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Robot braves ultra-harsh conditions

POSTED 07/30/2019  | By: Norbert Novotny, x-technik

To maintain competitive production costs in traditionally high-wage countries such as Austria while guaranteeing customers goods of consistently high quality, precision parts manufacturer Redtenbacher has opted for an exceptionally high degree of automation. The relevant machinery and equipment are mostly developed and built in-house. Their rotary indexing cell was designed and built for the machining of a customer-specific hinge solution for spectacle frames. Stäubli robot displays outstanding precision and process reliability despite the ultra-harsh production environment.

The Redtenbacher slogan Alles rund um die Brille (Everything about the glasses) is the company’s core business. Their headquarters are in Scharnstein (Upper Austria) and with 150 employees across two production sites in Slovenia and the Czech Republic, this multinational firm manufactures precision parts primarily for the eyewear industry – from spectacle hinges and arms to brand logos. “With unflinching precision and a deviation from the norm that is so negligible as to register only at the third percentage decimal point, we have established ourselves as world-beaters,” says Daniel Almhofer, Head of Work Technology and Design at Redtenbacher. It is a reputation that has spread to other industries: in recent years, various manufacturers in the automotive, horological and medical sectors have also asked Redtenbacher to supply them with precision parts.

One of the factors contributing to the success of the Austrian company is the extremely high level of vertical integration. In addition to machining operations such as milling, drilling, reaming and threading as well as non-cutting production with hydraulic presses and injection molding machines, Redtenbacher has acquired expertise in surface technology – from deburring and trowalizing to electrochemical polishing and electroplating. “With our modern machinery and SAP-accelerated enterprise resource planning, we are able to guarantee maximum efficiency in terms of delivery time and cost as well as a competitive price structure and qualitative consistency,” adds Almhofer.

Exceptional expertise in mechanical engineering

From rotary indexing machines to automatic assembly units, most of the machines and systems required for parts production and their automation are developed and built in-house. “In addition to a product-specific R&D department, we also have a team highly skilled in manufacturing technology and design that has acquired an extensive range of expertise in mechanical and plant engineering over the last 15 years on the basis of our own production experience,” says Almhofer proudly.

The RB16 range of equipment which is currently used as part of the 2014 machining line restructure. The rotary indexing machines can be equipped with up to 16 processing stations and with up to 32 CNC axes. Almhofer played a leading role in the development of the RB16 generation: “Due to their high flexibility, these machines can be readily switched between a wide variety of products. In addition, there are individual parts orders for which we design and build special machines.”

In order to minimize production costs and thereby compete with producers in low-wage countries, a high level of automation is absolutely essential for the Scharnstein-based company. “Taken in combination with our consistently high level of quality, this makes us more than competitive,” emphasizes Almhofer.

Stäubli the obvious choice

For a customer-specific spectacles hinge solution, one of the rotary transfer machines was equipped with a robot that is responsible for loading parts into the system. The basic requirement for this was to find a robot that was capable of handling precision parts in a harsh working environment. “Our processing machines have to work with phenomenal amounts of coolant oil, which can be a huge problem for certain robot components such as seals, rotary encoders and motors. The robots supplied by Stäubli have made a very positive impression on us,” adds Almhofer.

Stäubli robots have been designed to carry on working to specification even under the most adverse conditions. “All cables and media lines are routed inside the compact and fully enclosed robot arm,” says Alexander Müller, Branch Manager Austria at Stäubli. “For optimal protection, all connectors are located underneath the robot pedestal. What’s more, Stäubli manufactures its own gearboxes, which have been specially designed to reduce maintenance and increase the life of the robot.”

High-speed, high-precision

Due to the limited space available in the rotary indexing machine, the management opted for the six-axis TX40 robot with its range of 515 mm. Almhofer: “The compact dimensions reduce the space required to a minimum. The possibility of ceiling mounting meant that the robot could be easily integrated into the production cell. Its spherical working area also enables optimal use of the space available.”

The specific task assigned to the six-axis machine is the loading of the parts to be manufactured in the first of the 16 processing stations (milling/drilling). “The job required cycle time of 4.2 seconds and positioning accuracy of 0.03 mm, which Stäubli were able to provide right from the beginning,” says Almhofer approvingly. Once loaded, the part is manufactured in a rotary cycle that takes in all the individual machining units.

The mechanical and electrotechnical integration of the TX40 was carried out by two in-house assembly teams at Redtenbacher. Almhofer: “The high level of transparency of the robot controller with all its interfaces was extremely helpful. In addition, the support we received from Stäubli with integrating the robot into the machine control, programming and commissioning were exemplary.”

Safety and flexibility

Almhofer also gives credit to the sophisticated safety technology of the Stäubli robots compared to other pneumatic loading systems: “Thanks to the Stäubli Safe Robot technology, the risk of injury to the operator is zero.” The biggest plus point of the robot for him is its flexibility. “The machine can be converted to another product variant relatively quickly. With its versatile mounting options and six operational axes, the robot can load parts in any position. If required, it could also turn, reclamp or remove parts from the cell in any direction.”

Clearly, each individual application requires an assessment of whether the deployment of a robot makes sense in terms of cost-effectiveness. Almhofer nonetheless sees tremendous potential in robotics: “We have set ourselves the objective of having a pool of robots so that we can in future flexibly upgrade machines for suitable orders and thereby ensure optimal outcomes for our customers. In view of the high performance of the robot systems and the outstanding standard of service, Stäubli will continue to be our first point of contact in the future.”