Exploring the Benefits of Applying Dual-Pitch, Right-Angle Worm Reducers in High-Speed Servo ApplicationsSeptember 13, 2018
Precision gearheads play a critical role in motion control applications where torsional stiffness, high torque and low backlash are of crucial importance. The gearheads are often paired with servo motors and used to balance inertial loading conditions, increase torque and reduce motor speed — making them a useful mechanical interface for a wide range of transmission components, including pulleys, drums and cams.
In recent years, the use of gearheads with flanged outputs has increased significantly. These gearheads enable the machine to interface directly with the ISO 9409 Robotic Standard for mounting components and to integrate with dial-table type applications. They can also be used with shrink disc mounting systems in applications that require direct shaft mounting.
Right angle worm reducers are a specific type of flanged output gearhead that have traditionally been viewed by mechanical engineers and machine designers as a “low efficiency” solution. However, certain worm reducer designs, particularly those that use dual-pitch technology, possess many inherent advantages that lend themselves to high-speed servo applications where traditional bevel planetary gearheads are prevalent.
Overview of Right-Angle Worm Reducers
Right-angle worm reducers transmit power using a threaded worm and a wheel that meshes with the worm. The reducers offer high gear reduction and torque multiplication and feature an output shaft at a 90-degree angle to the motor shaft, which means that most of the gearhead housing and the entire motor housing is parallel to the side of the machine. This results in a smaller machine envelope, which is advantageous in dynamic cyclical and speed control servo applications where space is limited. Additionally, the right angle configuration of the worm reducer affords engineers increased design flexibility, with output shaft options ranging from hollow bore, robot flange and shrink disc, as well as solid shafts in both or one direction.
Despite these advantages, engineers and machine designers have not traditionally viewed worm reducers as a suitable alternative to bevel planetary gearheads in high-speed servo applications. Much of that is attributable to the widespread perception that worm reducers are low efficiency. While this is a valid concern in many worm gear solutions available on the market today, designs that use dual-pitch technology exhibit efficiency that is comparable to inline planetary gearboxes, making them ideal for a wide range of motion control applications, including robotics, packaging machines, press feeders, printing machines and medical systems.
Dual-Pitch Worm Reducer Benefits
Dual-pitch worm reducers possess a number of advantages that make them an effective alternative to inline reducers. Some of their notable benefits include:
Efficiency: Worm boxes have traditionally not been viewed as the most efficient form of gear reduction. However, single-stage, dual-pitch solutions, like the DYNABOX, have been known to deliver efficiencies as high as 96%, with gear ratios upwards of 100:1 in a single stage.
Backlash: The DYNABOX is available with three levels of backlash (from 10 arc minutes to less than one arc minute) and multiple output options (for example, single or double output shafts, hollow bore with keyway, hollow bore with shrink disc and rotary output flanges), enabling them to provide precise rotary motion for highly dynamic cyclical or speed control servo applications.
Optimized Contact Pattern: Unique to these gearboxes is the dual thread profiled worm and ring gear using the majority of each gear face area for gear-to-gear contact, distributing pressure and wear over the widest surface area. This increases the life of the gearbox, reduces downtime and lowers maintenance costs.
Preloaded Input Taper Bearings: This design feature incorporates the preloaded taper bearings and a third radial ball bearing to manage the worm shaft and maintain proper worm shaft alignment to the ring gear due to thermal elongation. The unique coupling’s design, large surface area and construction provide a thermal barrier between the motor and reducer. Additionally, the higher stiffness of the preloaded bearings ensures proper input shaft position, which increases life expectancy.
Adjustability, Compensation and Housing Construction: Dual-pitch worm reducers permit backlash correction and repair. Heat-treated aluminum-magnesium alloy delivers superior rigidity, low weight and superior heat transfer. The housing’s rigid design maintains shaft alignments, which in turn delivers predictable torque. The one-piece design eliminates stacked tolerance accumulation errors and benefits from consistency due to a state-of-the-art automated production process.
Servomotor Mounting: Motors can be mounted to the gearhead using a flexible bellows coupling solution. High stiffness bellows coupling eliminates shaft alignment problems. Increased torque and enhanced positional accuracy are delivered through the zero backlash bellows coupling.
Selecting and Applying the Optimal Gearing Solution
Selecting the proper flanged output gearhead for a given servo application is an important decision that can have lasting impacts on efficiency, maintenance and operational costs. As the process for identifying the optimal gearing solution can be complex, consulting with a qualified provider is critical.
While dual-pitch worm reducers afford certain advantages, such as high torque multiplication and gear reduction in a compact package, the optimal gearing solution will largely depend on the unique requirements of the application and objectives of the user.
DieQua Corporation offers a broad range of gearboxes, gearheads and speed reducers available from a single source, along with the know-how to select the appropriate solution for your application. For information regarding products or if you need help overcoming a power transmission- or motion control-related challenge, contact one of their qualified experts.