Roll changing

The film is wound to film rolls using a contact/surface winder with an option for automatic roll change (Fig. 9, 4). The production process can be controlled automatically, keeping meter weight and thickness distribution constant (Fig. 9, 5). This device enables automatic quality control in the production process. 

A typical coating line consists of fabric pay-off, the tower, and a take-up for the coated goods. Some lines also include a festoon (accumulator) to avoid the need for stopping the line if the web is being spliced or if the take-up has to be stopped for roll change or a problem. The take-up may be arranged as a turret for a faster roll change. 

Example of roll-change sequence winder (courtesy... 

Winders can use different methods of roll changing. Most winders used in the film industry are turret type, where the empty core is rotated into position by a turret mechanism and an automatic cutoff is made. 

Changeover frequency and method such as manual or subplated (rafted) roll change. 

Supercalenders are classic off-line machines as they have downtimes of 25-30% due to the fiUed roll change. To be able to keep pace with a high-speed paper machine at least two, sometimes even three, supercalenders were therefore required. This disadvantage of the supercalender led, at the begiiming of 1980, to the development of the soft calender. The soft calender consists of at least one heated roll and one resilient roll covered with synthetic material. Because synthetic rolls are much more resistant to marking than the filled rolls of the conventional supercalender, the soft calender was also able to be used on-line. In many cases, the online soft calender was very successful. However, not all quality demands on the paper surface could be met with it. For demanding papers, the supercalender equipped with filled rolls and which could therefore only be operated off-Hne remained the only alternative. 

The purpose of reeling is to wind up the continuously produced paper web on reel spools building up paper rolls of up to 4.5 m diameter. The paper rolls have to fit the requirements of any following process steps. These mainly concern the paper roll structure such as hardness and overall shape. As reehng is a discontinuous process economic aspects as regards broke due to roll change/tum-up are important as well. This concerns the so-called top broke at the outside of the finished parent roll and the bottom broke at the inner layers of the spool. 

In reeling one main requirement is a large paper roll diameter, for two main reasons First to reduce paper loss. A certain loss at each reel is unavoidable, so less reels with larger diameters for the same production reduce the overall loss. Secondly, to allow one single winder to cope with the paper machine output This can be reached by reducing the nonproductive time for parent roll change in this noncontinuous process step. Today Jumbo rolls with diameters of up to 4.5 m are produced. 

The machine on which reel slitting is done is commonly called a winder. Basically, wunders consist of equipment for parent roll change, an un-wind station for the parent rolls, a slitting station and a rewind station. 

Acceleration sensors are attached to bearings and close to roll shafts, to detect bearings at risk of failing and roll roundness abnormalities before they have a negative impact on the process. Thus bearing and roll changes can be done during the next planned shutdown of the machine, and do not cause extra... 

In this work, a microwave interferometric method and apparatus for vibration measurements is described. The principle of operation is based on measurement of the phase of reflected electromagnetic wave changing due to vibration. The most important features of the method are as follows simultaneous measurement of tlie magnitude and frequency of the rotating object high measurement accuracy weak influence of the roll diameter, shape and distance to the object under test. Besides, tlie reflecting surface can be either metallic or non-metallic. Some technical characteristics are given. 

Roll marks and the edge of the tube sheet provides distinct reference points as scan characteristics and tube thickness may change dramatically at these points. 

A web of molten plastic is pulled from the die into the nip between the top and middle roUs. At the nip, there is a very small rolling bank of melt. Pressure between the roUs is adjusted to produce sheet of the proper thickness and surface appearance. The necessary amount of pressure depends on the viscosity. For a given width, thickness depends on the balance between extmder output rate and the take-off rate of the pull roUs. A change in either the extmder screw speed or the puU-roU speed affects thickness. A constant thickness across the sheet requires a constant thickness of melt from the die. The die is equipped with bolts for adjusting the die-gap opening and with an adjustable choker bar or dam located inside the die a few centimeters behind the die opening. The choker bar restricts flow in the center of the die, helping to maintain a uniform flow rate across the entire die width. 

More recent developments in the rolling ball area include an automated micro viscometer, the Paar AMV 200, from Paar Physica. The specimen to be measured is introduced into a glass capillary down which a gold-covered steel ball roUs. The rolling time is measured automatically. The shear stress may be varied by changing the inclination angle of the capillary tube. The shear rate range is 10 1000, which makes the instmment useflil for... 

BlackTea. The black tea manufacturing process has evolved over hundreds of years, until the early part of the twentieth century, Httie was known about the chemical changes. The process consists of the unit operations of withering, rolling, fermentation, firing, and sorting (4). 

Roll presses are now manufactured by most cement-equipment manufacturers, for example Krupp-Polysius AG. For drives up to 1200 kW they are equipped with V-belt drives, allowing speed to be changed. Rolls in one particular crusher are 48 inches (1200 mm) in diameter and 30 inches (700-mm) wide and each weighs 90 tons. Machines with up to 2500 kW installed power and 1000 ton/h (900... 

When metals are rolled or forged, or drawn to wire, or when polymers are injection-moulded or pressed or drawn, energy is absorbed. The work done on a material to change its shape permanently is called the plastic work- its value, per unit volume, is the area of the cross-hatched region shown in Fig. 8.9 it may easily be found (if the stress-strain curve is known) for any amount of permanent plastic deformation, e. Plastic work is important in metal- and polymer-forming operations because it determines the forces that the rolls, or press, or moulding machine must exert on the material. 

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