During this series of Automation Design Tips, we will be covering design elements of transfer specifically with rollers. As technology advances, components become smaller and more compact which requires specific automation techniques and maintenance. Transfer mechanisms require high versatility in its capabilities.
General Principles of Roller Transfer
The principle of transfer is the control of the frictional force to move the individual loads being transferred. In practice, the rotational force of the drive motor for transport is transmitted to the feed rollers. Due to the weight of the pieces acting on the feed rollers and the coefficient of friction in the feed rollers, the frictional force is produced in the tangential direction. The reaction force to the frictional force is how each piece is transferred per the figure below, Figure 1.
Therefore, as a rule, such mechanical design is required that can cause the frictional force to be generated at the point of contact between individual pieces and feed rollers to ensure steady transfer.
To minimize any possible effects on the transported item such as bending, the weight must be equalized on the rollers
Another method to minimize effects on the transported item is to install rollers that have a larger coefficient of friction. For example, the item or substrate being transferred could be sliding on the rollers, to combat this, installing urethane rollers would be a possible solution. Rubber O-rings and urethane rubber can increase friction to the roller. See figure 3 for an example, on the right shows the roller with an O-ring for added friction.
Now that design principles of rollers have been reviewed. Let’s take a look at three roller transport systems.
Roller Transport Systems
1 – Two Row Configuration of feed rollers (Fig.4-a)
If the transported materials vary greatly in deflection or the O-rings are worn partially or unevenly, poor or inconsistent contact between the material and rollers can result, leading to possible damage or bending of the material. In the designing of roller materials and diameters, consideration may be given so as to make the feed rollers at the respective ends serve as main rollers and the feed rollers in the middle act as sub rollers, thereby ensuring stable transfer.
2 – Three Row Configuration independent arrangement of feed rollers (Fig.4-b)
In order to minimize the effects of deflection of thin materials in the two row configuration, the items are supported and transferred on the rollers arranged in three rows instead of two. By installing rubber O-rings on the outer circumference of rollers to transmit the frictional force, increased and stabilized friction coefficient and enhanced ease of maintenance are expected.
3 – Three Row Configuration of feed rollers connected through one ring (Fig.4-c)
This design can involve the following problems: direct susceptibility to any differences (related to friction coefficient) between the three O-rings in contact with the transferred items, increased parts cost, and/or increased staff-hours for assembling and/or maintenance for stabilized tension of O-rings.
Among the three configurations, the second one shown in Fig.4-b is more favorable for transfer of materials with reduced thickness and weight. In the next post, we will expand on the second configuration and explain the capability of transfer in a straight flow. Stay tuned!