A third classification of automation is a constantly moving or indexing device that conveys parts through the cleaning process. This can either be in the form of a conveyor that suspends parts on hooks or other fixtures that hang from an overhead track or in the form of a conveyor belt on which the parts rest as they are moved through the cleaning process. This type of automation is particularly attractive in cases where parts are already handled using a conveyor in manufacturing steps preceding or following cleaning and is also ideal in many “lean” applications. Good examples are sheet metal parts being cleaned prior to plating or painting. The use of a conveyor for cleaning often eliminates one or more handling steps which would otherwise be required if parts were cleaned in baskets or individual racks.
A clear benefit of using a conveyor system is that the cleaning process is continuous. Parts can enter the system at random intervals and still receive consistent processing. Parts progress through the cleaning process in order which means that batch integrity can be maintained if required.
Conveyors are probably best employed in applications where parts are not immersed for cleaning. Conveying parts through a spray washer, for example, is a relatively simple matter. Processing steps are aligned horizontally with the parts being moved by the conveyor. In cases where changing of the elevation of parts is required (as in an immersion process), the attraction of using a conveyor may be somewhat diluted.
One excellent application for a conveyor is in the processing of parts in “near field” ultrasonic applications. It is relatively simple to spin a part about its vertical axis using a simple sprocket arrangement similar to a rack and pinion mounted at the top of each suspension device.
- In order to immerse a part for cleaning, a conveyor must ramp vertically into and out of the immersion tank since most conveyors can not accommodate a drastic change in elevation within a short horizontal distance. Instead, the conveyor must gently slope to effect elevation changes. These gentle slopes can add considerable length to a cleaning system especially in cases where the vertical profile of the part being cleaned requires a considerable change in elevation for total immersion.
- In the case of a conveyor belt, immersion requires that the conveyor belt itself must be immersed in the cleaning process. In essence, the conveyor belt adds to the overall load on the cleaning system as, although it may not be dirty, it still adds to tank – to – tank carryover and requires drying on each pass.
As is the case with walking beams and pushers (which are really just intermittently indexing conveyors with a vertical motion component), a conveyorized process is relatively inflexible. The time in each processing step is determined by the relative horizontal length of each process step as the conveyor moves at a single speed. Slowing down or speeding up the conveyor will result in the duration of all process steps being increased or decreased accordingly and will, of course, result in a associated change in the total throughput capability of the system.
Although not applicable in all situations, conveyors are a viable option for automation for cleaning and are worthy of consideration especially in cases where parts are already being moved through the manufacturing process by a conveyor.
- FJF -