Why would you select a spur gearhead over a more popular planetary design for a DC servo system? Answer: back drivability.
More often than not a DC gear motor specified for an application with even modest space constraints will utilise planetary gearboxes. The fact is there are simply more teeth in a smaller space to spread the load.
However, many high ratio planetary gearhead designs have floating stages that when back driven will give irregular feedback torque characteristics. Even in some cases with dynamic inputs the planetary gearmotor can jam. It is in this instance that a spur gearhead can be a better solution. It must be said that not any spur gearhead will work. The automation market is flooded with low cost spur gearhead products that are often of such low quality that they would not be recommended by maxon motor for power transmission in either direction although the unit pictured is an exception. This 45mm spur gearhead features a very robust all metal construction with large output bearings capable of up to 190N radial load and 60N of dynamic axial load. Reduction gearing efficiency of 87% and a hardened stainless steel shaft. The shaft in this instance has been modified with a transverse bore directly alongside a milled flat to suit the customers load affixation method. A 60W 30mm diameter motor is being used which in itself required the machining of specialised adaptor flanges. Custom modifications such as these particularly suit the diverse and changing requirements of the robotic and haptic control fields.
Contact maxon motor engineers to “spur” your robot into motion. +61 2 9476 4777
Advancements in brushless dc motor technology are transforming linear actuation.
Shown here is an example of an 8mm diameter brushless DC motor fitted with an 8mm diameter planetary gearhead. The gearhead output flange contains not only the standard set of preloaded radial ball bearings, but also an additional set of bearings mounted between the radial bearings configured as an axial thrust block. By mounting the gearbox thrust bearings between the radial set, it provides additional separation and increased radial capability. The importance of this bearing system is intrinsically related to the shaft. Close scrutiny of the shaft on this tiny gearmotor reveals its true function – linear movement. The ceramic thread is manufactured with tight tolerances on runout and pitch and with extremely smooth surfaces.
On this example a thread of only 3mm diameter provides up to 27N. This, combined with the precise position control capabilities of DC servo motors, is what enables this device in a world of miniaturisation and automation. All combinations of motor gearhead and actuator are meticulously customised to suit the application and avoid any unnecessary size or weight compromises.
Contact maxon motor Australia for engineering and design assistance on +61 2 9476 4777.
8 mm brushless servomotor and linear actuator
© 2012 maxon motor.
Often the cost of IP rated brushless DC motors is not justifiable in an application.
A full IP rated brushless DC motor is often required for open operation in a food or pharmaceutical manufacturing facility. When all of the factory automation equipment is mounted in an open environment with the manufactured product, a full washdown capability, sealed or even motors with full food grade lubricants is required. However, there is a current trend to over specify a motors IP rating requirement when designing an automation device for use in these environments. For example, a brushless motor might only be a single part of a complex device being used in the environment. It could be a Gripper, automated guide, check weighing device or even a complete robotic arm. All these devices usually contain their drive motors in a casing that is itself a sealed housing. The only exposed part of the motor outside of its protective mounting flange is the shaft and the bearing. This is where this new style of brushless motor excels. A brushless DC outrunner style motor taking full advantage of a conventionally cooled winding that gives unprecedented power per volume characteristics combined with a completely sealed flange, rubber sealed bearing and stainless steel shaft. This style of brushless motor construction can provide an effectively sealed unit at a fraction of the cost of a full IP rated motor and also provide a much higher power to volume ratio.
Pictured here is a version of this style of brushless DC motor in 90mm diameter achieving up to 0.5 Nm with a custom configured winding to suit the speed requirements of direct drive joint actuations. Contact maxon motor Australia for assistance specifying a motor to suit your application. Sydney +61 2 9476 4777.
EC 90 flat, 90 Watt brushless flat motor with hall sensor, Ø90 mm