Case Studies Of Industrial Robots

Robots in action can be found everywhere. Robot Manufacturers give examples of robot applications in different industries.

Stäubli, France - IFR Partner

Robot instead of special purpose machine

September 2013

If a company that specializes in manufacturing customized machinery goes for an alternative solution, then it will have a valid reason - in this case, the Stäubli RX170 hsm. This innovative milling robot working away within a cell supplied by plant manufacturer Riexinger ensures abundant flexibility in the complete machining of large plastic parts. The five-axis robot also scores in terms of maximum availability and short cycle times.

Established half a century ago, Riexinger GmbH & Co. KG now operates on a global scale, specializing in plant and machinery for the processing of all types of plastics. The core competencies of the company range from the development and manufacture of plastic welding equipment, welding machines and pipe saws to the design and realization of complex special-purpose machinery for processing synthetic materials of all kinds.

When one of their customers, plastics and piping specialist Kubra GmbH, enquired about plant for the production of drainage chamber bases, Riexinger's initial idea was to construct a special purpose machine. In the case of the deep-drawn parts made of polyethylene which have a diameter of one meter, machining the external contour and the pipe connections is part of the process. Reliable and consistently reproducible processing of these chamber bases is essential for their subsequent use in drainage and sewage systems.

Preliminary research revealed that the construction of a dedicated plant would constitute a relatively complex undertaking with a certain residual risk in terms of availability and reliability. In the search for appropriate alternatives, Otto Angerhofer (former CEO of Manz and now a consultant for Riexinger) came up with a persuasive concept: the robotics specialist knew of the new Stäubli RX170 hsm milling robot and informed the Riexinger designers about this innovation.

Just the job in terms of flexibility

"In fact, the robotic solution turned out to be just the job," says Markus Theobald, Managing Director at Riexinger. "With its operating range of nearly two meters and the freedom of movement afforded by a five-axis model, the Stäubli robot can easily reach any working position on the large plastic parts. So we had found the perfect machine for this application and now only had to supply the system peripherals."

The realization went smoothly and quickly, and soon the machining center for chamber bases proved its worth in terms of flexibility and easily meets all other customer specifications with regard to cycle times and quality. The machining center is currently handling chamber bases in various versions with pipe connections of between 110mm and 315mm but all with an outer diameter of precisely 1.0 meters.

The chamber bases arrive at the machining center as deep-drawn parts made of polyethylene or polypropylene, with their outer contours and pipe connections as yet unformed. The job of the milling robot is to remove excess plastic material and thereby ensure a consistent outer radius. The five-axis robot is further tasked with the precise machining of the different pipe connections. The switch from one variant to the next is performed by the plant operator pressing a couple of buttons on the robot control console.

Because the plastic material is easy to cut,
the milling robot can go about its work in
dynamic fashion.

The Stäubli machine is equipped with a
high-precision milling spindle supplied by
Fischer Precise.

To facilitate uninterrupted complete machining,
the cell is equipped with an automatic tool
changing station.

Operating the robot is easy to learn and
can be a lot of fun.

No matter how many new variants may follow, the end user is well equipped for all eventualities with the Riexinger system. "The system is set up for maximum variation," adds Theobald. "Loading and unloading of the robot cell takes place manually. The Stäubli RX170 hsm milling robot then takes complete charge of machining the chamber base. Thanks to its enormous range, the five-axis robot readily copes with all the many possible designs and - by comparison with a CNC machining center - guarantees almost unlimited flexibility."

To facilitate uninterrupted complete machining of plastic parts by the robot, the cell is equipped with an automatic tool changing station. Here, the RX170 hsm autonomously selects the optimum cutter for each machining process. The quality of work done by the robot is in no way inferior to the result that might be expected from a machining center handling this same application. Because the plastic material is easy to cut, the RX170 hsm can go about its business in dynamic fashion, thereby reducing the cycle time for machining a chamber base to less than two minutes. The machined surfaces pass all tests in terms of fit and quality, ensuring that no rework is required.

Although Riexinger actually specializes in special-purpose machinery, Theobald is excited about the use of the milling robot: "In the Stäubli RX170 hsm, we have a turnkey plug-and-play solution that works absolutely reliably. By contrast with the time-consuming and expensive construction of a dedicated machine, the robot solution makes huge savings in terms of engineering costs. In addition, we have an integrated system with a significantly more manageable level of complexity, which in turn means higher availability, plus we also benefit from almost unlimited flexibility."

Innovative and simple: Milling with a robot

Stäubli's newly developed RX170 hsm milling robot is intended precisely for applications such as these, where fast and accurate processing of plastic and composite materials is called for. It introduces a new element of freedom and flexibility into the production line and is able to process large workpieces rapidly and with facility. In terms of performance too, the RX170 hsm is ideal for machining plastic parts: its repeatability is ±0.04 millimeters, which falls well within the requirements for the processing of the chamber bases.

"Wastewater engineering is obviously not an area where high-precision machining is critical," adds Theobald, "and yet the specifications for the machined surfaces are quite high and the tolerances are much lower than you might expect in this industry. With increased environmental legislation, manufacturers must comply with ever stricter standards. In any case, sewage systems are expected to function reliably over many years; this can only be ensured by error-free and high-quality machining of components."

The Stäubli robot operates reliably in any working position within its two-meter range.

A lot of professional expertise has gone into the making of this robot. The entire power supply as well as the spindle cooling and lubrication are contained within the arm. This represents a compact and highly reliable solution. Stäubli engineers also designed a new upper arm and a special wrist in which the sixth axis is replaced by a milling spindle. Here, Riexinger opted for the exceptionally high-quality Fischer Precise milling spindle. As the end customer operates the robot cell on a three-shift system around the clock, Riexinger quite logically uses only the best components available on the market.

With this robotic solution Riexinger is breaking new ground, though the terrain has proved to be remarkably smooth, as Markus Theobald explains: "By opting for a proven integrated system such as the Stäubli milling robot, we minimize the risks associated with the construction of a special purpose machine, and we know that we will have guaranteed availability right from the start. Wherever it makes sense, intelligent engineering should take advantage of turnkey solutions like this and resort to customized solutions only if they present a clearly defined benefit for the customer. We see this mix of standard component and in-house design as the perfect solution for the customer."

 

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