MACHINE TOOL

ABSTRACT

 

A machine tool is a powered mechanical device, typically used to fabricate metal components of machines by machining, which is the selective removal of metal. The term machine tool is usually reserved for tools that used a power source other than human movement, but they can be powered by people if appropriately set up. Many historians of technology consider that the true machine tools were born when direct human involvement was removed from the shaping or stamping process of the different kinds of tools.

 

INTRODUCTION

 

The earliest machine tools are Egyptian foot-operated lathes. This machine essentially developed to bring accuracy in manufacturing. A machine tool is design to perform certain primary function, but extend to which it can be exploited.

The machine tool has several classifications. The classification is given in the following lines.

 

1. General purpose machine tools (GPM)

These tools are design to perform a variety of machining operations on a wide ranging type of component. General purpose machine tools though capable of carrying out variety of task and not suitable for large production.

 

2. Production machine tools

These are those machine tools where a number functions are automated such that the operator skill are required to produce the component is reduces. They are useful only in case of a large volume of production.

 

 

3. Special purpose machine tools

These are those machine tools where the setting operation for the job and tool is practically eliminated and complete automation is achieved. This greatly reduces the cycle times and helps in reduction of cost. There are used in mass production.

 

4. Single purpose machine tools

These machine tools are those which are designed specifically for doing a single operation on a class job or a single job. They have highest amount of automation and are used for high rate of production.

 

OBJECTIVE

 

1. To specify the entire machine in “machine tools group”.
2. To know and learn about the machine tools process and application.
3. To know about the safety factors in workshop.
4. To explain the “ideal workshop” for our machine shop.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

EQUIPMENT

There are many machine tool lists down in the mechanical workshop for student to use or make some practical. The machine tools available in the mechanical engineering workshop are:

Band Saw Machine

Press Brake Machine

                                                                

Grinding Machine

Lathe Machine

                                         

Drilling Machine

Horizontal Band Saw Machine

                                                 

                                               

 

 

 

 

 

Vertical Milling Machine

 

 

PROCEDURES

1. The introduction towards machine tools in the workshop is given by the lecturer about what to observe on the machines equip in this workshop.
2. Discussion is also being done on the requirement in the report of the machine tools.
3. After the discussion every machine tools in the workshop is visited and observe by the students.
4. All the information of the machine that given by the lecturer is jotted down. At the same, the layout of the workshop is discussed and the picture of the machine is taken.

 

RESULTS AND DISCUSSIONS

 

1.      List down all the machines in the ‘machine tool’ group that are available in the Mechanical Workshop.

 

The machine tools found in the Mechanical Workshop trade fall into three broad categories;

a.             Chip Producing Tools – which form metal to size and shape by cutting away the unwanted.

                                                               i.            Shearing Machine

                                                             ii.            Press / Shearing Machine

 

b.   Non-Chip Producing Tools – which form metal to size and shape by pressing, drawing, or shearing.

                                                               i.            Sawing Machine

                                                             ii.            Grinding Machine

                                                            iii.            Milling Machine

                                                           iv.            Lathe Machine

                                                             v.            Drilling Machine

2.      Discuss one machine tool in part a) above (BUT not the lathe machine) in detail.

Grinding Machine.

 

Grinding is a chip-removal process that uses an individual abrasive grain as the cutting tools. A grinding machine is a machine tool used for producing very fine finishes or making very light cuts, using an abrasive wheel as the cutting device. The selection of a grinding process and machine for a particular application depends on workpiece shape and features, size, ease of fixturing, and the production rate required.

The relative movements of the wheel may be along the surface of the workpiece (traverse grinding, through-feed grinding, cross-feeding), or it may be move radially into the workpiece( plunge grinding ).Because each abrasive grain typically removes only a small amount of material at a time, high rates of material removal can be achieved only if a large number of these grains act together. The abrasive in a grinding wheel are held together by a bonding material, which acts as supporting posts or braces between the grains. This wheel can be made up of various sizes and types of stones, diamonds or of inorganic materials.

The grinding machine consists of a power driven grinding wheel spinning at the required speed (which is determined by the wheels diameter and manufacturers rating, usually by a formula) and a bed with a fixture to guide and hold the work-piece. The grinding head can be controlled to travel across a fixed work piece or the workpiece can be moved whilst the grind head stays in a fixed position. Very fine control of the grinding head or tables’ position is possible using a vernier calibrated hand wheel, or using the features of NC or CNC controls.

Material from the workpiece is removed by abrasion which can generate substantial amounts of heat, they therefore incorporate a coolant to cool the workpiece so that it does not overheat and go outside its tolerance, the coolant also benefits the machinist as the heat generated may cause burns in some cases. Beside that the coolant can improve parts surface finish and dimensional accuracy.

 

     

 

 

 

 

 

 

   Schematic illustration of a horizontal-spindle surface grinder

Surface Grinding is one of the most common operations, generally involving the grinding of the flat surfaces. Typically the work-piece is secured on a magnetic chuck attach to the work tables of the grinder fixture. A straight wheel is mounted on the horizontal spindle of the surface grinder. Traverse grinding occurs as the table raciprocates longitudinally and is fed laterally (in the direction of the spindle axis) after each stroke. In plunge grinding, the wheel is moved radially into the workpiece, as it is when grinding a groove.

 

 

 

 

 

 

 

 

 (a)  Traverse grinding with a horizontal-spindle Surface grinder,

 (b)  Plunge grinding with a horizontal-spindle surface grinder, producing a groove in   the workpiece.

 

 

 

 

3.      Explain briefly the honing machine.

            Honing is an abrading operation mostly for finishing round hoes but also to lesser extent external flat and curved surfaces by means of bonded abrasive stones. Typical applications are the finishing of automobile engine cylinders, bearings, gun barrels, ring gages, piston pins, shafts, and flange faces. A flexible honing tool consists of a brush with abrasive nodules on the ends of the bristles. The tool or work piece, or both, are rotated and reciprocated in relation to each other to hone a hole. The two movements are run purposely out of phase to cover all the surfaces without a regular pattern or scratches.

            The other name for honing is super finishing, the pressure applied is very light and the motion of the stone has a short stroke. The process is controlled so that the grains do not travel along the same path on the surface of the work piece being honed.

            Hone forming simultaneously plates metal onto a base material and abrade the new surface to a desired dimension and finish. While a honing tool is revolved and reciprocated, electrolyte is circulated through the hole, and a current is passed between the tool and the work piece. The operation is fast. For example, in one operation 50 μm (0.002 in.) of copper is deposited inside a steel cylinder, and the surface is cleaned and finished to size, all in less then a minute.  An example of performance is the removal of 0.1 mm (0.004 in.) of stock in each of eight cylinders in 30 seconds to tolerances of less then 12.5 μm (0.0005 in).

 

4.      Comment on slideways or guideways used by the machine tools in the workshop.

a.                   There is only a certain machine use a guideways or slide ways. It only used for moving machine tools such as carriage and bed in a lathe. The guideways are linear bearings for translational movement between two members of machine tools.

 

 

 

b.            They should provide alignment and fitting ample load carrying capacity, adjustment of wear and lubrication and should not have stick-slip jokes. The requirement of guide ways are high accuracy, high surface finish, low value of frictional force and low wear rate. There are 4 types of the guide ways used by the machined tools.

 

                           i.                  Flat slide

Normally being applied for heavy duty work on large and heavy machine tables. It enables the fitter to align mating part independently in two planes by separating the guiding actions in the vertical and also the horizontal directions.

 

                         ii.V slide

   The arrangements can be either upward or downwards and gives location into two directions. This type of slideway will automatically adjust the position due to the weight of the workpiece on the top part and even the wear is greater at the saddle part, this will not affect the accuracy of the alignment

 

                        iii.Cylindrical slide

The only purpose of this type of slideway to be used is to determine accurate and rigid alignment. Other than that, it functions as a slideway to move work holding device and machinery parts.

 

                       iv.Dove slide

 This type of slideway is normally found on lathe cross slides and milling machine tables. The reason for the slideway to be in such way is, it is used for the guidance of parts which involves feed movements. In this case, dovetail slideway is more suitable in terms of aligning the workpiece.

 

5. Discus the safety factors that you see at the workshop.

      The safety factor at the workshop is very important and should be followed by student, technician and anybody who entered the workshop. This is because the workshop is the most placed where the accident or injury always happened.

 

a. In the machine tools workshop, there are already noticed at the outside door of the workshop the rule that must be follow before enters the workshop. Some of the rule is,

i.               Get the permission from the lecturer or technician before enters the workshop.

ii.             Wear a safety glass to avoid a chip from a running machined fly into your eyes.

iii.            Check your clothes and hair to avoid your hair or clothes get caught in spinning machinery and wear a appropriate shoes that give a sure footing.

b.                        General safety signboard is too small and placed only at once location. A safety signboard should be placed at every angle in the workshop, but there are a few safety signboards in the workshop.

c. Only a few fire extinguisher and fire blanket are placed in the workshop. This workshop has enough emergency doors.

The main switch should be in the room, but we can see in the workshop that they placed in the waste area.

 

 

 

 

 

 

 

 

 

 

6. Comment on the machine layout.

From the machine layout of the workshop, we can conclude that there are some minor modification should be made. Firstly, the store or the place for material stocking should be place in a better or a larger place and closer to the entrance so that material handling will be easier. This is because; some of the materials are really big and long, so, when the material is cramp in a place such as this it is a little annoying and may be dangerous for the either students or technician. If materials is stock on top of each other on the rack in a small place like that, we do not know in due time, anything can happen. Closer to the entrance will also means in less time and energy use to handle the material.

Secondly, at the entrance of the workshop a large table is place. Although the table is use by the lecturer and students when the introduction and discussion are being done, but, it is inappropriate to be place there. The reason is that the table will block half of the entrance doorway and if a large material or machine needed to be transported into the workshop, then, it will be a problem because the table will need to be put aside before the material or machine can be transport. The entrance should also need to have a ramp so it will be easier to move heavy objects into the workshop.

Other than that, the other condition of the workshop is very good. The workshop has decided where to put the machines depends on the scale of metalworking they do which determines the clearance area around these machines if they need to handle long stock or large sheet goods. They have considered work flow to avoid an excess amount of running around the shop to accomplish tasks, as well as how to power the machines without turning the workshop into a snake pit of extension cords.
Most other machines tool work harmoniously lined up along the walls, where they are easy to power and connect. Other things such as the worktable and chair have sufficient volume for the students and the height is just perfect. 

 

 

 

7. What is the ‘ideal workshop’ in your opinion?

         In my opinion, the ‘ideal workshop’ must fulfill some criteria. The important thing is the arrangement of the machine tool. Because it may affects the production rate and the quality of the product. The workers must feel comfortable when their works in the workshop because this person fulfill their whole half day in this place.

         The lighting and air ventilation must good because it can cause injury when the workshop have poor lighting and not have good air flow. The workshop also must have higher safety detection and protection. it include the fire systems and other safety hazard.

 

 

CONCLUSIONS

 

From this tour, we had gain some important knowledge about the operation of the machine like band saw machine, lathe machine, milling machine, drilling machine and other machine that stated above. We also know about the important of the machine layout because it influences the productivity of the product. The safety in the workshop is also important because in the workshop, there have many hazardous and dangerous. The study of machine tool is very important because it are dangerous and their incorrect operation can result in serious injury and the workshop is not the place  to play because it is not the playground.