Screw conveyors work on the inclined plain principle of mechanics and is one of the simplest machines. As the screw rotates, the flighting inclines the product inducing both a forward and upward motion. The forward motion is what moves the product from the inlet to the discharge. The flighting is attached to the center pipe and driven by the driveshaft. In the world of screw conveyors there are two ways to make flighting with one being called helicoid flighting and the other sectional flighting.
Helicoid Flighting
Helicoid flighting starts off as coils of flatbar and under immense pressure is formed continuously into a spiral with a specific outside diameter, inside diameter and pitch. The pressure is so much the metal is actually deformed causing the inside of the flighting to be thicker than the outside. Although this process does require a very specialized piece of equipment, it is relatively quick and requires very little labor aside from the initial setup. There are several advantages and disadvantages to helicoid flighting mentioned here.
Helicoid Advantages
- Low Costs – Due to the minimal amount labor required once the machine is running and there being virtually no scrap metal created in the process.
- High Quality – Due to the continual nature of the process the flighting is very consistent from part to part.
- High Strength – Since the flighting is 1-piece, there are minimal potential failure points.
Helicoid Disadvantages
- Not Customizable – Due the high setup time on the machinery, it I not practical to make custom sizes or materials of construction.
Sectional Flighting
Sectional flighting starts off as flat plate. “Donuts” are burned on a CNC plasma table and then the donuts are pressed in specialty dies to the required pitch. Almost any metal, thickness or size of flighting can be made using this process. Each flight is one pitch and the flights are fitted and welded to the center pipe one at a time to make the continuous spiral. This process is highly customizable but also highly labor intensive. There are several advantages and disadvantages to sectional flighting mentioned here.
Sectional Advantages
- Highly Customizable – Due to the many options for outside diameter, inside diameter, pitch, thickness and materials of construction.
- High Wear Resistance – Due to the ability to use hardened steel.
Sectional Disadvantages
- High Costs – Due to the required labor at each step in the process.
- Low Ascetics – Due to the welding required at each joint.
