CNC machining or CNC milling is a subtractive manufacturing process that uses 3-axis, 4-axis and 5-axis indexed machining processes to cut solid plastic and metal blanks into end use parts. With a range of CNC machines, Additive Engineering can deliver CNC machining and CNC turning services to high precision for machined tools, prototypes and low volume production. Tight tolerances are +/- 0.5mm for metals and +/- 0.2mm for plastics. If you need a different tolerance, please contact us.
CNC machining services include :
Grinding machines for materials with high hardness including quenched steel and brittle materials including glass and ceramics. Dimensional accuracies are at 0.05 microns. Sizes range from 3,200×1,600mm to 12,500×6,300mm.
Electrical discharge machines are used for hard materials, for precision injection moulds, complex parts with deep holes and cavities, curved surfaces, narrow slits and thin walls.
Additive Engineering is an ISO9001 certified facility and has passed supplier audits for medical devices customers to ISO13485 standards. Besides standard inspection reports, we can also provide 3D scanning for inspections as a service.
For precision CNC machining, there are a few design guidelines that will help improve your CNC design and will improve the functionality of the parts delivered by this low volume manufacturing method. The following are some examples:
To CNC machine or 3D print? This is a common enquiry for 3D printing service bureaus especially for one-off components, prototypes and low volume production. Most would associate CNC machining as the manufacturing process for mass production and 3D printing as the rapid prototyping solution. Each manufacturing method has its strengths and understanding the differences will help in the selection process, whether for plastic parts or metal parts.
The key difference between CNC machining and 3D printing is that CNC is subtractive manufacturing while 3D printing is Additive manufacturing. CNC technology start with a blank block of material, and computer numerical control of the CNC milling machine cuts away at the material to create a finished part. Cutters and rotating tools are used to shape the part.
3D printing technology or additive manufacturing involves creating parts in layers of material ( nylon powder or liquid resin for plastic parts) and metal powder for metal 3D printing. A laser energy source in the 3D printer combines the layers to form the 3D printed part. 3D printing does not require tooling or fixtures like a CNC mill.
As a rule of thumb, there are about 5 key factors to consider.
If it is a complex part, lattice structures, a topology optimised part, part created by generative design, 3D printing as an additive process tends to be better than CNC machining. This is because of the machine tool access and clearances on cnc lathes, hold or mount points on cnc machining equipment and an inability to machine square corners due to tool geometry. Even 5-axis systems have its own limitations. An operator is required to rotate the part so the tools can access different angles. Jigs and fixtures are required for repositioning and adds to processing time and final part price. The limitations with a 3D printing process are much more manageable. Even the processes that require support structures do not diminish advantages with design freedom.
If tolerances to microns are required, cnc machining may be a better option. There is also the option to 3D print the near net shape to be further cnc machined to required tolerances. The minimum wall thickness of 3D printed parts are restricted by the laser spot size.
Metal 3D printing (DMLM)
Plastic 3D printing (SLS)
0.8mm for metal and 1.5mm for plastic
2000x800x1000mm; Lathe Ø 500 mm
100x100x100 mm to 440x220x320mm
200x250x300mm to 600x330x550mm
Costwise, it usually depends on the material required, the geometry (can it be done any other way), the part volume and the number of units required which impacts the post-processing time and cost. We have found 3D printing inconel and titanium to be more cost-effective than CNC machining inconel and titanium as these are notoriously difficult to machine.
Need fast turnaround? 3D printing is usually much quicker. There is no need for machine tool set up. CNC workflows tends to be more labour-intensive. The operator needs to decide on tool selection, spindle speed, cutting path and repositioning. Post processing steps also factor into the build time. These include bead blasting, anodising and powder coating.
For 3D printing, the workflow involves a digital file, choosing orientation, adding supports if necessary and the printer creates the slices required to build the part. There’s post-processing involved as well such as cleaning of loose powder, heat treatment for metal parts and removal of support structures, which can be labour-intensive. Other processes include sanding and polishing.
The turnaround time also depends on the required material and the number of parts needed.
When you need one-offs and small volumes, 3D printing tends to be more cost effective. When the numbers start increasing to hundreds, CNC machining may become comparable and in thousands, injection molding is the most cost effective, assuming the part geometry can be manufactured using other processes. This is a general guide, part geometry and size of parts are factors in volume batches. Additive Engineering provides all of the following services, ask us for a quote.
CNC machine or investment casting
CNC maching or injection moulding
investment or die casting
Additive manufacturing is complementary to CNC machining as demonstrated in this epsiode of The Cool Parts Show. This tool is 3D printed to be lightweight and is used in the manufacture of the motor housing in an electric car.
an end mill for precise metal cutting (typically aluminium) and used to be made with machining. Metal 3D printing made contoured internal channels possible for more effective delivery of coolant, improving machining.
Start time and content
1:02 How this 3D printed machining tool works
2:48 Conventional tool weight versus 3D printed tool
4:33 the 3D printed sections of the tool
6:10 Another 3D printed cutting tool with coolant channels
7:50 Different features of the tool
9:00 Three cutting tools in one
In a hurry? Stephanie Hendrixson does a minute summary from 12:12-13:28.
Inspired to 3D print your own tools or need CNC services? Contact the Additive Engineering team with your requirements.
In conclusion, which manufacturing you choose would depend on the priorities you place on the various factors highlighted. Additive Engineering can help in the decision-making process by providing quotes for both CNC machining and 3D printing as well as technical guidance to the manufacturability of your product based on the material, tolerances and expected mechanical performance.
If there is a material that is not listed, contact us with your requirements.