The Pros and Cons of Subtractive 3D Printing

If you are a 3D modeler, or just interested in 3D Printing, then you might have heard that there are two main methods in which you can create your prototypes. The first is additive manufacturing & the second is subtractive. Obviously, these methods are at opposite ends of the spectrum when it comes to the final development and printing of your product. And, while additive 3D Printing has remained the dominant method in which to create 3D Printed Designs, using the subtractive method has its pros and cons that should be considered.

What is the difference between the additive and subtractive method?

When you are building a model in a CAD Program you will need to know if you want to construct your design with additive or subtractive printing. Most Desktop 3D Printers use an additive layering method for the fabrication of the 3D model. This means that the material is heated and then the model is constructed by placing layer upon layer until the design is completed. In subtraction manufacturing, the printer starts off with a block of material relative to the size of the finished product. For example, if you are printing a gear that has a diameter of 10cm and a height of 10cm then your block would need to be at least 10cm by 10cm by 10cm. However, a block with excess material would be suggested to ensure all the detail is captured.

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To ensure a clean cut on the 10cm gear, it would be best to have 12cm so as not to compromise the points on the exterior. 3D Gear by Siclari Studios

How Subtractive Manufacturing potentiality saves materials

You may think that subtractive manufacturing would use more materials than additive. But this is debatable. Firstly, when you use additive manufacturing, you have a layered method which sometimes move out of alignment. When this occurs you have to make a reprint. This is not to say that the subtractive method is above error, but there are less risks. Why?

When you use the subtractive manufacturing, you already have the block of material that you are going to be using. Unlike additive manufacturing, there is not speculation as to how much 3D Printing Material you require because you are cutting away from material rather than adding fresh material. As the printer cuts away from the block to create the design, all you must consider is the physical size of the CAD Model being fabricated. If calculated properly, the only “wasted” material is that which is cut away from the mold. Yet, even the excess can be eliminated as you can recycle your waste for 3D Printing later, making filaments which can be used on your 3D Printer if you have one.

CNC vs. 3D Printing

CNC Milling is often associated with subtractive manufacturing. This process uses a various axis technique to cut away at the material until the design is complete. While some may think that this is a restricted method in which to design 3D components, it really is not. As the subtractive CNC Milling machines work off of various drills, bits, axis, computer systems, etc. it is quite common to have the capacity to produce the same model which you would normally create using 3D Printing.

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Subtractive manufacturing does not have to be simplistic as you can see from this YouTube
video.

Perhaps the greatest advantage of the subtractive manufacturing process is that it usually takes less time to fabricate a model than the additive method. Some have debated that the subtractive method yields results with less detail then the additive method, but as you have seen above, this is not always the case. Of course, the detail is solely dependent upon the material as well as the machine you choose to purchase.

The other advantage of the subtractive methodology is that you are creating model from a solid piece of material. This tends to give a higher threshold on the model’s durability than on a layered additive model. But again, it depends upon the material being used. Clearly, if you used metal in the additive method, and that metal was heated to form one component, it would be a solid construction. However, if you used a cheap filament on the additive process it would be weaker. The same is true for the subtractive method, if you used a solid block of cheap material it would be more apt to cracking and such than an additive model with higher quality material.

The biggest drawback to the subtractive manufacturing, specifically the CNC Milling process, is that is it rather expensive. Apart from the machines, the parts and materials tend to run higher than that of the Desktop 3D Printer. Additionally, in large scale projects, such as the house which was constructed with a 3D Printer in Dubai, could not have been accomplished with subtractive printing. Subtractive manufacturing is best suited to small scale objects and mass production of those smaller objects.

Which method should you choose?

The method you choose should be dependent on your skill level and budget. If you are new to manufacturing, 3D Printing is advised as the printers are more abundant, the materials are cheaper, and the helpful software such as Octoprint make mobile control and printing substantially easier for the CAD Designer.

The more seasoned manufacturer can utilize additive or subtractive manufacturing. It strictly depends on what applications you are using for it. Either way, watch this space as desktops subtractive machines are due to hit it big.

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