Close up of a hail gun

Motion solutions develop pioneering SABS Hail Gun

South Africa is one of the countries that are prone to severe hailstorms as it is situated in the mid-latitudes of the north and south equator. A hail storm can easily wreak havoc on gardens, car bodywork, windows and solar panels. Over the past years, Gauteng has been lashed by heavy hail storms raising interest in products that are resilient to nature’s bullets. In a pursuit for these products, South African Bureau of Standards (SABS), whose testing activities include a wide range of testing, calibration and inspection, approached Festo to help them design and build a fully automated Hail Gun for testing solar panels against hail damage.

Established in 1945, SABS is a company that focuses on lowering the risk of product and service failures in companies, industries and the economy. Festo has been supplying SABS with automation solutions for over 30 years and has played a role in ensuring that they receive optimum results. In this recent collaboration, we assisted SABS Pretoria with a complete solution to automate the movement of their Hail Gun. This gun is designed to pick up an ice ball and shoot it at a solar panel, to establish it’s endurance to the impact.

"Our solution included both pneumatic and electric drives as well as a customised control panel for the system,” explains Johannes Ngwenya, Festo Sales Engineer. A pneumatic vacuum generator is used to suck an ice ball through a barrel canister. Once the ice ball is in place, the L-port valve is activated to switch the vacuum off and open positive air, thus shooting the ice ball at the solar panel. “We required movement in 1mm increments,” says Herman Strauss of the SABS, “Electric drives have proven to be best suited to this application as they provide the fine motion control we needed".

The Hail Gun needed to be attached to X, Y, Z positional drives so that the ice balls can be directed at any point on the solar panel. “The mass of the Hail Gun and the panel dimensions of 2m x 2m x 1.5m helped us to size the electric drives and the required stroke,” says Ngwenya. A decision was to use the ELGA toothed belt drive, which is an ideal axis for linear gantries and cantilever axes. Additionally, this electric drive delivers speeds of up to 10 m/s, acceleration of up to 50 m/s2 and a repetition accuracy of up to ±0.08 mm. The ELGA masters tasks without breaking a sweat- making it the perfect choice to handle even your toughest applications.

Installed on each drive is the versatile EMMS-AS servo motor, a dynamic, brushless, permanently excited synchronous servo motor with a choice of 3 feedback systems which allows for single- or three-phase motor controllers, torque optimised or speed optimised winding variants. This high-performance series is designed for demanding drive and positioning tasks such as this application with such a small incremental movement required. In addition to these innovative solutions Gerhardt Strydom, Festo Applications Engineer commissioned and programmed this solution - Festo offers solutions for the entire value chain.

Control to the system was provided by the compact CMMO-ST motor controller - a cost-optimised solution. The motor controller served as a closed-loop and open-loop position controller. It offers quick, easy parameterisation through either the Festo Configuration Tool (FCT), as was done with this application, or via an Ethernet interface with an integrated webserver. The cost-effective CMMO-ST forms part of the Festo range of Optimised Motion Solutions products with ServoLite technology. Commissioning is convenient, simple and quick thanks to the built-in web browser.

Thanks to the Festo Operating Manual provided with the project; the customer can efficiently operate the Hail Gun. Festo offered SABS a tailor-made solution that perfectly met all their requirements.“The control panel was built at our Isando workshop, and the entire system was delivered within eight weeks” concludes Ngwenya.

March 2021