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The requirements for servomotors are particularly high in the food industry. They should not only be compact, cost-effective and powerful, but also meet the special quality requirements from the requirements for hygiene compliance. This has so far led to increased costs, as expensive, heavy stainless steel housing and other stainless steel components were needed. A new special coating now allows the use of "normal" servomotors without sacrificing hygiene or engine performance. The AKM motors by Kollmorgen are already equipped with it.

The material costs of AKM motors are about 30%, their commissioning and maintenance costs about 20% below those of conventional solutions for the food industry.
The high power density and the wide range of variants of the long-proven AKM models in other industries offer further advantages.

The food grade synchronous servomotors are called AKM washdown models designated. For many applications, they are a sensible alternative to motors with stainless steel housings. The heavy-duty stainless steel versions are usually just under a third more expensive than the standard versions. Weight and cost increase even further when standard motors are used in a stainless steel extra housing. In addition, a higher space requirement must be taken into account for the installation. Another disadvantage of these stainless steel versions is the generally poorer heat dissipation. In the case of the additional housing heat accumulation occurs - not only in the actual engine but also between the engine and the housing. On the other hand, the compact design of the AKM Washdown motors and the material used mean that they have a very good heat dissipation, which leads to an exceptionally long service life.

Hygienic design meets the requirements

Kollmorgen11122In order to meet the hygienic requirements, the servomotors were not only specially coated, but also subjected to a hygienic design. There are only rounded and smooth, medium-repellent surfaces and there are no germs or dirt-promoting corners. This simplifies thorough cleansing and germination. For bearing lubrication of the Washdown motors in "Food" design, only food grade lubricants are used according to FDA. Furthermore, shaft, screws and plugs come in a high-quality stainless steel design as well as a Teflon shaft seal that is highly resistant to chemicals. The materials used exclude all toxic risks. The specially milled motor nameplate also complies with the hygiene requirements, because it is not subject in this form a replacement like a conventional nameplate.

An 2 component epoxy coating in white (alternatively in stainless steel look) serves as a highly effective protective coating of the housing. It proves to be resistant to chemicals such as acids, lyes and in particular detergents with regard to PH values ​​between> 2 and <12 as well as against corrosion. The used coating material of the AKM-Washdown fulfilled the global migration requirementthe FDA. The Washdown engines equipped in this way were subjected to various rigorous tests at the factory as well as by authorities and institutes.

The coating has been approved and certified by the Hygiene Test Laboratory "Ecolab" after prolonged extensive testing and especially with the use of detergents. Additional protective measures for the motor housing, such as a casing using the expensive stainless steel, can be omitted. This significantly reduces space requirements and overall costs. The fulfillment of the IP 67 degree of protection allows a "wet cleaning" with cleaning agents and similar chemicals.

Good heat dissipation and lightweight construction

The AKM motors are also characterized by features such as highly dynamic behavior due to the integrated high-performance magnets and good heat dissipation without forced ventilation. Due to the brushless operation, the motors are maintenance-free. In addition, the rotary motors have proven their quality, concentricity (low cogging and balanced magnetic balance), fivefold overload capacity and long service life. A variety of technical measures have helped the engines achieve the same performance with 30 to 50% more compact design compared to conventional technology engines. This compactness is also accompanied by a significant weight reduction, making these engines lighter by 10 to 30%.

Flexible with up to 150.000 variants

The washdown motor can be optimally configured from the AKM modular system to individual requirements. With the sizes 2 to 6 available in Hygienic Design, the range of performance data includes, for example, standstill torques from 0,5 to 25 Nm for supply voltages from 75 to 480 V. Different overall lengths, various winding variants, feedback systems and connection techniques can be called up from the AKM catalog data and lead to optimal, needs-based configuration of the required engine.

With the overlap of the standstill torques and nominal speeds, there is a fine grading in relation to the power requirements of the respective applications. So there are motors with the same torque in different sizes selectable. For example, greater stability can be achieved in an application by giving preference to a larger-size motor than to a smaller one-each with the same torque. This is caused by a higher amount of inertia.

In the case of a very dynamic load, it is advantageous to use the compact engines, because it must be less mass than compared to the conventional motors to be moved. These overlapping steps, sizes or masses and moments provide the best conditions for adapting the ratio of the mass inertia of the motor to the external mass inertia. Optimal controllability results when these masses occupy approximately the same order of magnitude.

According to the manufacturer theoretically up to 150.000 variants can be created. The variety of options offered allows the plant manufacturer to configure a suitable and cost-effective motor. This gives him an energy-efficient solution designed with reserves and by no means oversized. Likewise, within the scope of the configuration, it is possible to call up specifications that deviate from the widely diversified standard in order to put together an engine version tailored to suit individual requirements. Only a few manufacturers offer this advantage. As a rule, the realization of a customized solution means a significant increase in investment.

Long life thanks to Magnetic Balance

One of the main reasons for the high degree of robustness of the AKM engines is that the front part or the front flange and the motor housing are made of a die-cast part. By casting all the individual elements in the engine with epoxy casting resin occurring frictional forces, short circuits and thus ultimately disturbances or production losses are avoided.

The long life cycle of the Washdown AKM engines is also helped by the "Magnetic Balance" achieved between the rotor and the stator. These are usually not available in other smaller engines. They have a more or less large magnetic asymmetry, which directly on the rotor loading on the bearing or effect. This circumstance causes strong radial forces to occur. Vibrations and noise are the result. An early failure of the bearings is pre-programmed, thus reducing the life of such engines.

Less service with more power

Kollmorgen Joerg PetersInitial use of washdown motors, for example in the meat processing industry or in bottling has already proven itself. With the use of the washdown version, 30% performance is higher than comparable stainless steel motors. In addition, extensive field tests have shown that lifespan can be extended three-fold. The washdown motor is virtually maintenance-free and replacement of machine parts is almost never necessary. This situation and the reduced costs for installation and commissioning are reflected in the savings of 20% in service and commissioning.

The author Jörg Peters is Director of Product Management at Kollmorgen Europe GmbH, Ratingen.

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