Small components mean you have incredibly tiny tolerances and litter room for error. Particularly in the case of small and micro components with sensitive bearings, absolute concentricity over the lifecycle of the device is a critical factor. The higher the speed and non-symmetrical weight, the greater the forces involved. Along with vibrations, this leads to increased strain on the bearings—and eventually to premature wear and tear.
Micro Präzision Marx’s balancing machines use Faulhaber drives to permit precise adjustment of testing procedures.
Micro Präzision Marx GmbH, located in Erlangen, Germany, offers a horizontal balancing machine specifically geared to testing the quality of small components. Registering the slightest imbalance means that the measuring pressures are very small, which is why every element of these test procedures must be adjustable to a high degree of precision. With this in mind, the Erlangen-based balancing experts chose Faulhaber motors for the drives.
There are issues with the armatures of electric motors. While wire-wound dc armatures made of dynamo sheet are non-magnetic, the armatures of modern, brushless dc-drives definitely require an antimagnetic testing device. Eddy currents caused by ill-positioned metal parts also impair the testing procedure. This is where specialist expertise is called for—these small parts require the highest degree of balancing precision, down to an accuracy of one-tenth of a milligram.
The particular shape of the balancing machine is designed to deal with all possible types of test pieces, while special controls ensure the test conditions are exactly the same for every test piece within a product line. For example, every two-gram rotor of a micro turbine running at 400,000 rpm must be balanced perfectly every single time. Highly accurate oscillation sensors, combined with precise evaluation deliver accurate readings. Synchronization, high speed and very good adjustability are key.
These types of tests require a drive that is reliable, capable of consistently high speeds and adjustable to a particular revolution profile. Designers came up with a brushless dc servomotor with a 35-mm diameter to meet these requirements. Preloaded ball bearings guarantee particularly quiet running; 90 W of power ensure highly dynamic performance for quick acceleration and braking. A high-resolution encoder inside the motor housing and a programmable positioning and speed control complete the drive.
Apart from its power supply (24 Vdc), the standard features include an analog input, an error output and an RS232 interface. The start module of the balancing device controls the direction of rotation and speed of the drive through these interfaces. These functions are complemented by a motor start/stop and speed display.
The servo drive can accelerate test pieces to speeds of 40,000 to 80,000 rpm during the measuring process. Modern, brushless dc servomotors offer a whole new range of options for miniature measuring and testing devices.
Filed Under: Factory automation, Drives (dc), Drives (servo) + amplifiers, Motion control • motor controls