Define “high speed.” What is considered leading edge today?

Anthony/Timken: High speed, referred to as dN, is calculated by multiplying the bearing bore diameter in millimeters by the shaft rpm. If the solution to this equation is greater than 1 million, it is often considered highspeed.
George/NSK: High speed in linear motion depends on the type of linear motion product. In terms of ballscrew drives, NSK has a 50-mm-diameter x 100- mm-lead ballscrew capable of 7 m/sec. However, it’s unlikely anyone would drive a ballscrew this fast. For linear motor drives, 5 m/sec seems to be the fastest practical speed. And belt-driven actuators are limited by the maximum allowable speed of the linear bearings. For linear guides, the maximum allowable speed is 5 m/sec.
George/Steinmeyer: In the world of linear devices driven by ballscrews, high speed motion is 60 m/min and higher, with acceleration of 1 g and greater.
Mike/Reliance: In terms of the rotational speed of squirrel-cage induction motors, or PM brushless motors, high speed is when rotor surface speed exceeds 75 m/sec. While motors can certainly be designed to run with higher rotor surface speeds, it might mean trade-offs in cost, complexity, and reliability.
Robbie/Moog: High speed is a relative term, and when dealing with motors, one missing part of the equation is frame size. While 20 krpm wouldn’t be considered high speed for a motor with a diameter less than 1 in., it would be fairly high speed for a motor with a 4 in. or larger diameter.

In what applications is speed of greatest importance?

Karl/Bosch Rexroth: In general there are productive and nonproductive times in machine cycle time. Any motion in the non-productive time doesn’t make money, so movements must be made in the shortest possible time.
Anthony/Timken: Speed is of great importance in metal cutting, medical, and aerospace applications, where high speeds are required for accuracy.
Brad/Nye: In high-speed dental hand pieces, material removal in cavity preparation requires precise cutting with an extremely high impact force because of the hard surface of tooth enamel and dentin. Burr design and speed help provide a more controlled impact for material removal, as opposed to applying a shear force as in most cutting operations.
Aubrey/igus: Speed plays a pivotal role in high-duty cycle applications where production numbers and capacities are determined by the speed at which the machine can operate. The faster the machine moves, the more it can produce and the more money your organization can make. Simply put: higher speed means higher throughput.
Nick/Oriental Motor: Speed is a factor when throughput is a major concern. In large machines like PCB inserters, the distance to be traversed can be long, so the time it takes to go from one end of the machine to the other is important.
John/alpha gear: Production, converting, and printing are key industries where speed is important. Slight speed increases, without a reduction in accuracy, can result in additional products being manufactured.
Mike/Reliance: With applications like press feeders or cut-to-length operations, speed should be looked at in the context of “speed of response.” These applications are challenging, requiring multiple accel/decel cycles per second. In the motion control world, speed of response is often measured in terms of torque-to-inertia ratio, or even as velocity- loop bandwidth. Another aspect of speed of response is how fast a process line can be changed from one product to another.
George/NSK: Speed is important in longstroke applications. Speed and acceleration requirements are often confused, and it’s common for machine manufacturers to publish a maximum speed capability the machine would never be able to reach because of acceleration limitations.
Jayson/NI: Speed is important in scanning. High-resolution scans over a large area can take significant amounts of time if the data-capture and triggering rates are slow. Using high-speed data acquisition and increasing communication speed between the motion control and I/O can help reduce the time it takes to do the scan.

What are the limiting factors in a motion system when trying to maximize speed?

Bill/MEI: The actual mechanical design of the system and available power to apply to the problem are limiting factors. Something stiff, but heavy, may require more power than available to move quickly; while a light and flimsy piece won’t be able to move quickly and maintain accuracy at the end of the move.
Mike/Reliance: In terms of speed of response, inertial effects are obstacles. In the context of absolute speed, limiting factors include speed-dependent losses, such as friction, windage, or motor lamination core losses. Vibration can also be a substantial issue; an amplitude of vibration only a fraction of a mil peak-to-peak can be excessive when it happens once per revolution at 10,000 rpm.
Robbie/Moog: One constraint when operating motors at high speeds is switching losses, whether electromechanical or electrical. Mechanical limitations are also constraints. In a typical brush motor, a major concern is keeping the winding wire contained in the slots. For brushless dc motors, the concern is keeping the magnets from leaving the motor shaft.
John/alpha gear: Heat, vibration, control, and reliability are the limiting factors of servosystems. Speeds as low as 1,500 rpm can generate enough heat, due to the small surface areas of today’s servoplanetary gearheads, to prematurely wear oil seals and cause leakage.
Anthony/Timken: Limiting factors are operating loads, heat generation, and machine life. It’s important to address these factors through bearing design, lubrication, and heat dissipation.
Brad/Nye: The biggest limiting factors for small precision bearings used in dental hand pieces are particulates from contamination or components in the material used to gel a grease. The retainers that secure the rolling elements in the bearings can be damaged when their strength is compromised by incompatible oil or other fluid or by contacting particles in operation. At high speeds, any solids in a bearing raceway can cause bearing failure.
Andy/Rockford: Besides the limits of critical shaft speed and maximum ball velocity, maintaining adequate lubrication is a must. Higher speeds can create excessive friction and heat buildup in the nut.
Aubrey/igus: Heat can degrade the sliding elements causing lower performance, and friction has a direct effect on the temperature range, which affects speed. Reduce friction and heat by using different bearing/shaft combinations.
Jayson/NI: One of the biggest limiting factors in automated machine control applications involving both motion and I/O is the rate of communication between the two. To overcome it, use high-speed data-acquisition boards in combination with a motion controller that can generate triggers at a high rate. The easiest way to do this is to use communication protocols that don’t require special wiring.

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