Additional Machine Investment - attachable to

any Standard Machine Tool Already Present in the

Shop

• Long Tool Life No Operator Skill Required Low

Torque & Power Requirements Maximum Parts

Interchangeability


Applications

• Bright burnishing tools are being used in

sectors like Automobile, Aircraft, Defense,

Spacecraft, Railways, Textile, Machine Tool,

Motors and Pump Industry, Hydraulic and

Pneumatic Farm Equipment, Home

Appliances etc., and areas where close

tolerance and superior surface finish is

required.


Polishing

• Polishing is a finishing operation to improve the surface

finish by means of a polishing wheel made of fabrics or

leather and rotating at high speed. The abrasive grains are

glued to the outside periphery of the polishing wheel.

• Polishing operations are often accomplished manually.

• Polishing is the process of creating a smooth and shiny

surface by rubbing it or using a chemical action, leaving a

surface with a significant specular reflection

• Polishing may be used to enhance and restore the looks of

certain metal parts or object on cars and other

vehicles, handrails, cookware, kitchenware, and

architectural metal.


Setup


Advantages & Disadvantages

ADVANTAGES

• Gives a natural appearance with a

high gloss and sheen.

• Produces a relatively durable finish.

• Never requires stripping.

• Can be applied with a standard low

speed weighted floor machine.

• If oxalic acid or oxalate is included

in the powder, it will remove fine to

medium scratches.

• Only done periodically, not daily or

weekly.

• Compounds composed of aluminum

oxide will not etch floor.

DISADVANTAGES

• A messy process, requiring

additional work to clean up.

• If oxalic acid is included in the

powder, it can cause etching or

blistering of marble and

limestone depending on the skill

of the person using it.

• Requires equipment (i.e., a floor

machine, wet vac, mop, mop

bucket, etc.).


Buffing

• Buffing is a finishing operation similar to polishing, in which

abrasive grains are not glued to the wheel but are contained in a

buffing compound that is pressed into the outside surface of the

buffing wheel while it rotates. As in polishing, the abrasive

particles must be periodically replenished.

• As in polishing, buffing is usually done manually, although

machines have been designed to perform the process

automatically.

• Buffing wheels are made of discs of linen, cotton, broad cloth

and canvas

• Buffing is also used to manufacture light reflectors.


Buffing


Summery of Abrasive machining processes


guest lecture lecture on advanced manufacturing processes prepared by prof. shinde vishal vasant...

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