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Metal 3D printing vs metal casting: How to choose?

Introduction

Additive Manufacturing is very often referred to as the new industrial revolution. From 3D printed car parts to airplanes or houses, 3D printing is changing the world around us. But how does the innovative and fairly young technology perform compared to classical Metal Casting which has been used for centuries?

Traditional Metal Casting

The history of Classical Metal Casting methods dates back to the middle ages. The process involves several steps. First of all, you need to produce a replica of your final product. To create replicas you can use different materials, one of them is wood, as shown in the example video. The design on the replica has to also include a filling system and some additional support.  Then, you need to create a mold based on this replica. There are several techniques for working with molding materials, the most popular is sand.

The first step is the preparation of the replica, this process will be different for different materials.  Once you have the copy of your final product, the filling system has to be designed. It’s important to remember that the replica has to come out of the sand mold, so it can’t be wider at the bottom than on top. This is called an undercut and means the copy is unremovable.  

While designing your parts and the filling system, you also have to think about the fact that liquid metal hardens fast and it might not reach a higher level of your design before it concrets. To avoid that you have to design a feed head. It’s later removed from your part.

Then it all has to be copied in a mold. It’s necessary to prepare two sand molds. Next step is to get the object mirrored in a special sand to create one mold. The second mold is used for the filling system, where the metal will be poured, and if necessary can also be used for the second part of your object. The molds are then stuck one of the top of the other, so the filling system matches the shape of your object.

Once two molds are connected, so the metal doesn’t leak between the two layers of sand, the metal is heated up and liquified. The casting processes involve the metal being poured into the mold through a filing system very quickly as it hardens fast.

The last step is to clean the object off the sand and remove the filling system. Now the object is ready for any additional polishing and removal of extra material if needed.

Metal 3D printing technologies

Selective Laser Melting

Selective Laser Melting (SLM) is an Additive Manufacturing technology that uses metal powder to create your parts. The metal 3D printer spreads a thin layer of the metal powder on the bed, then a laser melts the metal creating the shape of your 3D model. The next layer of powder is placed and the process repeats itself. The metal is melted at a high temperature, and the 3D printed parts require a cooling time.

With SLM technology you can integrate multiple components into a single object, which reduces the costs and saves time on assembling your parts. Choosing Selective Laser Melting for your production will also provide you with very strong parts, which at the same time can have thin walls lowering the weight of your parts. They also will have high-temperature resistance.

For SLM we offer Aluminium AISi10Mg0,6 composed mainly of aluminum (90%), silicon (7%) and magnesium (0.6%). This material has good mechanical properties and can be used for parts subjected to high voltages.

Direct Metal Laser Sintering

Direct Metal Laser Sintering (DMLS) technology also uses metal powder to 3D print your functional parts. The process is the same as for SLM, the metal 3D printer lays down a layer of metal powder, then a laser beam sinters the powder in the shape of your 3D model. The DMLS process is highly beneficial for those who need to produce their metal parts for prototyping or low-volume production by eliminating time-consuming tooling. It also allows creating complicated and highly detailed designs that wouldn’t be possible with any other technology, due to the limitations of the traditional manufacturing processes.

Properties of your parts metal printed using SLM and DSML will be similar. They will have good mechanical characteristics, your models can be quite detailed and also fully functional, prepared to be used or integrated into a larger object.

The difference between SLM and DMLS is the temperature the metal powder is melted at and the materials you can use. With DMLS we offer Stainless Steel 316L and Titanium 6AI-4V.

Binder Jetting

Like the technologies mentioned above, Binder Jetting is powder-based 3D printing method. However, with this Additive Manufacturing method, there is no laser involved. The metal powder is fused with a binding liquid agent and lightly cured between each layer. Binder Jetting is the fastest and the cheapest metal 3D printing process. The main benefit of Binder Jetting is high customization and fast production time, however, this technology is more suitable for prototyping needs, ornamental and decorative parts or jewelry.

At Sculpteo we offer two metal powders for 3D printing with Binder Jetting: Steel / Bronze 420SS/BR and Stainless Steel 316.

Lost-Wax Metal Casting

Lost-Wax Metal Casting is the only 3D printing method that doesn’t involve metal powder. The technology is based on injecting metal into a mold. The master model, typically built in wax, thanks to 3D printing is the perfect replica of the finished product. Once the master model is 3D printed, a mold made in plaster is poured over it. When the plaster mold is ready, liquid metal is injected into the mold to replace wax pattern which is drained away through a treelike structure to create the object.

To meet your needs for production, we offer you a variety of 3 metals for Casting: Silver, Brass, and Bronze.

Metal casting and 3D Printing: Making friends with the enemy

Additive Manufacturing doesn’t necessarily have to be a competitor to traditional metal casting. It can very well complement classical methods of production and improve them. The best example of combining Additive Manufacturing and Classical Foundry is to 3D print the replicas of the master objects. 3D printing allows a high level of details, which was not reachable before the use of Additive Manufacturing methods. And it also speeds up the pre-production process of traditional Metal Casting.

A good example of the two technologies working together is Lost-Wax Metal Casting. Thanks to Additive Manufacturing a high level of customization can be achieved for the 3D printed wax copy of the original design. The process is faster thanks to 3D printing and the wax replica is easily removable.

Another way of combining Additive Manufacturing and classical Metal Casting is to 3D print plastic copies of the final product. Like with the Lost-Wax Metal Casting, 3D printed replicas will melt out creating the perfect, custom-made mold that can be used for Traditional Foundry methods. The process is very well explained in the video below.

Moreover, 3D printed models are also great for the most commonly used Metal Casting molds made with sand. Thanks to Additive Manufacturing the model will be detailed and will leave the exact shape of your design in the sand to produce accurate metal products. A great example of combining both technologies is shown in the video of a 3D printed metal hammer:

When to use traditional Metal Casting

Classic foundry is great for big parts

If you’re planning to produce large mechanical parts, such as engine’s components, or big gears for machines, Classical Foundry is great for that purpose. Additive Manufacturing won’t be as effective with large sized parts due to the limitations of dimensions the 3D printer can reach. The main goal of producing mechanical parts is for them to be functional. The looks are not important at all, they have to have good mechanical properties and if big size is also essential for your production, traditional Metal Casting will provide you with great parts.

Traditional Metal Casting will be cheaper to produce a large number of parts

Classical foundry will also be beneficial if you need multiple copies of your parts. The costs of production decrease with the number of parts, whereas for using Additive Manufacturing, the cost stays the same.

How can you improve your production with Metal 3D printing?

As the process of metal 3D printing with Lost- Wax Metal Casting technology is quite similar to traditional Metal Casting in this chapter we will talk more about the benefits of using metal powder- based Additive Manufacturing.

Highly customized and articulated 3D printed parts

3D printing also allows for much more design freedom, a high level of details, customization, and if precision is important for your design, choose Additive Manufacturing. Moreover, with 3D printing, you can design your parts to be articulated which is impossible with traditional Metal Casting. It not only saves the assembly time but also gives you totally new design opportunities.

3D printing is faster

If time plays a big factor in your production process, Additive Manufacturing is the right solution for you. Metal 3D printing is much faster than traditional Metal Casting for several reasons. Starting with pre-production, to metal 3D print your parts you just need a 3D model. Compared to Metal Casting, where you not only need to design your parts, the filling system, and the feed head but also create a mold, 3D printing saves you a lot of time. For powder- based Additive Manufacturing technologies all you need to do it to upload the 3D model to our website.

Also, the post-production process is much quicker for metal 3D printed parts. Keep in mind that Metal Casting involves machining removal methods to unattach the filling system and feed head, as well as manual removal of metal that got spilled between the molds before you even move on to surface finishing. For 3D printed parts, the supports have to be removed, but that’s taken care of by our production team. We also provide you with several options for surface finishes such as polishing and plating which allows for your designs to reach another level of customization.

Additive Manufacturing gives you more control

The production itself might seem faster for Metal Casting as the liquid metal hardens quickly, but you have no control over the process. Additive Manufacturing has a much more stable process of production. There is a possibility for the 3D printer to crash, but we keep an eye on all our parts in production and if such situation happens, we can immediately react and stop the process. Metal Casting method doesn’t give you that option as you can’t see what’s happening inside the molds.

With traditional Metal Casting, there is also a risk of the liquid metal concreting before it reaches higher parts of your object. To avoid it, an additional part of the design has to be created called the feed head. It later has to be removed from the final product which slows down the post-production process. Also, during the filling, oxidation can cause the creation of bubbles in the metal, and small pieces of the sand mold can get inside of your part, which will affect the object’s properties.

3D printing helps you create lighter parts

If you need your parts to be light, Additive Manufacturing gives you lots of options to achieve that. To reduce the weight of your parts, your 3D printed parts can have walls filled with lattice structures. Your 3D model can also be hollowed, which is not the case with Metal Casting process.

Good mechanical properties

With Additive Manufacturing methods such as Selective Laser Melting and Direct Metal Laser Sintering, your metal printed parts will also be very strong and have high heat resistance. Metal 3D printed objects with SLM and DMLS will have better mechanical properties as they are produced at a higher temperature.

Is Metal 3D printing the new industrial revolution?

True that traditional methods of Metal Casting are beneficial if your parts have to be huge. However, if you require custom made and precise parts for your object to be fully functional, 3D printing is the way to go. Additive Manufacturing will give you the freedom you need to design exactly the model you need, provide you with fast results and can highly improve your production system. With the variety of 3D technologies your metal printed parts can be designed and manufactured on your computer, just upload your 3D model to our website.

It’s very important to choose the right material to decide which metal 3D printing technology to use with the best results to empower your manufacturing process. To help you with that we prepared for you a blog post explaining in detail each of our metal materials, and you can always ask one of our consultants.

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