Robotic spot welder uses rodless pneumatic cylinder

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A production problem at a vending machine manufacturer was solved recently by automation specialists Robotix of Rugby, which supplied a tailor-made spot welding machine with the precision movement provided by a rodless pneumatic cylinder from Hoerbiger-Origa.

The robot-loaded CNC press brake sheet metal forming cell at Ripley Engineering of Basingstoke manufactures the front and side panels for vending machines. Flat sheet is cut out on a laser profiling machine and the edges are folded. Experience has shown that compound bends around the front edge of the cabinet can cause vibration during operation - unless the flanges are secured.

After some discussion, Robotix was contracted to design and manufacture a suitable spot-welding machine, capable of attaching the flange to the side panel with no visible marking to the outside of the panel. In the press brake cell, the robot offers the flanged edge of the panel to the spot welder, which performs six spot welds in two working positions, completing the task in one operation. To eliminate unsightly marks, a flat swivel pad electrode is used on the outside of the panel. This, combined with the precise positioning of the weld head and control of the welding process, ensures that the panel is unmarked.

"We asked Hoerbiger-Origa to provide us with a complete solution for the movement between the working positions," explains Robotix director, Bob Jepp. "They supplied us with a compact unit complete with solenoid valves, guides and end stop hydraulic shock absorbers. It makes the design much easier to buy the integrated system complete from one company and to have total confidence in its reliability, knowing that there is good service support if needed."

A counterbalance weight running inside the hollow column and connected to the spot-weld assembly by roller-chain eliminates any risk of run-away should the air-supply fail, but the Hoerbiger-Origa OSP-P rodless cylinder has an inertia load of some 110kg to move smoothly and accurately between the welding points.

Smooth operation at slow speeds

The 40mm bore, 1000mm stroke OSP-P rodless cylinder has a maximum load carrying capacity of 1500N, an exceptionally smooth operation, even at slow speeds, as well as an integrated scraper system and grease nipples for the re-application of grease to the guide system to ensure a long service life. The Starline linear guidance system uses recirculating linear ball bearings to provide a dynamic load-bearing platform.

"We always use Hoerbiger-Origa for linear rodless cylinder applications," says Bob Jepp. "We appreciate the support at design stage and throughout projects, and it is a benefit to source all of the components from one supplier. Above all, reliability is the key and why we keep using Hoerbiger equipment."

Robotix provides bespoke systems for manufacturing, including a wide range of robotic systems for plasma or laser-cutting, welding, pick-and-place for loading, unloading or packaging, and automation systems for almost anything from prototyping to panel building, as well as programming for robots, PLCs, CNCs and other industrial hardware.

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