Cutting-Tool Machine Characteristics - Assignment Example

Abstract In this paper focus was at machine tools and characteristics. The cutting tool required to make a plumb bob have been identified, the materials they are manufactured from and the associated angles when in use. Some of the cutting tools identified in the manufacture process are: facing tool, knurling tool, round nose among others. In the calculation part the quantities calculated included feed rate; torque and force. The papers also looks into the causes of tool wear and how catastrophic failure may occur and how they can be avoided. Introduction In this there paper there focus is on the details of manufacturing objects on machine tools. A machine tool findings usefulness when it comes to shaping and machining metallic objects by grinding, cutting, boring shearing or any other forms of deformation. Task 1 During the course of the practical workshop activities, you would have encountered a range of cutting tools, from generating tools (for cutting flat/parallel profiles) to forming tools (for cutting particular profiles). With reference to the attached drawing (Appendix A), select the cutting tools that you plan to use for performing its required function. Included for each tool selected, identify the material it is made from and cutting angles (as appropriate). Plumb bob body Operation Tool Tool materials /angles  Face off (datum) Facing tool (1800) HSS Centre drill Centre drill bit (900) HSS drill6.8mm×19mm Drilling bit (900) Carbide turn19.5mm×50mm Round nose(450) HSS Knurl material Knurling tool (900) HSS turn16mm×10mm Round nose(450) HSS Chamfer1mm×45 Chamfering tool HSS Turn chamfer Turning tool HSS Turn taper40 Round nose (450) HSS Internal threading Threading tool(900) Carbide Plumb bob screw Operation Tool Tool materials  5-Face off (datum) Facing tool (1800) HSS  6-Centre drill Centre drill bit (900) HSS  7-Drill3.5mm×16mm Drilling bit Carbide  8-Turn11.5mm30mm Round nose HSS 9- Knurl material Knurling tool HSS  10-Turn8mm×12mm Round nose HSS  11-Chamfer 1mm45o Chamfering tool HSS  12-Undercut7mm×1mm Cutting tool (450) carbide  13-Thread m8×1.25mm Threading tool (900) HSS  14-Undercut to half diameter Cutting tool (450) Carbide Task 2 From the previous practical exercises you have performed, you would have turned a mild steel bar from Ø1” to Ø20mm by 80mm long. If the surface/cutting speed for mild steel is 28m/mm and feed/tooth on average is 0.05mm/rev determine what the cutting force will be for this process (use the formula sheet provide). Specific energy = 2 W.s/mm³. Refer to Appendix B for formula sheet. = 0.05x1x351=17.55mm/min Task 3 Calculate the speeds and feed rates for the following (referring to Appendix C): a) Spindle speed for turning a mild steel bar of Ø20mm with carbide tipped cutting tool. = 0.05x1x445.9=22.295mm/min b) Spindle speed for milling a high carbon steel material, using an Ø125mm high-speed steel HSS cutter. = 0.05x1x45.86=2.293mm/min c) Feed rate using a 4-tooth Ø25mm HSS end mill for cutting brass. = 0.05x4x573.2=114.64mm/min d) Feed rate using an HSS slot drill for cutting a 12mm wide slot in aluminium. = 0.05x1x1592.36=79.62mm/min Task 4 Produce a written report that describes the possible causes of tool wear and catastrophic failure that you could encounter during a manufacturing activity. NB: If you happen to experience any issues, relating to tool wear or catastrophic failure during your practical activity you can refer to them for this task. Tool wear may be seen as coming about as a result of several factors affecting the cutting edge. Tool failure may be catastrophic when the tool completely breaks or the work piece is destroyed beyond recovery. The survival of a tool cutting edge is determined by a number of forces that strive to ensure that the edge undergo changes. This comes into play by virtue of the interaction between the tool and workpiece material in the environment that has been provided for the machining process. We have four factors that come into play: mechanical, chemical, thermal and abrasive. A lot of heat is generated during the process of metal cutting both at the chip face as well as at flank of insert. There is very high level of thermal load that is subjected to tool materials and in some in milling operations a dynamic factor further come into play Thermal load is considerable on the took material and in some operations such as milling, there is also dynamic factor when edges leave and re-enter the workpiece. In the cheap formatting process there is continuous production of fresh metal interface and is forced to move along the tool material at high pressure and temperature as can be observed in (fig 1).There is creation of a zone which is conducive for diffusion and chemical reaction of the metals. Figure 1 In the workpiece there are always some hard particles whose hardness measure to that of the tool materials. This means that the tool is vulnerable to grinding, and abrasive effect. As a result of the tool being subjected to stresses, there is emergence of five wear mechanisms namely: abrasion wear; diffusion wear; oxidation wear; fatigue wear and adhesion wear. The effects the wear mechanisms will have on the tool is all dependant on the ability of the tool resisting loads. The most common wear type is abrasion and it comes as a result of the hard particles in the workpiece. Tool hardness defines the tool’s cutting edge ability to resist the abrasion encountered. Having a tool that is densely packed with hardest particles will equip the tool to withstand abrasive wear but the tool will not be immune to other load factors encountered during the machining process. Diffusion wear is fuelled by the chemical load present when cutting process is being undertaken. The chemical composition of the tool material and the affinity of the material for the material for the workpiece will dictate if and the extent of development of diffusion wears mechanism. The type of metallurgical relationship that exists between materials dictates the level of wear mechanism achieved. While some tools maybe un reactive to the workpiece materials, there may be tools which are vulnerable owing to there high affinity. A good case is that of Tungesten carbide tool and steel workpiece where there is high affinity to each other that leads to development of diffusion wear mechanism. The diffusion wear results to a crater being formed on the chip face on the insert. With the mechanism being dependant on the temperature level, it will be found in cases involving high speed cutting those results to rise in temperatures. There is occurrence of atomic interchange where there is movement ferrite from the steel into the tool and with carbon having a smaller size and being ready to move in iron, it thus diffuses into the chip. Having a combination of high temperature and air gives a conducive condition for oxidation. When these conditions are presented for Tungsten and Cobalt, then we will have porous oxide film being formed and these are readily removed by the chip. On the other hand there are other oxides such as aluminium oxides which will exhibit high level of hardness. This means that cutting tools will have varied proneness to wear that comes as a result of wear , more so when the area of focus the interface edge part where we have chip width finishing at the depth of cut and there is air access to the cutting process. Here oxidation is likely to result in production of typical notches in the edge though this phenomenon is rarely witnessed in modern machining. Task 5 Given that Vtⁿ = C, calculate the tool life expectancy of a High Speed Steel lathe tool operating for 4 hours at a cutting speed of 80 m/min. Once you have determined this, estimate the new cutting speed that will give a tool life of 10 hours (n = 0.125). Vtⁿ = C Rearranging C= Vtⁿ Taking log for both sides LogC=LogV+nLogt1 Substituting for given values LogC=Log80+0.125xLog240 LogC=1.9+0.298 LogC=2.198 From Vtⁿ = C Dividing both sides by tⁿ We have  Taking logs on both sides LogV=LogC-nLogt1 LogV=2.198-0.125Log600 LogVmax =1.85 Vmax = 101.85 = 70.8m/min Discussion In this paper we have looked at various issues with regards to machine tools and related issues. In the first task focus on the cutting tools and how they are used in the manufacturing process of objects. Some of the tools that were featured were the turning tool, the knurling tool, the drill bit, the chamfer tool among others. Apart from having the right tool it is important that the tool and the workpiece to held firmly. The workpiece is supposed to be held by the chuck as the piece in worked on a lathe machine. A workpiece held firmly by the chuck ensures that there is resistance the attempt of the workpiece to rotate under the force of the tool at the same time deflection is resisted. In using any cutting tool the angles involved in cutting comes into play as this determines the success of the process. An ideal angle will ensure minimal wear of the tool while some angles may result to the destruction of the workpiece and the cutting tool. Task 2 involved calculating the cutting force where the diameter of a mild steel workpiece was to be reduced from mm to 20mm. In the process of calculation it was important to calculate other quantities including power required; power dissipated and torque. In the third task there calculation were made and it was established that the spindle speed requirement was dependant on both the dimension of workpiece and cutting speed of the tool being used. Using the spindle speed the feed rate then calculated where the number of tooth being used was put into consideration. Tusk 4 involved the description of causes of tool wear. From the description it can it was found that high speed cutting leads to higher temperatures and this creates a conducive environment diffusion wear of tool depending on the material of cutting tool and workpiece. This is an indication that the usability of a tool on a certain workpiece may be dependant of the speed limit that is to be operated at. Conclusion In conclusion it can be said that manufacture of products choosing the right tool for the workpiece is very important. In addition to the tools it is important to operate at appropriate speed to avoid catastrophic failures. References Parker, Dana T.(2013). Building Victory: Aircraft Manufacturing in the Los Angeles Area in World War II, pp. 5, 7-8, Cypress, CA. ISBN 978-0-9897906-0-4. Thomson, Ross (2009), Structures of Change in the Mechanical Age: Technological Invention in the United States 1790-1865, Baltimore, MD: The Johns Hopkins University Press, ISBN 978-0-8018-9141-0 Zelinski, Peter (2013)."Hybrid machine combines milling and additive manufacturing", Modern Machine Shop Read More