In a convectional mechanical workshop, students are made familiar with machines which are used in production and manufacturing processes. The machines require labour since they are manual.
â€¢ Read the operatorâ€™s manual and observe all safety precautions for all equipment.
Keep all guards and shields in place.
â€¢ Give the task your full attention.
â€¢ Let each tool work at its own speed; do not force it.
â€¢ Always wear appropriate personal protective clothing.this includes safety boots,helmet and dust coats
â€¢ Maintain secure footing and balance at all times.
â€¢ Keep tools clean and sharp.
â€¢ Turn the switch off immediately if the power tool stalls or jams.
â€¢ Wherever possible, use clamps or a vice to hold your work.
â€¢ Provide enough light so you can see what you are doing.
â€¢ Store power tools safely to prevent damage to the tool and cord, and to prevent unauthorized use.
â€¢ Maintain power tools in good working order. Replace or repair worn or faulty equipment immediately.
MACHINE SAFETY PRECAUTIONS
â€¢ Never remove or try to defeat machine safeguards.
â€¢ Donâ€™t create new hazards, such as allowing objects to fall into the moving parts or by creating a new pinch point.
â€¢ Report problems with machine safeguards to your supervisor immediately.
â€¢ Never leave machines unattended with parts still moving. Remember that parts may still be moving after the machine has been turned off.
â€¢ Remove guards only when the machine has been locked out and tagged out.
â€¢ If possible, lubricate machine parts without removing the safeguard; otherwise, turn the machine off and lock it out before lubricating.
â€¢ Operate equipment only when guards are in place and properly adjusted.
â€¢ Do not use unauthorized or damaged guards.
â€¢ Do not wear loose clothing, jewelry, or long hair around machinesâ€”these increase the risk of being caught in the machinery.
â€¢ Ask your supervisor if you have any questions about a machine safety or how to work with machine guards safely.
â€¢ Follow instructions as indicated on the machines’ notices
COLLEGUE SAFETY PRECATIONS
â€¢ Ensure that your colleague is safe and away from moving parts of a machine.
â€¢ Handle tools with care to prevent injuring fellow colleagues. E.g. Passing knives should be through handle rather than the sharp edge.
â€¢ Ensure machines are tight to avoid machines parts from coming out of their useful points of the machine and hurting/injuring those near it.
â€¢ Maintain enough space between each other to allow ventilation and provide space for comfortability and easy escape incase of fire or accident.
ROLES AND RENSPOSIBILITIES IN THE LAB
â€¢ Mark the gang way. This is a path marked in yellow which in case of an emergency like fire, the occupants restrict themselves along it so that at no one point one comes into contact with machines which could still be running at the moment.
â€¢ Ensure that notices are in the lab so that the occupants are aware of the precautions to be followed in the lab.
â€¢ Ensure escape gate is there which may be very useful incase of an emergency in the lab
â€¢ Ensure first aid kit to care for any one who gets injured or hurt while within the lab. This might stop excessive bleeding and further infections before intensive care in a hospital.
â€¢ Ensure enough light and ventilation. Light will prevent accidents while ventilation ensures there is enough circulation of air.
â€¢ Ensure the occupants of the workshop have enough personal protective equipment(PPEs). These include; gloves, eye protection devices, helmets, safety boots, respirators and protective hearing devices.
â€¢ provide and adhere safety workshop act to the occupants to ensure they follow all the rules of the workshop.
TYPES OF WORKSHOP LAYOUT
The workshop layout is the art of planning and positioning the machine tools, equipment, allied equipment, employee amenities, and other required utilities/spaces to achieve maximum utilization of labor, machinery, and space and increase the overall efficiency
I. FIXED POSITION LAYOUT
This is a workshop layout which is suitable for manufacture of heavy products, such as; commercial sips, giant aircrafts, warships etc. in this layout, the building starts at the wide space with the heaviest part and other parts brought to that location. The product is then built step by step until completion.
II. PRODUCT WORKSHOP LAYOUT
This is a layout which is adapted where there is mass production of standard products in an established process. In this layout, a coveyor belt is used as workers assemble different parts on the belt and allow the product to move to the next worker station. At the end of the belt, tit is tested and moved out. It is advantaged in that there is a high level of labor and also equipment utilization. There is low cost per unit product and also a high volume of production.
It however creates boredom due to monotonous nature and the product layout is not flexible.
III. PROCESS LAYOUT
This a workshop layout used when there is no specific end product. They work on orders from different customers and so the jobs will be different. Itâ€™s oriented on a process rather than an end product. The process layout is also referred to as functional layouts. It is advantaged since it is flexible and can accommodate a variety of jobs. The workers are also trained on a variety of machines allowing them to go where there is excess demand. This might do away with the boredom of the workers.
Its however have low, machine utilization since it depends on the kind of job at hand.
There are various machines in a convectional mechanics workshop; they include:
1. LATHE MACHINE
A lathe machine is a machine tool that rotates a workpiece about an axis of rotation to perfom various operations.
There are various types of lathe machine;
The turret lathe is a form of metalworking lathe that is used for repetitive production of duplicate parts, which by the nature of their cutting process are usually interchangeable.
The name was derived from the way early turrets took the general form of a flattened cylindrical block mounted to the lathe`s cross-side capable of rotating about the vertical axis and with toolholders projecting out to all sides and thus resembled a gun turret.
Capstan lathe is a milling machine that is used to produce same parts over and over again. The cutting bits are mounted on a rotatable turret known as a capstan, which allows the user to quickly change the orientation of the bits for cutting without having to take off the first bit and then mount the second.
Work Holding Devices in Lathe Machine
Chuck, Face Plate, Lathe Centers, Steady Rest and Mandrels, etc. are common lathe machine accessories and the functions of these holding tools work as work holding devices.
There is the following work holding devices in the lathe machine:
Chuck is one of the types of work holding devices in lathe machines that are used in various operations for holding the workpieces or a job.There are following types of chuck are used: four jaw chunk, three jaw chunk, magnetic chunk, collet chunk etc
The Center is a work holding devices in a lathe that is used to support long jobs in between headstock and tailstock to carry out a lathe operation. Lathe centers are often made of high carbon steel and then it is hardened, tempered, and grinded.
â€¢ Steady Rest
Steady rest is a type of work holding devices in lathe machine that is used to hold or support long cylinders or thin jobs.The job is supported by this to maintain a stable position of the job while turning.
The carrier or dog is a work holding devices in lathe machine used tohold a job when it needs to be fixed between the centers.Work or a job inserted into the hole of a carrier and then tightly fixed.
â€¢ Driving Plate
It is a circular plate used when turning jobs in between centers.It is used with a straight tail or bent tail carrier to give a positive drive to the job
â€¢ Face Plate
This is a circular plate used to perform various turning operations on a large flat, irregular shaped jobs, castings, etc.The face plate is fixed on the lathe spindle and the job can be mounted on it to perform turning operations.
The lathe mandrel is used to hold the workpieces or a job that is already bored or drilled.The mandrel is often hardened with tool steel and grinded to a specified size.It is grinded on a 1: 2000 taper.
FUNCTIONS OF A LATHE MACHINE
Facing is when you remove metal from a cylindrical work piece. This creates a smooth surface. However, if you use a chuck you can face rectangular, square or other unusual-shaped pieces. When facing, begin with a slower speed and gradually increase to a faster speed. Also, the work piece should not extend farther out of the lathe than around three times its own size. When facing, gouges, parting and chisel tools can be used to create the desired results.
Turning is when a turning tool is applied to the work piece to create groves, ridges and indents in the work piece. Turning creates metal as the piece turns on the lathe. The work piece spins between two end points to hold it in place. The speed can be adjusted as necessary depending on the size of the work piece and the desired results.
Boring is enlarging an existing hole. The hole can be a drilled, molded, cast or a forged hole. The work piece is placed in the lathe chuck and will be spinning while the boring tool is slowly driven into the opening. Boring tools are cylindrical in shape and will have a cutting tool protruding from them. Two different boring tools can be mounted together to make two different cuts at one time.
It is used to remove material from the inside of a work piece. This process utilizes standard drill bits held stationary in the tail stock or tool turret of the lathe.
The cutting of a serrated pattern onto the surface of a part to use as a hand grip using a special purpose knurling tool
This process is used to create deep grooves which will remove a completed or partcomplete component from its parent stock.
It is like parting, except that grooves are cut to a specific depth by a form tool instead of a severing a complete component from the stock. Grooving can be performed on internal and external surfaces, as well as on the face of the part.
It is a light finishing operation performed with a multi-edge tool giving high-precision holes. Very good surface finish and close dimensional tolerance are achieved at high penetration rates. The pre-machined hole needs to be within close limits and the radial depth of cut is small.
Threading operation on lathe is performed with the help of a single point cutting tool. Lathes that have auto feed carriages can be made to perform threading so such a lathe will be provided with a set of change gears or a built in, lever operated gear box to allow easy setting of gear train combinations for any thread pitch to be cut. ThreadingWhile cutting right hand threads, cutting tool is moved towards the spindle and for left hand threads, the direction of feed is reversed. Internal threads are cut in the same manner but the tool is a bit different.
PARTS OF A LATHE MACHINE
2. MILLING MACHINES
FUNCTIONS OF A MILLING MACHINE
â€¢ It is a machine which is used to remove metals from the workpiece with the help of a revolving cutter called milling cutter.
â€¢ It is used to machine the flat, rough and irregular surfaces and this is done by feeding the workpiece against a rotating milling cutter.
Parts of milling machine
The base of the machine is grey iron casting and serves as a foundation member for all other parts which rests on it.
The column is the main supporting frame mounted on the base. It is box-shaped and houses all the driving mechanism for the spindle and feed table.
The knee is a fixed grey iron casting that slides up and down on the vertical ways of the column face.
The knee houses the feed mechanism of the table and controls to operate it.
On the top of the knee is placed the saddle which slides on guideways set exactly at 90 degrees to the column face. The top of the saddle is precisely machined to provide guideways for the table.
It rests on guideways on the saddle and travels longitudinally. The top of the table is finished accurately and T-slots are provided for clamping the work.
Overhanging arm act as a support for the arbor.
It is extra support which provides rigidly to the arbor and knee.
The spindle of the machine is located in the upper part of the column and receives power from the motor through belts, gears and clutches and transmit it to the arbor.
Arbor is an extension of the machine spindle on which milling cutters are securely mounted and rotated.
The arbor may be supported at the farthest end from the overhanging arm or maybe of cantilever type which is called stub arbor.
1.T-BOLTS AND CLAMPS
â€¢ Bulky workpieces of irregular shapes are clamped directly on the milling machine table by using T- bolts and clamps. All these clamps carry a log hole through which clamping bolt passes. The holes permit the bolt for adjustment according to the size and shape of the job.
2. ANGLE BOLTS
â€¢ Angle plates are used to support work surfaces at right angles. Angle plates also may be used to hold the workpiece square to the table during marking-out operations.Slotted holes or â€œTâ€ bolt slots are machined into the surfaces to enable the secure attachment or clamping of workpieces to the plate, and also of the plate to the worktable.The angle plate is made from high-quality material (generally spheroidal cast iron) that has been stabilized to prevent further movement or distortion.
They are used for holding shafts on a milling machine table in which keyways and slots are to be milled.
Vices are the most common appliance for holding work on milling machine tables. According to its quick loading and unloading arrangement.
3. SURFACE GRINDING MACHINE
Surface grinding machine is a type of grinding machine that is mainly used to produce flat surfaces. It is mostly operated by the periphery of the grinding wheel or by the flat of the grinding wheel.
WORK HOLDING DEVICES
â€¢ For cylindrical shaped workpiece
For cylindrical grinding machines, which grind the periphery and end faces of cylindrical workpieces, the method of gripping the workpiece is similar to lathes. Thus, like lathes, they mainly use chucks and centers.
However, centerless grinding machines, which are more powerful for mass-production machining, do not use jigs or other fixtures. In centerless grinders, the workpiece is supported and machined at three points: the grindstone, the supporting plate, and the regulating wheel.
â€¢ For plate, block material workpiece
Surface grinding machines that grind the flat surfaces of plate or block materials often use a magnetic chuck that uses electromagnets or permanent magnets to lock the workpiece in place.
Magnetic chucks can firmly fix workpieces made of iron, nickel, or other ferromagnetic materials that easily stick to magnets.
To hold workpieces that do not stick to magnets, such as aluminum, a vacuum chuck is used, which uses vacuum force to grab the workpiece.
5. CYLINDRICAL GRINDING MACHINE
Cylindrical grinding machine is a machinery whose purpose is mainly to grind the outer and inner parts of the workpieces.Within the cylindrical grinding machine the workpiece is rotated between two centers on its axis. From a high speed rotation the grinding wheel grinds the two centers on its axis so as to produce a smooth surface.
PARTS OF A CYLINDRICAL GRINDING MACHINE
This is the main part of the machine. It is heavy and provides strength and support to the whole machine.
This wheel head is mounted on the cross slide. It moves vertically so that the depth of cut can be fed by the cross-feed handwheel or via a power source.
Cross feed Hand Wheel
The cross feed hand wheel is used to move the wheel head to set the depth of cut in the workpiece.
The working table is mounted on the guideways that reciprocate longitudinally back and forth.
It can be moved by table traverse hand wheel or via a power source.
The headstock is mounted on the left end of the table. And, it houses the motor that can be used to drive the workpiece.
The headstock supports the workpiece through a center and the job is carried out by a carrier or dog.
A chuck is a type of working holding device attached to the headstock.
It is used in a grinding operation for holding the workpiece or a job.
A belt pulley is used to transmit rotation from one rotating pulley to another.
This is mounted on the right end of the table.
It can be moved and locked at any position along with the table so as to hold workpieces of different lengths.
There are the following types of cylindrical grinding machines;
1. External Cylindrical Grinder
2. Internal Cylindrical Grinder
3. Universal Cylindrical Grinder
4. Centerless Cylindrical Grinder
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