CNC machining is rapidly taking a foothold as the method of choice in the manufacturing industry – not to mention in heavy industry, the medical world and many other commercial markets – thanks to its efficiency, cost-effectiveness and ability to produce amazingly accurate items continually. One of the major benefits of using CNC – it stands for computer numerical control – is that it eliminates the possibility of human error in the production process, as it is fully automated.
However, this does put the emphasis on the design process. CNC machines require the details of the design to be input into the machine digitally, in the form of numerical directions. These are created and provided by the computer aided design (CAD) software that the designer works with. An experienced designer will be able to see potential mistakes during this stage of the process, but there are common CNC machining design errors that do occur. Let’s have a look at the most frequent examples.
Frequently Seen Mistakes
Simple Design Reduces Run Time – it is important for the designer to aim for the fewest required cutting or milling processes to produce an item. It’s all very well having a finished item that looks fabulous, but if it includes unnecessary machining processes – in other words, if it could perform its function and be made quicker – then it’s going to cost more. Simplicity is the purposes if CNC in every single aspect of the process.
Keep Text Recessed – many times you will need to add text, perhaps a part number or name, to an item during the production process. There are two big mistakes: making it too small, and having it raised. Small text is slower to create thanks to the size of the milling tools, and raised text requires the entire surface to be machined around it. Larger, recessed text is much easier and quicker to produce.
3:1 Width-to Height Wall Ratio – one common mistake in designing for CNC production is that the designer will aim for the thinnest walls possible (where walls make up part of the product). This is great as it looks better and saves weight. The problem comes when it is in the machining process. Tall, thin walls do not come out well in CNC production, and can even break. The reason is that the tools used are made from extremely hard material. Never make a wall thinner than 0.020 inches, and always check that it meets the 3:1 width to height ratio.
Optimize Parts for Machining – we’ll keep this general: some items are simply not going to be suitable for CNC machining. These may be parts that would work better if they were molded. It pays to talk to a machining expert when deciding on this. Taking advice is sensible and will cut down on costs in the long run.
The above are all errors in design that are seen often – and they usually come about because a part has not been specifically designed for CNC machining – so follow these carefully and you should find things go as smoothly as possible.