CNC Mistakes: 7 Design No-Nos to Avoid

The manufacturing industry has seen huge developments over the last 80 years and none more so than in the digitisation of machinery. CNC machining, which stands for computer numerical control, is a computerised metal machining method. A numerical code instructs the machine on everything from the RPM of the spindle to the movement of the cutting head. Although CNCs are used frequently in a range of industries, many people still commit basic CNC mistakes. Here at Milo Tools we will take you through the seven design no-nos to avoid when using a CNC machine.

CNC machinery is used in a wide range of industries, including electrical, defence, mining, aerospace, automotive and more, and has become a reliable and efficient way to produce parts. When designing these parts, people tend to make several CNC mistakes. Before we get into the design mistakes, let’s explore the topic of CNC machines a little further.

How CNC Machining Works

CNC machines are fully automated machinery that requires digital instructions about tooling and cutting trajectories. The process starts by designing the part you want to create using computer-aided design software (CAD), which is then fed into computer-aided manufacturing (CAM) software. This prepares the model and then guides the cutting head throughout the manufacturing process. All that is left is to choose the right parameters and wait for the information to be translated into codes that the machine can understand and utilise.

Types of CNC Machines

CNC machinery is used to automate a range of machining processes. Some examples of standard CNC machines are:

• Milling machines
• Turning machines
• Laser cutters
• Waterjet cutters
• Press Brakes

CNC machinery is hugely valuable to the machining process as automation means that human error is reduced, accuracy is greatly improved, and repeatability is ensured.

7 Common CNC Design Mistakes

Although human error is significantly reduced during the machining process thanks to machine precision and accuracy, the design process is still an area where errors or mistakes can occur. Below are the most common examples of design mistakes that designers make when using CNC machines.

1. Over Complicated Design

We all want to work on complex and exciting projects, but that is sometimes not feasible for CNC machining. Unfortunately, as a designer, you may need to make adjustments when it comes to milling and cutting requirements to reduce the cost of your product. If you fail to simplify your design you run the risk of increasing costs, lead times, and part failure.

2. Avoid Text

CNC machines are perfectly capable of engraving text into your product, and having some detailed logo or small sentences can look cool. However, adding text can increase the cost. Using a CNC machine to take care of your aesthetic features and text is usually a waste of time.

Adding text will generally need a different cutting tool, which will add time and complexity to the process. On top of that, there are more efficient ways of adding text to your product once the machining is complete (e.g. laser marking).

3. Over Complicated Design

Understanding the right tools for the job is essential in any line of work, and that is no different with CNC machining. If you are new to this form of machining, it might be tempting to use a CNC machine for all machining. However, some parts may work better if they are moulded instead. It is a good idea to talk to machining experts during the design process to save you time and money.

4. Over Complicated Design

We all like making things look nice but focusing on aesthetics for CNC machining is a major mistake. Saving on costs and time is a key part of CNC machining, and, therefore, you should always keep in mind the amount of material you are removing and the process you are using to do this. If you ask yourself whether the material should be removed just to look nicer, it probably isn’t worth it.

Don’t make this simple CNC mistake. Instead, check out potential post-machining processes such as electro-polishing that you could use instead.

5. Over Complicated Design

Another one of the most common CNC mistakes is not taking into account the height and width of your walls. Often designers will try to produce the thinnest walls possible because it looks good and saves on weight. However, tall thin walls do not come out well in CNC machine production and are easy to break completely.

To avoid this simple CNC mistake, don’t make any of your walls thinner than 0.020 inches and always ensure that your width to height ratio is 3-1. Stick to our advice, and you shouldn’t go wrong.

6. Over Complicated Design

Always pay attention to the depth of the cavities you are designing. Cutting cavities that are too deep is another CNC mistake you can avoid. Milling tools are most efficient when they are milling cavities two or three times their diameter in-depth. Therefore, a deep cavity may lead to many problems, including the tool being unable to reach the surface you are attempting to mill, tool fracture, tool deflection, etc.

7. Over Complicated Design

Unfortunately, the cost is often a limiting factor in most things we want to do, and this is no different when it comes to CNC machining. Many users forget to work out how much a project might cost to complete or forget to factor in aspects, such as the cost of materials, time frame for completion and the chances of a successful project.

It might sound obvious, but when it comes to avoiding making any CNC mistakes, you will want to ensure that your budget can cover the costs.

CNC machining is a key part of the manufacturing industry, and when used correctly, it can be a reliable and versatile manufacturing process. No matter how familiar you are with the process, it is still easy to make CNC mistakes, especially during the design stage. As well as reading our guide to avoiding the most common CNC mistakes, it is worth consulting experienced professionals like those you will find at Milo Tools.