1 Teaching Innovation - Entrepreneurial - Global The Centre for Technology enabled Teaching & Learning MGI, INDIA DTEL DTEL (Department for Technology Enhanced Learning)

DEPARTMENT OF MECHANICAL ENGINEERING V –SEMESTER 2 UNIT NO.6 SUPERFINISHING PROCESSESS

CHAPTER 1:- SYLLABUSDTEL Lapping,Honning,Buffing,Electroplating 2 Advantages and Disadvantages of the Processes 3 LASER in Surface Modification 4 3. Principle of Super finishing Processes 1

CHAPTER-1 SPECIFIC OBJECTIVE / COURSE OUTCOMEDTEL Understand the different Super finishing Process 1 There practical application 2 4 The student will be able to: How it can be used in Surface Modification 3

DTEL INTRODUCTION 5 LECTURE 1:- Why Super finishing is required? The Defects Are Chatter Marks, Helical Type Scratches, Surface Cracks, Smear Metal Etc. Are Responsible For Wearing Out The Parts. In Certain Circumstances High Surface Quality Is Required. Hence For Removing Grinding Defects, To Obtain Desired Surface Finish And To Improve The Geometrical Shape Finishing Processes Are Used. It Includes Honing, Lapping, And Super Finishing. Super Finishing :-

DTEL SUPER FINISHING 6 LECTURE 1:- FINISHING METHODS :- With Material Removal – Generative Methods. Fine Machining, Honing, Super Finishing. Lapping, Buffing, Electroplating. Material Removal – Forming Method. Glazing, Blasting, Tumbling, Polishing.

DTEL TYPES 7 LECTURE 1:- TYPES OF SUPER FINISHING PROCESS :- Honing. Lapping. Hand Lapping. Machine Lapping. Buffing. Electroplating.

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DTEL LAPPING 9 LECTURE 2:- LAPPING :- Lapping is a machining operation, in which two surfaces are rubbed together with an abrasive between them, by hand movement or by way of a machine. This can take two forms. The first type of lapping (traditionally called grinding), typically involves rubbing a brittle material such as glass against a surface such as iron or glass itself (also known as the "lap" or grinding tool) with an abrasive such as aluminum oxide, jeweler's rouge, optician's rouge, emery, silicon carbide, diamond, etc., in between them. This produces microscopic conchoidal fractures as the abrasive rolls about between the two surfaces and removes material from both.

DTEL LAPPING 10 LECTURE 2:- The other form of lapping involves a softer material such as pitch or a ceramic for the lap, which is "charged" with the abrasive. The lap is then used to cut a harder material the work piece. Fig:- 6.2 Lapping

DTEL HAND LAPPING 11 LECTURE 2:- HAND LAPPING :- In this method lapping compound is spread on cast iron plate and work piece is moved manually on it on a path like English figure – 8. Fig:- 6.2 Hand Lapping

DTEL Machine lapping 12 LECTURE 2:- Machine lapping :- In this method a rotating table is used in place of the plate. Again the work piece to be lapped is given rotary by a cage and rotated on the surface of the table. Rotating lap is used above & below the work piece to produce parallel surfaces. Fig:- 6.3 Machine Lapping

DTEL ADVANTAGES 13 LECTURE 2:- Advantages :- Economical. Labour saving. High rate of Production. High operational efficiency. Less down time of engine. Precision. Longer life of valves. Consistency in lapping & quality of work. Skilled labor not required.

DTEL APPLICATION 14 LECTURE 2 :- Application Of Lapping :- Machine lapping process is carried out for, Gauge Blocks, Piston Pin, Ball Bearings, Engine Valves. Fig:- 6.4 Lapping

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DTEL HONING 16 LECTURE 3 :- HONING :- Hole made by boring is obtained to required dimension and finishing by honing. In this process abrasive stone is used. The dimension to an accuracy of mm can be obtained by honing process. Honing is wet cutting process. 6 to 8 honing sticks are held together and metal is removed by rotating or reciprocating the holder. Honing tool is rotated at a speed of m/s and reciprocates at a speed of 0.2 – 0.5 m/s Fig:- 6.5 Honing

DTEL HONNING 17 LECTURE 3 :- HONING STONES :- Abrasive particles must withstand the cutting pressure for metal removal. Bond must be strong enough to hold the grit. Not so hard as to rub the bore and retard cutting. Honing stones are made from common abrasive and bonding materials, often impregnated with sulphur, resin, or wax to improve cutting action and tool life.

DTEL GRIT SIZE 18 LECTURE 3 :- Size ranges from Most widely used size : Selection depends on, – Material removal rate – Required finish

DTEL ADVANTAGES 19 LECTURE 3 :- Advantages:- Preferred for large quantities when tolerances are extremely close. Work pieces need not be fixtured. This reduces tooling investment. Permits immediate changeover from one job to another. End to end reversal of work pieces. Change of stroke length for required accuracy. Necessary corrections can be made as stroking proceeds. Employed as final touch.

DTEL APPLICATION 20 LECTURE 3 :- Application :- Honing Of Automobile Cylinder. Honing Is Also Used For Repair Work. Fig:- 6.6 Automobile Cylinder

DTEL BUFFING 21 LECTURE 4 :- Buffing is similar to polishing in appearance, but its function is different. Buffing is used to provide attractive surfaces with high luster. Buffing is like a polishing operation in which the workpiece is brought in contact with a revolving cloth buffing wheel that usually has been charged with a very find abrasive. Buffing wheels are made of discs of liners, cotton, broad cloth and canvas. These are made more or less firm by the amount of stitching used to fasten the layers of the cloth together. Buffing tools are enough flexible to polish upto interior of intricate cavities. The buffing tools are named as BUFFING ROUGES. The workpiece are held in fixtures on a suitable rotating worktable so as to move the buffing wheels.

DTEL BUFFING 22 LECTURE 4 :- Fig:- 6.7 Buffing

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DTEL ELECTROPLATING 24 LECTURE 5:- Electroplating :-  Electroplating is used to change the surface properties of a metal part by adding a metal coating by the action of electric current; it is also called "electrodeposition,".  The object to be coated receives a negative charge and is immersed into a solution that contains a salt of the metal to be deposited.  The metallic ions of the salt carry a positive charge and are attracted to the object. Surface pretreatment by chemical or mechanical means is important for electroplating, as the successful adhesion of the surface coating depends on removing contaminants and films from the substrate.  In addition, the geometric shape and contour of the object affects the thickness of the deposited layer.

DTEL ELECTROPLATING 25 LECTURE 5:- Electroplating :-  Objects with sharp corners and features will have thicker deposits on the outside corners and thinner ones in the recessed areas, because the current flows more densely to prominent points than to less accessible areas.  This characteristic of electroplating limits applications with uneven surfaces or that have depressions or hidden holes.  Some metals used in electroplating are aluminum, brass, bronze, cadmium, copper, chromium, iron, lead, nickel, tin, and zinc, as well as precious metals such as gold, platinum, and silver.  Different types of coatings can be achieved through control of parameters such as voltage, amperage, temperature, residence times, and purity of the bath solutions.

DTEL APPLICATIONS 26 LECTURE 5:- APPLICATIONS:-  It is an inexpensive and simple method.  It is used in all aspects of electronics, optics.  It is used in the automobile industry.  Chrome plating is used to enhance the corrosion resistance of metal parts.  Jewelry, electrical and electronic parts, household Goods.  Hydraulics, mold making, vehicles, shafts, and bearings.  Extreme corrosion resistance combined with high thermal stress, e.g., car exhausts, engine elements, and electronics parts.

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DTEL LASER in Surface Modification 28 LECTURE 6:- Laser Surface Modification :-  The laser has some unique properties for surface heating.  The electromagnetic radiation of a laser beam is absorbed within the top atomic layers for opaque materials, such as metals.  There are no associated hot gas jets, eddy currents or even radiation spillage outside the optically defined beam area.  In fact the applied energy can be placed precisely on the surface only where it is needed.

DTEL LASER SURFACE MODIFICATION 29 LECTURE 6:- Surface Modification :-  Surface heating for transformation hardening or annealing.  Surface melting for homogenization, microstructure refinement generation of rapid solidification structures and surface sealing.  Surface alloying for improvement of corrosion, wear or appearance.  Surface cladding for wear, corrosion or physical property manipulation such as melting point or thermal conductivity.  Surface texturing for improved paint appearance.  Plating by Laser Chemical Vapour Deposition (LCVD), Laser Physical Vapour Deposition (LPVD).

DTEL LASER HEAT TREATMENT 30 LECTURE 6 :- Laser Heat Treatment :-  The initial goal of laser heat treatment was selective surface hardening for wear reduction.  Now it is also used to change metallurgical and mechanical properties.  There are many competing processes in the large area surface heat treatment.  The laser usually competitive due to lack of distortion and high productivity.

DTEL LASER SURFACE MODIFICATION 31 LECTURE 6 :- Advantages :-  Chemical cleanliness.  Controlled thermal penetration and therefore distortion.  Controlled thermal profile and therefore shape and location of heat affected region can be predicted.  Little-to-no finish machining is required.  Remote non contact processing is usually possible.  Relatively easy to automate.

DTEL 32 LECTURE 6 :- Laser Surface Applications :-  Hardness increase.  Strength increase.  Reduced friction.  Wear reduction.  Increase in fatigue life.  Surface carbide creation.  Creation of unique geometrical wear patterns.  Tempering. LASER SURFACE MODIFICATION

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