Classification of automatic transfer lines

1. An automatic transfer line (transfer machine) is a system of machine tools, work transference devices, and checking devices, which automatically carry out machining or assembling with predetermined interconnection and sequence, being operated by a central control system. Automatic transfer lines represent a higher stage of manufacturing process organization.

2. Automatic transfer lines (or simply transfer lines) fall into nine categories, depending on the mode of feeding blanks into the line and ejecting finished parts out of the line (piece-by-piece, a group of parts, a continuous flow of parts). Depending on the rate of production, transfer lines are classified as single-flow (progressive action) lines and multiple-flow (parallel-progressive) lines. As to the type of machine tools employed, there are transfer lines with special machine tools designed and built for a given line, with unit-built machines, with semi- and fully-automatic general-purpose machines, and with modernized (automated) universal machines.

3. As to the type of intermachine transfer system, transfer lines are classified as:

a) the pass-through type in which the workpiece passes through the clamping zone (this type being used for machining housing-type parts on automatic unit-built machines);

b) the overhead type, where the workpiece is conveyed horizontally in a longitudinal direction and vertically in a transverse direction;

c) the side-loading (frontal) type with longitudinal and transverse conveying movements;

d) the combined-transfer type;

e) the rotary conveying type, used in rotary transfer lines.

4. With respect to the arrangement of equipment, transfer lines are divided into closed-loop and open-loop types. Closed-loop transfer lines may be circular and rectangular. Circular transfer lines, for example, rotary transfer machines, feature a small number of stations and a rotary indexing table. Most transfer lines have an open-loop arrangement, such as straight-line (in line), L-shaped, U-shaped, W-shaped, and zigzag.

5. The kind of workpiece and the sequence of operations in a manufacturing process are the key factors which determine the type of transfer line. As to the kind of workpieces machined the transfer lines are classified, as those for housing-type parts, for shafts, for disc-shaped parts (gear wheels, etc.), for antifriction bearing races, and for small parts (screws, pins, rollers, etc.).

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The rate of production and the control system are the key factors which determine the type of transfer line.

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