What is CNC? Hermle explains.

What do a Spartan helmet, a mould for Swabian dumplings and a carnival mask have in common? The answer is that they are all parts that we at Hermle have milled from solid metal blocks at our manufacturing facility. Each has been engraved and decorated with intricate details and embellishments. We've added our logo, too. Not because we wanted to pitch ourselves to Hollywood as outfitters for any big-screen epics in the pipeline, or because we've been paying tribute to Swabian cuisine (although admittedly, we'd like to do that as well) or promoting the Alemannic traditions of southern Germany. We've done it because we can. The reason we can do it is that we have absolutely mastered the art of computer-aided manufacturing processes.

We're talking about CNC (computer numerical control). In our high-tech world with its wide range of computer-controlled systems, computer numerical control has a pivotal role to play in an array of different sectors. But what is CNC? It's a groundbreaking technology and a method of precisely machining all manner of materials. In this article, we are going to be exploring CNC technology, explaining how it works and shedding some light on what benefits it has to offer in an industrial setting, particularly for milling, turning and drilling metal, but also for mechanical and plant engineering, aerospace and other industries. We're also going to take a closer look at certain characteristics such as the three types of control used in CNC machines, as well as key distinctions such as G-code and M-code. First, though, let's address the basics.

What is CNC? A definition.

1. CNC technology enables materials such as metals, timber, plastics, MDF (medium-density fibreboard) and others to be machined to an exceptional degree of precision using computer-aided machinery. Its development and introduction have revolutionised the manufacturing industry. That is because instead of having to carry out procedures by hand, CNC makes it possible to automate the entire production process. Using pre-programmed instructions, a CNC machine can deliver accurate and reproducible results. Not only that, but it can also do so on more or less any conceivable object – as the introduction illustrates.
2. The way in which CNC works is based on a combination of hardware and software. The hardware consists of a CNC machine fitted with motors, servomotors and tools. The software comprises a computer program that controls the machine and contains the operating instructions. Both need to be precisely synchronised with each other.

The process begins with the creation of a digital model or a drawing of the workpiece to be machined. This model is created using special CAD (computer-aided design) software. The model is then imported into CAM (computer-aided manufacturing) software, which prepares the machining process and generates the necessary toolpaths.

Once the CAM software has generated the toolpaths, they are transferred to the CNC machine. The machine positions the workpiece precisely and executes the milling movements required to create the desired end product.

The CNC machine constantly gathers data throughout the process to ensure the accuracy and quality of the machining operation.

There are numerous benefits to CNC technology.

CNC technology offers a host of advantages over conventional manual machining methods. Read on to find out about some of the most important.

Better precision and exact reproducibility.

CNC can carry out high-precision machining operations that would be very difficult to achieve by hand – not to mention the fact that doing so would involve spending considerably more time and money. The pre-programmed instructions allow for extraordinary accuracy and reproducibility, which results in consistent and high-quality products. In other words, a CNC machine is a guarantor of identical products of identical quality. That brings us to the next advantage.

Higher efficiency and productivity.

By automating a manufacturing process, CNC makes it possible to increase efficiency and productivity by quite some measure. The machines work at a faster pace than any human ever could, should or would even be allowed to, running around the clock without interruption. They take some of the strain off staff, allowing them to focus on the essentials. Overall, CNC cuts machining times per piece and, by extension, increases production output.

Complex machining operations.

Numerically controlled systems make it possible to machine complex shapes and structures that would be difficult or even impossible to achieve using conventional methods. By using advanced tools, cutters and milling methods, CNC machines can produce complex workpieces with excellent levels of precision and efficiency.

Greater flexibility and optimised adaptability.

Because they are programmable, CNC machines can respond rapidly to new requirements and adapt to all sorts of production conditions. With simple changes to the software, it is possible to manufacture different products without having to retool the entire machine.

Point-to-point, continuous-path or simultaneous multi-axis – the CNC machinery control types.

There are three main types of control for CNC machinery: point-to-point, continuous-path and simultaneous multi-axis control.

Getting straight to the point.

Point-to-point control is the simplest type of CNC control. It defines the motions of the tool or the machine axis between two points. This type of control is well-suited to simple machining operations with straight lines and less demanding requirements in terms of complex movements.

Never straying from the path.

Continuous-path control is the next step up. It manages the machining of complex shapes by means of specific programmed toolpaths. This method enables precise control via the movements of the tool and is suitable for a wide variety of machining jobs.

Simultaneous across multiple axes.

Simultaneous multi-axis control is the most advanced form of CNC control. It involves multiple machine axes at the same time to machine complex and three-dimensional shapes. Consequently, this type of control is used to create complex workpieces to a high level of precision and opens up new avenues of possibility in production engineering. Hermle offers five-axis machining in its machining centres.

Time for a brief summary of what we've learnt so far.

Let's quickly go over what we know at this point. CNC machines are based on computer-aided design – CAD – being translated, vector by vector, into instructions for computer-aided manufacturing, or CAM. If you're interested in learning more about the interaction between CAD and CAM specifically, you can find plenty of detailed information in our article entitled CAD/CAM – Hirn und Hand im Fertigungsprozess [CAD/CAM – the brains and the brawn of the manufacturing process]. Here, we're focusing on the CNC process as a whole. One thing to note is that the instructions for the operations are generated via two different types of code – G-codes and M-codes.

Translating CAD into specific instructions.

G-codes and M-codes are sets of commands that are used in CNC programming to control machine tools. They may sound similar, but they perform different functions, as we explain below.

The CNC software used in a Hermle machining centre combines G-code and M-code commands to define a series of instructions that control the machine tool. For example, a CNC program can start with a G-code command that specifies the position of the tool, followed by M-code commands that switch on the spindle and activate the coolant. After that, there may be additional G-code commands used to move the tool along defined paths.

It is important to bear in mind that the specific G-code and M-code commands may vary depending on the machinery manufacturer and the type of control. However, there are a few universal commands that can be used on most CNC systems. We recommend consulting the documentation for your specific machinery to find out exactly which G-code and M-code commands it supports. In the case of Hermle, you can depend on the fact that all our machining centres are based on the same control type.

What does CNC bring to a Hermle machining centre?

Someone once told us that Hermle machining centres were among the best machines of their kind. One of the main reasons behind that is the CNC technology that they use, because it goes without saying that our machinery, which is used to machine precision parts, is controlled entirely by commands from computers. A CNC machine works with a computer program containing specific instructions about how a workpiece is to be machined. As mentioned previously, these instructions are drawn up in special CNC software known as CAD (computer-aided design). The CNC controller then translates these instructions into defined motions and operations that are executed by the machine. All of that was probably already clear from the explanations given above. However, there can be marked variations between manufacturers. At Hermle, we consider intuitive operability to be a key objective in the development and execution of our products.

How exactly does a Hermle CNC machine work?

The simple answer: very precisely. We're talking thousandths of a millimetre. In fact, a five-axis CNC machine can handle workpieces to an extraordinary level of accuracy. Using computer-controlled instructions, a CNC machine can carry out reproducible and highly precise movements far more accurately than any human operator could manage, at least without considerable difficulty. However, this impressive CNC machine accuracy depends on a diverse array of factors, such as the quality of the machine, the software used and the material to be machined. The latest CNC machines can achieve accuracies measured in micrometres. Hermle machining centres are among them. The designs of our machines are entirely calibrated to the work to be performed.

What is the purpose of a Hermle CNC controller?

In a different article, we've described CAD and CAM as the brains and the brawn of computer-controlled manufacturing. We would add that the CNC controller represents the heart of a Hermle CNC machine. It receives commands generated by the computer and converts them into control signals for steering the movement of the machine. The CNC controller manages the five axes of the machine to position the tool precisely and carry out the required machining. The CNC controller also monitors various parameters such as speed, feed rate and tool changes to ensure that machining is being performed correctly and efficiently.

Supplying machinery is not all that Hermle does. The company is also a dependable fixture on the market for services. After all, setting up our machining centres also requires the operators to be trained in how to use the machinery and equipment, and that training needs to be tailored to suit a wide range of sectors such as mechanical engineering, the automotive industry, aerospace and many other industries besides. That's why we offer our customers in-depth consulting services for milling, programming and how to operate our products. That also includes set-up and an introduction to CNC programming.

What does the average milling process look like?

A milling process will usually use milling machines, lathes or machining centres controlled with CAD software and special programs. The programs are generated, the milling and drilling tools defined and the appropriate clamping devices specified based on the technical drawing or the specifications for the workpiece. During the machine's program sequence, the workpiece blanks are clamped and the tools machine the raw material to produce the desired shape, dimensions and surface quality in accordance with the drawing or the applicable requirements.

The chips that are created in the process need to be transported continuously out of the workspace to keep the workpiece clean and to dissipate heat. One type of milling machine employed extensively in the woodworking industry in particular is the router, which is used for precise machining on workpieces such as doors. It allows for excellent accuracy and quality in milling operations. All in all, industrial milling jobs enable precise machining of workpieces of all shapes and sizes. They play a vital role in numerous industries and make it possible to manufacture parts and components in line with the requirements and specifications set out by customers.

A precise solution for every industry – controlled by CNC, of course.

Speaking about Hermle specifically, it really can be said that there is virtually nothing that cannot be machined with a Hermle mill. The helmet, the dumpling mould and the mask that we mentioned at the beginning should be proof enough of that. Nothing is impossible – and we demonstrate that at Hermle every day. We show it with our products and services and with our machining centres, which really do deliver 'milling at its best', just like our brand promise says. We've put together an overview of the technology behind it all for you to enjoy. After all, specific examples of the equipment in action are far more impressive than any description could ever be. To see them, visit our applications page. (https://www.hermle.de/en/machining_centres/applications)

These examples provide compelling evidence of our expertise in model-making – and there's more than just the helmet. Models that we've produced include a dragon, a bull, a bear, even an ice cream – not to mention the Eiffel Tower or a SpaceMouse unit. Then there are the solutions that we've implemented for making tools and moulds, controlled by CNC. Watch a Hermle C 12 U machining a knife die, a Hermle C 650 showing off its five-axis skills on an automotive connecting rod or a Hermle C 400 making a die plate. For the sport and leisure industry, you'll find videos of our machining centres creating a specialist bicycle pedal for downhill cycling, a valve cap and an alloy wheel. These are all disparate products manufactured with various machines to completely different requirements and specifications. Yet it is exactly that versatility that demonstrates the breadth of our expertise and the capabilities of our machinery. Our solutions for the aerospace industry underline that expertise yet further. After all, in no other field do you encounter such exacting requirements with regard to safety, quality and reliability. Our CNC machines are equal to the task. For example, there's the Hermle C 42 U dynamic performing four-axis machining on an impeller, or the Hermle C 32 U dynamic milling titanium structural parts for use in the industry.

The examples from the worlds of aerospace, mould-making, toolmaking and modelling are impressive enough by themselves, but then there are past projects from the field of medical technology, such as an implant holder machined with a Hermle C 12 U or centrifuge suspension equipment made with Hermle machinery. Again, these are just two of a whole array of examples of components that would be utterly inconceivable without the use of CNC. This is another area in which we consider ourselves part of the solution.

Of course, we can't provide an exhaustive list of all possible applications here, and nor would we want to, but we can't finish without offering a brief glimpse at precision engineering, because machining a watch case provides a prime example of the fine and delicate work that goes into this manufacturing method. At this point, you won't be surprised to learn that we also offer solutions for automotive engineering, machine-making and the consumer goods industry. Any time you have metal that needs milling, whether it's titanium, aluminium or something else entirely, we'll be happy to work with you.

Want to know more about CNC, or anything else relating to milling?

From M-codes and G-codes to point-to-point, continuous-path and simultaneous multi-axis control, if you have any questions about CNC operations and software that we haven't answered here, feel free to get in touch. After all, talking things through is what gets results in the end. We are at your service. Computer-aided manufacturing systems may be important, but there's something that's even more so, and that's the personal touch. One thing that you will notice in addition to the total reliability of our CNC machinery is that partnership holds just as much significance to us, because we believe that nothing is more vital than the trust of our customers. That is what spurs us on. It's also what makes us certain that we can offer you a solution for your Hermle that will give you the performance you need to manufacture at a rate that will put you one step ahead – all numerically controlled with CNC, of course (how could it be any different, given everything we've mentioned in this article so far?).

In summary: CNC is a master of manufacturing processes – and Hermle is a master of CNC.

So, what is CNC? It is a technology that has revolutionised our methods of machining materials and manufacturing products. CNC offers a multitude of advantages over conventional methods, particularly in industrial milling of metal products for mechanical and plant engineering, as well as in the aerospace sector and all the other industries mentioned above. CNC machines make it possible to manufacture high-quality products within short time frames and at low cost thanks to their incredible performance in terms of their precision and reproducibility, their efficiency and productivity and their flexibility and adaptability.

With its three different control types – point-to-point, continuous-path and simultaneous multi-axis – CNC technology also offers a wide range of options for meeting the requirements of various machining jobs. In the future, we can expect CNC technology to keep on delivering the kind of innovations and progress that will shape the manufacturing industry for years to come. At Hermle, we'll be there to make the most of it – right at the front of the pack. We'll be there for you and for everyone who uses a Hermle machining centre – or wants to.

1. G-code (geometry code): G-code commands control the geometric movements of the machine tool. They specify the kinds of motion that the tool is required to execute relative to the workpiece. For example, G-code commands can instruct a machine to move on a particular axis, mill along a circular or rectangular path or cut a thread. Specifically, these are commands that coordinate movements on the five axes of a Hermle machining centre.
2. M-code (miscellaneous or machine code): M-code commands control the non-geometric functions of the machine tool. They specify the actions that the machine is to carry out; for example, tool changes on drills, mills or cutting tools; switching the spindle on and off; starting and stopping the coolant pump and so forth. M-codes are essentially machine commands.