Why 3D Printing Isn’t Enough

Since their first commercial appearance in the late 1980s, desktop 3D printers have captured a large base of users. The device is popular for enthusiasts and professional users because it is relatively easy to use, can be relatively inexpensive and can create a wide range of object

But, whether it employs FDM, SLA or SLS technology, 3D printers have several major limitations that inevitably bracket its possibilities.

First of all, the devices are limited to using some form of plastic. Even if that plastic has embedded short fibers to increase its strength, the result will be objects that are weaker than they would be if created from non-plastics.

3D printing in 5 axes, available in our machines, does increase the object’s strength somewhat because it allows layers to be cross-deposited against each other. But inexpensive 3D printers generally print horizontal layer on horizontal layer – resulting in weak spots because of the plastic and because the layers all go in one direction.

By contrast, milling machines can employ virtually any material, including solid metal and wood.

Plastic and Mesh Models

Then there’s the matter of accuracy.

In an 3D printer, plastic is heated up for extrusion or deposition, a process that slightly warps the material, and then it shrinks when cooled.

Additionally, 3D printing is limited by the mesh model, which is the predominant form of virtual model used for 3D printing. Mesh models, defined by spatial coordinates and composed of many virtual triangles or squares, cannot reach the level of accuracy possible in NURBS models, which are mathematically defined. Milling machines can use NURBS or mesh models.

Because of these two factors – the lack of precision in depositing heated plastic and in some kinds of mesh models – the accuracy level of 3D printing is substantially less than milling. According to a study by researchers at Örebro University in Sweden, 3D printing is as much as ten-times less accurate than milling.

Hours Versus Minutes

Finally, there’s the matter of speed.

3D printers are very slow – on average, about eight times as slow as CNC milling machines. This means the number of objects that can be made over a given period of time is low.

For example, a dentist can 3D-print a teeth arch for aligners – but it could take up to two hours for each arch. On the other hand, a milling machine can carve an arch in a matter of minutes.

It’s for these reasons that milling is commonly used to create many of the objects we see around us, such as the body of a smart phone or the casing for a laptop computer. 3D printing is most often used for small objects that don’t require much strength, such as a picture frame, and for mockups or other presentational components.

The Best Solution

The two technologies also have different needs for upkeep. For instance, 3D printers require meticulous cleaning, while milling devices send chips everywhere, so they’re generally enclosed to trap the chips and insulate the loud sound.  

Because of those chips and the sound, users are sometimes wary of milling machines. But the milling machine in our 5AXISMAKER stops when it is opened, and it is as easy to use as a 3D printer, with on-screen instructions on what to do next. The steep learning curve for milling is a thing of the past.

While 3D printing has its drawbacks, its advantages include the ability to inexpensively make a wide range of mockups or small parts. The best solution to the tradeoffs in the two technologies is what we’ve done with our 5AXISMAKER --  have both 3D printing and milling in the same device.