Special Machines and Accessories
Pulled and cut products:
Most extruded products that undergo direct expansion are cut immediately after they emerge from the die opening using a rotary cutter, which is mounted on the die face, and the cutting blades move across the die opening. It is possible to create a range of interesting shapes using this cutting system. Schaaf holds the patent for the cutting system for making three-dimensional product shapes, which is based on this type of cutting process.
There is however often demand for products which are cut straight and long. Typical examples of such products include long cut stick-shaped products or extruded strips cut into longer pieces to look like rectangular chips. These products cannot be cut at the die-face and must be cut using a pulling and cutting machine. The product strands are pulled out of the die using pulling rollers. As the product moves through the air, it cools and loses moisture, and stiffens. This maintains its straight shape when it is cut using a rotary cutter; here, the rotating blades move transverse to the product strands cutting them into pieces.
Crispbread-type sliced products: another new type of product in this category is the sliced product where a product strand is extruded and then sliced into pieces after its structure has hardened sufficiently. This type of cutting leads to product pieces with an open cell structure on the cut surface, giving a visual impression similar to cut bread slices.
Machines for pulled and cut products:
- The Pulling and Cutting machine - as the name suggests, this machine is employed for the basic functions of pulling and cutting. It is used to manufacture products like sticks, hollow pipes and long cut chips. The pulling rollers and the cutting roller have variable speeds for adjusting the product speed and controlling the product length.
- The stripes printing machine - in this machine, the product strips are pulled and passed through a printing system for applying coloured patterns to both sides of the product. This is followed by a crimping process to give the product a wavy shape before it is finally cut to the specified length.
- The bread chip slicing machine - as the name suggests, this machine is used to slice a strip of extrudate into slices. The special design of the cutting unit in this machine allows for slicing either perpendicular to the grain or at a specified angle to maximise the cut surface area.
Products using colour injection:
The dual coloured products are a new category of products developed by Schaaf. Here colouring material can be selectively applied to certain parts or sections of the product to create very interesting visual patterns. Eg. it may be possible to create a disc with a special coloured central area or a special coloured border area. The products are coloured inside the processing section by injecting colouring materials into specially designed TURBO extrusion process sections to achieve products which are truly dual coloured and thus more attractive to potential consumers.
In order to be able to inject colour into the high pressure zones in the extruder processing area special pumps and delivery systems are used.
Co-extruded products are manufactured from a soft-centre-filled pipe with the help of different moulding/cutting systems.
- Co-extrusion die system - this is a special die system that allows the continual forming as well the filling of an extruded tube while it is being extruded. It contains all the necessary forming parts and filling pins needed, and is connected directly to the extruder processing section. Some models are capable of forming 1 to 6 filled pipes simultaneously.
- Filling mass pumping system - whilst the dough mass required for the outer pipe enters the co-extrusion die from the extruder processing section, it is necessary to have a separate unit to ensure a constant supply of the filling mass to the co-extrusion die at a controllable rate. This function is performed by the filling mass pumping system, which has between 1 and 6 pumps depending on the number of pipes to be filled. These special pumps are connected to a collective holding tank and have a variable speed for controlling the flow rate of the filling mass.
- Embossing machines for filled co-extruded pipes are used extensively to transform co-extruded pipes into interesting shapes. The filled pipe is guided between 2 rollers that have moulds for the desired shape. When pressed between the 2 rollers, the pipe is converted into a string of product pieces in the chosen shape; the product is then further processed as required.
- The embossed product usually remains a strip of connected pieces, which must then be passed over a suitable conveyor. This ensures steady transportation and assists in separating the individual pieces of product from the strip.
- Since most embossed products are separated from a strip of product pieces, a certain amount of fines is always generated. It is important to ensure that these fines are properly sieved out at the earliest possible opportunity so that do not enter further processing points.
- Different versions of the embossing machine are also used to manufacture special filled products with extremely small cross sections, which are otherwise not achievable using conventional co-extrusion technology.
- Other co-extruded product cutting systems include custom-made rotary cutters and guillotines. These are used for special products such as open-ended pieces.
Schaaf is always looking to develop new accessories for basic extrusion systems so that novel and innovative product ideas can be achieved and brought to the market. To facilitate this, the machine design and R&D departments at Schaaf are continually working in numerous areas of application of food extrusion technology. In addition, Schaaf holds patents for numerous processes and devices for food extrusion and aims to develop these into commercial equipment in the near future.