CNC Machining vs. 3D Printing: How To Choose the Best One for Your Situation

time:2021-07-23| Author:Admin

As a product designer or engineer, you’re often confronted by countless choices during product design. For example, you’re likely to be at a crossroads when choosing a suitable engineering material or manufacturing method for your prototype (and production) parts.

CNC machining and 3D printing — two of the most popular manufacturing methods today — can save you a considerable amount of time and money while still ensuring high-quality parts. But these methods are not one-size-fits-all; they both have many different capabilities that make them ideal for different engineering design scenarios.

This article covers some of the key areas you need to evaluate before deciding between CNC machining vs. 3D printing for your prototyping or production project.

5 Key Areas You Must Evaluate Before Choosing Between CNC Machining vs. 3D Printing

To make the right choice between 3D printing vs. CNC machining, here are five key areas you need to evaluate:

  1. Minimum Feature Size
  2. Geometry
  3. Tolerance
  4. Engineering Material
  5. Costs and Lead Times

#1 Minimum Feature Size

Minimum feature size describes the smallest scale at which you can create a feature on a workpiece using machining equipment. Since CNC machining is a subtractive manufacturing technology, the cutting tool diameter dictates this feature size. In contrast, nozzle size dictates the smallest possible feature that you can produce using 3D printers.

As a rule, you should opt for 3D printing technology if you’re looking to create parts with a minimum feature size ranging between 0.25 mm and 0.8 mm. CNC machines have their minimum feature size ranging between 1 mm and 3 mm- about four times the size of 3D printing technologies.

#2 Geometry

Because CNC cutting tools make contact with the workpiece from the top, you might experience difficulty fabricating some shapes. For example, hidden features and undercuts are especially challenging to create using CNC machines. In such scenarios, you might be better off relying on additive manufacturing processes like 3D printing.

However, if you do your homework and realize that CNC machining works for your design, then be sure to choose the right CNC equipment. CNC milling machines are ideal for creating cavities and angled cuts on regularly shaped workpieces, while CNC lathes are better suited for machining complex cylindrical shapes. (Related Post: Here are 5 Types of CNC Machines You Should Absolutely Know About)

#3 Tolerance

Now that you know 3D printers can create pretty much any design, you can proceed to 3D print prototype and production designs, right? Wrong!

An essential factor you need to consider before 3D printing your parts is tolerance. If you’re comfortable with a tolerance ranging between ±0.1 mm and ±0.3 mm, then you can proceed with 3D printing your design. But if your design requires a more stringent tolerance requirement, say ±0.04 mm, then you must use CNC machines.

With a tolerance ranging between ±0.025 mm and ±0.125 mm, CNC machines are superior to all 3D printing technologies, including SLS, FDM, and DMLS metal 3D printing.

At this point, you’re probably wondering whether it’s possible to CNC machine extremely complex geometries with hidden cavities while meeting tight tolerance requirements. Yes, it’s absolutely possible; all you have to do is use an auxiliary cutting tool in place of standard CNC cutting tools.

#4 Engineering Material

One of the most significant advantages CNC machines have over 3D printers is that they are compatible with a broader range of materials. With CNC, you can fabricate pretty much any block of material, including plastics, metals, and composites.

In contrast, 3D printers are only compatible with thermoplastics (ABS, PLA, nylon, among others) and a few metals like aluminum and stainless steel.

There is one thing you need to know, though: because a 3D printer builds parts layer by layer, it changes the properties (or the way the parts will respond under stress). Hence, you must confirm that 3D printing processes will not alter the properties needed for your design to function as expected.

#5 Costs and Lead Times

We can talk about minimum feature size, geometry, tolerances, and a ton of other things to consider all day. Still, none of these carry as much importance to businesses as manufacturing costs and lead times. Fast and cost-effective manufacturing technologies are every product designer’s dream.

CNC machining is generally cheaper and faster than 3D printing, especially if you’re looking to create over 100 units of identical parts. This is primarily due to the fact that CNC machining eliminates the post-processing operations (such as removal of support structures and surface finishing operations) required for 3D printed parts.


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