One Ring to Rule Them All
Weiss develops a heavy-duty ring table with a large center opening to achieve robotic production efficiencies.
By Bill Eppich
Weiss North America Inc.
A development partner for the transportation industry with a global operating workforce of over 5600, EDAG (Detroit, MI; Fulda, Germany) recently was faced with the task of designing a heavy-duty ring for a new production concept. The system, designed for small-lot production of vehicle components, was required not only to bear the weight of car body tools weighing up to four tons, but also provide sufficient room at its center for a heavy-duty robot.
At the initial stages of development, EDAG engineers found that the heavy-duty rings currently available on the market were too small to bear the weight of four heavy car body tools while at the same time providing sufficient room for handling systems and a robot in the center—not just on the outside of the ring. EDAG’s Managing Director/COO Manfred Hahl swiftly sought out a solution to the new production concept that would ultimately provide its customers cost advantages and quality-enhancing innovation.
Hahl commissioned Weiss North America Inc. (Willoughby, OH), and its’ parent company, Weiss (Buchen, Germany)—specialists in rotary tables and automation—to initiate detailed and collaborative engineering discussions with them to develop a complete, integrated solution for EDAG’s unique production system.
Based on its powerful CR series range of heavy-duty rings, which feature large open centers, Weiss North America began customizing engineering specifications for a unique CR 2600 rotary table that could ultimately accommodate four tools and a robot in the center.
Collaborative Design Challenge
After a few rounds of reviews between EDAG and Weiss specialists on both sides of the Atlantic, the design goals became clear. What was desired was a rotary table that could efficiently accommodate four tools and be capable of production on one or two of the tools even while the two idle positions were being either manually or automatically equipped with new tools. The goal was not only flexibility in terms of tooling but also fast availability of different tooling. The table should also feature sufficient space in the center for a robot to carry out both machining and logistics functions—further enhancing the productivity and flexibility of the system while reducing its overall footprint.
Key specifications for the new CR 2600 heavy-duty ring quickly came into focus:
- A drive plate with a vertical axis rated dynamically at 500 kN and statically at 1000 kN
- A central opening of 2 m and a freely programmable drive
- A low installation height of only 300 mm to enable stepless, ergonomically favorable manual loading alongside automatic loading
- Implementing Weiss Application Software (WAS) to ensure fast setup and uncomplicated integration into all production cycles
Additionally, this new member of the WEISS CR family would inherit all the positive design characteristics of the series’ range: a flat design, zero backlash and optimum power transmission, as well as a drive unit positioned far to the outside that can easily be sent into action with WAS.
According to Stanislav Cafuta, a Weiss system developer, “The key was designing the ring’s central opening with a diameter of 2 m, tool weights of up to 20 t, and a reach of up to 2.5 m—demands that even our largest heavy-duty rings were unable to meet at the time.“
Bearing a Technical Hurdle
Several technical hurdles had to be overcome before the new-generation CR 2600 was able to achieve its production goals. With its very high vertical integration rate, Weiss was able to monitor and guarantee quality while procuring large parts with long delivery times more quickly.
One of these critical parts was the bearing. The development of a so-called YRT bearing, a combination of two axial bearings and a radial bearing, is a time-consuming matter. To overcome this issue, the Weiss engineers decided to speed up the process by giving the bearing supplier, Schaeffler (Fort Mill, SC), a helping hand by assuming responsibility for the development of the bearing cages themselves. As a result, the total development time and delivery for the new CR 2600 heavy-duty ring was compressed to six months.
Featuring a distinctly large central opening, the CR 2600 is a unique combination for this size of a classic rotary table and a shuttle system in which robots can access the workpiece from both sides. The system is currently running with two tools for two components, so that the rear hatches and hoods can be manufactured in a combined process.
Ultimately, the CR 2600’s unique configuration opens up other possibilities for the installation. This is due to the user-programmability of the table, as well as savings in floor space brought about by the option of positioning even large robots at its center.
Bill Eppich was appointed vice president and managing director of Weiss North America Inc in 2007. He works closely with design engineers from inception to completion to achieve customer specific solutions for systems and machines. Prior to this appointment Eppich served in a similar capacity with the Precision Detroit Co. (PDC). PDC was formerly the exclusive partner for Weiss products in North America and was acquired by Weiss in October 2007.
This article was first published as a digital exclusive feature for the 2013 edition of the Motorized Vehicle Manufacturing Yearbook.