Linear Motors Offer New Motion Capabilities

LinMot Division of Sulzer Electronics, Zurich, Switzerland

The linear motor was invented in the mid-nineteenth century, at much the same time as its brother, the rotating electric motor. Because the linear motor always has to effect a reversing movement - from one end of the motor to the other and back again - it has physical drawbacks as a source of energy as compared with the rotating version, and is therefore less frequently used.

If, however, short-stroke linear motions are needed, as is often the case for applications in the construction of textile and packaging machinery or for handling purposes, the linear motor becomes an ideal form of drive. Gears, levers, and belts can be dispensed with, thus also reducing the space required as well as wear. The linear motion is generated directly by the electromagnetic force.

Figure 1. Technical Properties of LinMot P Linear Motors include free positioning, electronic cam disc function, extreme acceleration, cyclical movement frequencies, and high dependability and life expectancy, even in harsh industrial environments.

The decisive innovation in the LinMot P family of linear motors (see Figure 1) resides in the rational implementation of the basic concept of a modern design element. Figure 2 shows that, from the motor components as such via the bearing to position-determination and electronic-sensor systems, all the components are integrated into a strong metal cylinder. The whole structure is based on shaped and pressed components; the sole purpose of the two screws is to satisfy the directives for electromagnetic compatibility when the cable is fixed in position. This innovative design for linear motors is the first to satisfy the tough requirements placed on a component used in industrial machine construction.

LinMot P motors are a suitable replacement or supplement to conventional linear motor technologies such as stepper motors, servo motors, mechanical cams, pneumatic cylinders, and mechanical levers. These motors are suitable for numerous precision linear motion applications, including robotics and laboratory automation.

Figure 2. In the innovative Design of LinMot P Linear Motors, all the components are integrated into a robust metal cylinder, and the entire structure is based on pressed and shaped components

The special technical qualities of these linear motors can be summarized as follows: they can be freely positioned; they have an electronic cam disc function; extreme accelerations are possible (>200 m/sec²); cyclical movement frequencies can be greater than 10 Hz; they are dependable, even in harsh industrial environments; and they have high life expectancy.

In comparison, pneumatic solutions cannot be freely positioned, and their dynamics do not offer comparable values. The free programmability of LinMot P is a particular advantage over purely mechanical components such as levers or cam discs.

With LinMot P, the speed of movement can be freely chosen, and other positions, movement profiles, or modes of operation preset by clicking a mouse. LinMot P movement profiles and movement sequences are defined by software and performed immediately. The process-led programming assisted by LinMot permits decentralized functional units.

The design of a machine is determined essentially by two forces: the task which the machine is to perform, and the technical possibilities available to the designer. The previous need to perform fast linear motions by means of centrally driven cam discs and levers determined the structure of many machines. LinMot P represents a real breakthrough in this regard, because the engineering designer now only needs to concentrate on the implementation of the target function: if he needs a linear motion he uses the LinMot component that performs this movement on the site. This enables decentralized functional units to be produced easily. Synchronization, starting characteristics, and the emergency stop situation are defined by software. The decentralized functional units become modules that can be coupled together. A machine can therefore be made up from functional modules and does not have to be redesigned on each occasion.

For more information, contact Dr. Ronald Rohner, manager of LinMot, Zurich, Switzerland, and the author of this brief, at PO Box 521, Rogers, MN 55374-0521; toll free: 1-877-LINEAR-0; fax: 612-274-0224; E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.; www.linmot.com .