A centreless screw conveyor system consists of a casing and a rotating screw. Only when those two elements are appropriately finished and stand in good balance can products be conveyed from one point to another effectively.
To improve this process, there are different finish levels with several options. For example, rolled screws or those composed of separate screw blades.
A high gloss polished screw is not always the most suitable for conveying all types of products. In this article, we’ll discuss what level of finish ensures the best results.
Rolled Screws vs Separate Blade Screws
Before exploring different finishes for screw conveyor systems, let’s discuss the difference between the two screw types. Where material type and mechanical quality are concerned, the two screws are similar. The main difference lies in the finish.
The surface of a rolled screw is rougher. It doesn’t take as long to produce a rolled screw because it consists of fewer independent parts. Additionally, the blades of rolled screws taper, whereas a screw with separate blades has consistent blade thickness.
Rolled screws are created by moving the screw blade directly around the inner tube. As a result of this, the starting material is pushed between two rollers around the tube. The blade on the inside is thicker than on the outside. This construction process has few disadvantages and is easy and quick to repeat.
Rough vs Smooth Surfaces
As we’ve hinted, a smooth finish doesn’t always link to the best results.
First of all, the smooth finish of a screw with multiple independent blades consists of much manual work. The blades for the screw are cut from sheet material and a hydraulic press presses them to the right pitch. Once the blades are fixed to the screw tube, this provides a completely smooth, high-gloss surface that helps convey products in a more streamlined fashion.
The high-quality appeal of the screws often makes people believe that they are the better finish type all around. This, however, is misleading.
A smooth finish isn’t suitable for all types of products. In fact, a smooth surface makes it more likely for the product to stick to the screw. Rougher surfaces can prevent sticking and therefore push the product along more efficiently.
How The Finish Affects Conveyor Performance
Of course, the screw isn’t solely responsible for conveying the product. It has to work in conjunction with the body (casing) to be effective. Whilst the screw pushes the product forward, the type and amount of movement correlate to the casing type.
In other words, a combination of the correct movement and friction dictate how well a screw conveyor system can perform.
A higher level of finish may be achieved with screws composed of several blades when the conveyor system handles a non-sticky substance where there is no risk of fouling. The wrong choice of the screw could affect conveyor performance. So if the material you’re conveying is likely to stick to surfaces, avoid a smooth finish.
There’s a Screw for Every Industry
The product you convey matters and should be your primary consideration when deciding on a finish for your screw conveyor system. That’s why nearly every industry has a preference for a specific type of finish.
Many pharmaceutical companies opt for the smoothest finish. But a smooth finish is also popular in the food sector. This is because smooth screws lead to a flexible conveyance process and make it unlikely for bacteria to get stuck in chinks and holes in the screw.
Unsanded screw finishes with a rougher surface find their purpose in the recycling industry. Here, chopped plastic flakes and rubber granules risk sticking to the surface and are more easily warded off by rolled screws.
The same goes for industries in which the product is semi-finished and in a state of wetness or moisture.
To enjoy the best performance for your screw conveyor system, it’s essential to pair the appropriate finish level with the casing.