Production Machining

SEP 2018

Production Machining - Your access to the precision machining industrial buyer.

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The Advantages of Direct-Drive Technology for Manufacturing Contributed by Brian Zlotorzycki D irect-drive technology has been around for more than 40 years, but many machine builders still do not fully understand its benefits. Even those who are familiar with the technology may not have a desire to adopt it, consid- ering it as too high-end when compared with, for example, a gearbox drive solution that has been sufficient for many years. But in the same way smartphones and the internet have evolved from a luxury to a necessity despite lower-end technology still existing, eventually the benefits of more advanced technology become too difficult to ignore. In today's highly competitive world, the better people under- stand the advantages and benefits of direct-drive technology, the more they will have an advantage in machine building, giving them an edge over their competition. To understand these benefits, start with the basic concept of direct drive whereby the force of a motor is directly applied to a mecha- nism without any intermediate drivetrain such as a gearbox or toothed belt. e core working principles of direct-drive motor technology are, in essence, based on the right-hand rule of electromagnetism, whereby a current moving through a wound coil in a known direc- tion creates a magnetic field. Changing the direction of current changes polarity, and changing the amount of current changes the magnetic force. Putting a highly conduc- tive material within the coil, such as iron, exponentially increases the magnetic force. One more factor is to have some magnetic material with which this field can interact. In this case, it is a row of permanent magnets. Depending on the coil's location relative to the magnet, the current can be adjusted in terms of its strength and polarity, creating a push/pull force on the magnets. e resulting force is capable of moving an object without making physical contact. is force gener- ates a linear motion when using a flatbed track of magnets and a rotary motion when using a curled-up ring of magnets. e applications may be different, but the technology is exactly the same. Each coil is called a pole, and to get the desired motion, their polarity and strength need to be changed relative to the magnets to maximize the force delivered. e standard today calls for three different coil behaviors, called phases, acting upon the magnets at the same time. For this reason, the type of motors using this method are referred to as three-phase synchronous motors. All that a motor has as an input when it comes to performance are three wires for current and, for this reason, motors do not have any compatibility issues with different controllers. Once the working principle is understood, it is easier to see the benefits of this technology, including the large force density it brings. With the motor having only two parts (the magnets and coils), they are compact for the power they deliver. e small moving carriage of a linear motor, and the large hollow shaft of a torque motor allow the payload to be Current Current MAGNETIC FIELD Current Current MAGNETIC FIELD :: Ironless motors have a weaker force. :: Iron is used to vastly increase the force. TECH BRIEF 28 PRODUCTION MACHINING :: SEPTEMBER 2018

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