How Are Flexible Manufacturing Lines Laid Out?

The overall layout of a flexible manufacturing line describes how its machine tools, auxiliary devices, and connecting workpiece-transfer equipment are arranged and linked.

Layout depends on production type, workpiece structure, transfer method, plant conditions, process sequence, and production program. Differences in part geometry, size, and rigidity require different transfer methods, and the transfer method largely determines the final line arrangement.

1. Direct Transfer

Direct-transfer equipment moves each workpiece sequentially between stations, using one of the workpiece surfaces as the transfer datum. Arrangements can be through-flow or side-transfer. Through-flow layouts include straight, angled, parallel-branch, and rectangular-loop forms.

1. Straight through-flow. The conveyor passes through the entire line. Two indexing devices divide it into three sections, and parts enter at one end and leave at the other. Transfer is simple and production floor space is used efficiently.

2. Angled through-flow. When a line has many stations or is too long for a straight shop layout, it can turn at one or more corners. At two corners, the workpiece can index naturally through 90°, eliminating separate horizontal indexing devices.
3. Parallel branches. When one operation takes much longer than the others, several identical machines can be installed in parallel to balance production takt.
4. Rectangular loop. This form suits lines that use traveling fixtures. The fixtures circulate naturally, eliminating a separate return system.
5. Side-transfer or non-through-flow. The main conveyor runs alongside the machines. A transfer unit moves each workpiece from the conveyor into the machine or fixture and returns it after processing. This supports multi-face machining and accurate relationships between surfaces, but requires a transverse transfer mechanism and more floor space.

2. Traveling-Fixture Transfer

The workpiece is mounted on a traveling fixture that moves through all stations. Fixtures can return horizontally, directly above or below the line, or along an inclined upper or lower path. A traveling fixture can carry a part around the line so that two side faces and the top face are machined in one circuit.

1. Horizontal return. The main and return conveyors form a closed loop in one horizontal plane. Fixtures circulate continuously, but the layout consumes considerable floor space.

2. Direct overhead return. The fixture rises at the end of the line, travels along an overhead roller track above the main conveyor, and descends at the start. This saves floor space, and an inclined track can use gravity to simplify return. It is generally unsuitable where vertical machines would force the track too high for convenient maintenance.

Direct underfloor return. The fixture returns through the machine bases below the main conveyor. This saves space, keeps the line open for adjustment and maintenance, and suits small fixtures and workpieces where shop area is limited.

3. Inclined upper or lower return. This arrangement is used when floor area, chip disposal, or vertical machines rule out horizontal, overhead, or underfloor return. For an inclined upper return, a chain drive raises the fixture to an overhead track behind vertical or inclined machines; it is suitable for larger workpieces and fixtures. For an inclined lower return, the passage is placed behind horizontal machines and suits smaller workpieces and fixtures.

3. Overhead Transfer

Overhead transfer suits shaft-type parts and complex workpieces without a suitable transfer datum. A gantry above the machines supports equally spaced handling robots. The robots transfer parts between machines and perform loading and unloading. The structure is simple and works well on lines with a relatively long takt, but it is limited to smaller, complex-shaped workpieces.