As Industry 4.0 and the Industrial Internet of Things (IIoT) become more popular, the concept of automation is quietly changing. Automation covers the concepts of high precision, high speed, high efficiency and predictive maintenance. This is driven by digital, programmable systems that have been developed and perfected for decades.
   Computer Digital Control (CNC), for example, automates machine tools with computers that execute pre-programmed sequences. CNC was also developed from computer aided manufacturing (CAM) in about 50 years of the 20th century. With the development of computers and servo systems, it can help manufacturers meet their increasing demands for repeatable, high-precision production.CNC has become synonymous with accuracy and control. It is mainly composed of 5 components -- sequencer, interpolator, servo controller, logic controller and operator control interface. Twenty years after the concept of numerical control systems was proposed, a cheaper and simpler form of computer-aided control appeared, that is, programmable logic controllers (PLCS).
    PLC was developed in the 1970s to replace the relay logic control system. These relay systems are often uneconomical, inflexible, and difficult to use because they rely on hardware to perform critical functions. PLC has input and output functions and can be programmed to perform sequential operations, data processing or simple axis control.
     However, PLC's mission is not to replace CNC. "The two controllers serve different purposes and markets and each has its own advantages. So no one in the industry is going to say, 'I've invested in CNC, there's no place for PLCS anymore,' precisely because they're two completely different controls." "Said Ian Baird, CNC applications manager for Fanuc's factory automation division.
    Because of its use, beyond simple input/output (I/O) algorithm, CNC and automation more. Modern CNC is a flexible, digitally controlled system designed to meet the needs of manufacturers without the need to reprogram the entire system. Most modern CNCS also include user interfaces equipped with built-in operating, maintenance, and diagnostic screens. "For this reason, CNC is popular with people who want complete control of their machines, because of its capabilities that allow you to take charge after a simple training session." Braid said.
   Due to its great flexibility, CNC is suitable for complex, multi-axis machining in any industry. Any application requiring precise motion control can be achieved through CNC, whether it is the manufacture of watch parts and medical devices, or the etching of reactive atoms and plasma.

Simple and complex control tasks

   Baird thinks PLCS are better for simple control tasks. If you have an application that does not require high accuracy or flexible motion control, such as an AC electric transmission belt, then PLCS are often the best choice and are less expensive than CNC. As a result, CNC is considered more suitable for complex applications.
   However, although PLC is simple, it also has some disadvantages. "PLCS don't have the flexibility of CNC," Baird says. If you need to change the program slightly, you must completely reprogram it. It also does not have the precision of CNC, so it is best used as a low-cost solution for basic tasks. Despite the low cost of PLCS, many manufacturers continue to opt for CNC, partly because of its lower life-cycle costs."
  It is interesting that many designers switch to CNC after installing PLCS, mainly for the reasons of flexibility, reliability and cost. The initial cost of numerical control systems is higher than that of PLC, but the long-term return on investment may be higher due to the improvement of reliability and control capability of numerical control systems. It also gives system designers the flexibility to decide how much control they want users to have over their machines.
The long-term cost effectiveness of CNC systems, thanks to their advanced user programmable features, can minimize downtime, control machine energy efficiency or machine output.
   Many CNCS are equipped with artificial intelligence contour control. This means that the machine can be controlled to run within a certain workload, or adaptive control of the machine to complete night work. For example, companies can use energy more economically by programming it to work at 80% load. The CNC is also equipped with energy efficiency features such as a charging module.
CNC also has safety features that provide a good guarantee for collaborative action with humans. "The CNC is equipped with a digital algorithm that performs motion control," Baird said. "The digital system consists of two parts, a real digital data system and a target digital system. The target system is the expected value of the 'ideal' and provides the machine with target operating parameters. The real system and the target system are both driven by the same command, so they should work exactly the same way."
   If the real system experiences an outage, such as an unexpected load, the actual data will deviate from the target data. The machine will convert it into a conflict and react in one of two ways. If the movement is slow, it stops, if it is fast, a "vector back" is performed, which retracts any moving machinery to avoid damage to the device. For high-end machines, 3D technology can also be incorporated to prevent five-axis machines from moving outside their pre-determined working area.
   Zero downtime is also an important consideration for manufacturers looking to automate their processes. Unplanned outages are costly and can halt production for days, weeks or even months. Undetected faults may cause irreversible damage to the machine and may even injure workers.

Minimize downtime

  "While it's unrealistic to expect a factory to run 24/7, we can minimize downtime due to glitches or errors, which is where predictive maintenance comes in."Baird says, "CNC technology is driving the evolution of predictive maintenance," Predictive maintenance allows us to detect potential problems before they arise and act on them before they become serious. We achieve predictive maintenance by using the automation technology that controls the machine as the guardian."
   Does this mean CNC is destined to be the only tool in the factory of the future? Baird doesn't think so. "PLC still has a vital role to play. The best example is the production line. CNC can control robot arms, tooling, milling and grinding, while PLC can control the transmission of the belt, the product or material from one process of the production line to the next process. Due to the complexity of CNC, it is not able to complete these tasks well, and it is a bit overqualified. As part of a factory floor where simple and complex tasks are done at the same time, CNC and PLC work perfectly together."
    CNC and PLC both have a place in manufacturing toolkits, how will they develop in the future? "Industrial control systems (ICS) will continue to evolve and will take the form of specialisation suitable for specific industries." Baird said. Third parties will also use the concept of open interfaces to connect factories to the Internet of Things. With that comes large-scale intelligent machines, data collection and analysis that will help achieve even greater process improvement.
    While it's unclear what role CNC and PLC will play in the factory of the future, they will all be part of it, even if they don't always work together.