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Milling in gentle mode
OscilloWitt from Frewitt
There are various methods for crushing or grinding solids. "Frewitting" is a tried and tested method and is still as relevant today as it was in the past.
Frewitt SA from Fribourg is a global company specializing in mechanical process engineering and the handling of powders of all kinds. Frewitt originally developed the grinding principle for heat-sensitive products in the pharmaceutical industry. For a long time now, "Frewittizing", the principle for crushing and grinding a wide variety of products, has also been firmly established in the fine chemicals and food industries.
Oscillation instead of rotation
Solids can be calibrated, crushed or ground in very different ways. Experts refer to one of these processes as "frewitting". This operating principle differs from other mills in one element in particular. The rotor does not rotate or turn, but swings and oscillates. This oscillating rotor movement brings significant advantages such as gentle grinding and a narrow grain spectrum, thus meeting the increasing product requirements of our time. The oscillating screen mill (OscilloWitt) is particularly suitable for grinding heat-sensitive products and products that are difficult to process.
The mill is suitable for both dry and wet grinding. If potentially explosive materials are to be ground on the oscillating screen mill, the ATEX version ensures guaranteed safety in the process.
Dynamic drives and a good partner required
When selecting the drive components for the screen mill (OscilloWitt), Frewitt relies on dynamic drives from Parkem AG. The demanding oscillating movements require a drive train with a very low moment of inertia.
This is achieved by the low-inertia and compact SMH115 servomotor and a flange planetary gearbox, which ensures high output torques and high tilting rigidity.
Alternatively, the EX servomotors with explosion-proof motor housing and an ATEX-certified gearbox version are available in the ATEX version. The power and encoder cables are specially manufactured for Frewitt in a flame-retardant version.
The servomotors are controlled by the multifunctional Compax3 servodrive. It is suitable for use both as an autonomous system and for integration into existing systems.
In stand-alone operation, the Compax3, which is freely programmable in accordance with IEC-61131-3, takes over the entire control of the various oscillating movement functions and the direct evaluation of the user interface. Additional components such as valves can be controlled via digital outputs. Thanks to Compax3, there is no need for a costly PLC.
If the system is integrated into a plant, the control commands are received by a higher-level PLC. Numerous fieldbus options are available for this purpose. The dynamic movement calculations, their execution and monitoring still take place in the controller. Only the desired function must be communicated by the PLC.
Parkem and Frewitt have a close partnership. On the one hand, Parkem supplies complete drive packages with controller, cable, motor and gearbox, which significantly reduces Frewitt's procurement costs. On the other hand, Frewitt also makes use of Parkem's wide range of services. During the project phase, Parkem drew up a specification sheet for the software and then developed the software. Frewitt was familiarized with the products, the Compax3 servo manager and the IEC software by means of on-site training. These training sessions were also used to further develop the software and incorporate new findings. Parkem also carried out various dynamic endurance tests on the prototype, in which the temperature behavior in the various oscillation profiles in particular was determined. All of these are the best prerequisites for ensuring that this latest generation of screen mill (Oscillowitt) will also be able to perform its service in "free-wheeling" for decades to come.
