Emre Ayaroglu - 7th Week Unanswered

Power tooling

Turning centres, like any lathe, normally feed a stationary tool into the rotating workpiece. This is satisfactory for components that are circular about their rotational axis or if holes are required along the machine’s rotational centre-line. However, if features that cannot be produced by such relative motion are required, then, after all turning operations are completed, it is necessary for the part to pass to other forms of machine tool, such as a milling machine or drill. With the advent of power tooling, these separate operations can often now be avoided. A power tool, as its name implies, is tooling that has its own power supply, which enables it to rotate independently of the main rotational axis of the machine tool. With the component still clamped in themachine’s chuck, but of course not rotating, the turning centre can then be programmed to bring in suchpower tooling to any required position relative to the workpiece. In this way machining radial holes, flats, etc.is possible, and even cam-type profiles can be produced by controlling precision feed in the C-axis relative to movement of the power tool in the x-axis. In many cases, by judicious planning, quite complex parts can be completed entirely on the turning centre.This avoids the time and cost of setting up a succession of secondary machines and the queuing delays that inevitably occur as batches of parts pass from one machine tool to another. Thus, productivity can be dramatically increased with a modest capital outlay in power tooling monitoring (Waters F., Fundamentals of Manufacturing for Engineers, p. 259).

Powder rolling

It is possible to produce rolled metal strip commercially by the PM. The metal powder, instead of be ingpoured into a die, is continuously fed into a rolling mill, which then produces a preform in the form of an endless strip. The strip next passes through a sintering oven, and is then rerolled (a form of continuous coming), to produce the final strip material . This process is particularly attractive for the production of small quantities of special metal mixes and for metals such as stainless steel that require a number of annealing steps if rolled from wrought material monitoring (Waters F., Fundamentals of Manufacturing for Engineers, p. 180).

Selçuk TEVRÜZ, 030070128, 8th week

4 Bar Linkage (March 31, 2011 - 01:07)

In all applications of 4-bar linkages one bar is fixed and is termed the frame; see AB in the figure above. The two bars which rotate about the fixed points A and B are termed cranks, while the bar DC opposite the frame is called the coupler.

The characteristics of a given 4-bar linkages clearly depend on the relative lengths a, b, c, d of the bars and which bar is chosen as the frame. For the linkage to exist at all it is clear that no single bar can be longer than the sum of the remaining three, so:

a < b + c + d

b < a + c + d

c < a + b + d

d < a + b + c

but other relevant inequalities are not so obvious.

(Bolt B., Mathematics meets technology, 2007, pg. 82)

Plastic Welding (March 31, 2011 - 00:40)

Although most types of plastics can be repaired with adhesive materials, hot-air welding is usually preferred for thermoplastics because of its speed and ease. A plastic welder only takes a couple of minutes to heat up to operating temperatures and, once hot, can weld at speeds ranging from 5 to 30 inches per minute, depending on the application. Best of all one can go directly to and from welding to sanding and painting without waiting for the repair to cure (although it might be necessary to allow a few minutes for the welded plastic to cool).

Many adhesives do require mixing and can take anywhere from 30 minutes to several hours to cure, but heat can be used to shorten the curing time. This is not necessarily a disadvantage because repair technicians can always find something else to do while the adhesive cures. As for surface preparation, both welding and adhesives require some grinding, sanding, or trimming for good adhesion. More preparation is generally needed with adhesives, however, because the edges of the damaged area often have to be featheredged before the adhesive is applied. Some adhesives also require reinforcing or support patches behind the damaged area, making the repair a several step process.

To accomplish a plastic weld, either of two types of equipment can be used:

Hot-air welder

Airless

(Scharff R., Mullen K., Corinchock J.A., Complete Automotive Estimating, 1990, pg. 106)

Hooke's Coupling (Universal Joint) (March 31, 2011 - 00:52)

It is a rigid coupling that connects two shafts, whose axes intersect if extended. It consists of two forks which are keyed to the shafts. The two forks are pin joined to a central block, which has two arms at right angle to each other in the form of a cross. The angle between the shafts may be varied even while the shafts are rotating.

(Narayana K.L., Kannaiah P., Reddy K.V., Machine drawing, third edition, 2006, pg. 123)

Stitching (March 3, 2011 - 01:24)

Stitching has been used for more than 20 years to provide through the thickness reinforcement in composite structures, primarily to improve damage tolerance. The major manufacturing advancement in recent years has been the introduction of liquid molding processes which allows stitching of dry preforms rather than prepreg material. This enhances speed, allows stitching through thicker material, and greatly reduces damage to the in-plane fibers. Besides enhancing the damage tolerance, stitching also aids fabrication. Many textile processes generate preforms that cannot serve as the complete structure. Stitching provides a mechanical connection between the preform elements before the resin is introduced, allowing the completed preform to be handled without shifting or damage. In addition, stitching compacts (debulks) the fiber preform closer to the final desired thickness. Therefore, less mechanical compaction needs to be applied to the preform in the tool.

(Campbell F.C., Manufacturing processes for advanced composites, 2004, pg. 312)

Çağatay Taylan TAN 030070119 8th week

Fillet Weld
A fillet weld is used to fill in the edges of plates created by corner, lap and tee joints.Filler metal is used to provide a cross section approximately the shape of a right traingle.It is the most common weld type in arc and oxyfuel welding because it requires minimum edge preparation- the basic square edges of the parts are used.Fillet welds can be single or double (i.e., welded on one side or both) and can be continuous or intermittent. (i.e., welded along the entire length of the joint or with unwelded spaces along the length.)

(Fundamentals of modern manufacturing,materials,processes and systems,3rd edition Mikell P.Groover, p.694)

Sewing
Sewing is a common joining method for soft, flexible parts such as cloth and leather.The method involves the use of a long thread or cord interwoven with the parts so as to produce a continuous seam between them.The process is widely used in the needle trades industry for assembling garments.

(Fundamentals of modern manufacturing,materials,processes and systems,3rd edition, Mikell P.Groover, p.775)

Stapling
In stampling, preformed U-shaped staples are punched through the two parts to be attached.The staples are supplied in convenient strips.The individual staples are lightly stuck together to form the strip, but they can be seperated by stapling tool for driving.The staples come with various point styles to facilitate their entry into the work.Staples are usually applied by means of portable pneumatic guns, into which strips containing several hundred staples can be loaded.Applications of industrial stapling include ;furniture and upholstery , assembly of car seats, and various light-gage sheetmetal and plastic assembly jobs.

(Fundamentals of modern manufacturing,materials,processes and systems,3rd edition, Mikell P.Groover, p.775) 00.45

Cotter Pins

Cotter pins are fasteners formed from half round wire into a single two-stem pin.They vary in diameter ,ranging between 0.8 mm and 19 mm ,and in point style.Cotter pins are inserted into holes in the mating parts and their legs are split to lock the assembly.They are used to secure parts onto shafts and similar application.

(Fundamentals of modern manufacturing,materials,processes and systems,3rd edition, Mikell P.Groover, p.775) 01.00

Gökhan UÇAN- 030070028- 8th week

Adhesive Bonding 31.03 2011 00.17
Adhesive bonding is a joining process in which a filler material is used to hold two (or more) closely spaced parts together by surface attachment. The filler material that binds the parts together is the adhesive. It is a nonmetallic substance—usually a polymer. The parts being joined are called adherends. Adhesives of greatest interest in engineering are structural adhesives, which are capable of forming strong, permanent joints between strong, rigid adherends, A large number of commercially available adhesives are cured by various mechanisms and suited to the bonding of various materials. Curing refers to the process by which the adhesive's physical properties are changed from a liquid to a solid, usually by chemical reaction, to accomplish the surface attachment of the parts. The chemical reaction may involve polymerization, condensation, or vulcanization. Curing is often motivated by heat and/or a catalyst, and pressure is sometimes applied between the two parts to activate the bonding process. If heat is required, the curing temperatures are relatively low, and so the materials being joined are usually unaffected—an advantage for adhesive bonding. The curing or hardening of the adhesive takes time, called curing time or setting time. In some cases this time is significant—generally a disadvantage in manufacturing.
(Mikell P. Groover,Fundamentals of Modern Manufacturing,4th Edition,pg.756)

Blast Finishing: 31.03 2011 00.35
Blast finishing uses the high-velocity impact of particulate media to clean and finish a surface. The most well known of these methods is sand blasting, which uses grits of sand (S1O2) as the blasting media. Various other media are also used in blast finishing, including hard abrasives such as aluminum oxide {AI2O3) and silicon carbide (SiC), and soft media such as nylon beads and crushed nut shells. The media is propelled at the target surface by pressurized air or centrifugal force. In some applications, the process is performed wet, in which fine particles in a water slurry are directed under hydraulic pressure at the surface.
(Mikell P. Groover,Fundamentals of Modern Manufacturing,4th Edition,pg.663)

Vibratory Finishing: 31.03 2011 00.44
Vibratory finishing was introduced in the late 1950s as an alternative to tumbling. The vibrating vessel subjects all parts to agitation with the abrasive media, as opposed to only the top layer as in barrel finishing. Consequently, processing times for vibratory finishing are significantly reduced. The open tubs used in this method permit inspection of the parts during processing, and noise is reduced.
Most of the media in these operations are abrasive; however, some media per­form nonabrasive finishing operations such as burnishing and surface hardening. The media may be natural or synthetic materials. Natural media include corundum, granite, limestone, and even hardwood. The problem with these materials is that they are generally softer (and therefore wear more rapidly) and nonuniform in size (and sometimes clog in the workparts). Synthetic media can be made with greater consistency, both in size and hardness. These materials include AI2O3 and SIC, compacted into a desired shape and size using a bonding material such as a polyester resin.
(Mikell P. Groover,Fundamentals of Modern Manufacturing,4th Edition,pg.664)

Emulsion Cleaning: 31.03 2011 00.51
This cleaning method uses organic solvents (oils) dispersed in an aqueous solution. The use of suitable emulsifiers (soaps) results in a two-phase cleaning fluid (oil-in-water), which functions by dissolving or emulsifying the soils on the part surface. The process can be used on either metal or nonmetallic parts. Emulsion cleaning must be followed by alkaline cleaning to eliminate all residues of the organic solvent prior to plating.
(Mikell P. Groover,Fundamentals of Modern Manufacturing,4th Edition,pg.662)