Robot Machining Cell Cleaning of Iron Cast Parts Without Rework

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GF Casting Solutios manufactures heavy structural parts from cast iron. By reversing the machining logic with a nesting arrangement of their existing cast part machining centers and using form nest-specific program variants, machine builder Fill has created a system that allows even smaller cast iron parts to be automatically fettled.

When the word "cast iron" is mentioned, many think of grilling in the backyard or architectural design elements from earlier times, such as street lamps, manhole covers, hydrants, or bridge railings. Although cast iron has now largely been replaced by other materials in these areas, the material is far from obsolete.

Because cast iron is very suitable for casting due to its lower melting point, it is the material of choice for highly stressed components for engines or the drivetrain of commercial vehicles and mobile work machines.

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The globally active Swiss industrial company Georg Fischer (GF) offers products and solutions for the safe transport of liquids and gases, as well as lightweight cast components and high-precision manufacturing technologies. Its subsidiary GF Casting Solutions GmbH from Leipzig (Germany) manufactures structural parts from iron casting for agricultural and forestry machinery and construction machines, as well as systems for renewable energy. "Casting technology is the best choice for a high degree of functional integration in complex components," explains production manager Andriy Malaschkin. "We support our customers in the development and production of highly complex iron casting solutions up to a box format of 2,500 mm × 1,600 mm × 500 mm (approx. 98 inches × 62 inches × 19 inches)." The company covers the entire process chain with a certified environmental management system, from mold and core production through melting and casting, to coating, CNC machining, and assembly.

Important Process Step: Deburring

After the casting process, the components still exhibit excess material at the mold parting lines and gating channels in the form of runners, burrs, and risers. These need to be removed before further processing. For this task, GF Casting Solutions has been using several automated cleaning stations for years. In them, an industrial robot fully automatically performs the various machining steps.

This works very well for most workpieces, but for some parts, the frequent tool changes and nesting-related variations in dimensional accuracy affect the cycle time. Among other reasons, because the existing systems were fully utilized, the cleaning of these parts was mostly done by hand until recently or was partially outsourced to external service providers. "Finding personnel for this physically demanding, loud, dirty, and monotonous work is becoming increasingly difficult," reports Malaschkin. "Outsourcing is also not a long-term solution, as transportation involves delays, costs, and other uncertainties."

Automation Gaps Closed

Therefore, the production manager set out to find a solution for automating the deburring and removal of feeders from parts up to 250 kilograms. This had to enable the machining of numerous different components based on the target contours from their CAD data with short cycle times and thereby close the aforementioned automation gap.

Since smaller components often come from a mold in multiples, the process should also be able to account for differences in residual material occurrence with components from different form nests. According to Andriy Malaschkin, these nesting-related differences were the main reason why this process had previously resisted automation.

Of the invited mechanical engineering companies, Fill, based in Gurten (Upper Austria), presented the most convincing concept. The mechanical engineering experts of the globally operating premium manufacturer have been developing and producing systems and machines for foundry technology for almost 30 years.

Machining Logic Reversed

Fill developed a completely new cleaning and grinding cell according to the specifications of GF Casting Solutions Leipzig, with a robot as the central element. However, that's where the similarities with the existing systems end. "To achieve the required cycle times, we reversed the machining logic," explains Thomas Rathner, head of the competence center for foundry technology at Fill. "With the Grind Performer, the robot moves the component to the various fixed-position tools instead of moving the tool to the stationary component." This eliminates the delays caused by the otherwise necessary tool change.

The loading of the components into the grinding and deburring cell is also time-saving via a rotary table. The workpiece is not clamped but placed flat. A camera system detects the part, its position, and orientation, so the robot can approach and pick it up correctly.

Consistently High Quality Ensured

Another camera system identifies the mold nest identification applied in plain text on the component. This information enables the retrieval of a mold nest-specific variant of the machining program that was created during the run-in of a new component. "When manually cleaning, the worker can spontaneously react to the different defect patterns," says Andriy Malaschkin. "Although the machine can't do that, it achieves an extremely consistent result with the nesting-specific programming, and that with consistently high quality."

After knocking off the riser with a hydraulic hammer, the robot moves the workpiece to several grinding, cutting, and milling tools. In the process, all burrs and other excess material are removed. "A certain challenge was not just bending fine burrs, but actually removing them completely," reports Thomas Rathner. "To achieve the desired 100 percent result here, we had to conduct several test series with different grinding and machining tools."

Easy Operation, Safe Operation

No experiments are required for the programming and operation of the robot cleaning cell. The Grind Performer is operated via Cybernetics Studio, a software tool developed by Fill itself, which enables simple programming. To create a new component, employees do not need programming knowledge. They define the required machining steps and process parameters through visual settings on its 3D CAD model. In doing so, they inform the machine program where burrs or similar are expected, based on the mold parting lines known from the CAD data of the casting mold.

The execution of the programs created in this way always takes place in the computer simulation on the digital twin of the system. This ensures that collisions in the workspace can be reliably avoided. Since the simulation also runs concurrently during main time, it helps to detect unplanned states or deviations from the target early and to respond to them appropriately. Later changes or optimizations to the programs can also be easily implemented through parameterization.

Rapid Going-Live and Reliable Results

Even before the final system decision was made, trials were conducted with all manufacturers on the shortlist, including at the test center at Fill's main location in Gurten. Subsequently, the machine builder received the order for this unique system. About a year later, it was delivered and commissioned. "As is to be expected with a system manufactured for the first time, some optimizations were still necessary afterward," confirms Andreas Sallaberger, sales and project engineering for foundry technology at Fill. "In particular, the reliability of the plain text recognition for nest identification had to be increased to the required level due to inconsistent writing styles."

In addition to improving working conditions for personnel by eliminating manual cleaning, the Grind Performer brings high process stability and reproducibility of machining steps. Not least, the nesting-specific program versions ensure consistently high quality of the reworked components. "The automated cleaning of the new iron cast parts in the Grind Performer is another important step towards the automation of our process chain and provides an important contribution to securing the location," confirms Matthias Heinrich, Managing Director of GF Casting Solutions Leipzig. "Unlike the existing machines, almost no rework is required with this system."

*Peter Kemptner is a freelance technical journalist

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