Halil Kayhan_030070090_2nd week_answers

1- Six Sigma, Previous :

A quality standard. Six sigma means that there are only 3.4 defective parts per million parts on each side of the distribution (or a total of 6.8 parts per million). Because of the nature of statistical distributions, this tacitly forces improvements in process capability to reduce variability. The six sigma concept also has been extended to business and office processes and operations.

(Kalpakjian S., Schmid S. R., Manufacturing engineering and technology, 1123)

Six Sigma, New:

Group: Quality Tool

Sigma (σ) is a letter in the Greek alphabet that has become the statistical symbol and metric of process variation. The sigma scale of measure is perfectly correlated to such characteristics as defects-per-unit, parts-per-million defectives, and the probability of a failure. Six is the number of sigma measured in a process, when the variation around the target is such that only 3.4 outputs out of one million are defects under the assumption that the process average may drift over the long term by as much as 1.5 standard deviations. Six Sigma may be defined in several ways. Tomkins (1997) defines Six Sigma to be “a program aimed at the near-elimination of defects from every product, process and transaction.” Harry (1998) defines Six Sigma to be “a strategic initiative to boost profitability, increase market share and improve customer satisfaction through statistical tools that can lead to breakthrough quantum gains in quality.”

The core objective of Six Sigma is to improve the perfor-mance of processes. By improving processes, it attempts to achieve three things: the first is to reduce costs, the second is to improve customer satisfaction, and the third is to increase revenue, thereby, increasing profits.

(Park, S. H., Six Sigma for Quality and Productivity Promotion, 2003)

New one is better, because it has detailed information.

2- Cutting Tool, Previous: 

A cutting tool has one or more sharp cutting edges and is made of a material that is harder than the work material. The cutting edge serves to separate a chip from the parent work material. Connected to the cutting edge are two surfaces od the tool: the rake face and the flank. The rake face, which directs the flow of the newly formed chip, is oriented at a certain angle called the rake angle. It is measured relative to a plane perpendicular to the work surface. The rake angle can be positive or negative. The flank of the tool provides a clearence between the tool and the newly generated work surface, thus protecting the surface from abrasion, which would degrade the finish. This flank surface is oriented at an angle called the relief angle.

(Ermutlu K., Groover M. P., Fundamentals of Modern Manufacturing: Materials, Processes and Systems, 4th Ed., pg. 486)

Cutting Tool, New:

Group: Machining Tool

A cutting device used in machining workpieces on regular, turret, and vertical lathes, boring and slotting machines, planers, gear-shaping machines, and special machine tools. It consists of a shank comprising a head with the cutting element and a holder that secures the cutter to the machine tool. 

Cutting tools are classified according to the shape of the head as straight, bent, cranked, and round-nosed cutters and according to the cross section of the holder as rectangular, square, and round. Cutting-tool designs may feature a head or cutting blade that is welded on, a blade that is soldered on, a head that is guided by a slide or produced in the form of an insert, or a blade that is mechanically fixed. Various types of cutting tools are distinguished according to the intended purpose, including straightway, facing, cut-off and grooving, boring, thread-cutting, radiusing, and shaping cutters. Depending on the machining process, cutting tools may also be classified as roughing, finishing, fine turning, and smoothing. A distinction is made between right-hand and left-hand cutters according to the feed direction. Among the materials used for the cutting element are tool steel, including high-speed steel, hard alloys, mineral and ceramic materials, synthetic diamonds, and Elbor (a synthetic corundumlike material). 

(The Great Soviet Encyclopedia, 3rd Edition (1970-1979)) 

The new one is better, because it has examples.

3- Feed rate, Previous: 

Feed rate is the velocity at which a tool is fed into a workpiece. Feedrates are expressed two ways: inches per minute of spindle travel and inches per revolution of the spindle. For milling applications, federates are generally given in inches per minute(ipm). For turning they are expressed most often in inches per revolution(ipr). Feedrates are critical to the effectiveness of a job. Too heavy a feedrate will result in premature dulling and burning of tools. Feedrates which are to light will result in tool chipping. This chipping will rapidly lead to tool burning and brake.

(Warren S. Seames, Computer Numerical Control: Concepts and Programming, pg. 72)

Feed rate, New:

Group: Machining Parameter

Feed rate is the velocity at which the cutter is fed, that is, advanced against the workpiece. It is expressed in units of distance per revolution for turning and boring (typically inches per revolution [ipr] or millimeters per revolution). It can be expressed thus for milling also, but it is often expressed in units of distance per time for milling (typically inches per minute [ipm] or millimeters per minute), with considerations of how many teeth (or flutes) the cutter has then determining what that means for each tooth. 

Feedrate is dependent on the: 

• Type of tool (a small drill or a large drill, high speed or carbide, a boxtool or recess, a thin form tool or wide form tool, a slide knurl or a turret straddle knurl).
• Surface finish desired.
• Power available at the spindle (to prevent stalling of the cutter or workpiece). 
• Rigidity of the machine and tooling setup (ability to withstand vibration or chatter).
• Strength of the workpiece (high feed rates will collapse thin wall tubing)
• Characteristics of the material being cut, chip flow depends on material type and feed rate. The ideal chip shape is small and breaks free early, carrying heat away from the tool and work.
• Threads per inch (TPI) for taps, die heads and threading tools. 

When deciding what feed rate to use for a certain cutting operation, the calculation is fairly straightforward for single-point cutting tools, because all of the cutting work is done at one point (done by "one tooth", as it were). With a milling machine or jointer, where multi-tipped/multi-fluted cutting tools are involved, then the desirable feed rate becomes dependent on the number of teeth on the cutter, as well as the desired amount of material per tooth to cut (expressed as chip load). The greater the number of cutting edges, the higher the feed rate permissible: for a cutting edge to work efficiently it must remove sufficient material to cut rather than rub; it also must do its fair share of work. 

(Peter, Smid, CNC Programming Handbook, 3rd edition, 2008, pg. 345)

New one is better, because it has detailed information.

4- CNC Milling, Previous:

CNC milling machine or machining centres are computer-operated milling machines. If you compare a conventional milling machine to a CNC machining centre, you will be able to identify the same components such as the chuck, the cutting tool and the bed. The only real difference between a CNC machining centre and a milling machine is that the CNC machining centre has a computer control.

(Brink C., McNamara B., Engineering Fabrication-Sheet Metal Work, p.151)

CNC Milling, New:

Group: Machining Type/Cutting Process

Many different types of CNC machines are used in industry, and the majority of them are CNC
machining centers and CNC lathes.The description of CNC milling machines is so large.All machine tools from a simole knee type milling machine up to a five axis profiler can be included in this category. They vary in size, features, suitability for certain work, etc., but they do all have one common denominator-their primary axes are the X and Y axes- and for this reason, they are called the XY machines.
Milling machine is a machine capable of a simultaneous cutting motion, using an end mill as the primary cutting tool, along at least two axes at the same time.

(Peter Smid, CNC programming handbook: a comprehensive guide to practical CNC programming, p.8)

The new one is better, because it has detailed information.
5- Planar Coating:(previous)

Planar coating is used to coat fabrics, paper, cardboard, and metal foil; these items are major products for some plastics. The important polymers include polyethylene and polypropylene, with lesser applications for nylon, PVC, and polyester. In most cases, the coating is only 0.01 to 0.05 mm (0.0005-0.002 in) thick… In the roll method, the polymer coating material is squeezed against the substrate by means of opposing rolls. In the doctor blade method, a sharp knife edge controls the amount of polymer melt that is coated onto the substrate. In both cases, the coating material is supplied either by a slit-die extrusion process or by calendaring.

(Groover, M.P., Fundamentals of Modern Manufacturing: Materials, Processes, and Systems, 4th Edition, p.285-286)

Planar coating: (New)
Group: Surface process

Coating processes involve forming a layer of polymer on a substrate, and a distinction may be drawn between 'planar' coating, where the substrate is a film or sheet, and 'contour' coating of three-dimensional objects.
Planar coating processes are used to coat a wide range of substrates-including thin metal foils (commonly aluminium), paper, cardboard, textiles and polymer film and sheet-with liquid polymer systems such as PVC plastisols, polyurethanes, rubber solutions and latices, to produce products as diverse as packaging films, waterproof fabrics, flooring, adhesive tapes and wallpaper.

(Arthur N. Wikinson, Anthony J. Ryan, Polymer processing and structure development, p 132 )

The previous one is better, because only groover book has the best detailed information.