With recent advancements in 3D printing capabilities, it is becoming easier for manufacturers to use additive manufacturing to create parts from a wide variety of materials, including polymers like ABS, TPE, and PLA as well as carbon fiber composites, nylon, and polycarbonates. Even pricey metals like Titanium, Stainless Steel, and Inconel are becoming increasingly common in the world of additive manufacturing as well.
There is no doubt that the additive manufacturing space will continue to develop and grow in the coming years, but will it render subtractive manufacturing methods like CNC Machining obsolete? Absolutely not. In fact, precision CNC machining is likely more important to the additive manufacturing process than you may think, as a new process called “hybrid manufacturing” is quickly taking hold in the industry.
Additive Manufacturing vs. Subtractive Manufacturing
Before implementing a hybrid manufacturing approach, it is important to understand the pros and cons of each method. Here is a quick breakdown of both additive and subtractive manufacturing, and the benefits and drawbacks of each.
|Adds material layers to create parts
|Removes material layers to create parts
|Slower process, better for small production runs
|Faster process, better for large production runs
|Better for smaller parts
|Better for larger parts
|Rough surface finish that requires significant post-operation finishing
|More definied surface finish with minimal post-operation finishing required
|Less precise part tolerances
|Able to hold extremely precise part tolerances
|Cheaper material costs
|More expensive material costs
|Less material waste
|More material waste
|Intricate details easier to create
|Intricate details can require complex programs and additional capabilities (5 axis)
Using CNC Machining to Create Precise 3D Printed Parts
Looking at the chart above, you will notice that one of the key differences between additive manufacturing and subtractive manufacturing is the surface finish and tolerances that can be achieved with each method. This is where a hybrid approach to additive manufacturing can be extremely beneficial.
As parts come off the printer, they can be quickly moved into a CNC machine with a program designed for part completion. The CNC machine will be able to get 3D printed parts down to the tight tolerances required by many industries and reach the desired surface finish. Advanced finishing tools and long reach, tapered tools from brands like Harvey Tool can easily machine the tight geometries of 3D printed parts, while extremely sharp diamond-coated tooling and material-specific tools designed for plastics and composites can work to create a beautiful, in-tolerance finished part regardless of the material.
By designing a workflow like this in your shop, you can spend less time worrying about the precision of printed parts by adding in subtractive operations to keep material costs low, create less waste, and keep parts in tight tolerances for precision machining excellence.
Using 3D Printing to Increase CNC Machining Efficiency
If your shop is focused completely on subtractive manufacturing methods, you are probably thinking that there is no need for an additive option in your shop. Can’t a CNC machine create everything a 3D printer can, and in less time? Not necessarily. Again, by using the two methods together and taking a hybrid approach, you may be able to lower your manufacturing and material costs.
For example, you could machine the bulk of a part with typical subtractive machines, which would likely take a very long time using additive methods. Then you can go back to that part with a 3D printer to add intricate features to the part that may take complex programming and hours of planning on a subtractive machine. An impeller is a great example, where the bulk of that part can be machined, but the tricky fins and blades could be printed onto the part, and then finished back on the CNC machine.
The ability of additive machines to literally “add-on” to a part can also make for a cheaper approach to part design. Instead of using expensive materials like Inconel or Titanium to machine an entire part, portions of the part that do not require extreme heat resistance could be machined out of cheaper steel, while the heat resistant portions using expensive materials can be added later through additive methods.
Hybrid Manufacturing Machines
As hybrid manufacturing workflows become more popular, so do new hybrid manufacturing machines. These hybrid machines are all-in-one machines where both additive and subtractive manufacturing can be performed in a single setup. Many of these machines offer metal 3D printing as well as multi-axis machining capabilities, ready for even the most complex parts thrown their way. With a bit of customization, large-scale 3D printing machines or CNC mills can be retrofit to allow for hybrid manufacturing with add-ons from companies like Hybrid Manufacuring Technologies.
As manufacturing and design techniques get progressively “smarter” with CAM/CAD programs offering generative design and artificial intelligence, these hybrid machines could become a new standard in high-end machine shops working in advanced manufacturing industries like aerospace, medical, defense, and the mold, tool & die market.
Overall, in 2021 we are still early on in this new revolution of hybrid machining and advanced design methods, but it is important to understand the role that adding a CNC machine could have in your additive-focused shop, and vice versa. By combining additive and subtractive together, shops can mitigate the cons of each method and take full advantage of the benefits of having both options available on the shop floor.