Electricity is replacing hydraulics, and servo electric cylinders are replacing hydraulic systems—mechatronics drive technology is increasingly being adopted for fully automated workpiece forming, pressing, or automated assembly. For users, in addition to significantly reduced operating costs, the stepless adjustment characteristic is a primary and decisive advantage. Ortlieb Precision Equipment uses motor feedback systems such as SICK Stegmann's SKS36 in its SERAC® servo electric cylinders to ensure highly available and accurate displacement measurement and position adjustment. (See Figure 1.)
Processing workpieces and blanks of varying strengths on the same machine, executing multiple operations using a single electric cylinder motion mode, and seamlessly moving to different processing positions—in many cases, servo technology holds a decisive advantage over hydraulic and pneumatic drives. “Therefore, mechatronic systems with motion control capabilities are unstoppable,” explains Niels Selig, Product Manager at Ortlieb Precision Equipment Ltd. in Kirchheim/Teck. “At this point, we’ve noticed a shift in the market, whether for new equipment or refurbishment—especially when comparing operating costs, servo drive technology is significantly superior to hydraulic and pneumatic systems.” To enable mechatronic systems to perform high-precision molding or riveting processes, and, when necessary, synchronize multiple servo axes, servo electric cylinders (such as those in Ortlieb’s SERAC® product line) utilize highly available, precise displacement measurement systems—for example, the SICK Stegmann rotary motor feedback system SKS36 with a HIPERFACE® interface.
Ortlieb: The "Precision Company" of Clamping and Servo Screw Technology
For over 100 years, Ortlieb, located in Kirchheim/Teck, has positioned itself as a "precision company," providing economical and precise solutions in workpiece and tool clamping and servo electric cylinders. "Based on our R&D and patents, we have defined many important DIN standards for clamping technologies," notes Niels Selig. "From standard clamping clamps to individually manufactured non-standard clamping solutions, we offer a one-stop shop for flexible, standardized, and customized solutions." Mechatronic components and servo electric cylinders have become the company's increasingly important second pillar, and in the spring of 2017, it will move into one of the most innovative, architecturally and energy-efficient office buildings in Baden-Württemberg. A key focus is the pre-installed, complete solution, consisting of modularly configurable servo electric cylinders. "The motor, lead screw, encoder, and brake (if required) are all fully integrated into the cylinder," says Niels Selig. Based on the company's unique patented technology in lead screw technology, the SERAC® servo electric cylinder exhibits exceptional performance.
SERAC® servo electric cylinders combine proprietary technologies from the aerospace and mechanical manufacturing industries.
As its slogan "Electric over Hydraulic" suggests, Ortlieb offers innovative solutions to replace hydraulic and pneumatic cylinders with its SERAC® servo electric cylinder product line. Each model differs in housing construction, motor specifications, torsional stop devices, and fixing methods, all excelling in high concentrated thrust and integration. This product line has been proven under extremely harsh operating conditions in various industrial applications, including small parts assembly, stamping, forming, and riveting. The technological foundation of the SERAC electric cylinder is a special planetary roller screw originally developed for the aerospace industry, characterized by its extremely light weight and ability to achieve precise positioning without additional reduction gears. Based on DLR's (German Aerospace Center) global patent portfolio, Ortlieb developed the ASCA® planetary screw and mass-produced it for use in mechatronic systems. Many SERAC® models achieve a lead of only one millimeter, enabling extremely precise work point movement via the electric cylinder. This is predicated on encoders that support equally precise displacement measurement and positioning, such as the SKS36 motor feedback system.
SKS36 motor feedback system for precise positioning
Ortlieb applies the SICK Stegmann SKS36 motor feedback system, equipped with a HIPERFACE® interface, to all its SERAC® product lines. “Its compact design ensures a shorter motor mounting length,” Niels Selig states, highlighting a key structural advantage. Indeed, the carefully designed system structure results in a housing diameter of only 36mm and a minimal structural height (excluding the shaft) of just 37mm. As a result, this motor feedback system weighs only 65g, making it one of the most compact encoders in its class. As a single-turn encoder system in Ortlieb's servo electric cylinder digital control circuitry, the SKS36 provides numerical values for direction, speed, and absolute position information through a single rotation subdivided into 128 sine/cosine cycles. Simultaneously, the system boasts extremely high reliability and accuracy—primarily achieved through a tiny code disk located in the center of the rotating shaft, eliminating any eccentricity errors. This code disk has 128 lines, scanned by a specially developed Opto ASIC to generate a sinusoidal signal with extremely high linearity and interpolation feasibility. “This allows for extremely precise measurement of the SERAC lead screw's feed rate and is used for accurate positioning,” Niels Selig explained. This is because planetary roller lead screws operate not through form-fit but through rolling friction. “Therefore, significantly more force can be transmitted without affecting the lead screw's lifespan,” Niels Selig stated. “The working principle causes slippage during lead screw operation, thus requiring an additional linear measurement system in addition to the encoder. This, through the cooperation of two encoder systems, achieves positioning accuracy of <0.01mm and repeatability of ±0.01mm.” The SKS36 thus excels in its high precision, high availability, and robustness. “The maximum permissible operating temperature in the servo cylinder is well below the 125°C specified by the encoder,” Niels Selig described. “Vibrations and shocks that may occur during stamping, forming, and pressing will not compromise the functional reliability of the SKS36. For example, during sheet metal forming, the SERAC®KH electric cylinder equipped with this motor feedback system can complete over 40 million cycles within a three-second synchronization signal without any problems.”
Multi-coil and safety solutions for mechatronics systems
In Ortlieb electric cylinders, the single-turn motor feedback system SKS36 is compelling due to its accuracy, convenient integration, and usability. For task settings requiring repetitive rotational displacement measurement and positioning, the multi-turn motor feedback system SKM36, with its built-in miniature mechanical drive, measures up to 4,096 rotations and outputs at a resolution of up to 16,777,219 steps.
When considering mechatronics systems and drive technology solutions with safety as a primary concern, SICKSTEGMANN's SIL2 motor feedback systems, SKS36S and SKM36S, stand out as safety encoders for dynamic, precision servo control circuits. These systems can be used in applications conforming to SIL2 classification according to EN62061 and IEC61508, and performance class (PLd) according to ENISO13849-1. Therefore, they provide certified functional safety, enabling safety-oriented monitoring of the functions and functional chains of servo electric cylinders and mechatronics systems regarding speed, direction, and stopping status. SICKStegmann's motor feedback systems thus offer a variety of displacement measurement and positioning options in mechatronics systems—not just in Ortlieb's electric cylinders. (Figure 3)
