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Mönchengladbach, October 21, 2019

Additive Manufacturing - a new way of thinking

Design of function-oriented components for the metals industry

3D printing has become a serious alternative to conventional manufacturing technologies. SMS group successfully implemented Additive Manufacturing to produce machine parts for steelmaking or forging despite the harsh conditions and high temperatures given in these processes. Our expert Sarah Hornickel explains the design principles for additive manufacturing, the advantages of this technology and its implementation at the SMS group using a few examples.

Function-oriented instead of production-oriented design

To tap the full potential of the 3D printing, it is crucial to release oneself from conventional production-oriented design thinking. It is no longer necessary to consider the geometry of the input stock or the specific requirements posed by machining processes such as milling or drilling. The design of components needs to be rethought; a new way of thinking is required. Nowadays in Additive Manufacturing (AM), the shape of the component follows strictly and exclusively its function, meaning that the function of a part or even of an assembly needs to be analyzed first.

When the main function or purpose of the part is clarified, the shape is adjusted to it. In contrast to the conventional manufacturing methods, Additive Manufacturing has not to consider the restrictions of the available tools in the workshop, because it is a tool-independent technology. Thus, e.g. channels in hydraulic valves can be generated in a flow optimized shape. Since the conventional manufacturing often results in rectangular orientated bores, where significant flow loss is the consequence and further the stall leads to sediments within the channels, 3D printing enables to design the channels in a more smooth and woven way. By doing so, flow losses can be minimized and the flow velocity is going to be homogenous.

The picture above shows the non-uniform flow velocity resulting from the conventional drilled channels and the stall at the sharp edges (blue colored area). Right there, a flow loss and sediments will be the consequence. In contrast to that, the additive manufactured channel exhibits a nearly uniform flow velocity over the complete geometry. Since the flow velocity is uniform there will be no turbulences within the channel, which does also affect the reduction of energy input. The transfer of these flow optimized shapes for a hydraulic valve could consequently lead to a resizing of the peripheral equipment, e.g. the pump station.

Design example: Lubrication distributor

One example for such flow optimized channels is the lubrication distributor. Its function can be described by distributing and transporting two media, i.e. water and lubricant. For this part small space requirements are challenging since the lubrication distributor’s outer diameter is limited to a value of 48 mm.

For the conventional design, several channels are drilled in a cylinder of full material, which proofed to be difficult, as the holes need to be drilled in three axes. Therefore, Additive Manufacturing also offers an excellent approach for designing parts that are limited in space. By means of 3D printing nearly every shape can be realized so that the holes can be arranged quite compact. Nevertheless, the freedom of design is restricted to process regarding peculiarities and certainly the costs should be considered, too.

On the one hand, the height of the component should be as low as possible with respect to build job time respectively the occupancy of the machine and on the other hand orientating the components vertically leads to an optimal utilized build platform and increased efficiency. So it is mandatory to find the most advantageous compromise.

The lubrication distributor is oriented vertically. This will end up in a long processing time, but it can be reasoned by two crucial aspects; first, the channels for the transport of media exhibit a diameter of 12 mm. A flat and horizontal orientation support structure would require to additionally support the inner diameters of the channels. Second, the post-processing is more complex the more support structure is added to the part. The other holes of the lubrication distributor need to be reworked after the manufacturing in any case, due to the thread cutting. By doing so, the support structure (blue colored area) can easily be removed. An ideal part design for AM exhibits nearly no support structure, so that the design is selfsupporting.

Far more than prototypes

In the past, the technology of building a part layer by layer was subjected to only generate demonstrators respectively prototypes. Today, AM technology has developed into a real alternative to conventional manufacturing as the following examples show.

Application: Connecting support for extrusion presses

The connecting support is a component of feeding systems in an extrusion press. Its function is described by supporting and bearing a cylinder rod. There are a lot of connecting supports within the entire extrusion press. Due to wear, the part needs to be replaced after a certain operating time. However, not every connecting support exhibits the same wear rate, meaning that only the worn components need to be replaced by new ones. Therefore, the demand of spare parts for the customer is quite low, but the lead time should be very short since the plant has to be stopped, and the customer is not able to produce anymore.

In the past casting is used for manufacturing these components, but the time for manufacturing the mold, the casting itself and the subsequent machining results in long delivery times. Thus, using the technology of laser-based powder bed fusion empowers SMS group to provide spare parts for the customer within a few days. Thereby, it is not necessary to produce the connecting supports in Germany since they can also manufactured locally all over the world. In future, the file of the CAD data can simply sent to a 3D printer close to the customer.

For the layer-based manufacturing of components, it would be contradictory to copy the shape of the parts without changing and adopting them with respect to the technology. Therefore, a redesign of the connecting support is necessary. For realizing the benefits of Additive Manufacturing, the component is analyzed to its present loads and a topology optimization provides the optimized shape to bear them. Before calculating, the non-design space is defined, since the requirement of the constant mounting points and the equal diameter for bearing the piston of the roll need to be considered.

After the redesign of the topology optimized shape one further FEM analysis is done. The new design exhibits a higher strength so that even the factor of safety increases in comparison to the conventional design. Due to material saving, the weight of the component is reduced and regarding the production of spare parts on demand, the stock-holding costs can be omitted.

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Conventional manufactured bearing support
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Additively manufactured bearing support

Application: SIS injector

Another impressive application that is far from just a prototype is the Siemag Injection System Injector (SIS) that is a part integrated in an electric arc furnace (EAF). It is combining a burner and an injector system to melt steel scrap. The big and stable flames can also melt scrap in colder furnace areas. The function of this component is transporting, accelerating and mixing media at defined stages.

The conventional design of the SIS injector based on a welded assembly, which is made of eight individual parts. It weighs approx. 18 kg. The installation of this massive design turns out to be difficult due to the space requirements. In addition, the manufacturing of the welded assembly is very costly.

To reduce the amount of parts and to resize the SIS injector, a new design is developed. The AM design consists of one monolithic part and the weight is reduced by 80 %. Due to good thermal properties, a copper alloy is chosen. Furthermore, an optimized shape of the implemented Laval nozzle is calculated.

With respect to the building process of laser-based powder bed fusion of metals, the geometry is self-supporting, so that there are no support structures inside of the component when the build process proceeds.

The functionality of the SIS injector was investigated under operational conditions (operating temperature of 1,500 °C) at the Gas und Wärme Institut (GWI) in Essen, Germany. The aim was to analyze the ignition behavior by means of a spark plug in the pilot mode at different stoichiometric air ratios and to set a stable pilot operation. The additive manufactured SIS injector is equipped with extensive measuring technology to record data of pressure and temperature while operating before it was inserted to the furnace.

Engineering for additive manufacturing as a service

SMS group offers the engineering and design AM-parts as a service for other companies. Our experts assist you in finding answers to all engineering questions from the identification and analysis of potential parts to part design, optimization of parts to process simulation. 

The benefits of such a cooperation are: 

  • Many years of experience in the design and engineering of additively manufactured machine components
  • Use of calculation and optimization software for the ideal component design
  • Extremely good network in the world of additive manufacturing
Summary

As a company of heavy machinery industry, SMS group has already implemented a great number of innovative solutions for machine parts based on digital 3D design data, which impressively demonstrate the advantages Additive Manufacturing processes provide. Their most important benefits include significant weight reduction of dynamically actuated components, improvement of energy efficiency as a result of optimized flow patterns and minimized weight, simplification of mounting and adjusting procedures, easily customized design, dramatically shortened delivery periods and the possibility to produce locally. Using the technology of Additive Manufacturing offers completely new manufacturing opportunities and it effectively contributes to significant increase in performance of the plants of SMS group’s customers.