In automated manufacturing, linear transfer systems are becoming increasingly important. There are multiple forms of linear transfer systems including Robot Transfer Units, sometimes called 7th axis robots. One type of linear transfer system is a conveyor. Conveyors use a continuous looping surface in order to establish a means to move parts or assemblies along an assembly operation.
In some manufacturing operations, the parts or assemblies being moved have to be precisely positioned in order for the manufacturing operations being performed on them to be able to be accurately performed. One way to do this is with a precision conveyor. As you can imagine, constructing a precision conveyor system that will provide very accurate positioning in a repeatable way for long periods of time can be a design challenge.
Precision conveyor designers need to select drive and control systems that will deliver the required accuracy. They also need to select the conveyor surface and underlying support and alignment systems which will deliver accuracy and not require constant maintenance. Then holding parts and assemblies to the conveyor that will ensure accurate enough positioning is a challenge.
Two types of precision conveyors have evolved, precision belt conveyors and precision link conveyors. Each has its advantages and dis-advantages.
Precision Conveyor Type 1 - Precision Belt Conveyor
Precision Belt Conveyors as you’d imagine use a belt much like you’d see on a normal conveyor. Historically, belt conveyors were limited in their ability to precisely move components because the inertia of the belt and the load it carries causes the belt to slip on it’s driving roller. The difference between a normal belted conveyor and a precision belt conveyor is that on the inside of the precision conveyor, there are teeth that are molded into the belt. These teeth engage with mating teeth on the driving rollers, thereby preventing slippage. A precision belt conveyor can be an affordable solution where the precision that is delivered by precisely machined metal parts is not needed and where regular adjustment of the system can be tolerated as belts stretch and wear.
Precision Conveyor Type 2 - Precision Link Conveyor
Precision Link Conveyors utilize a ‘belt’ assembled of links, much like a chain. These links are individually machined to precise tolerances. When coupled with a precision drive system like a rotary index drive, precision link conveyors provide unparalleled repeatable accuracy in linear positioning. Wear is reduced by using high quality bearing sets at joints and by having hardened wear surfaces such as linear guide surfaces. Precision link conveyors can operate for extended periods of time with no calibration or adjustment.
When considering a precision conveyor system, engineers and buyers need to consider lifetime costs beyond the purchase price. Systems that won’t achieve accuracy goals can lead to low production or defective products. Constant operator intervention and adjustments are expensive as is having to frequently adjust or replace worn or stretched parts.