August 2011 Archives

A work transfer conveyor (Photo 1) with an auto-pause function for three stations is discussed here as an example of LCA mechanism design. A perspective view of this LCA mechanism is second from the right, bottom row in "Typical Applications of Standard Components: 1" on the center-page spread of the "FACE-FA Mechanical Standard Components Catalog."

(1) Main components of the work transfer conveyor

This simplified automated system (LCA) for positioning and transferring incoming workpieces on a conveyor can be used as an auxiliary system for a series of operations including, for example, feeding, positioning/inspection, and pre-ejection pauses. The components of this system are as follows:

1. Flat belt driven mechanism and belt tension adjustment mechanism
2. Motor torque transmission chain mechanism
3. Work positioning mechanism
4. Work detecting and drive controlling sensor system

(2) Points in work transfer conveyor design

Some creativity has gone into the following points to realize a low-cost, assembly-, adjustment-, and maintenance-friendly LCA system:

Gravity-operated feeder systems that require no drive mechanisms can be built inexpensively. This section outlines the principles and features of these feeder systems.

[Table 1] Features of gravity-operated feeder systems (chute type systems)

1. Descriptions

(1) Drop type

The distance (L) from storage hopper to workpiece holding carrier and the time (t) required for workpiece feeding can be determined using the following formula (See Fig. 1a):

The orientation of the workpiece can be kept unchanged while dropping using the characteristics of the shape of each workpiece and the position of the center of gravity.

(2) Sliding type

The feeding speed can be controlled using two design parameters: angle (θ) and friction coefficient (μ) of the slide chute (See Fig. 1b):

The friction coefficient (μ) is adjustable to some degree using the contact area of the transferred workpiece with the sliding surface. Therefore, the sliding speed can be controlled via the chute sliding surface, which may consist of, e.g., punched plates. The time t required for feeding can be determined using the following formula:

If equipped with a vibrational parts feeder, a sliding type feeder system is capable of aligned feeding of workpieces with complicated shapes. This section assumes the use of simplistic jigs, such as auxiliary jigs, for use in one-piece flow production lines.

In order to cope with various loads (weight, form factor: liquids and gases, micro components, etc.) different degrees of mechanization exist. The mechanization levels are classified and explained in the following table.

* Note 1)
Velocity control of linear transfers is commonly achieved by varying motor velocity, but LCA can be adopted for this by the use of non-linear gear combinations.