Amazone Tests New Production Processes With 3-D Printing Amazone (Hasbergen, Germany),

an agricultural machinery manufac- turer, was able to save 18% in weight when producing a prototype for a new bogey chassis. The company quickly printed the sand molds and cores with the VX4000 3-D printer from voxeljet, and they were able to do so without any special tools and using just a CAD file. Consistent progress has been made

in the evolution of harrows, which farmers drag along the ground with a tractor to break up the soil and prepare it for sowing seeds. Manufacturers strive to make the equipment more stable, durable and lighter in order to adhere to the permitted axle loads when driving on the road. Amazone produces the Catros

compact disc harrow with a bogey chassis. Tis is a towed device which is fixed to a tractor and can be used in different configurations. Te compact disc harrow is used for shallow and intensive soil cultivation for a working depth of up to 5.9 in. (15 cm). The bogey chassis connects

the device to the axle to enable the device to be transported from the farm to the field. The original welded construction had a weight of 540 lbs. (245 kg) and a welding seam length of 54.1 ft. (16.5 m), making it very complex and production- intensive. To reduce costs and make the component more stable and lighter, Amazone decided to replace the bogey chassis with a cast component. Using topology optimization software, the Amazone devel- opment team created a design that was suitable for the load and could be cast. Due to the materials being

distributed in a manner suit- able for the amount of force, the cast bogey chassis is over 99.2 lbs. (45 kg) lighter than the welded component. At the same time, the new design ensures a 272% longer service

life because the design avoids the variations in rigidity in the cast component compared to the welding component. To guarantee the mate- rial quality, metal flow simulations were also run. In this way, they were able to reduce the risk of internal defects caused by trapped gases before the actual casting process and optimize the quality of cast parts. The optimized design led to the increased service life and decreased the weight compared to the welded component by 18%. The creation of the sand mold using 3-D printing makes it pos- sible to quickly source prototype components and significantly reduce development times. Manufacturing casting molds for

such a complex component is gener- ally time-consuming, partly because

complex specialist tools are required. For this reason, it was decided to use the VX4000 by voxeljet, a 3-D printing system. “Because the complexity of the

component does not affect the cost of the 3-D printing, even difficult geometric shapes can be created at a low cost,” said Tobias King, director marketing & application, voxeljet. Voxeljet converted the CAD file

of the component into a negative CAD file to digitally represent the four-part casting mold. The work- ers then fed this data into the 3-D system. Then the printing began. Here, a coater spreads the print- ing material (quartz sand) onto the construction platform. Then the print head moves over the plat- form and binds the grains of sand together with a binding agent–de- pending on the geometry of the object in the CAD file. For this, the print head works with a resolution of 300 dpi. While the construc- tion platform itself remains static, the coater and print head move their working height gradually upwards by 300 micrometers until the casting mold is complete. Once the printing proce-

The old welded bogey chassis (left) and two new designs for the cast component in comparison (center and right). With the use of 3-D printing, the version on the right is 99.2 lbs. lighter than the original and 272% more durable.

The CAD software is used to create the casting mold, which is made from a total of just four parts.

dure has finished, the workers remove the side walls of the construction platform that were printed with the component and remove any non-printed, loose quartz sand. Tis leaves the casting mold. Te foundry gives the casting mold just one coating–the barrier layer between sand and metal, which protects the casting mold from thermal stress. Despite all of this, the shape is lost after the casting–just as with traditional casting molds. It is destroyed after the core of the cast bogey chassis is removed. Te previous computer simulation for casting ensured that the cast material flows into the original size the first time.

August 2017 MODERN CASTING | 47

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