For clean room SCARA robots, the power supply system needs to pass the hard tests of both high speed and cleanliness. The equipment and components used in the production of such products often have to minimize possible friction to avoid contamination of the surrounding air. But this is not easy, especially for SCARA robots, four-axis manipulators shaped like human arms that run at high speeds and have cycle times well below one second. At these high speeds, there is a high risk of particles being generated by friction on the robot’s bellows.
To solve the problem of power supply for such applications, igus developed SCARA-powered drag tubes in 2020 and is now building on this with a SCARA-powered solution specifically for clean rooms – the new Clean SCARA dust-free drag tubes. They are reliable, compact, simple to use, and easy to retrofit.
The Birth of SCARA Cable Solutions
The sheer speed at which SCARA robots work may make your head spin. That’s because this horizontally articulated arm robot needs to run fast on four axes. Its inner and outer arms perform horizontal rotational movements, while the ball screws used to grasp objects perform rotational and linear movements. This allows the arm to reach almost any position within its working radius.
But this high-load operation also means that the cables and hoses wired to the outside of the arm need to be replaced or repaired frequently. This is also a problem that some manufacturers in the automotive industry are facing and want to optimize their energy supply systems, including bellows and rotary bearings. For this reason, igus has developed an alternative that can be retrofitted with SCARA cable solutions to significantly extend service life.
Construction: Ball Bearings and Additional Reinforcement
The SCARA cable solution has three constituent parts, a swivel joint (straight ① or elbow ②) for the mobile end, a swivel joint ③ for the stationary end, and a corrugated hose with e-rib ④. The special feature is that the swivel absorbs torsional forces and the integrated ball bearing ensures that the energy supply system operates smoothly even under high acceleration.
In addition, the corrugated hose is reinforced by means of an e-rib so that it can only be moved in one spatial direction. Side guiding elements then enable the bellows to have a certain overhead length.
Upgrade: Cleanroom-certified Clean SCARA Power Supply Solutions
Designing the right cable and hose guidance system for cleanroom SCARA robots is a challenging task in itself. High-speed movements further increase the stress on components, which can easily lead to wear and release particles into the surrounding environment.
The core component of the new Clean SCARA dust-free energy supply system is the e-skin soft, a modular drag chain that is primarily used to guide the cables and hoses connecting the robot’s vertical arm to the end-effector. Its upper and lower housings can be separated and combined to create a closed drag tube that is both dust- and waterproof. As a result, particles from the cables and hoses are not easily released into the air outside the drag tube, even when the system is running at ultra-high speeds.
To take the strain off the cables and make them more durable, the new solution is designed with a swiveling bracket that connects the fixed and mobile ends of the energy supply system. This is what makes the new system so special. In addition, the swivel bearing has been specially designed to ensure that it does not generate any particles, even when operating at ultra-high speeds.
The drag chains themselves are also extremely wear-resistant thanks to the use of high-performance engineering plastics with optimized friction characteristics. ISO certification by the Fraunhofer Institute (IPA): This Clean SCARA energy supply solution has a clean room rating of ISO class 2, which means that the system has excellent wear resistance, with no more than 100 particles with a size of fewer than 0.1 microns per cubic meter of air during operation. To put this into perspective, a sheet of paper with a thickness of 80 microns is 800 times the size of such a particle.
Highly dynamic applications are also possible when used in conjunction with Skin’s SKS20 series, which has been tested in clean rooms of the highest class. the SKS20’s proven zip-opening principle allows for quick and easy filling of cables. The new clean SCARA cable solution can be used for all known connections of standard SCARA cable solutions.
Other Advantages of the Clean SCARA Energy Supply Solution
The new Clean SCARA energy supply system can be used as an alternative to conventional bellows. In addition to clean room compatibility, it has two other advantages over traditional bellows.
Firstly, the bellows commonly used in robots have a thin, rigid structure that kinks easily. And since there are no bearings to absorb the torque, they are also prone to breakage. Unlike traditional bellows, the Clean SCARA energy supply solution is self-supporting and comes with a unique rotary bearing. As a result, it is ideally suited for short overhead travel and highly dynamic applications. The elliptical shape further increases the strength of the system, which is particularly beneficial for improving the lateral stability of the towing tube.
A second advantage is that the zip-around design makes it very easy to open and close, so the tube can be filled quickly. In addition, the system can be fitted with an optional internal divider element, which adds extra protection to the system that is not available with conventional bellows. Upon request, igus can also provide ready-to-use complete supply kits pre-assembled with chainflex high-flex cables. More than 900 highly flexible cables in IPA clean room class 1 are available.
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