Efficient separation of material

A separating roller separator, mounted at the outlet of the conveyor belt, is suitable in many cases for separating parts and sprues with different surface areas from each other. During this separation process, the larger, flat sprues run over the rollers, while the small parts fall through between the rollers. Depending on the type of components, it is also possible to use a disc separator. This is available as an attachment or as a free-standing device.

As with the screw separators, the main focus here is on stable, double-sided mounting of the individual rollers and individual speed control in order to achieve optimum separation results.

In addition, different roller coatings should be used wherever possible. Depending on the task at hand and the behaviour of the parts, it may be necessary for the roller coatings to be very grippy or smooth.

Separation drums are generally used for larger throughput quantities or component-sprue combinations where circulation can improve the separation result. The circulation process significantly improves the separation of entangled parts compared to separation attachments.

Roller separation drums are used to separate components and sprues with different heights. They can be used for a wide range of separation tasks. Separation drums are available with individual adjustment of the separation gap or with central adjustment (see photo).

With individual adjustment, each roller is fixed individually in the drum cage. The distance between two rollers defines the separation gap. As this adjustment is relatively time-consuming, this type of separation drum is only suitable for applications in which a machine is occupied with one article for a long period of time or in which several similar component-sprue combinations can be separated with a single adjustment.

Separation drums with central adjustment of the separation gaps are suitable, however, if a wide range of products is to be separated using the drum. The central adjustment allows quick adjustment – it can be set to a new product combination within a few seconds. Two rollers always form a fixed pair, so that only every second gap between the rollers is also a separation gap. This reduces the number of separation gaps compared to a separation drum with individual adjustment – the maximum throughput is lower.

In roller separation drums, it usually makes sense to drive the rollers by means of a belt tensioned around the cage. This results in counter-rotation of the rollers, which prevents jamming. In addition, the rotation of the rollers also increases the separation area within the drum cage. This significantly increases the throughput and also the separation efficiency compared to a drum cage with fixed bars.

Separation drums with perforated cages are used when the parts to be separated differ not in their height but in their surface area (e.g. coins with different diameters but the same material thickness). The advantage of perforated drums is their low price and high throughput. The entire cage can be perforated, and if the hole spacing is very small, the smaller components have many opportunities to fall out of the drum with each rotation.

The disadvantage of perforated drums is that the hole geometry is fixed and therefore only suitable for a limited range of parts. However, complete drum cages can be easily exchanged to cover a correspondingly larger range.

Depending on the application, many different materials are used for the drum cages. In addition to steel and stainless steel cages, rubber or silicone materials can be used, for example, to ensure the best possible protection of parts and noise minimisation.

Hedgehog separation drums are a special type of perforated drum for specific part geometries. In this process developed by MTF, sleeve tubes with the same geometry and size as the holes are attached to the outer circumference of the drum cage in line with the holes. This ensures that S-shaped parts, for example, cannot "wiggle" through the holes.

These parts can only dip into the sleeve tube with their tip, but then fall back into the drum cage. The sleeve tubes also prevent parts that are prone to snagging, such as sprues, from getting stuck in the holes.

The rectangular drums are a completely independent type of separating drum and are mostly used for very complex part geometries or soft materials. These separating drums have four separating columns, each consisting of two 80 mm wide parallel surfaces. The drum cage is made entirely of stainless steel, which means that the rectangular drums can also be used in the production of medical devices or in clean room environments. The smooth surfaces are very easy to clean.

As with the roller separation drums and screw separators, separation is also achieved here by the height of the components. However, the parallel design of the separation gap also prevents components from "slipping through".

The separation gap is adjusted using threaded spindles. The height of the separation gap can be precisely adjusted and read using scales. This ensures a high degree of repeat accuracy.

Another key feature of the rectangular drum is the MTF Technik-patented process whereby the separation gap opens with each rotation. A special mechanism causes the separation gaps to open briefly in the upper area. This allows components that can become jammed in other drums, such as very small or pointed components, to be separated in the rectangular drums. Even very soft materials (e.g. rubber or silicone) can be processed very well in this type of drum.