5.8 Stability analysis of machine operation
The stability of the operation of the machine has been described above, but it is limited to a certain situation, and it is analyzed from the perspective of the whole. If the machine is operated stably, the load is constant and the moment of inertia should also be constant. But in fact, due to the mechanism of variable-speed movement inside the printing machine, there is a concession value (due to the gap of the cylinder) in the operation of the cylinder, so its rotational inertia and load change. The moving parts on the printing press are divided into two categories: centering and non-centering. The former's moment of inertia is constant, and the latter's moment of inertia is variable. Then the total moment of inertia is:
J = J (constant) + J (variable)
To make the total moment of inertia J constant or close to constant, J (variable) should be close to zero, which requires the least number of non-uniformly moving parts on the machine. even if:
J = J (constant) + J (variable) = J (constant)
The total load is divided into three categories from the big aspect: â‘ the load formed by the printing pressure; â‘¡ the load formed by the opening and closing tooth force; â‘¢ the load formed by the friction force of each link. Due to the gap in the cylinder, the printing pressure changes once a week. It is a non-constant load. The opening and closing force is also performed once a week, and it is also a non-constant load. The friction of each link cannot be always constant due to the above two reasons. It can be seen from the above analysis that to make it a constant load, the printing pressure should be zero, and there is no switching action of opening and closing teeth, which is obviously impossible. In the actual process, the printing pressure should be controlled to a minimum, so that it starts from near zero. The force to open and close the teeth should also be minimal. In addition, it is necessary to avoid opening and closing the teeth at all junctions at the same time, otherwise a large impact will be formed. It is best to make all the opening and closing teeth of the drum move at intervals. This should include changes in printing pressure.
Chests of drawers have traditionally been made and used for storing clothing , especially underwear , socks, and other items not normally hung in or otherwise stored in a closet . They are usually placed in a bedroom for this purpose, but can actually be used to store anything that will fit inside and can be placed anywhere in a house or another place. Various personal sundry items are also often stored in a chest of drawers. It has a long history as one of the stand-bys of a carpenter's workshop. A typical chest is approximately rectangular in overall shape and often has short legs at the bottom corners for placement on the floor.
Chests of drawers often come in 5-, 6-, and 7-drawer varieties, with either a single or a double top drawer. The chest illustrated at right would be described as a '5 over 2 chest-on-chest', the latter term deriving from the fact that at one time it would have been made as 2 separable pieces. They are commonly made of wood, similar to many other kinds of furniture, but of course can be made of other materials. The inside of the drawers can be accessed by pulling them out at the front side. It is often placed so that the back side faces a wall since access to the back is not necessary. The lateral sides are also usually made such that they can be placed against a wall or in a corner. Although they can be plain in appearance, chests of drawers can also be made with a fancy or ornamental appearance, including finishes and various external color tones. Traditionally, drawers would slide out on smooth wood rails. Most modern cabinets use roll-out shelf sliders, made of metal, with rollers.
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