Ahmet Gökay Öztürk 030050143 (11th week)

Rafted (Plated, Cassetted) Mills
The development of rafted mills was a major breakthrough in reducing roll change time from 8 hr or more on a large panel mill (or 4 hr on a smaller mill) to between 30 and 45 min and as low as 5 min. The mill has a bed on which the drive is located and the interchangeable plates are placed. The plates are holding four to eight or more stands. The number of stands on a plate is usually restricted by the lifting capacity (crane) at the user’s plant.
Both the operator-side and the drive-side stands are typical operator-side-type stands, complete with shafts and tooling. The drive-side stands usually have larger bearing blocks to accommodate pairs of cone bearings which rigidly hold the shafts in position during the operation and when the operator-side stand is removed for occasional roll change.
To allow quick plate (profile) change, the drive must have quick disconnect/connect feature. To further reduce the changeover time, only the bottom shafts are usually driven by the drive train firmly attached to the bed. All or some of the upper shafts can be driven by gears located at the drive-side end of the mill shafts.
(George T. Halmos, Roll Forming Handbook, pg. 2-11)


Phenolformaldehyde(Bakelite)

PF, the original “Bakelite,” is usually filled with 50 to 70% wood flour for molded nonstressed or lightly stressed parts. Other fillers are mica for electrical parts, asbestos for heat resistance, glass fiber for strength and electrical properties, nylon, and graphite. Phenolics represent one of the best polymers for low-creep applications. Moldings have good strength, good gloss, and good temperature range (150°C wood filled; intermittent use 220°C), but are rather brittle. Applications include electrical circuit board, gears, cams, and car brake linings (when filled with asbestos, glass, metal powder, etc.). The cost is low and the compressive strength very high.
(Frank Kreith, Mechanical Engineering Handbook CRC Press LLC, 1999, pg. 12-29)


Polyvinylchloride(PVC)

This is one of the most widely used of all plastics. With the resin mixed with stabilizers, lubricants, fillers, pigments, and plasticizers, a wide range of properties is possible from flexible to hard types, in transparent, opaque, and colored forms. It is tough, strong, with good resistance to chemicals, good low-temperature characteristics and flame-retardant properties. PVC does not retain good mechanical performance above 80°C. It is used for electrical conduit and trunking, junction boxes, rainwater pipes andgutters, decorative profile extrusions, tanks, guards, ducts, etc.
(Frank Kreith, Mechanical Engineering Handbook CRC Press LLC, 1999, pg. 12-28)



Doctor-Blade Process

Doctor-Blade Process (Tape casting) is used to make flat ceramic sheets having a thickness up to about 1 mm. The process was developed during the 1940s for capacitor dielectrics. The production of ceramic capacitors is still one of the most important applications of tape casting.
In tape casting, a slurry (also called a slip) containing a powdered ceramic together with a complex mixture of solvents and binders is spread onto a moving polymer (such as MylarTM) sheet as shown in Figure 27.1. In the early form of tape casting the slurry was actually spread onto moving plaster-of-Paris plates. The use of a polymer sheet was patented in 1961 and since then the process has not significantly changed. The principle of the process is essentially identical to spreading plaster on a wall, icing on a cake, or painting.
(C.C. Barry, M.G. Norton, Ceramic materials : Science and Engineering, pg. 480-481)