CNC machining is now one of the primary methods of manufacturing parts for larger and smaller equipment. The precision, repeatability of the process or the high working efficiency make this production technology ideally suited to the needs of many industries. Although it is considered modern, it is a technology created in the 1950s, whose development goes hand in hand with new information technology and advances in material science. What is CNC machining, what materials can be formed using it and, finally, what machining techniques does it cover?
What is CNC machining: basic information and short history
CNC (from Computerised Numerical Control) machining is an automated technology for forming parts. The operation of a specific CNC machines is managed by a special controller, which executes a preset programme that is translated (via motors and actuators) into sequences of movements of the tool that forms the block of material: the cutter in a milling machine spindle, the lathe blade or the pushers in a hydraulic press. Although CNC machining is most often associated with the machining method (cavity machining, involving the removal of excess material), numerical controllers can control the operation of a wide range of equipment in a manufacturing company's machinery park - also for plastic machining (such as the aforementioned CNC hydraulic presses) or incremental machining (such as 3D printing).
The machining process itself is based on the implementation of a programme which defines the parameters of the machine's operation - e.g. the speed of the feed movement, the sequence of movements carried out and many others, depending on the type of material to be machined (including its susceptibility to moulding with a specific method), the tools used (e.g. types of cutter, weight of the abrasive disc) or the expected effect (e.g. the need to obtain a high quality surface). Sequences are formulated using G-Code, standardised markers understood by modern CNC equipment. Such a programme is created based on a CAD file supplied by the customer with a part design or technical drawing, which the specialist first transfers into computer assisted design (CAD) software and then converts into work sequences comprehensible to the machine controller.
Through the use of numerical (computerised) control, it is possible to produce a large number of repeatable parts in a much shorter time than with traditional machining equipment. Today, the most commonly used numerical machining methods are:
- CNC milling - allowing the production of parts of almost any shape - a lump of material is formed by a cutter on a spindle,,
- CNC turning - enabling automated production of cylindrical parts while machining rotating lumps,
- CNC grinding - used in finishing operations focused on achieving the highest possible surface quality,
- CNC press brake forming - used for the plastic forming of larger and smaller parts.
In a nutshell: most of the automatic machines (lathes, milling machines, grinding machines, etc.) used in manufacturing plants for centuries have a numerically controlled counterpart.
Nowadays, CNC machines can be used to produce parts from a wide range of materials:
- metals - from iron alloys (steel), through various aluminium and titanium series, to copper or bronze,
- plastics - both acrylic glass and high-performance polymers with mechanical properties similar to those of light metal alloys,
- wood - CNC machining is one of the cornerstones of today's furniture industry,
- glass,
- and many other materials.
CNC machining itself is linked to the development of military aviation - this technology was developed in the 1950s for the US Air Force. The main reason for commissioning the development of this form of machining was the need to produce reproducible jet engine components, which should be perfectly balanced. The machining technologies used up to that point, even those based on precision templates, could not meet the demand of the rapidly growing military aviation. Aviation needed a technology that combined precision machining with speed of production.
This was the origin of the first numerically controlled (NC) cutting machines, which implemented commands given via punch cards (also: very advanced in the 1950s). The development of information technology and the miniaturisation of computers allowed for greater use of microprocessors in machining - this is what led to the first computerised numerical control (NC) machines in the 1970s. They no longer needed punch cards - subsequent commands were executed based on a programme entered into the computer.
How the CNC machining process is prepared?
This conversion of the part design into G-Code tags understandable to the CNC machine controller - i.e. preparation of the CNC machining process - usually consists of several steps:
- creating a model of the part in a computer program, usually CAD. Such a digital model allows all aspects of the workpiece to be visualised and forms the basis for creating the CNC machine sequence.
- translation by CAM software (Computer Aided Manufacturing) of the CAD design into a language that can be understood by the CNC machine tool (G-Code). CAM programmes - based on 2D drawings or 3D objects - allow the creation of control programmes for the milling machine or CNC lathe.
- CNC machining. This is the final stage in which the CNC machine performs the cutting according to the loaded CAM programme. The correctness of the programme is first tested - first in the diagnostic software and then also on a sample material. After successful testing, automated production begins on the basis of the tested design. Depending on the machine tools used - operators may be involved in assembling and disassembling the machined parts (this is not the case with feeder machines) and controlling the correctness of the operating parameters - usually of more than one CNC machining centre.
What are the key advantages of CNC machining?
The opportunities offered by CNC machining for modern industry cannot be overestimated. With this technology, modern manufacturing becomes more efficient and precise, resulting in higher quality manufactured items and lower cost per unit production.
Key advantages of CNC machining technology include:
- repeatability of manufactured parts - one of the significant advantages of CNC milling machines and other numerically controlled equipment is the ability to produce a large batch of almost identical parts. Maintaining minimum tolerances makes it easier to obtain parts with repeatable dimensions. In practice - this was one of the main reasons that led to the development of numerical control technology.
- the possibility of batch production - CNC technology makes it possible to noticeably shorten production processes, even for parts with complex shapes. In addition, a single operator can supervise the operation of multiple machine tools, which - with the use of automated feeders - can operate around the clock, with virtually no human intervention. This makes it impossible for even the most efficient automatic machine tool operator to maintain the production rate provided by a CNC machine.
- production flexibility and the ability to produce successive batches of parts almost immediately - this is possible thanks to standardised CAM files, which enable work to begin once the proven manufacturing programme has been uploaded to a suitably calibrated CNC machining centre and a block of material with adequate parameters has been introduced into the work area.
- lower unit cost of part manufacture - this is an extremely important advantage of this technology. In spite of the longer and more labour-intensive production preparation process, the production of the part itself is fast and thus: allows significant savings to be achieved, especially with large batches of parts. On the other hand - manufacturing a small number of parts using CNC equipment (at RADMOT from 100 per batch) may not be profitable. In addition, the precision of numerically controlled equipment reduces rejects during quality control, which also translates into lower costs.
- Quality of manufactured parts, compliance with specifications and full dimensional compatibility - CNC cutting precision also means higher quality manufactured parts. Thanks to computer control, errors resulting from human inattention or fatigue are minimised. Precision also extends the life of the product, as well as the ease of interchanging parts manufactured on different CNC centres.
- Operator`s safety - CNC machining does not require direct human-machine contact. The operator responsible for controlling the CNC machine (or more precisely: supervising its operation) monitors the status of the machine via an interface. This reduces the risk of injury.
CNC machining - the challenges of Industry 4.0
CNC technology - in addition to its many advantages - poses many challenges for the industry. Among the key ones, at the moment, are:
- the high price of numerically controlled machines (CNC centres). They are much more expensive to purchase than automatic (manually controlled) machine tools.
- the high qualifications of the operators. Working with CNC machine tools requires competence in programming, material science, design and a wide range of engineering and technical knowledge. This makes it likely to take longer to both acquire the necessary competencies and to deploy an employee in a particular manufacturing company.
3 Interaction of multiple production departments. Modern production, particularly for industries in Industry 4.0, is much more complex and requires the coordinated work of many specialists and the execution of many processes in the right sequence. It is not just about removing layer after layer of material with a cutter - CNC-based manufacturing companies, in order to remain competitive, offer many additional services as part of the part manufacturing process. Part washing, electroplating, painting and varnishing or, last but not least, the logistical handling of a batch of parts - these are just a few of the additional services that allow companies such as RADMOT to stand out from the competition. Furthermore, the precision required by Industry 4.0 means that production itself should be embedded in a process that takes into account issues such as:
- strict quality control,
- quality measurements of materials used for processing,
- maintenance and application of failure prevention methods,
- continuous maintenance of the best possible calibration of CNC machining equipment,
- providing the best possible specialists to handle production.
These are just a few of the challenges facing CNC machining companies today.
Many of these are addressed by technological innovations such as artificial intelligence, applied to numerically controlled processes. These allow manufacturing processes to be optimised, thereby reducing the unit cost of producing parts.
What affects the price of CNC machining?
CNC machining - thanks to the automation of the process - makes it possible to drastically reduce production costs, especially for large batches of parts. However, it is worth pointing out what influences the cost and when a CNC machining job is profitable.
Among the key factors influencing this are:
- the type of material being machined,
- the dimensions of the part (e.g. whether it fits within the working area available on your CNC centres),
- the complexity of the project (whether it is simple milling or 5-axis machining is required),
- the completeness of the technical documentation for the order (e.g. does the customer provide CAD files with the part design),
- additional services (e.g. electroplating),
- the batch size of the order (this has a huge impact on the final order quote),
- the lead time of the order - the shorter, the higher the price will be.
Each of these elements translates into the final production price of a batch of parts. Due to the aforementioned complexity of the preparation process, it is most expensive to start production and produce the first batch of parts. This makes CNC machining below a certain break-even point unprofitable for the customer (e.g. 100 parts per batch or 1,000 per year), especially when compared to traditional cutting methods (e.g. on automatic milling machines).
On the other hand, each CNC machining order that comes to RADMOT is considered individually. Therefore, we only quote a final price for CNC machining once we have agreed with the customer what their order should look like. We always explain where the price quote comes from and what elements it consists of. If we see an opportunity to optimise costs (e.g. using other alloys with similar parameters or the possibility of dispensing with certain additional processes), we inform the customer. Therefore, when approaching RADMOT with a request for a quote for CNC machining, you can be sure that it will be analysed in depth by professionals.
One order, many benefits - this is how you work with RADMOT
At RADMOT, we offer CNC milling services, CNC turning services, as well as many additional services, including washing, aluminum anodizing, laser marking and assembly. We have at your disposal over 80 modern machines in our machine park, all from renowned manufacturers. Download the presentation and check on which machine tools we produce CNC turned parts and CNC milled parts.
Contact us and tell us what you need. We have been providing CNC services for almost 40 years. Our valuation is completely free. And if you're in doubt about which technology will work best for you, our expertise is at your service.
