Milling & grinding machines SHARANABASAPPA V Bhurke ASST. PROFESSOR Dept. of mechanical Engg. DBIT-BENGALURU

CONTENTS Milling Milling Machines Milling Operations Specifications of Milling Machine Grinding Abrasives & Bonding Materials Grinding Machines

MILLING Milling: is a metal cutting operation in which the excess material from the work piece is removed by rotating multipoint cutting tool called milling cutter. Milling machine: is a power operated machine tool in which work piece mounted on a moving table is machined to various shapes when moved under a slow revolving serrated cutter.

PRINCIPLE OF MILLING

COMPARISON BETWEEN UP MILLING & DOWN MILLING SL. NO. UP MILLING (CONVENTIONAL MILLING) DOWN MILLING (CLIMB MILLING) 01 Work piece fed in the opposite direction that of the cutter. Work piece fed in the same direction that of the cutter. 02 Chips are progressively thicker. Chips are progressively thinner. 03 Strong clamping is required since the cutting force is directed upwards & tends to lift the work piece. Strong clamping is not required since the cutting force is directed downwards & keep the work piece pressed to the table. 04 Gives poor surface finish, since chips gets accumulated at the cutting zone. Gives good surface finish, since the chips are thrown away during cutting. 05 Used for hard materials. Used for soft materials and finishing operations.

CLASSIFICATION OF MILLING MACHINES 1. Column and knee milling machines a. Plain column & knee type milling machine - Horizontal spindle type - Vertical spindle type 2. Bed type milling machine 3. Planer type milling machine 4. Special purpose milling machine a. Tracer controlled milling machine b. Thread milling machine c. CNC milling machine

HORIZONTAL MILLING MACHINE MAJOR PARTS : BASE COLUMN SPINDLE OVERARM KNEE SADDLE WORKTABLE FIG. HORIZONTAL MILLING MACHINE

VERTICAL MILLING MACHINE MAJOR PARTS : BASE COLUMN SPINDLE SPINDLE HEAD KNEE SADDLE WORKTABLE FIG. VERTICAL MILLING MACHINE

DIFFERENCES BETWEEN HORIZONTAL & VERTICAL MILLING MACHINES SL. NO. HORIZONTAL MILLING MACHINE VERTICAL MILLING MACHINE 01 Spindle is horizontal & parallel to the worktable. Spindle is vertical & perpendicular to the worktable. 02 Cutter cannot be moved up & down. Cutter can be moved up & down. 03 Cutter is mounted on the arbor. Cutter is directly mounted on the spindle. 04 Spindle cannot be tilted. Spindle can be tilted for angular cutting. 05 Operations such as plain milling, gear cutting, form milling, straddle milling, gang milling etc., can be performed. Operations such as slot milling, T-slot milling, angular milling, flat milling etc., can be performed and also drilling, boring and reaming can be carried out.

MILLING OPERATIONS Plain or slab milling Face milling End milling Slot milling Angular milling Form milling Straddle milling Gang milling Slitting or saw milling Gear cutting

PLAIN/SURFACE/ SLAB MILLING Plain Milling: Process to get the flat surface on the work piece in which the cutter axis and work piece axis are parallel. Cutter: Plain/ Slab milling cutter. Machine: Horizontal Milling m/c. FIG. PLAIN MILLING

FACE MILLING Face Milling: Operation carried out for producing a flat surface, which is perpendicular to the axis of rotating cutter. Cutter: Face milling cutter. Machine: Vertical Milling Machine FIG. FACE MILLING

END MILLING End Milling: Operation performed for producing flat surfaces, slots, grooves or finishing the edges of the work piece. Cutter: End milling cutter. Machine: Vertical Milling Machine FIG. END MILLING

SLOT MILLING SLOT Milling: Operation of producing slots like T-slots, plain slots, dovetail slots etc., Cutter: End milling cutter, T-slot cutter, dovetail cutter or side milling cutter Machine: Vertical Milling Machine FIG. T-SLOT MILLING FIG. DOVE TAIL SLOT MILLING

ANGULAR MILLING Angular Milling: Operation of producing all types of angular cuts like V-notches and grooves, serrations and angular surfaces. Cutter: Double angle cutter. Machine: Horizontal Milling Machine FIG. ANGULAR MILLING

FORM MILLING End Milling: Operation of producing all types of angular cuts like V-notches and grooves, serrations and angular surfaces. Cutter: Double angle cutter. Machine: Horizontal Milling Machine FIG. FORM MILLING

STRADDLE MILLING Straddle Milling: Operation of machining two parallel surfaces simultaneously on a work piece. Cutter: 2 or more side & face milling cutters Machine: Horizontal Milling Machine FIG. STRADDLE MILLING

GANG MILLING Gang Milling: Process to get different profiles on the work piece simultaneously with two or more cutters at one stretch. Cutter: Different cutters as required. Machine: Horizontal Milling Machine FIG. GANG MILLING

SPECIFICATIONS OF MILLING MACHINE Size of the work table: expressed in length x width Eg: 1500 x 30mm. Longitudinal movement: Total movement of table in mm(X-direction). Eg:800mm Transverse movement: Total movement of saddle along with table in mm(Y-direction). Eg:200mm Vertical movement: Total movement of table, saddle & knee in mm mm(Z-direction). Eg:380mm Range of the speed: Speed variation in the gear box in RPM. Eg: 45 to 200 rpm. Power capacity of the motor in HP. Eg: 2 HP

GRINDING(Abrasive machining) Grinding is a surface finishing operation where very thin layer of material is removed in the form of fine dust particles. (thickness 0.25-0.5mm) Grinding can be defined as a material removal process by the abrasive action between rotating abrasive wheel & the work piece. Grinding machine is a power operated machine tool where, the work piece is fed against a constantly rotating abrasive wheel which is also called as Grinding wheel so that a thin layer of material is removed from the work piece.

PRINCIPLE OF GRINDING The work piece is fed against a constantly rotating abrasive wheel so that a thin layer of material is removed from the it. FIG. GRINDING

GRINDING WHEEL Abrasives Bonding materials Grinding wheels

ABRASIVES Abrasives: These are the mineral materials employed for sharpening, grinding & polishing operations. Abrasives are classified as natural & artificial. Natural Abrasives: Emery, Corundum, Diamond etc,. Artificial Abrasives: Silicon Carbide(SiC), Aluminum Oxide(Al2O3), Cubic Boron Nitride(CBN) etc,.

Bonding materials & Process Vitrified Process: Abrasive+ Fed spar & clay, heated at higher temperatures in kilns.75-80% of grinding wheels are made by this process. Silicate Process: Abrasive+ Silicate of soda. Baked @ 260°C for 20 to 80 Hrs. Elastic Process: Abrasives + Shellac. Baked @150°C for few hours. Vulcanite or Rubber Process: Abrasive+ Pure rubber+ Sulphur.

FIG. COATED &MOUNTED ABRASIVE WHEELS

CLASSIFICATION OF GRINDING MACHINES Grinding machines are classified based on their construction & type of surface produced. Bench Grinding Machine Surface Grinding Machine Cylindrical Grinding Machine Centerless Grinding Machine Internal Grinding Machine Special Purpose Grinding Machine

SURFACE GRINDING MACHINE Principle: The work piece is fed against a constantly rotating abrasive wheel so that a thin layer of material is removed from the it. Work Piece Type: Flat, Angular & Irregular surfaces FIG. PRINCIPLE OF SURFACE GRINDING

FIG. SURFACE GRINDING MACHINE

CYLINDRICAL GRINDING MACHINE Principle: The work piece is held between two centers & and the rotating grinding wheel is fed against it. External Grinding machine Work Piece Type: Cylindrical surfaces may be straight, curved or contoured. FIG. PRINCIPLE OF CYLINDRICAL GRINDING

FIG. CYLINDRICAL GRINDING MACHINE

CENTERLESS GRINDING MACHINE Principle: The work piece is placed on work rest blade between two wheels namely grinding & regulating wheel, which are rotating in clockwise & work piece rotates counter clockwise. Grinding wheel remove material from W/P surface & regulating wheel regulates the W/P. Centerless: Means work piece is not held between centers. Work Piece Type: Curved or Cylindrical surfaces of long slender rods which cannot be ground on cylindrical grinding. FIG. PRINCIPLE OF CENTERLESS GRINDING

FIG. CENTERLESS GRINDING MACHINE

ASSIGNMENT With sketch explain the principle of milling & grinding. Distinguish between up milling and down milling. With neat sketch explain the column and knee milling machine. Draw a neat sketch of vertical milling machine and explain its parts. Distinguish between horizontal milling m/c and vertical milling m/c. List the different operations performed on milling machine and briefly explain the operations. What are abrasives? Give some examples of natural and artificial abrasives. Sketch and explain centerless grinding with principle. Write a note on bonding materials & processes. Give the specifications of milling machine. Sketch and explain the following operations (i) Surface grinding (ii) Cylindrical grinding.

REFERENCES www.google.com www.youtube.com A Text Book of Mechanical Engineering - K R Gopalkrishna Elements of Mechanical Engineering -M Sreenivasa Reddy - Kestoor Pravin

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