Title Page Introduction 2 Objectives 2 Theory 2 Fitting 3 Turning 5 Shaping and Grinding 7 Milling 8 Conclusion 11 Reference 11 1
Introduction Machining Machining is a manufacturing process in which a cutting tool is used to remove excess material from a work part so that the remaining material is the desired part shape. And it is some times called Materials removal processes. Objectives To know about the machines used in this operation, its name parts and jobs. To distinguish when to use a machine and for what type of parts. Theory and background: Machining is the final operation of making the working piece, this operation contains cutting parts from the working piece to make soft surfaces. Cutting conditions: The cutting speed: It is expressed with unit of meter per minute. It is defined as the largest of the relative velocities between the cutting tool and the work piece. The depth of the cut: It is expressed in millimeter and is defined as the distance that the cutting tool project below the original surface of the work. The feed: It is expressed with the unit mm per revolution It is defined as the movement between the tool and the work piece during the operation. Note that is some operation the cutting speed depends on the diameter of the work piece such as in turning, in other operations the cutting speed depends on the diameter of the cutting tool. When I will talk about the machines it I will discuss it on three axes the name, Operation and parts. 2
Fitting: It is the operation a student or an engineer does to produce a working piece using manual tools. Three Apparatuses should be available for the fitting operation: 1. The working table. 2. The vice. 3. The files. And here I gave a brief of each one: 1. The work table: It must satisfy the following: It should be made from a heavy metal or wood, so that the movement and the vibrations won t affect on it during working and knocking on it. Natural or manufactured lighting should be available in the working place. The height of the working table should be 80 cm so it fits most of the worker length. Drawers and shelves should be available in the working table. 2. Vice It has the following parts: Moving jaw. Fixed jaw. Body. Sliding part. Handle. Chuck release, it is used to release the moving jaw in the vice so we can move it faster. Caring about the vice: 1. The vice is made of casting metal, which breaks easily when knocking it. 3
2. Oil the screws regularly. 3. Never fix on the vice a piece that is bigger than its size. 4. Clean the vice regularly. 5. Never hammer on the top of the sliding part. 6. When fixing apiece into the vice never push the handle using external forces. A problem with vices: On the jaws of the vice, a rough metal pieces to prevent the working pieces from slipping, however, when dealing with soft metal pieces the jaws might ruin the finished pieces. The solution: The invention of vice shoes from soft metals as well, solved this problem. So when I deal with a soft metal pieced all I have to do to prevent it form scratching or being ruined is to attach the vice shoes on the vice jaws. 3. Files: Files are made of a mixture of metals, so that it can be used with any type of working pieces. To specify a file the following information should be given: File length. The length of the file is directly proportional with the length of the working piece. File shape. It is also proportional with the shape of the working pieces. Grade of cut. There are three grades of cut: Roughing, Bastard, Smooth and dead file. Caring of files: 1. Clean the file using the wire purse. Unless that, chips of metal will be stuck on the file and so the finished piece will be dirty. 2. Never place the files on each other. 3. Use the file only for filling and never use it to knock on the working piece to edit its position. 4
Some notes on the filling operation: The file should be elevated for about 5 mm above the vice. Why? Because in that way the filling sound will be acceptable otherwise it will be annoying. The cutting edges of the files are always to the front direction. The cutting edges angle equals 45 degrees. As the finished piece is harder the angle of the cutting is smaller. The sawing Operation: The saw consists of tow parts: Handle and The Hack. When starting the sawing operation, we should start with more than one tooth. We noticed that the teeth have a set of sides, and that is to cause the blade to cut a slit wider than it self, and prevents the body of the blade from rubbing and jamming the saw cut. Blades might break for the following reasons: Rapid and erratic strokes. Too much pressure. Blade held to loosely in the frame. And that why blades are changeable. Turning: Turning is carried out on a machine tool called lathe. And is used to shape round pieces of metal. The jobs of the Lathe machine: To decrease the outside diameter. To increase the inside diameter. Making configuration turning. 5
Parts of the machine: They are summarized in table 1. Name Function Descriptions Head stock It contains the gearbox and the spindle. The spindle can be related with two types of chucks: The bed The Saddle Tail stock As a slide for the saddle and the tail stock. It consists of the following parts: Carriage: It moves the group forward and backward, to give parallel turning to the spindle. Cross slide: It moves the group left and right, It gives depth of cut in the long turning, And gives feed rate in cross turning. The compound slide: It 3 jaw chuck 4 jaws chuck It is hard. To link regular cylindrical shapes and triangular shapes. To link the irregular shapes. gives Precision A H in turning, M 531 Parallel turning, taper turning, and boring turning. Tool post: Carries the cutting tool which is made from high speed steel. To support the long work pieces. It gives drilling. Taper turning. The cutting tool cuts every thing which is less tough, But if the working piece was tougher we use diamond cutting tools. The correct rotation of the cutting tools is counter clock wise. It is placed at the end of the machine. Feed change gear box Base It controls the feed rate and the cutting speed automatically. Support the parts of the turning machine. Table 1 6
The procedures: We were doing the finishing of a circular metal piece we made by casting. And here I describe the procedures of turning to this piece. 1. Facing: Turning the circumference of the working piece then we place the measurements. 2. Straight turning: Here we reduced the diameter to 125mm. 3. Shoulder turning: We measure from the pieces surface to the inside of it and we reduce the front diameter to 115mm. 4. Finishing: To get rid of the riser. The remaining thickness should be 10mm. Shaping and grinding: Shaping: The machines name>> Shaping machine. The machines operation>> Production of soft surface. The machines specification>> 1- The machine gives linear motion on the Surface of the working piece. 2- The cutting tools is attached with the head. 3- The working piece is attached to the Vice. The machines disadvantage>> It is too slow. Note that we use shaping when the number of working pieces is small. The machine parts>> 1. Ramp 2. Head, it contains a micrometers the gives a precision of 0.1 mm. 3. Column that contains the gear box. Grinding: 7
The machines name>> Surface grinding machine. The machines operation>> Production of highly soft plains. The machines apparatus>> Are described in table 2 Name Operation Description Column It contains the gearbox It contains a micrometer that gives a precision of 0.01 mm. Grinding Wheel (Cutting tool) Cross slide Table Vice The cooling liquid Does the cutting operation. Carries the table. Carries the vice It is made of a mixture of sand and carbide materials. The cutting edges are infinity. Its speed is high and equal to 2860 rev/min Fixes the working A H M pieces 531 magnetically. The Civil Reduce Engineering friction Center Reduce resistance Reduce heat Remove the chips from the working piece surface. Protect the working piece from oxidizing. Table 2 It is made of seed oil and water. 8
Milling: Main operation of milling is the production of flat surfaces. It is more accurate and speeds than the shaping operation but is more expensive. There are two types of milling: 1. Horizontal milling. 2. Vertical milling. Table 3 compares between the two types. Compare Horizontal Milling Vertical Milling Spindle Horizontal Vertical Operation Peripheral milling Face milling Holding cutting tools Stud Arbor Cullet chuck Holding the working piece If the working piece was small we use the vice otherwise we use the working table, And for cylindrical pieces we use the V-Block Table 3 Note: One muse distinguish between the rotation direction and the direction of the spindle. Type of face milling: They differ in the diameter of the cutting tool. 1. Conventional milling 2. Partial milling 3. End milling 4. Profile milling 5. Pocket milling 6. Surface milling Note that for polygon pockets we use Pocket milling but for circular pockets we use drilling. 9
Types of Peripheral milling: They differ in the width of the cutting tool. 1. Slab milling 2. Slot milling 3. Sid milling 4. Straddle milling For more information about these types see figures Direction of rotation: 1. Up milling 2. Down milling But Up milling is better because there is no vibration results from it, opposite of the down milling. The Vertical milling machine parts: 1. Base 2. Column 3. Lead, change the spindle from horizontal to vertical and it carries the cullet chuck. 4. knee, movement in the Z axis. 5. Saddle, movement in the Y axis. 6. Work table, Movement in the X axis. 7. Vice. The parts of the Horizontal milling machine are the same except that there is Over Arm head to fix the holding arbor. 10
Conclusion: After 4 weeks of working on this report, I concluded the each of the machines we have studied have a specific operations that we should distinguish, for example, If the working piece has around shape then I will do the cutting using the turning machine, The cube and polygon shapes are cut using the milling or the shaping machine and that depends on the cost of the piece and the quantity, If I want to make holes in pieces then I will use the drill. And I also concluded the main differences between Shaping, Grinding, Turning and Milling and summarized that in table 4. Compare Shaping Grinding Turning Milling Cutting tool One Infinity One Multi edges edges Rotation No Rotation The cutting Working Cutting tool The Civil Engineering tool rotates Piece Center rotates rotates. References: Instructors Notes. Workshop Manual. 11