CNC machines, often called more precise 'numerically controlled machines' are the devices that contemporary production heavily relies on.
Thus: their impact on contemporary manufacturing and production is so strong we can tell with certainty that their form was shaped by CNC devices.
High availability, ease of manufacturing of big quantities of elements with minimum tolerances, or low cost of unit production – these are only a few advantages of CNC manufacturing that make that technology industry standard.
Although – mechanically – looks similar to the traditional (automatic) machining tool, numerically controlled devices do not require hand-held leading to the removal of excess material.
That numerical control allows fast manufacturing of almost identical parts, speeds up the whole production and significantly decreases unit cost.
What are the CNC machines and how do they work?
CNC machine tools – in a nutshell – are the devices that allow the removal of excess material and shape parts due to the control of a specialized (computerized) controller. Such devices are sending commands to actuators and engines that execute the work, based on previously prepared CAM programs – accordingly and within specifications.
In other words – the whole control, that in automatic devices rely on humans and hand-leading, is executed by the driver. A human operator is required at the beginning of the whole process to create a program and only maintain the whole process.
Among many advantages of CNC machines it is worth mentioning:
- optimization of working time,
- possibility to produce big batches of high-quality parts,
- increase of repeatability of manufacturing,
- higher precision of manufacturing and lover tolerances – even below 0.02 mm,
- increasing the speed of manufacturing high quantities of parts,
- decrease of unit cost production – in traditional machining one operator can produce a finite number of parts during one shift. CNC machines, although require more time to start production, when started can manufacture parts on a clock.
The disadvantages of CNC machines are for sure:
- machine cost – CNC milling machines or CNC cutting tools are much more expensive than traditional,
- time to start production – is significantly higher and can impact the cost of manufacturing smaller quantities,
- require higher skills from the CNC operators.
For that reason numerically controlled machine processes are perfect for manufacturing big quantities of parts; in that context, the technology shows all of its advantages. For smaller batches or one-offs traditional machining devices are still the best.
The CNC acronym comes from computerized numerical control and describes technology that was created and developed in the 1950s for the US Air Force in cooperation with MIT (Massachusetts Institute of Technology).
Initially, it was used to produce parts for jet engines – cutting-edge technology at the time – but with time CNC machining became popular in other industries.
The first applications of the CNC devices were focused on manufacturing parts out of alloys – mainly steel and aluminum; with time it found application in shaping a vast variety of materials – from polymers and wood to even oddities like stone or ice.
The first CNC machines – mainly mills and lathes – executed commands delivered on the punched cards. With the development of microcomputers (the 1970s), programming CNC machines became easier, and more available memory allowed them to execute even more complex processes of machining.
Programming of the contemporary CNC machine (in a nutshell) looks like that:1. The project of machined part is prepared within CAD (computer-assisted design) software that puts 2D drawings into a 3D digital context,
2. The final project for machining – is prepared in the controlling panel of the machine (CAM) that describes the following moves of the machining tools (eg. face mill) and parameters of work (eg. feed rate for flat sections) for selected material during a particular step in processing (eg. for machining carbon steel or raw material). That final CNC project is in practice a way to convert a CAD file for a language understandable for machining tools (G-Code / RS-274) by a machine operator.
3. Said CNC operator uploads commands to the CNC module of the machine and checks its readiness (eg. proper mounting of machined material or status of the spindle). When the process is ready – turn on the device.
As you can see, turning on the CNC machine – properly – requires much preparation.
Often such preparations include quality control of the material BEFORE machining to provide the best quality of machined parts.
That is why that technology is the best suited for mass manufacturing – especially parts in big batches. Machining with CNC technology can be cheaper than with traditional mills or lathes but requires the machine operator's knowledge of technology, machining, programming, and metallurgy.
What is even more important – the software for the CNC machines allows many types of controlling processes of milling:
- shape control – that allows performing a complete machining process (eg. 5-axis milling, with all movements executed in one device) – also spatial objects,
- selectional control – often used in machining longitudinal elements (eg. pipe shape) that require precisely programmed movements on a specific track,
- point control – used in subsequent stages of machining on almost every CNC device (eg. for drilling).
Each controlling method allows different types of results and its selection depends on the machine operator.
Types of CNC machines
Machining with a CNC machine is usually connected with a numerically controlled mill.
These are the most popular but not only CNC devices.
Among the most often used in machining shops and plants we can mention:
- CNC mills (2-, 3-, and more axis),
- CNC lathes,
- CNC grinders,
- CNC machining centers (2-, 3-, 4-, or 5-axis),
- CNC laser cutters, plotters, waterjet.
Basically: every automatic device used in machining can have its counterpart in a 'computer numerical control'.
Due to high production capacity and control modern CNC machines can be found in almost every industry.
Just like traditional mills (manual, automatic) are used for chip processing and their principle is almost the same (removal of excess material with a cutter) – only the controlling actor is different.
The machining itself is executed with a specialized cutter mounted in the rotating spindle.
Cutting bit removes material and shapes its desired form.
CNC mills are controlled by a programmed device that executes moves with planned speeds and sequences of moves. CNC mills allow the machine of flat parts (2D) and spatial machining (eg. 5-axis mills).
CNC lathes allow fast and precise production of high quantities of cylindrical objects (eg. rings, pins, or bearing balls).
Parameters of movement of cutting bit, depth of cutting, or RPM of the spindle are controlled numerically, not by hand. That allows for increasing the efficiency of a machining process, especially combined with automatized feeders.
As the CNC mills and lathes allow to speed up the process of shaping material, the CNC grinders can increase faster surface finishing.
Such devices deliver low depth of machining – that is why they are perfect for polishing the surface to remove marks from cutting tools. It is worth mentioning the CNC grinders are included in the group of sanding processes.
Other types of CNC devices
As mentioned, the usage of computerized numerical control is possible for many devices used in machining and shaping materials.
Devices such as plotters, waterjets, machining centers, or even laser engravers use CNC technology. Just like in the case of mills – it allows to increase the precision of machining and decrease the time required to produce part.
The CNC technology is also more available each year – small home CNC mills or lasers are perfect for prototyping or amateur applications (eg. in the production of one-off elements or very small batches of elements made of plywood). Although similar in principle, such small CNC devices are no match for professional mills or lasers – rigidity, working area, or efficiency of work are dedicated to the home application and not much more.
Nasz park maszynowy to ponad 80 maszyn CNC - sprawdź na czym produkujemy.
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 more than 80 modern machines at your disposal in our machine park, all from reputable manufacturers. Download a presentation and check out the machine tools we produce parts on.
Contact us and tell us what you need. We have been providing CNC services for almost 40 years. Our quote is completely free. And if you have any doubts about what technology will work best for you, our expertise is at your service.