Integrating the additive powder bed process into the manufacturing process chain

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A central goal of the strategic cooperation between GF Machining Solutions and EOS GmbH is to integrate the powder bed process into the processes involved in mould and die manufacturing as well as into the production of individual and serial components for industrial applications. Apart from a few particular exceptions, the integration into conventional process steps for the preparation and/or further processing of additively manufactured components is an aspect which should not be overlooked.

The challenges

The nature of primary shaping processes—the powder bed process must be considered as such—is that they usually directly precede the actual manufacturing process chain, rather than being an integral part of it. In particular, the identity, as well as the geometric and physical reference of an individual component, is often missing. However, this exact information as well as the physical properties are prerequisites for the typical process chain in mould and die manufacturing (figure 1). The cooperation between GF Machining Solutions and EOS GmbH was significantly motivated by the desire to close this gap across all application segments. The necessary approach seems simple at first glance; in industrial practice, however, it represents a massive potential increase in productivity for the entire process chain. 

The solution

While established conventional production processes—particularly in mould and die production—are based on a reference system to link successive production steps without complicated setup or loss in accuracy, this is not yet an established standard in additive manufacturing. Compatible reference systems in machinery for the powder bed process are the exception. Currently, only the AgieCharmilles AM S 290 Tooling is equipped with a fully integrated System 3R MacroMagnum reference system as a standard. A reference system offers significant advantages for typical problems in generative production, such as:

  • The obligatory orientation of the build plate parallel to the working level (recoater level) without manual readjustment
  • The clamping and alignment of "preforms" for hybrid mould inserts without manual readjustment
  • The positioning of components to be generated on the build plate in a geometrically defined position relative to the reference system
  • The simple clamping and alignment of build plates on spark-erosion wire-cutting systems for separating the workpieces produced by the powder bed process
  • The refurbishment of the build plates for example through milling or grinding

Integrating the reference system is merely the first step towards seamlessly integrating additive manufacturing into the industrial production process. GF Machining Solutions is, therefore, addressing the current gaps on multiple levels.

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The most straightforward issue to deal with is ensuring that components are not just placed anywhere in the workspace by a simple "drag-and-drop" process, but placed in a geometric position defined in the digital process chain. To do this, the AgieCharmilles AM S 290 Tooling is equipped as standard with the required software functionality. 

 A more difficult issue to address is the digital integration of the powder bed process in workshop management systems which are designed by conventional, sequentially operating production processes. In the powder bed process, however, multiple components can be generated simultaneously, which is desired to benefit from a subsequent reduction in proportional auxiliary process time. However, this parallel process poses a challenge for established workshop management systems when it comes to tracking the status and identity of components—a challenge GF Machining Solutions has committed to solving with its in-house System 3R WorkShopManager software. 

No less challenging is the fact that the powder bed process requires a solid metallic base to which the component is fixed by a melted layer of metal. Consequently, a separation process (e.g. spark-erosion wire cutting) is required for the components generated on the build plate. This process of separation from the build plate, which—depending on the component and process design—is carried out before or after any required heat treatment, causes the components to lose their physical and geometric position and to arrive in an undefined position somewhere in the work tank of the spark-erosion wire cutting system. Collected there, they must be individually re-clamped for further processing by conventional production processes and their exact geometric position must be re-established. 

Adding reference surfaces to the CAD model in the design phase and building them when generating the component (figure 2) can, in many cases, solve this issue. However, this solution is not practical or feasible in all situations. Here, GF Machining Solutions suggests a concept which consists of a reference platform (3R MasterPal) and multiple recyclable component-specific mini pallets (3R MiniPal; figure 4). In this concept, the components are still generated directly on the 3R MiniPal; however, these are fixed to the 3R MasterPal by a detachable connection and referenced relative to the integrated chuck of the AgieCharmilles AM S 290 Tooling using locating pins. The component generated by Additive Manufacturing on top of the 3R MiniPal can now be separated easily from the 3R MasterPal and, if necessary, proceed to heat treatment including the 3R MiniPal. Subsequently, thanks to the attached 3R MiniPal, the component can be re-fixed onto standard reference elements (e.g. System 3R MacroHP). It is thereby oriented and physically fixed in a geometric position which is sufficiently accurate for the remaining conventional production process chain. The component is separated from the 3R MiniPal either as a final step of the milling or turning operation or using spark-erosion wire cutting. This entire process is shown schematically in figure 4. 

Identical logic can be used specially in mould and die production for referencing preforms or standard mould plates. Taking the reference hole pattern on the 3R MasterPal into consideration when manufacturing the preforms enables simple fixation and simultaneously includes the exact position relative to the reference system of the AgieCharmilles AM S 290 Tooling. The routing via a coordinate measuring machine also becomes a standard process, as the coordinate measuring machine and the AgieCharmilles AM S 290 Tooling use the same physical reference concept—that is, the measured coordinates can be transferred for Additive Manufacturing. 

Additionally, the 3R MasterPal is compatible with standard mould plates from HASCO or Meusburger. This is a significant advantage for directly producing mould inserts on standard mould components; it can, for example, considerably accelerate the production of mould inserts for prototypes.

Conclusion

Integrating the powder bed process in the manufacturing process chain poses physical and digital interface problems at various points. GF Machining Solutions has developed suitable solution approaches which take into consideration the particular constraints of the powder bed process and enable practical, practice-oriented integration.