Roller materials

The rollers themselves or pockets and indentations that are machined into the working surfaces of the rolls form compacts or briquettes. Between smooth, fluted, corrugated, or waffled rollers, material is compacted into dense sheets (Fig. 8.118, see also Chapter 6, Fig. 6.5, lower left). Normally, these sheets are crushed and screened to yield a granular product. This process is called compaction/granulation. If the two rollers carry rows of identical pockets or moulds and the rolls are timed such that the pockets, representing roughly one half of the final product shape, match exactly (Fig. 8.119), so called briquettes are produced (see also Chapter 6, Fig. 6.5, lower right). 

FIGURE 4.6 Flexo-printing process schematic. Ink is transferred from a well to a flexible printing cliche by an anilox roller, and then from the cliche to the substrate. The choice of anilox roller material and well size and the position of the doctor blade, which removes excess ink from the anilox roller, determine how much ink is transferred. 

In a process requiring moving contact between two rollers, the design engineer must select roller materials that will have a maximum coefficient of friction for a given frictional force and applied load. One roller must be made of stainless steel. The second may be of stainless steel, butyl rubber, or a viscoelastic polymer. Which material will the engineer probably select Why ... 

Figure S.13 The production method of the roller materials using BF and nonwoven fabric.

The nonwoven fabric made from PP was used in the sample trial production experiment A 5wt% of PP was denatured with maleic acid and simultaneously mixed in the nonwoven fabric. The NF materials in the nonwoven fabric are called roller materials. These roller materials were manually injected into the screw of TSE and the pellet with 50-60 wt% BE was manufactured. The extruding machine used for the trial production is Kobe Steel KTX-30 and has the following technical specifications. 

The photographs of roller material and the pellets are shown in Figure 5.13 and Figure 5.14, respectively. 

Figure 5.14 Bamboo fiber reinforced thermo plastics (BFRTP) manufactured using roller materials.

Roller materials are supplied to the inner side of the resin under the driving force provided by the rotation of the screw of the TSE. If nonwoven fabric of considerable length is used, a pellet of uniform composition will be manufactured by continuous mnning. 

Using this system, roller materials were adjusted so that the ratio of the weight of BF and PP could be set at 50 50. Roller materials were supplied to the TSE and BE-reinforced PP pellets were manufactured. The screw rotated at a speed of 180 rpm and the sleeve temperature was set as 180 °C. In order to check the effectivity of this system, the tensile and flexural strengths with and without the system were compared. The results obtained are shown in figure 5.17. Bamboo fiber reinforced thermo plastics-automatically (BFRTP-AT)shows the case where... 

Roller materials are placed in positions A and B, shown in Figure 5.18. Two kinds of pellets were manufactured. These pellets were called Type A and Type B, respectively. First, the position of B is closer to the outlet than the positionof A. Thescrew... 

Glue, used for this purpose, should be of a not too dark average kind, and is mixed with so much glycerine as seems necessary for the roller mass. Roller material intended for printing needs far less glycerine than the roller mass intended for the transmission... 

Belt-conveyor scales determine the amount of material being conveyed on a belt. A section of belt is weighed by placing the belt support rollers on a scale the belt speed is also measured. Weight and speed data are suppHed to a controller which integrates them to arrive at a material flow rate, often stated in tons per hour. The controller may display a flow rate, shut the conveyor down when a predeterrnined amount of material has passed, or it may be used to maintain a specified flow rate. Accuracy is limited because of the number of detrimental influences involved, eg, variable belt tension. 

A belt press commonly uses two belts of woven material. Fmit mash is deposited on, and spread out evenly between, the two belts which converge and press the mash between them. The belts wrap around a series of successively smaller cylinders or pass between rollers (less efficient) for the pressing action. Juice yield for the wraparound belt press is 72%, and increases to 92% with secondary water addition (15). 

Pellet Mills. Pellet mills differ from roU briquetting and compacting machines in that the particulates are compressed and formed into agglomerates by extmsion through a die rather than by squeezing as they are carried into the nip between two roUs. Several types of equipment that use the extmsion principle are available. The die may be a horizontal perforated plate with rollers acting on its upper surface to press material through the plate. 

Fig. 10. Operating principle of a common design of pellet mill A, loose material is fed into pelleting chamber B, rotation of die and roller pressure forces material through die, compressing it into pellets and C, adjustable knives cut pellets to desired length. Courtesy of California Pellet Mill Co.

As only a small proportion of the material is in contact with the roUs and friction on the rollers is low, hard materials can be processed with tittle wear. The high pressure action creates a slab of ultrafine particles which usually requires a low speed impact milting system to disagglomerate. Used in closed circuit with such a disagglomerator and an air classifier, such machines can reduce the energy requirement for fine grinding many minerals. 

Roller Mills Pendulum, Table, and Bowl Type. This is a group of machines commonly applied for grinding of mineral powders down to approximately 97% below 75 p.m, or even finer in some instances. The mills operate at medium speed, up to approximately 30 m/s, and can handle materials with up to Mohs hardness 5 before wear rates become prohibitive. Many different designs are available the two most commonly encountered variants are pendulum mills and the table roUer mill. 

Ball- and roller-bearing materials ate commonly selected to provide a minimum Rockwell hardness of 58—60 R at load-carrying contacts (37,38). Below this level, fatigue strength drops so rapidly as to seriously impair the utiUty of a material for rolling beatings which involve contact stresses in the 700—2800 MPa... 

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