Roll feeding

The main problem with a feed controlled condition is that throughput is determined entirely by what the feed end manages to pull in and this is very sensitive to the conditions in the feed area. For this reason it is better to keep the machine running full so that the conveying characteristics of the screw determine output rather than the combined characteristics of screw, feed roll, feed opening and feed strip. The compression designed into a screw should therefore be sufficient to achieve complete filling at the lowest likely head pressure. 

Atmospheric single drum, applicator roll feed. 

Application of a vacuum to the feed material just prior to the rollers eliminates air pockets within the powder bed. This result in better venting and a more homogenous material feed into the compression zone. Regardless of roller orientation, vacuum deaeration was shown to reduce the leakage rate significantly (5). The location of the deaeration relative to the rolls/feed screws may impact its effectiveness. 

Roll feeding The simplest form of feeding roller presses is by gravity (choke feeding). A mass flow hopper with a rectangular feed opening to the nip between the rollers should be used for this purpose. 

Jaw crusher feed diameter 0.1 to 1.5 m reduction ratio 5 1 to 10 1 capacity 1 to 300 kg/s Mohs hardness <9 (reduction by compression). Gyratory crusher feed diameter 0.75 to 1.5 m reduction ratio 5 1 to 10 1, usually 8 1 capacity 140 to 1,000 kg/s Mohs hardness <9. More suitable for slabby feeds than jaw crusher (reduction by compression). Roll crusher feed diameter 1 cm reduction ratio 5 1 to 10 1 capacity 0.3 to 20 kg/s Mohs hardness <7.5. Suitable for softer, friable, and nonabrasive materials. OK for wet and sticky materials. Cone crusher and short head cone feed diameter <25 cm reduction ratio 5 1 to 10 1, usually 7 1 capacity 5 to 300 kg/s Mohs hardness <8. Usually secondary or tertiary crusher. Impact crusher pulverizers, shredders, or smooth roll feed diameter 1 cm with a reduction ratio of 7 1 to 10 1 capacity 0.3 to 50 kg/s. Mills, hammer, feed diameter 10 mm, reduction ratio 10 1 to 50 1, capacity 0.01 to 5 kg/s Mohs hardness <4.5. Maximum fines feed not hard or abrasive. Mills, ball, and rod feed diameter 0.5 mm with a reduction ratio of 10 1 to 50 1 Mohs hardness <9. Mills, autogenous, semiautogenous feed diameter 200 mm, reduction ratio 10 1 to 50 1 capacity 0.1 to 100 kg/s Mohs hardness <6. Mills, fluid energy feed diameter 50 pm reduction ratio 10 1 to 50 1 capacity <2 kg/s Mohs hardness <4.5. 

Special care should be taken when cut labels are used and when overprinting is carried out off-line, and in hand-packaging operations. Roll-feed labels are normally preferable to cut labels in helping to avoid mix-ups. On-line verification of all labels by automated electronic means can be helpful in preventing mix-ups, but checks should be made to ensure that any electronic code readers, label counters, or similar devices are operating correctly. 

Special care should be taken when using cut-labels and when over-printing is carried out off-line. Roll-feed labels are normally preferable to cut-labels, in helping to avoid mix-ups. 

Use of label code readers and label and pack counters. Use of roll-feed labels and electronic scanning of them before use, or on line, paying particular attention to labels on either side of any splice. 

Impact crusher pulverizers, shredders or smooth roll feed diameter 1 cm with a reduction ratio of 7 1 to 10 1 capacity 0.3 to 50 kg/s. 

Flaker c/s standard single roll, feed pan, knife and holder, variable speed drive FOB cost 175 000 at drum surface area = 2.5 m with n = 0.60 for the range 0.1-18. L+M = 2.6-2.75. L/M = 0.3-0.36. Alloy cost factors c/s, X 1.00. Prilling tower installed tower, spray unit, scrubber, pump, sump, ductwork and piping excluding air pollution control devices. PM cost = 14 250000 for a prilled capacity of 1000 Mg/d with n = 0.57 for the range 300-1200. Factor include wet scrubber for the vent gas, X 1.22. 

This system uses a slack loop to allow the leveler to operate continuously while the material is momentarily stopped for shearing (Fig. 12). After being uncoiled, the material passes through the leveler and continues into the accumulation loop. Upon emerging from the loop, the material enters the roll feed. The roll feed then measures the strip as it is fed into the shear. During each feed cycle, the material is stopped just prior to being sheared. Once cut, the finished parts are normally conveyed to a stacker. 

Figure 12 A typical looping-type cut-to-length line using a roll feed.

The leveler feed is normally driven by a DC motor. Similar to the roll feed, the motors used to drive the leveler have the ability to compensate for electronic feed error. However, unlike the roll feed, because of the number and size of the leveling rolls and the pressure that is exerted on the material during leveling (Fig. 17), the leveler feed is less susceptible to slippage. 

This type of multicut blanking line is similar to the slitter/roll feed system except that the leveler takes the place of the roll feed. After being uncoiled, the material passes through a simple straightener and continues into a slitter (Fig. 15). After being slit, strip dividers are used to separate the strands as they enter an accumulation loop. As the strips leave the loop, a second set of dividers align the strips... 

The same setup considerations that apply to the slitter/roll feed system described earlier would also apply to the slitter and stacker used in this system. This would also be true for material threading and scrap handling as well. Again,... 

Servo-driven roll feeds share many of the advantages with the press-driven variety, such as minimal space requirement, low maintenance, and high speeds. However, servo feeds also provide benefits that press-driven units cannot. The fact that they utilize a microprocessor-based control gives them an added dimension. Features such as programmable move patterns, self-diagnostics, auto correction, and the ability to communicate with automation—just to name a few—set them apart from other types of feeds. 

Servo-powered gripper feeds utilize a closed-loop servo drive coupled to a ball screw and nut to position the gripper they do not use stops or cushions. Feed set up information is programmed into the control unit via an operator interface or can be serially downloaded from another device. The control unit then commands the servo drive to position the gripper accordingly. Servo-driven units enjoy many of the advantages of electronic roll feeds in terms of programmability and the ability to interface with press automation systems. 

In general, roll-feed labels are preferable to cut-labels in order to prevent mix-ups. With the label accountability, also... 

Fig. 10. Automatic vacuum forming machine with roll feed and cutter. (Courtesy of M L Shelley Partners Ltd.)...

Further automation can be provided with thinner sheet formings by continuous roll feed as shown in Fig. 10. 

A more important module type for membrane applications is the spiral-wound module. Initially it was developed for reverse osmosis applications and is nowadays also used in ultra-filtration and gas permeation applications." The spiral-wound module is the next logical step from a flat membrane. It is in fact a plate-and-frame system wrapped around a central collection pipe, similar to a sandwich roll. Feed and permeate-side spacer material is glued along three edges to build a membrane envelope. A feed-side spacer is separating the top layer of two flat membranes simultaneously acting as a turbulence promoter (Figure 5.6). ... 

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