In recent years, attention has been drawn to home 3D printers using resin materials and "metal 3D printers," which use metal materials. Since this is a method of forming one layer at a time, it can be used for shapes that are difficult to work with other methods. The above solution is mainly introduced in the aerospace and medical industries and uses the advantages of 3D printers. This article will explain the advantages and disadvantages of metal 3D printers, comparing them with fused deposition type 3D printers, which use resin materials. We will also outline the industries that are likely to benefit.
What is a metal 3D printer?
A metal 3D printer is a device that shapes metal materials, such as titanium, aluminum, and stainless steel, based on 3D CAD data. In general, 3D printers using resin as a modeling material are widely used in industry, but the current situation is that few companies have introduced expensive metal 3D printers.
How does a 3D metal printer work?
Based on cross-sectional data created with dedicated software, 3D metal printers create objects of any shape by combining metal materials layer by layer and repeating the lamination. Unlike the cutting process, which shaves a lump of metal, or the forging process, which molds it under pressure, metal 3D printers are designed to layer and develop metal materials to handle complex shapes such as mesh structures and hollow designs. Another point is that metal parts can be created without preparing a particular mold - similar to casting.
What are the methods of 3D metal printing?
There are different types of 3D printers for metal. The most popular methods they perform are:
- powder bed method,
- directed energy deposition method,
- hot lamination method,
- binder jet method,
What do they consist of in practice?
How does the powder bed method work in a 3D printer?
The powder bed method is molding that irradiates a beam onto a powder bed coated with metal powder and repeats melting and solidification for each layer. After molding with this method, the powder that the beam has not irradiated can be collected and sifted for reuse, preventing material loss. Two types of beams lead to material processing:
It should be noted here that the properties of the formed object obtained by each heat source differ.For example - using a laser, compared to the electron beam method, it is possible to create a model with a smooth surface, but applying it to materials that do not absorb the beam isn't easy. In addition, the metal powder used should have a high degree of sphericity and easy flowability to be accurately distributed. Therefore, a commonly used raw material is a spherical powder obtained by the "gas atomization" method, which uses an inert gas.
Directed energy deposition method
In the directed energy deposition method, a modeled product is produced by feeding a powder or wire, melting it with a laser or electron beam, and depositing it. In general, powders are used and delivered using an inert gas. Since the supplied material is used for the model without waste, it is a manufacturing process with little material loss and good efficiency. The above method is most often used to repair metal parts. Nevertheless, since it can be used to form large parts with simple shapes, the use of this scheme is being considered in the aerospace field. The advantage of using this device is that the surface can be machined during forming, eliminating the need for post-processing.
What is the hot lamination method?
The hot lamination method, also known as "material extrusion," is a molding method in which metal powder is introduced into a thermoplastic resin and then laminated while melting. The shape can then be freely molded and controlled with the thermoplastic resin, which softens when heated. However, since the resin remains after molding, it is removed in skimming. Shaping is complete after the sintering of the skimmed molding and solidifying of the metal powder. The gap disappears as the resin is removed during sintering, and the volume shrinks by about 20%. Therefore, it is essential to design CAD data considering the amount of shrinkage and create a model of appropriate size. The fused lamination method has traditionally been used as a resin 3D printer.
What is the binder jet method?
The binder jet method is a method in which a liquid binding agent, "binder," is sprayed from a nozzle onto the metal powder. After the binder is sprayed and solidified for each layer, the modeling plate is lowered, and the powder is placed again. This process is repeated and sintered in a high-temperature oven or heater to remove the binder. During this time, the model shrinks by about 20%, so the material's volume change must be considered when modeling. Objects produced by the binder method tend to have a lower density than those produced by the powder bed method, which creates a problem in practical applications. This is the molding method used for small parts with fine shapes.
What are the advantages of 3D printers for metal?
3D printers for the metal have advantages over conventional processing methods such as cutting, casting, and forging, and there are high expectations for their further technological development in the future.
3D printer for metal:
- Can print metal parts with excellent strength and durability.
- It offers short-term production of prototypes and small-batch products.
- Prototypes can be easily produced due to reduced costs.
What are the disadvantages of 3D printers for metal?
3D printers for metal have various advantages, but they are not universal devices. This is because there are three disadvantages that we need to mention:
- Using the equipment requires knowledge of modeling.
- The initial cost is expensive.
- 3D metal printers are expensive to operate.
With 3D printers for metal, materials can be stacked and shaped, so even complex shapes that are difficult to cut can be produced. When cutting, it is difficult to install a cooling water pipe inside the mold, as there is a limit to the area that can be cut by the tool. However, 3D metal printers can mold even hollow structures and produce products that cannot be made with conventional machining. Such equipment is also suitable for "difficult-to-machine materials" that are too complicated to cut. For example - until now, in the aerospace industry, titanium alloy parts have been produced by casting and machining. However, titanium alloy is a difficult material to work with, so 3D printers for metal that do not require cutting have begun to be used and have been successfully introduced into practical use.
3D printers in medicine
3D metal printers are also suitable for medical products. In this case, it is essential to finish artificial bones and dentures in a shape that matches the skeleton and shape of each patient's teeth. The traditional casting process requires time and effort to remake the mold for each patient. If you're using a metal 3D printer, you can change the product's shape simply by improving the CAD data, so you'll be able to mold it quickly. In this way, metal 3D printers are a manufacturing process suitable for high-variety, low-volume production.
Examples of 3D metal printers used in industry
3D metal printers are used in the following industries due to their many advantages:
- Medical field.
- The automotive industry.
In the medical industry, 3D metal printers are beginning to be used effectively. This is because it is necessary to provide "artificial bones" and "prostheses" designed in the optimal shape for the patient. 3D metal printers can freely control the form using CAD data, so the optimal model can be created for each patient. For this reason, even in Japan, more and more companies and research groups are obtaining "pharmaceutical approval (approval required for manufacturing and marketing)" for artificial bones made with metal 3D printers.
Metal 3D printers can also be used in the aerospace industry. Metal 3D printers are suitable for turbine blades and combustion nozzles used in aircraft engines, which have complex shapes that are difficult to cast and cut. GE Aviation, a U.S.-based aircraft engine manufacturer, has successfully modeled a combustion nozzle installed in an engine. Conventionally, more than 20 parts were assembled, but using metal 3D printers, the product can be integrated.
Automobiles use many titanium materials, which are difficult to cut, and parts with complex shapes. Therefore, the automotive industry is an area that can easily benefit from the advantages of metal 3D printers. Italian carmaker Bugatti produces a model consisting solely of parts made with a 3D metal printer. However, the model is a supercar limited to 40 units and has not gone into mass production. Metal 3D printers will be used more often if mass production challenges can be overcome.
How to use a metal 3D printer and cut?
Cutting with a machining center or NC lathe has excellent machining accuracy. Therefore, if the shape can be quickly produced - use classic cutting. However, if the product's condition is complicated, keep in mind that there are cases where it is difficult to machine because there is no way to insert a knife. In addition, it is difficult to cut materials resistant to the blade, such as "titanium," which easily ignites chips when cutting, and "stainless steel," in which molten metal easily adheres to the blade. If the product has a complicated shape and cannot be manufactured, or if you want to process materials that are difficult to cut, it is better to use a 3D printer for metal. In addition, for products requiring multiple cutting processes, using a 3D metal printer can shorten the production process and produce them quickly. If you want to prevent material loss, it is a good idea to use a metal 3D printer. This is because there is a loss of material during the cutting process due to the removal of the resulting chips. In practice, metal 3D printers only use the necessary amount of materials, reducing raw material waste and improving productivity.
3D metal printers are mainly used when cutting, casting, and forging are challenging to perform and for products with complex shapes. However, since the initial and operating costs are very high, there is a problem that is not easy to implement compared to a 3D printer using the fused lamination method. Either way - it is expensive and complicated equipment, but if we find a niche where we can use it, it is worth it.