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1460139678-repAUTOMATICDRILLINGANDTAPPINGMACHINE.docx (Size: 1.09 MB / Downloads: 6)
ABSTRACT
This project deals with the Fabrication of an Automatic Drilling and Tapping Machine. In the present market the combined drilling cum tapping machine is not available. For tapping we need either a manual process or a tapping attached in a drilling machine. The former one consumes lot of time the latter is quite costlier.
For tapping operation we need to rotate the spindle in both clockwise and counter clockwise direction. In our machine we have made bevel gear arrangement for auto reversal of the spindle. Thus based on the functional and economical aspects we have fabricated a unique machine.
With the help of this single machine, the operations such as drilling and tapping can be performed. This machine reduces the human effort. Also the drilling and tapping operations carried out individually consumes lot of time which is eliminated with this machine. Hence this machine is an added advantage in every industry such that it does the drilling and tapping operations in a single machine and lot of time of the workers are saved.
INTRODUCTION
The drilling machine is one of the most important machine tool. Drilling machines are used to drill holes of different sizes and shapes based on the requirement. The holes are generated by the rotating edge of the cutting tool known as the drill which exerts large force on the workpiece clamped on the table. As the machine exerts vertical pressure to originate a hole it is also called as a “Drill Press”. Drill machines are usually available in the market with great specifications which are of high cost.
Tapping is the operation of cutting internal threads in a hole using a cutting tool called tap. A tap has cutting edges in the shape of threads. When the tap is screwed into a hole it removes metal and cuts internal threads for tapping, the hole drilled will be smaller than the tap size. Usually in the tapping operation, the tool is rotated in one direction for the metal removal and the tool is taken out by rotating them in the opposite direction. If the tool is taken out as such, the threads may be damaged and the job may be rejected.
Tap drill size = 0.8 * Outer diameter of the threads
In our project, the both operations that we saw above can be performed by just changing the tool. The drill bit is inserted first and the hole is drilled and then the drill bit is replaced with the tap and the process of thread cutting is carried out.
MANUFACTURING PROCESS
Manufacturing processes are the steps through which raw materials are transformed into a final product. The manufacturing process begins with the creation of the materials from which the design is made. These materials are then modified through manufacturing processes to become the required part. Manufacturing processes can include treating (such as heat treating or coating), machining, or reshaping the material. The manufacturing process also includes tests and checks for quality assurance during or after the manufacturing, and planning the production process prior to manufacturing.
In all machining processes, the work piece is a shape that can entirely cover the final part shape. The objective is to cut away the excess material and obtain the final part. This cutting usually requires to be completed in several steps – in each step, the part is held in a fixture, and the exposed portion can be accessed by the tool to machine in that portion. Common fixtures include vise, clamps, 3-jaw or 4-jaw chucks, etc. Each position of holding the part is called a setup. One or more cutting operation may be performed, using one or more cutting tools, in each setup. To switch from one setup to the next, we must release the part from the previous fixture, change the fixture on the machine, clamp the part in the new position on the new fixture, set the coordinates of the machine tool with respect to the new location of the part, and finally start the machining operations for this setup.
Therefore, setup changes are time-consuming and expensive, and so we should try to do the entire cutting process in a minimum number of setups; the task of determining the sequence of the individual operations, grouping them into (a minimum number of) setups, and determination of the fixture used for each setup, is called process planning.
These notes will be organized in three sections:
(i) Introduction to the processes,
(ii) The orthogonal cutting model and tool life optimization and
(iii) Process planning and machining planning for milling.
SAWING
Cold saws are saws that make use of a circular saw blade to cut through various types of metal, including sheet metal. The name of the saw has to do with the action that takes place during the cutting process, which manages to keep both the metal and the blade from becoming too hot. A cold saw is powered with electricity and is usually a stationary type of saw machine rather than a portable type of saw.
The circular saw blades used with a cold saw are often constructed of high speed steel. Steel blades of this type are resistant to wear even under daily usage. The end result is that it is possible to complete a number of cutting projects before there is a need to replace the blade. High speed steel blades are especially useful when the saws are used for cutting through thicker sections of metal.
Along with the high speed steel blades, a cold saw may also be equipped with a blade that is tipped with tungsten carbide. This type of blade construction also helps to resist wear and tear. One major difference is that tungsten tipped blades can be re-sharpened from time to time, extending the life of the blade. This type of blade is a good fit for use with sheet metal and other metallic components that are relatively thin in design.
WELDING
Welding is a process for joining similar metals. Welding joins metals by melting and fusing 1, the base metals being joined and 2, the filler metal applied. Welding employs pinpointed, localized heat input. Most welding involves ferrous-based metals such as steel and stainless steel. Weld joints are usually stronger than or as strong as the base metals being joined.
Welding is used for making permanent joints. It is used in the manufacture of automobile bodies, aircraft frames, railway wagons, machine frames, structural works, tanks, furniture, boilers, general repair work and ship building.
OPERATION
Several welding processes are based on heating with an electric arc, only a few are considered here, starting with the oldest, simple arc welding, also known as shielded metal arc welding (SMAW) or stick welding. In this process an electrical machine (which may be DC or AC, but nowadays is usually AC) supplies current to an electrode holder which carries an electrode which is normally coated with a mixture of chemicals or flux. An earth cable connects the work piece to the welding machine to provide a return path for the current. The weld is initiated by tapping ('striking') the tip of the electrode against the work piece which initiates an electric arc. The high temperature generated (about 6000oC) almost instantly produces a molten pool and the end of the electrode continuously melts into this pool and forms the joint.
In the shielded metal arc welding process (SMAW) the 'stick' electrode is covered with an extruded coating of flux. The heat of the arc melts the flux which generates a gaseous shield to keep air away from the molten pool and also flux ingredients react with unwanted impurities such as surface oxides, creating a slag which floats to the surface of the weld pool. This forms a crust which protects the weld while it is cooling. When the weld is cold the slag is chipped off.
The SMAW process cannot be used on steel thinner than about 3mm and being a discontinuous process it is only suitable for manual operation. It is very widely used in jobbing shops and for onsite steel construction work. A wide range of electrode materials and coatings are available enabling the process to be applied to most steels, heat resisting alloys and many types of cast iron.
DRILLNG
Drilling is a cutting process that uses a drill bit to cut or enlarge a hole of circular cross-section in solid materials. The drill bit is a rotary cutting tool, often multipoint. The bit is pressed against the workpiece and rotated at rates from hundreds to thousands of revolutions per minute. This forces the cutting edge against the workpiece, cutting off chips (swarf) from the hole as it is drilled.
OPERATION
The geometry of the common twist drill tool (called drill bit) is complex; it has straight cutting teeth at the bottom – these teeth do most of the metal cutting, and it has curved cutting teeth along its cylindrical surface. The grooves created by the helical teeth are called flutes, and are useful in pushing the chips out from the hole as it is being machined. Clearly, the velocity of the tip of the drill is zero, and so this region of the tool cannot do much cutting. Therefore it is common to machine a small hole in the material, called a center-hole, before utilizing the drill. Center-holes are made by special drills called center-drills; they also provide a good way for the drill bit to get aligned with the location of the center of the hole. There are hundreds of different types of drill shapes and sizes; here, we will only restrict ourselves to some general facts about drills.
Common drill bit materials include hardened steel (High Speed Steel, Titanium Nitride coated steel); for cutting harder materials, drills with hard inserts, e.g. carbide or CBN inserts, are used;
In general, drills for cutting softer materials have smaller point angle, while those for cutting hard and brittle materials have larger point angle;
If the Length/Diameter ratio of the hole to be machined is large, then we need a special guiding support for the drill, which itself has to be very long; such operations are called gun-drilling. This process is used for holes with diameter of few mm or more, and L/D ratio up to 300. These are used for making barrels of guns;