Engineers rely on CNC (Computer Numerical Control) machines to develop and create bespoke parts for mechanical, manufacturing and design purposes.
Over our 58-year history, we have acquired an excellent reputation in the precision engineering, component manufacturing and training sectors for our products, services and facilities, along with our highly skilled workforce and apprenticeship programmes.
Our guide is to offer engineers of diverse backgrounds a deeper understanding of the key factors they should consider when designing a part for CNC machining.
What is CNC machining?
CNC machining is a manufacturing process that uses subtractive machining technology and Computer-Aided Design (CAD) to create high-quality components thanks to an efficient method of cutting, drilling and shaping materials.
Having a computer control this process reduces lead times and the chance of human error, leading to a high-quality and exceedingly precise output of anything from bespoke, one-off parts through to mass production runs.
CNC machining safely
As this is our ultimate guide for using CNC machines for engineers, there is no better place to begin than with safety, as we abide by vigorous health and safety standards to ensure the safety of our entire team.
When setting up a CNC lathe for a work holding device, it’s important that tool safety precautions are considered for:
- Tool selection
- Tool positioning
- Tool condition
- Tool post condition
There are many safety precautions to be taken for the protection of the machine operator as well as the machine. This includes:
- Ensuring the machine is isolated before interacting with the workpiece or bed
- Wearing correct PPE
- Ensuring heavy tools are handled in the correct way
You will find full details of safety procedures in our blog, How to operate a CNC machine
What else should engineers consider?
When designing a part for CNC machining, engineers should consider the overall part size and the number of re-orientations required to machine the part as these will directly influence the machining and set-up time, thus affecting not only the cost of the part but also the lead time.
If you are wanting CNC parts fast, look to reduce the complexity of the design and ensure the machining can be completed in as few operations as possible.
And consider that different materials require different cutting speeds and feeds, so it is important to take this into account to choose the best material type and tool tips – two factors that should always be respected.
Tolerance
Tolerance is the range for a dimension – on initial drawings and designs that reflect how the final part will be used and how it will interface with other components.
While the specific end use of the final part may differ between projects, the fundamental principles of CNC machine engineering will always remain the same.
It is imperative engineers use a realistic tolerance, overly tight tolerances increase costs and lead times, so try to determine the tolerance you require instead of specifying a generic tolerance.
Standard CNC tolerances are determined by the type of process being applied, and there are many different types of tolerances, such as positional, flatness, parallelism, thread tolerances etc.
We recommend engineers looking at CNC engineering should familiarise themselves with GD&T (Geometric Dimensioning and Tolerancing), if they have not already, which is a methodology and language for communicating engineering tolerances.
CAD and CAM
CAD (Computer Aided Design) and CAM (Computer Aided Manufacturing) are used to design a job and programme the manufacturing processes. CAD file formats are another factor for design engineers to consider when designing a part for CNC. CAM software utilizes CAD software drawings to generate toolpaths for the CNC machine.
It is important to consider that CNC machining may not be compatible with different software packages and file formats. The type of CAD software being utilized should also be considered.
Ultimately, CAD and CAM software helps to improve efficiencies on CNC machines by increasing productivity, automatically translating designs into instructions, and enabling programmes to be modified for use on other jobs with similar specifications.
What are the different types of CNC machines?
CNC machining is sometimes used as an all-encompassing term to describe the various types of computer-controlled subtractive machining technologies. The two main types of CNC machining are CNC Turning & CNC Milling.
There are a range of standard cutting tools that can be used on a CNC machine, which includes:
- Facing / Turning
- Grooving
- Boring
- Threading
- Part off
- Centre drilling
- Twist drills
The most common method of holding tools within a CNC lathe is by using the tool post magazine which can be used to store and change tools.
Another method is by using a carousel which is a large tool holder that can hold multiple tools at once. Although more expensive, carousels enable convenient tool swapping during machining operations which makes them a common choice for modern machines due to the increase in efficiency.
Get in touch
To find out more about DPC’s CNC machining, please get in touch.