Large format 3D printing in the foundry sector

Smelting - ancestral process

Casting in any of its variants, such as casting in sand molds or the lost wax process, is a very ancient technique validated over centuries and very useful for the manufacture of metal parts in sizes ranging from a few centimeters to gigantic parts of several meters, such as components for industrial machines, ships, turbines, sculptures, among others. 

The nature of the process, which involves handling high temperatures to bring the metals to the melting point, the complex lifting systems needed to handle the enormous weights and the volumetry of the metal parts, makes outsourcing very difficult, so any technological innovation must be absorbed and performed in-house. 

One of the innovations that foundry companies have begun to incorporate is desktop 3D printing, which helps them to optimize mold design and development times by manufacturing and validating prototypes to scale. Recently, advances in technology have enabled the development of large-format 3D printers, such as Trideo's Big-T, capable of manufacturing models with dimensions up to 1000mm x 1000mm x 1000mm in a single run and in a matter of hours. 

3D casting models

The casting process has many variants, but any of them have in common the need to manufacture a master model, which is traditionally made by a craftsman using materials such as wood, aluminum, polystyrene, resins; requiring long development times, a huge dependence on the operator and a high exposure to errors in the interpretation of drawings and technical errors during the manufacture and post-processing craft that in the foundry business is associated with huge economic costs.

Digital models

Replacing physical models with models designed with 3D CAD software and transferring the know-how of the casting process to its digital version is a change of philosophy that takes time within this type of traditional companies. 

However, the advantage of being able to make redesigns, derivations and continuous improvements to the digital models; of being able to store hundreds of them without requiring physical space; and of being able to guarantee dimensional accuracy and repeatability every time, more than justifies the change.

Special materials

The development of 3D printing materials for the foundry sector has grown a lot in recent years, to the point that today we have available materials with different characteristics of fluidity and melting temperatures that allow adapting their use to different processes. One example is the materials designed for the lost wax process, which allow models to be melted and removed from the mold without leaving residues in the cavity, in those cases where the nature of the part makes it impossible to demold (see Fig. 2).

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There are foundries that have already made some progress towards digital manufacturing with desktop 3D printing, which allows them to produce small/medium models, or create interlocking parts to generate larger models, but assuming a large number of failure variables related to fit tolerances, dimensional problems due to thermal shrinkage, among others that can be solved with the use of large format 3D printers. Other substitute technologies such as CNC machining or routing, being a chip removal technology, generates a large amount of waste that raises costs, while it is not capable of manufacturing complex shapes as those achieved in the 3D printing spectrum, where the additional complexity is free. 

Large format printing - A new paradigm 

The main technical challenges of large 3D printing are extrusion speed and increased machine reliability. Trideo's range of Big-T 3D printers, for example, feature a high-flow extruder that can deposit up to 8 times more material than desktop machines, radically reducing manufacturing times for giant parts and allowing companies to have competitive production rates. Regarding the reliability of the machines, the use of innovative sensors, electronic functions and software permanently control the operation of the equipment and guarantee a minimum failure rate. In addition, a 3D printing machine such as the Big-T can simultaneously manufacture short series of small parts, distributing them over every corner of its 1m x 1m surface.

Another great advantage of large-format 3D printing is that, once the digital files have been debugged, modifications and refinements to the printed mold should be minimal, and the replicability and dimensional accuracy of the part would be guaranteed, eliminating variability in the process and standardizing the quality of the final product.

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Post-processing 

Another important cost item is the post-processing of the model, which in many cases can demand an enormous amount of time, and which in the case of numerical control technologies such as CNC or 3D printing is much less necessary. In the case of 3D printing, for example, the stacking of the layers in the vertical direction generates a characteristic roughness on the lateral faces that can be eliminated with the application of products such as fillers, primers or resins. 

Other advantages of digital manufacturing in foundries

• Storage: Over time, companies accumulate patterns that gradually deteriorate if they are not used frequently, and take up significant physical space in the company and are very costly to repair. Using 3D scanning or modeling techniques, these patterns could be digitized and stored until they need to be manufactured again. 
• Spare parts: But it is also possible for companies to digitize or model spare parts of process machines that are susceptible to be replaced by 3D printing, and that due to obsolescence are difficult to procure, thus improving availability and avoiding the cost of storage.
• Jigs and fixtures: 3D printing applies equally well to the manufacture of tooling and process aids, unlocking the possibility of developing customized production configurations at any stage of the process.
  

Conclusion

Large format 3D printing in the foundry sector is a challenge that contrasts with the inertia of years of tradition and know-how. However, the irrefutable benefits it offers both technically and economically have paved the way for large-scale digital manufacturing in the sector:

• More accurate: Digital manufacturing produces repeatable and reliable results, unattainable by traditional craft methods, which translates into increased quality and productivity.
  

• Faster: Large-format industrial 3D printers can work 24/7, which multiplies productivity compared to availability and cost of operator time. In addition, the possibility of quickly modifying the 3D digital design and repeating the model in case of any problem radically improves development times.
  

• Cheaper: The FDM 3D printing model development process is associated with a great decrease in raw material costs, not only because 3D printing filaments are proportionally cheaper, but also because there is a great decrease in final waste. In addition, less human resources are required because the machines are autonomous and the digital designs are made only once and then the manufacturing codes are repeated over and over again in an automated way.
  

In companies that have already started their transformation by introducing desktop 3D printers, machines like Trideo's Big-T with its enormous workload unlock new levels that were not possible before, and even unprofitable due to the time consumed in assembling multiple parts of the same model.