M ANUFACTURING Processes and Techniques O UTLINE THEORY OF METAL - PowerPoint PPT Presentation

KINGDOM OF SAUDI ARABIA ةيدوعسلا ةيبرعلا ةكلمملا Prince Sattam bin Abdulaziz ريملؤا ةعماجماطس زيزعلا دبع نب University ةسدنهلا مسق ةيكيناكيملا Mechanical Engineering Department M ANUFACTURING Processes and Techniques

O UTLINE  THEORY OF METAL CUTTING  TRADITIONAL AND NON-TRADITIONAL MACHINING PROCESSES.  WELDING & CASTING.  TOLERANCE AND FITS  METAL FORMING

THEORY OF METAL CUTTING

M ACHINING Positive rake angles: Make the tool more sharp and pointed. • Reduce cutting forces and power • requirements. Helps in the formation of continuous chips • in ductile materials. Help avoid the formation of a built-up edge. • Negative rake angles, by contrast: Increasing the strength of the cutting edge. • Increase the cutting forces. • Increase friction, resulting in higher • temperatures. Improve surface finish. •

W HY MACHINING IS I MPORTANT

C UTTING TOOL

T YPES OF C HIPS

T YPES OF C HIPS

METAL CUTTING CALCULATIONS The time to machine from one end of a cylindrical workpart to the other is given by: Where T m = machining time, min; and L = length of the cylindrical workpart, mm (in) more direct computation of the machining time is provided by the following equation: Where D o = work diameter, mm (in); L = workpart length, mm (in); f = feed, mm/rev (in/rev); and v = cutting speed, mm/min (in/min).

METAL CUTTING CALCULATIONS The material removal rate . The rotational speed in turning is related to the desired cutting speed at the surface of the cylindrical workpiece by the equation Where N = rotational speed, rev/min; v = cutting speed, m/min (ft/min); and D o = original diameter of the part, m (ft).

METAL CUTTING CALCULATIONS The turning operation reduces the diameter of the work from its original diameter D o to a final diameter D f , as determined by the depth of cut d : The feed in turning is generally expressed in mm/rev (in/rev). This feed can be converted to a linear travel rate in mm/min (in/min) by the formula: Where fr = feed rate, mm/min (in/min); and f = feed, mm/rev (in/rev).

T RADITIONAL AND NON - TRADITIONAL MACHINING PROCESSES

T RADITIONAL M ACHINING PROCESSES M ACHINING BY C UTTING Drilling Turning Milling (face) Milling (peripheral)

T RADITIONAL M ACHINING PROCESSES M ACHINING BY C UTTING In shaping , the primary motion is performed by the tool, and feed by the workpiece. In Planing , the primary cutting motion is performed by the workpiece and feed motion is imparted to the cutting tool. Broaching : use of a multiple-tooth cutting tool moved linearly relative to the workpiece in the direction of the tool axis

T RADITIONAL M ACHINING PROCESSES M ACHINING BY A BRASION Surface Grinding Cylindrical Grinding

T RADITIONAL M ACHINING PROCESSES M ACHINING BY A BRASION Honing Lapping

N ON -T RADITIONAL M ACHINING PROCESSES M ECHANICAL E NERGY P ROCESSES Ultrasonic machining Water Jet Cutting (WJC) 0.05 to 0.125 mm Abrasive Jet Machining (AJM) fine abrasive particles 0.025 mm Speed 300 m/s

N ON T RADITIONAL M ACHINING PROCESSES E LECTROCHEMICAL M ACHINING P ROCESSES Electrochemical Machining (ECM) Electrochemical Grinding (ECG)

N ON -T RADITIONAL M ACHINING PROCESSES T HERMAL E NERGY P ROCESSES (Wire EDM) EDM Laser Beam Plasma Arc Machining Cutting (LBM) (PAC)

M ULTIPLE C HOICE Q UESTIONS (MCQ) - Complete the Tool and WP motions for traditional machine tools. Machining Tool and WP movements Process Turning WP Tool Drilling Tool Tool Milling Tool WP Shaping Tool WP Cylindrical Tool WP grinding

M ULTIPLE C HOICE Q UESTIONS - The process utilizing mainly thermal energy for removing material is (a) Ultrasonic Machining (b) Electrochemical Machining (c) Abrasive Jet Machining (d) Laser Beam Machining - Match the following traditional and non-traditional machining processes with the corresponding material removal mechanisms Machining process Mechanism of material removal P. Grinding 1. Abrasion Q. Turning 2. Erosion R. Chemical machining 3. Chip removal S. Electro-discharge 4. Corrosive reaction machining T. Ultrasonic machining 5. Fusion and vaporization P-1 ; Q-3 ; R-4 ; S-5 ; T-2

W ELDING & C ASTING

T YPES OF WELDING

A RC W ELDING MIG welding TIG Welding Submerged SMAW(MMA) welding arc welding

SMAW(MMA) & TIG WELDING Coating is a combination of chemicals in SMAW(MMA) welding: Cellulosic electrodes contain cellulose Rutile electrodes titanium oxide (rutile) Basic electrodes contain calcium carbonate (limestone) and calcium fluoride (fluorspar)

O XYACETYLENE WELDING Reducing or Carburizing: Excess acetylene (0.9:1) (Alloy steels and aluminium alloys) Oxidizing : Excess oxygen (1.5:1) (Brass, Bronzes, copper) Neutral : Equal acetylene & oxygen (low carbon steel, mild steels).

R ESISTANCE WELDING

W ELDING  Types of welded joints:

S OLDERING AND B RAZING

M.C.Q B RAZING S OLDERING & The commonly used flux in brazing is Borax  Rosin  Lead sulphide  Zinc chloride  Which of the following is function(s) of flux used in brazing? i- Protect surface from oxidation ii- Reduce surface tension of filler iii- Assist its penetration i only  ii only  i and ii  i, ii and iii  In soldering the melting point of filler metal is a - below 420 ◦ C  b- below 450 ◦ C  c - below 460 ◦ C  d - below 540 ◦ C   The composition of soft solder is a- lead 37% tin 63%  b- lead 50% tin 50%  c- lead 63% tin 37%  d- lead 70% tin 30% 

S AMPLES OF M.C.Q W ELDING Which of the following welding process uses non-consumable electrodes? TIG welding  MIG welding  Manual arc welding  Submerged arc welding  The temperature of oxy-hydrogen flame is __________ oxy-acetylene flame. same as  less than  more than  In submerged arc welding, an arc is produced between a carbon electrode and the work  metal electrode and the work  bare metal electrode and the work  two tungsten electrodes and the work  In shielded arc welding large electrode is used  welding rod coated with slag is used  welding rod coated with fluxing material is used  none of the above  In electric resistance welding, voltage required for heating is 1 to 5 volts  6 to 10 volts  11 to 20 volts  50 to 100 volts  The oxy-acetylene gas used in gas welding produce a flame temperature of 1800°C  2100°C  2400°C  3200°C 

C ASTING

P ATTERN PATTERN

M OLDING M ATERIALS Major part of Molding material in sand casting are: 1. 70-85% silica sand (SiO2) 2. 10-12% bonding material e.g., clay cereal etc. 3. 3-6% water Classification of sand casting defects

C ASTING WITH EXPENDABLE MOULD : I NVESTMENT C ASTING

P ERMANENT MOULD CASTING : D IE CASTING In Die casting the molten metal is forced to flow into a permanent metallic mold under moderate to high pressures, and held under pressure during solidification

D IE C ASTING This uses pressures up to 35 MPa and is used for zinc, tin, lead, and their alloys In this process, pressures as high as 150 MPa are used. The storing chamber is not heated. This process is used mainly for metals and alloys having relatively higher melting point e.g., aluminium, magnesium and their alloys.

C ENTRIFUGAL C ASTING - A permanent mold made of metal or ceramic is rotated at high speed (300 to 3000 rpm). The molten metal is then poured into the mold cavity and due to centrifugal action the molten metal conform to the cavity provided in the mould. - Castings are known for their higher densities in the outer most regions. - The process gives good surface finish - Applications: pipes, bushings, gears, flywheels etc.

S AMPLES OF M.C.Q C ASTING  Sand casting is which of the following types? (a) expendable mold, or (b) permanent mold.  The upper half of a sand casting mold is called which of the following ? (a) cope, or (b) drag.  In casting, a flask is which one of the following? (a) beverage bottle for foundry men, (b) box which holds the cope and drag, (c) container for holding liquid metal, (d) metal which extrudes

S AMPLES OF M.C.Q C ASTING In foundry work, a runner is which one of the following? (a) channel in the mold leading from the Down sprue to the main mold cavity, (b) foundry man who moves the molten metal to the mold, or (c) vertical channel into which molten metal is poured into the mold. Total solidification time is defined as which one of the following? (a) time between pouring and complete solidification, (b) time between pouring and cooling to room temperature, (c) time between solidification and cooling to room temperature, or (d) time to give up the heat of fusion. In a cold chamber die casting machine  melting pot is separate from the machine  melting pot is an integral part of the machine  melting pot may have any location  low temperature and pressure is used

T OLERANCE AND FITS