Drona Gyaan
Drona Gyaan MACHINING-INTRODUCTION Manufacturing is a VALUE ADDITION process by which raw materials or objects of low value due to inadequate material properties, poor or irregular size, shape and finish are converted into HIGH UTILITY and HIGH VALUE products with proper size , form , dimensions and finish , imparting some functional ability. Manufacturing is classified into: FORMING PROCESSES: e.g. Rolling, Extrusion. MACHINING PROCESSES: e.g. Drilling, Milling MOULDING PROCESSES: e.g. Blow and Dip moulding CASTING PROCESSES : e.g. Sand and Centrifugal casting. “Machining” is basically a removal process by which jobs of desired dimensions and surface finish are produced by gradually removing the excess material from the preformed blank in the form of chips, with the help of cutting tools moved past the work surface. Every machining process requires choice of accurate input parameters. In this round you need to choose the four essential input parameters, namely: Material, Feed, Speed and Depth of cut (M,F,S,D). The three key mechanical inputs in metal removal operations are feed, speed, and depth of cut. Manipulating the feed, speed and depth of cut can maximize the benefits of a particular cutting fluid and can increase productivity. However, like most decisions, the choice of feed, speed and depth of cut must be based on the customer’s objectives. What is their goal in this application? Do they want to manufacture parts faster or maximize tool life? How important is the surface finish and dimensional accuracy of the part? Answers to these questions will drive their decisions on feeds, speeds and depth of cut. MATERIAL-Material implies the type of work material which is selected for machining operations. Here are commonly used work material:- Carbon steel, Alloy Steels, Cast Iron, Stainless steel, Aluminium , Aluminium alloys, Magnesium Alloys. FEED- Feed rate is the relative velocity with which the cutter is advanced along the work piece. Feed rate units depend on the motion of the tool and workpiece; when the workpiece rotates (e.g., in turning and boring), the units are almost always distance per spindle revolution (inches per revolution [in/rev or ipr] or millimeters per revolution (mm/rev). DEPTH OF CUT - The measurement (normally in inches or millimeters) of how wide and deep the tool cuts into the workpiece. SPEED- Speed is the rate of rotation of the spindle where the tool is held. It is measured in revolutions per minute (RPMs). Machine Tools: A machine tool is defined as one which while holding the cutting tools, would be able to remove metal from a workpiece so as to generate job of required shape, size and surface finish. They are classified into – 1. General purpose machine tools(GPM) : are those designed to perform a variety of machining operations on a wide range of components. e.g. lathe, shaper, milling machine. 2. Production machine tools: are those where a number of functions of the machine tools are automated such that the operator skill required to produce the component is reduced. Hence these machine tools can be used for large volumes of production. 3. Special purpose machine tools(SPM) : are those machine tools in which the setting operation for the job and tools is practically eliminated and complete automation is achieved. e.g. cam shaft grinding machine, piston turning lathe. 4. Single purpose machine tools : are those which are designed specifically for doing a single operation on a class of jobs or on a single job. These tools have highest amount of automation and are used for really high rates of production. e.g. transfer lines composed of unit heads for completely machining any given product. LATHE : is the oldest machine tool invented, starting with the Egyptian tree lathes. This primitive device has evolved over the last two centuries to be one of the most fundamental and versatile machine tools with large variants, to be used practically in all the manufacturing shops. The principle form of surface produced in a lathe is the cylindrical surface. TURNING Material Cast iron Cast steel AISI 1020 AISI 1040 Manganese steel Nickel steel Stainless steel Spring steel Tool steel Tool steel Tool steel Tool steel Malleable iron Glass Copper Brass Bronze Zinc alloys Hardness 200 280-300 110-160 170-200 PARTING 185-215 200-240 150 400 150 200 215 300 110-130 80-85 190-200 180-200 110-125 Speed m/min Feed mm/rev 25-35 0.13-0.30 12-15 0.06-0.19 35 0.20-0.50 Common 25 0.13-0.30 DRILLING Lathe 5 0.06-0.19 Operations 18 0.06-0.19 15 0.13-0.30 6 0.06-0.19 23 0.20-0.50 18 0.13-0.30 15 0.13-0.30 KNURLING 12 0.06-0.19 26 0.20-0.50 4.5 0.06-0.19 21 0.06-0.19 70 0.20-0.50 54 0.20-0.50 70 0.20-0.50 SAMPLE PARAMETER VALUES FOR DRILLING OPERATION MOULDING- INTRODUCTION “Moulding” is the process of manufacturing by shaping liquid or soft raw material using a rigid frame called a mould. Moulding Flask: A moulding flask is one which holds the sand mould intact . Depending upon the position of the flask in the mould structure , flask is referred by various names such as DRAG- lower moulding flask COPE- upper moulding flask CHEEK- intermediate moulding flask, used in three piece moulding. Pattern is the replica of the component which we are going to manufacture. Materials used for making patternWood TYPES OF MOULDING SAND: GREEN SAND: It is also known as natural sand and is obtained from natural resources. It is a mixture of silica sand ,with 18 to 30% clay and 6 to 8% water. The clay and water give bonding strength to green sand. It is fine, soft, light and porous. Green sand is used for casting small or medium sized moulds. Coal dust is mixed in green sand to prevent defects in castings. DRY SAND: Dry sand moulding is employed for large castings. The moulds prepared in green sand are dried or baked to remove all moisture of the moist sand. LOAM SAND: Loam sand is a mixture of clay and sand milled with water to a thin plastic paste from which moulds are built up on a backing of soft bricks. It contains 50% clay and fire clay. Loam is dried very slowly and completely before it is ready for casting. BACKING SAND: It is black in colour due to addition of coal dust and burning or coming in contact with molten metal. It is used to fill in mould at the back of facing layer. PARTING SAND: Parting sand is used to keep the green sand from sticking to the pattern. EQUIPMENTS USED IN MOULDING Showel Riddle Rammer Trowel Slicks Lifters Draw spikes Swab Rawhide mallot Gate cutter Clamp TWO BOX MOULDING: Two box moulding uses the moulding box made in two parts. The upper part is known as COPE and the lower one is known as DRAG. Two parts are fitted with a suitable clamping and locating device. Clamping prevents the cope from lifting due to the pressure of the molten metal while pouring. Locating device enables the two parts to maintain proper alignment at all times. In this method drag and pattern are placed on the moulding box and the sand is rammed in the drag. The drag is then rolled over the box. The other part of the pattern is fitted over bottom one and cope is placed over the drag.
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