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What is CNC Machining?

It seems to be one of those things which everybody in the engineering world assumes you just know, but nobody ever explains exactly what is CNC machining. So, let us do that for you now.

What is CNC Machining?

So, what does CNC mean? It stands for Computer Numerical Control, which doesn’t tell you much except that a computer numerically controls the machine. So basically, this means a computer-controlled machine, which begs the question of why Axiom are so proud of their highly skilled staff (we will come back to this later).

A CNC milling machine (which we have six of at Axiom) is a machine which uses a high-speed cutter to remove material mechanically; this can be almost any form of material but is most commonly used for metallics but could also be model board or plastics. Once you have cut away, you are left with a product’s shape. We put a block of material into the machine, set the high-speed cutter going and, finally, out pops a finished product (if only it were that easy).

How is it done?

For a CNC machine to mill the shape of a product, you need to start with a CAD file (another acronym, Computer Aided Design). A designer will create the shape to be manufactured in a 3-dimensional CAD program. The Axiom design team has this facility in-house, so we can design your product for you if you need a CAD facility or can take your existing 3D CAD file. Or Axiom can convert your 2-dimensional design drawing into a 3D CAD design file.

However, the CNC milling machine can not read a 3D CAD file (nothing is ever that simple!), so this file must be converted into CAM software (even more acronyms, CAM is Computer Aided Manufacturing), which the machine can read. This file instructs the machine which cutters to select to mill the various parts of the shape, where to place its cutter and the speed to rotate the cutter to cut away the relevant material.

Are all CNC machines equal?

Not all CNC milling machines are equal; they come in varied sizes and abilities, and the size limits the block of material with which you can start. Axiom has large capacity machines that can machine a block of material up to 2.0 metres.

When a CNC Milling machine cuts away the material, the number of axis leads to the degree of accuracy and complexity the cutter can move in. Milling machines can cut in 3, 4 or 5 axis depending on the sophistication of the machine. A 5-axis machine, such as Axiom has, can produce a much more complex and intricate shape than a 3-axis machine. A 5-axis machine combines rotating the cutting head against the block of material and rotating the block of material, ensuring the precision cutting of the most complex geometric shapes.

The skilled staff come into play at all stages

Design staff ensure the initial 3D CAD file has the data required for the conversion to a CAM file and also ensure that the final product will meet the customers’ specifications.

The conversion to CAM software, selection of cutters and machine set-up is also a skilled process which requires experienced Machinists. The machinist takes the 3D CAD File and, using his knowledge, generates the CAM file for the machine to read. They place the product required within the block of material to be cut and generate the CAM file for the machine to read. Numerous varieties of high-speed cutters may be selected to mill the material; the machinist selects the best cutter for the product and places them into the carousel on the machine. The block of material is placed precisely into a vice to be held by the machine. The machine must be told exactly where the block is on its machining bed, which cutters to use for each section of the shape to be cut and the speed to rotate its cutters, considering the degree of accuracy required for the finished products. If the customer needs a tight tolerance product, then the setting up of the CNC milling machine will be more complex to meet this degree of accuracy. Axiom is trusted by many of its customers to produce tight tolerance CNC milled products.

All products are passed through Axiom’s inspection area for checking against the original CAD model and any additional customer requirements.

The beauty of CNC milling is that once the CAM programme has been written, the manufactured item can be reproduced precisely unlimited times.

Contact us to see how we can help you with any CNC machining requirements.

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