Enclosed and open-frame direct drive rotary motors have replaced traditional servo motor systems with mechanical drives in many applications. Now, a new type of direct drive rotary (DDR) technology called modular (cartridge) DDR combines the performance advantages of open-frame DDR motors with the ease of installation of full-frame motors, and at a much lower price than traditional direct drive technologies.
Traditional motor/drive system
Most servo applications today employ traditional servo motor systems with mechanical drives. The initial cost of traditional systems is attractive, and their performance has been proven in a variety of applications, including electronics assembly, packaging, aerospace, and defense. However, the additional costs associated with the design and integration of these systems are often overlooked. These additional expenses are for additional mechanical components such as pulleys, gearboxes, and belts. These components wear out over the machine's lifespan, further increasing the total lifespan cost.
Positioning errors and tuning difficulties are common problems in these systems, caused by the flexibility and ineffective backlash of the transmission. The maintenance of belts, pulleys, and gearboxes, as well as the replacement of these wear-prone parts, are costly: firstly, users have to manage a larger inventory of parts; secondly, system failures caused by these additional parts increase unplanned downtime, leading to a decrease in machine output.
Direct drive rotary motor
A direct-drive rotary motor is essentially a high-torque permanent magnet motor that is directly connected to the load. This design eliminates all mechanical transmission components such as gearboxes, belts, pulleys, and couplings. Direct-drive rotary systems offer numerous advantages to designers and users.
Because mechanical transmissions require regular maintenance and frequently cause unplanned downtime, direct drive rotary motor technology fundamentally improves machine reliability and reduces maintenance time and costs. By eliminating the inflexibility of mechanical transmissions, direct drive designs avoid the hassle of inertial matching between the motor and the load, while also improving positioning and speed accuracy by up to 50 times. Direct drive motors also offer another benefit: a reduction in audible noise of up to 20 dB.
DDR motors are an ideal solution for semiconductor process equipment because they are directly connected to the driven load, eliminating the belts, pulleys, and gearboxes typically required in traditional servo motor systems. The reduction in the number of components also allows for a smaller overall machine size, enabling production managers to place more high-value-added process equipment within a single process compartment. The elimination of mechanical transmission components results in a maintenance-free system that operates more quietly.
Frameless DDR motor
Frameless direct drive rotary motors are the "grandfather" of DDR technology, and they undoubtedly offer the most compact mechanical servo solutions available today. Frameless direct drive rotary motors use separate rotors and stators, eliminating the use of bearings. These components become an integral part of the machine, also including the necessary feedback mechanisms. They are ideal for applications where space is limited or where overall weight is critical.
These motors are essentially custom-made, making them more expensive and requiring weeks or even months of design and integration time. Furthermore, replacing the motor or feedback device in case of system failure is extremely complex. Therefore, frameless DDR technology is not suitable for every application. Its most widespread applications are in airborne and ground vehicles, such as night vision devices, radar systems, and weapon system targeting control, as well as high-end industrial applications with strict requirements for size, weight, and/or performance, such as robots or precision grinding machines.
Enclosed DDR motor
Enclosed direct-drive rotary motors (DDDs) integrate the rotor, stator, and factory-aligned feedback mechanism into a single housing with precision bearings, offering a complete solution. Enclosed DDDs are ideal for applications where the load can ride on the motor bearings. For motors already using bearings, connecting the motor to the load or aligning three or more bearings is a laborious and time-consuming process. Therefore, enclosed DDDs are generally used in indexing and rate turntable applications.
Modular direct drive rotary motor
The modular (cartridge) DDRC motor is a novel direct drive solution. Its structure includes a unique bearingless housing with an integrated rotor, stator, and factory-aligned high-resolution feedback unit. The use of cylindrical DDRC technology eliminates mechanical transmission components, retaining all the advantages of direct drive while avoiding the complexity and cost of traditional enclosed or frameless DDRC solutions. The modular direct drive rotary motor utilizes a novel compression coupling to connect the rotor to the shaft and includes a unique chuck design, enabling "plug and play" operation in under 30 minutes.
The advantages of modular technology, along with its competitive pricing and significant reduction in total lifecycle costs, will accelerate the application of direct drive technology in the design of new machines across numerous sectors, such as metallurgy, packaging, printing, semiconductors, and factory automation. Consider the following example: a packaging OEM striving to increase its machines' output to over 150 pieces per minute faced the challenge of mechanical interference introduced by the flexibility of the gearbox on a critical axis as it attempted to increase output. By installing a modular direct drive rotary motor on this axis, the mechanical flexibility was eliminated, enabling the OEM to increase its machine's output to 180 pieces per minute. In addition to increased output, the OEM also experienced benefits such as zero maintenance, improved reliability, and reduced audible noise.
Here's another example of a modular direct drive application: An OEM providing test/measurement equipment to the tire and automotive industries found that using direct drive technology improved measurement quality and machine reliability by eliminating wasted travel and other external influences from belt and pulley systems. Their initial design used a frameless direct drive motor, which offered several advantages over traditional solutions, but also suffered from assembly and installation difficulties—in fact, assembling the frameless motor and aligning the feedback device could take a whole day. The company then switched to modular direct drive technology, finding that its simple installation and integration took only about 30 minutes, resulting in significant savings in both time and cost. Furthermore, they were pleased to see that the modular motor had a higher torque density compared to the frameless direct drive model.
Due to its unique design, the modular DDR motor is more competitively priced compared to traditional mechanically driven servo motors. Even though its initial cost is slightly higher, the operating cost of this new technology is significantly lower than that of traditional systems over a total 5-year lifespan.
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