Design

WR Series brakes reduce footprint of six-axis robot

8th January 2021
Alex Lynn

Six-axis robots have become the standard solution for automated assembly tasks due to their ability to carry out complex manoeuvres. As they have grown in popularity, robot OEMs have strived to reduce the size and mass of their six-axis designs to promote space efficiency and productivity.

When a German manufacturer of stepper motors was approached by a robot OEM to downsize its assemblies for a six-axis robot, they turned to Warner Electric to deliver highly compact X-Small (XS) and WR Series brakes.

Able to approach a work piece from any angle, six-axis robots are now a common sight on manufacturing lines. However, floorspace is still at a premium, so there is a continuing design trend towards decreasing the size and mass of robots. Reducing size improves space efficiency, allowing for the addition of more robots or other equipment on the line. Minimising mass allows for six-axis robots to enhance speed and acceleration without compromising payload – which results in increased productivity.

The end goal is a production line with a high density of robots, working within reduced space, delivering high output. Therefore, any advantage that can be gained from reducing the size and mass of components and assemblies must be seized by robot OEMs.

Specifying an optimal robot brake

This has been exemplified by a robot OEM, which asked its German supplier of stepper motors to assess downsizing opportunities for an updated six-axis robot design optimised for small component assembly. The German manufacturer quickly identified the brakes mounted on the back of each stepper motor as an area for optimisation.

The brakes provide static holding in precise positions, ensuring the accuracy of the assembly process. Particularly, the stepper motor controlling the sixth axis of movement, which holds and turns the tooling at the end of the robot arm, required a specialised braking solution.

The manufacturer contacted Warner Electric, due to its expertise regarding advanced braking technologies. After collaboration with the customer’s engineering team, Warner Electric experts recommended a XS electrically-released, spring-set brake to fit the stepper motor on the sixth axis.

Warner Electric’s range of XS brakes is specifically designed for applications where weight saving and space efficiency are paramount. Each model offers reliable braking to an optimised torque level. Consequently, XS brakes are often specified for applications in aeronautics and robotics. It is a highly versatile range featuring six standard sizes, with Warner Electric able to customise designs to exactly match application requirements.

The XSB33S supplied to the German motor manufacturer offered a torque rating of 35 Ncm and a weight of only 90g. Its design ensured a significant size and mass advantage compared to the previously utilised brake. A customised adaptor flange was also included to allow for customer-specific mounting.

Delivering tangible improvement

For the higher braking torques required on the other five axes of the robot, Warner Electric supplied highly compact Model WR220 and WR225 spring-applied, electrically-released brakes. These are specifically designed as statically engaged/disengaged holding brakes, ensuring reliable positioning of the robot arm in operation.

With the new brakes now installed, the German motor manufacturer could approach the robot OEM with a highly optimised design that reduced footprint without compromising productivity. This delivered increased space efficiency for end users, improving available floorspace and enhancing production capacity.

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