030070162 Selin KÖK 8th week

1. DoE

(old)

Design of experiemts (DOE) is a planned approach for determining cause and effect relationships. It can be applied to any process with measurable inputs and outputs. DOE was developed originally for agricultural purposes but during World War II and thereafter, it became a tool for quality improvement, along with statistical process control (SPC). Until 1980, DOE was mainly used in the process industries perhaps because of the ease with which engineers manipulate factors such as time.temperature, pressure and flow rate. Then, stimulated by the tremendous success of Japanese electronics and automobiles, SPC and DOE underwent a renaissance. The advent of personal computers further catalyzed the use of these numerically-intense methods.

DOE is now used for a number of different purposes, including:

Development of new products and processes, Enhancement of existing products and processes, Optimization of quality and performance of a product, Optimization of an existing manufacturing procedure, Screening important factors, Minimization of production costs and pollution and Robustness testing of products and processes.

(Mark J. Anderson, DOE Simplified: Practical Tools For Effective Experimentation,p.ix)

(new/better)

Design of Experiments (DOE) is a powerful technique used for exploring new processes, gaining increased knowledge of the existing processes and optimizing these processes for achieving world class performance.

DOE never has been a favourite technique for manyof today’s engineers and managers in organizations due to the number crunching involved and the statistical jargon incorporated into the teaching mode by many statisticians.

Design of Experiments refers to the process of planning, designing and analysing the experiment so that valid and objective conclusions can be drawn effectively and efficiently. In order to draw statistically sound conclusions from the experimen, it is necessary to integrate simple and powerful statistical methods into the experiment design methodology. The success of any industrially designed experiment depends on sound planning, appropriate choice of design, statistical analysis of data and teamwork skills.

(Jiju Antony, Design of Experiments for Engineers and Scientists, p.7)

2. Spindle Head

(old)

The CNC machine differs from a conventional manual machine in several respects. The principle of operation of a numerical controlled machine can be explained with the help of Fig. 12.1. The figure shows a vertical milling machine. For carrying out an operation like end milling the spindle head is to be positioned in Z- axis and the table in X and Y coordinate axes. The feed movement is to be realized by the individual or simultaneous movement of X and Y axes. Thus the milling machine requires three
slide movements, which are usually referred as axes feed drives. A special feature of a CNC machine is that a separate motor called a servomotor individually drives each axis. AC servomotors are the preferred choice for this purpose today. DC servomotors were widely used earlier. The slides are driven by the servomotors through recirculating ball screw and nut assemblies. The use of re-circulating ball screw reduces friction, backlash and wear. The low friction reduces the torque required at the motor and the lost motion through torsional deflection of the screw. The use of ball screws also improves the dynamic response of the system. In some modern designs, particularly in the case of high-speed machines, linear motors are used in the place of servomotor ball screw combination. 

In this type of machining X-axis table or column provides traverse and spindle head provides Y-axis traverse. The saddle or column, or headstock or spindle head provides the Z-axis traverse. These machines are invariably used with a rotary indexing table to facilitate multiphase machining at different angles in a single setup. The axis of rotary table is parallel to Y-axis and is called ‘B’ axis.
( CAD/CAM/CIM, P. Radhakrishnan S. Subramanian V. Raju,p343-356)

(new/better)

Spindle head is a ram slide mounted on a vertical column.  Depending upon the number of spindles these are also classified as simplexi duplex or triplex machines. These machines have manual adjustment of all slides. They also have an automatic table control. Some of these are equipped for automatic cycling of the spindle heads and a few have automatic control of the table and spindle head.

( Hmt,Hmt, H M T Bangalore Production Technology, p. 188)

3. VFD

(old)

Vacuum florescent displays invented in japan in 1965 and were originally used only in calculators.But now they are a practical display device consisting of flat multi digit panels and is used in audio and video equipment household electronics automobiles office equipment and instrumentation.
VFD tubes operates in the same way with CRTs.The fiament(or filaments) is a very fine wire that is heated to a temperature just below incandescence.At that temperature it remains virtually invisible but it emits thermoelectrons.Accelerated electrons emitted from cathode bombard anode coated with phosphore and phosphor then emits CL.But kinetic energy of accelerated in VFD is much small compared to CRT.In CRTs electron beam constructed into a fine beam is scanned over phosphor layer from top to bottom to produce image while in VFDs electron beam is broadly difused and irradiated layer segmets gives the desired display.(Lumenescence and Display Phosphors :Phonomena and Applications ,Arunachalam Lakshmanan,p:67)

(new/better)

Vacuum florescent displays (VFDs) are now commonly used in consumer electronic products anda re recognizable by their green or blue-green glow. The basic structure of a VFD is shown in figure. The glass anode substrate holds the connector conductors, the insulation layer, the anode, and phosphor layer. These structures are formed by thin-film and thick-film processing. The grid structure is positioned over the anode and the cathode filaments are stretched and held aboce the grid. The entire structure is then  sealed in an evacuated cell.

(Joseph A. Castellano, Handbook of Display Technology, p. 163)

 

 

4. Clipping  

(old)

There is no old definition

(new/better)

Clipping is the process of determining the visible portions of a drawing lying within a window. In clipping each graphic element of the display is examined to determine whether or not it is completely inside the window, completely outside the window or crosses a window boundary. Portions outside the boundary are not drawn. If the element of a drawing crosses the boundary the point of inter-section is determined and only portions which lie inside are drawn. Readers are advised to refer to books on computer graphics for typical clipping algorithms like Cohen-Sutherland clipping algorithm ( P. Radhakrishnan,S. Subramanyan,V. Raju Cad/cam/cim , p. 51)

5. Electrolytic grinding

(old)

Electrolytic grinding is a combination of the electrochemical machinig and conventional grinding.A rotating abrasive wheel which s a metal-bonded diamond wheel is used as tool electrode.The wheel is a good conductor of electricity.The electrolyte is fed between the wheel and the work surface in the direction of the wheel rotation.The electrolyte is fed at the wheel periphery and is carried past the work surface by the action of work rotation.A constant gap is maintained between the wheel and the work surface.

(Singal R.K. Et.Al,R K Singal,Mridual Singal,Fundamentals of Machining and Machine Tools, page 176)

(new/better)

When the workpiece contacts the bed of the machine, an electrolytic cell is formed, with teh work piece as anode and the body of the grinding wheel as cathode. The insulating abrasive particles in the grinding wheel protude evenly above the wheel surface, and when the workpiece is pressed into contact with these, the height of the abrasive particles above the whee determines the effective gap between the anode and cathode. It is in this space that electolysis actually takes place.

( P. C. Pandey,H. S. Shan, Modern MacHining Processes, p.76-77)