CNC Overview:  CNC Definition and CNC Process

CNC is the modern acronym for Computer Numerical Control, which advanced the manufacturing process capabilities of automated machining from the earlier (late 1970’s) Numerical Control (NC) automated tool controls which were generally proprietary electronic control assemblies employing a mixture of analog and digital electronics where the programmed instructions were entered into the controls with punched paper tape.  Upgrades of these controls employed electronic assemblies which were known as DNC, (Direct Numeric Control) interfaces where the instructions were downloaded to the control from Personal Computers (PC’s) in blocks as the controls became ready for the next instructions.  With the advances in computer technology, and low cost computer memory, completely digital based controls began to dominate, and the term CNC (Computer Numeric Control) became more popular.  Today’s high speed automated control of machine tools increasingly employs PC based Control Software, where only the final stages of the motor controls are electronic hardware based. 

The CNC process consists of CNC machine motion control through programmed instructions (G-code and M-code), which results in precise automated positional and speed control.  The G-codes mainly control the cutting axis, and the M-codes control functions that might be referred to as manual, or auxiliary functions.  The lines between these areas of control are also increasingly blurred.  Earlier controls utilized separate electronic PLC (Programmable Logic Controllers) to control these auxiliary functions, whereas today, increasingly, the CNC control controls all of the machine functions. 

The CNC Controls have utilized a variety of methods of controlling motors which move the machine tools.  A very popular output from controls made in the last thirty years was the +-10 volt analog signal which was sent from the CNC control to the motor drive system.  The motor drive systems employed circuitry which controlled the velocity of the motor through feedback signals from the motor.  Today a variety of different digital interfaces between the CNC control and Motor Drives are being developed and marketed. 

Servo controls constantly correct position and speed errors in multi-axis coordinated motion control processes utilizing closed loop circuits.  As can be observed in the migration away from analog electronically based CNC controls, the motor drive systems are now being built using very high speed embedded computers.  These Servo systems control the motors through position or position and velocity feedback to the control or drive system.  Thus, through the above brief review of the development of the modern CNC, one can see that Digital Control is rapidly dominating every function in what was once a rather closed industry that was based on electronic hardware.  The older controls are rapidly being replaced by lower cost, faster, and more feature rich PC based CNC controls and are easily installed on the still usable “Iron” of the old machines.

In summary, by utilizing Digital based CNC controls, the modern manufacturing process increases the machinists’ efficiency, repeatability, precision and the machine tool’s effectiveness in part manufacturing.   Moreover, not only does CNC reduce the errors in manufacturing parts, CNC allows for the automation of parts 24/7 demanding little human supervision.  The number of CNC applications is steadily increasing, and with the shift from expensive electronic hardware to affordable software controls, even Home Shop machining is increasingly becoming automated.  Even in the small shop machining industry, CNC is making precision machining and manufacturing available to a wider base of creative people.  Furthermore, people with little machining training or experience can now produce complex designs, utilizing “canned cycles” which are increasingly being provided with the PC based controls.

Recap of the History of CNC.

CNC Controls operating CNC machines started to become more apparent in the 1960’s from the introduction of NC by John Parson’s in the 1940’s.  However, GE did not come out with their first CNC model until August 1974 because their NC workhorse, the NC 550 served them well throughout the 1960’s.

As mentioned above, one of the major CNC breakthroughs was to allow the automation of machines through development of CNC software and CNC hardware that did not depend on the hard wiring of the predecessor NC machines.  This included the ability for the machine instructions for motion to be stored in a memory device in lieu of a punch hole card or tape that was passed through a teletype machine to be interpreted by the machine via G-code.  Prior to the employment of the modern Computer based CNC controls, all of the G-coding was done by a programmer in an office somewhere who produced the programmed media and then delivered it to the machine shop where the actual machining was performed by the machinist.  Every change in the program involved re-punching the card or tapes.  In today’s controls, the machinist can make changes to the code on the spot and store these changes, saving time.

CNC controls of the 1990’s mainly consisted of G and M code interpreters with a few added functions.  Today’s CNC controls typically offer, in addition to the G Code Interpreter, a rich set of pre-programmed functions and often include conversational programming to allow the operator to program many complex parts and store his programs while standing next to the machine itself.  This functionality and the development of CAD/CAM programs have multiplied the productivity of the modern machine shop.  The advances in automated manufacturing in the last century have paralleled the advances in productivity seen in the office:  Typewriter to word processor, hand crank operated adding machine to modern computer.

CNC Components [CNC Control(s): 

The modern PC based CNC Control often employs the following components:  CNC PC Computer & CNC Software, typically interfaced with a CNC breakout board and CNC connectors, with the CNC Control typically contained in a CNC console or CNC enclosure.  Also, CNC Drives, CNC Motors, CNC Cables that attach to the limit switches, CNC tool changers, CNC power supplies, and CNC Spindle Motor.  The drive components are often enclosed in a CNC Electrical Cabinet located behind the machine tool.

The G-code program instructions are interpreted by the CNC, and the CNC interface breakout board conditions, converts or buffers the signals and sends the appropriate signals to the motor drives.  The breakout board also does amplification and provides noise suppression/reduction, and often opto-isolation for the CNC inputs and CNC output signals.  The CNC driver in turn controls the motion of the motor that is operating the CNC machine.  To provide a CNC turn-key system the CNC Control typically depicted as the computer software and hardware in conjunction with the CNC breakout board is usually deemed the CNC control and the addition of the CNC drives and CNC motors for each required axes of motion is referred to as a complete CNC system.

CNC Technologies & Recent Development:

The proliferations of the PC, starting in the late 70’s and early 80’s provided the initial piercing wedge that began to reduce the corporate cornering of the market for computing power and information access.  What once took an entire room to contain a mainframe computer can now be contained on a desktop computer through the advances of both computer hardware and software.  The continual advances in computing speed, miniaturization, and storage paved the way to the eventual closing of the gap between who could benefit from the CNC concepts and processes.  Due to the transformation into the digital world, there has been a tendency to migrate from analog signals which actuated the motors that control the machine to digital signals.  Moreover, the advances in user friendly interfaces and software has enabled most people with little to no experience with machining and manufacturing to be able to now use CNC in their hobby shop/garage.

Mr. Arthur Fenerty founded ArtSoft and introduced his first version of his PC windows based CNC software control, Master5, in 2001.  On the surface, the tendency was for the CNC industry to dismiss this PC based CNC control, considering its capability as being just for hobbyists’ or do-it-yourself (DIY) CNC users.  However, the introduction of the PC based control driving CNC systems is starting to revolutionize the entire CNC industry, with the outcome being to close the gap between what used to be a huge corporate only CNC playground with high end and expensive systems [geared toward propriety systems that were specifically designed to just work with certain motors and drives utilizing PLC’s and elaborate tool changers].  These high end and expensive CNC systems required very skilled and knowledgeable people who had a tremendous amount of experience down to the G-code level in order to operate.  In comparison with today’s PC Based CNC systems with Mach3, the larger more expensive systems are often considered rather cumbersome and limited due to their inflexibility when compared to what the PC Based systems offer the inexperienced CNC user.

With the introduction and advances in computer ports and interfaces, the PC Based CNC system, particularly with the USB port and plug and play capability, has allowed for the design of manufacturing blueprints and the sharing of computer files with tremendous ease without even re-starting the computer.  Even though the original USB concept was developed in the mid 90’s, and, Apple was the first to lead the way in implementation, the Micro-USB connector just came out in 2007.

Moreover the advances in circuit design and hardware component parts within the printed circuit board (PCB) design level has provided a more reliable and streamlined capability to develop interfaces between the CNC Control and the CNC drivers.

Digital PC based CNC Controls generally interface to two different basic drive systems controlling two different types of motors.  These consist of the Stepper CNC Drives and motors and the Servo CNC Drives.  The motor drives often connect to the PC based  CNC control through either a break out board or a motherboard, which connects to the PC parallel port, serial port or USB port.  Ethernet and other interfaces are generally in the development stages at this time.

Stepper CNC Controllers:  Stepper motors are brushless motors that work by toggling/energizing electromagnets in phases to produce a circular motion in a sequence of steps.  This approach tends to increase the vibrations generated by the motor; however, the methodology also allows operation in open loop commutation.  The open loop advantages results in considerably less cost due to the simplicity; yet, the technology is also rugged.  At high speeds (RPM), torque can drop considerably and in the case of induced error due to no error feedback control, efforts have been made to combine an encoder or resolver to reduce the probability that error grows in the open loop motors.  Bridgeport sold thousands of Stepper Based CNC Milling Machines during the 1980’s and many of these are still in use today.  For the hobbyist, CNC stepper controllers and CNC stepper motors provide a very reasonable and viable monetary solution to control motion in multiple axes.  Stepper motors used in CNC systems usually have two hundred steps per rotation, but through microstepping, the resolution can be multiplied to as much as eight times that resolution.

Servomechanism CNC Motors: Servo motors are either DC brush type or Brushless (BLDC) motors.  Some Brushless servo drive systems are called AC Drives, although there is very little technical difference between AC Servo Drives and DC Servo Drives. All Servo motors provide feedback to for a closed loop servo system.    This technology is more expensive than the stepper motor approach; although it provides for a more precise, and higher torque system at higher velocities.  Servo loops are typically favored in the higher end more CNC industrial based applications.

CNC Trends: 

The dramatic reduction in price of PC hardware and software commensurate with PC capabilities due to the expansion of PC use, has enabled developers to produce a user friendly software control, such as Mach 3.  In combination with advances in surface mount hardware technology, computer ports (USB), and alternatives to expensive motors and drives, current CNC trends are departing from high end expensive propriety approaches toward the more reasonable and user-friendly PC based CNC systems that can be universally applied, while providing the end user with a capability that does not require a thorough understanding of the intricacies of what is occurring at the CNC hardware component level.  Although, individuals may be able to acquire the CNC Mach3 software, PC, and match the other servo system components, including the stepper drives, CNC stepper motors,  and CNC breakout board interfaces there are still many choices and decisions the system integrator must make, and the task is daunting for many.  There are companies and individuals that would like to be able to take advantage of the features that modern PC based CNC control offers, and this need prompted David Eldredge, the founder and owner of the Machmotion, to do the integration for users and offer turn key integrated PC based CNC systems in handsome enclosures at very competitive prices.

MachMotion, with over two decades of experience with machines, manufacturing, machine tools and motion control, is at the tip of the spear and leading the pack with their specialization in turn key CNC systems that are PC based and capable of cross platform/manufacture usage.  MachMotion’s complete easy to use and easy to install turn key integrated universal breakout board package, as part of the combined CNC control contained in either a CNC console or CNC enclosure with retractable keyboard, plug n’play USB ports, CNC power bus, and touch screen capabilities, have captured the attention of both the hobbyist and the industrial CNC industry.  Mach Motion’s CNC industrial panels, CNC computers, and CNC enclosures have protective ports that increase the reliability and durability of the computer hardware within the harsh manufacturing environments and allow large corporations and manufacturers to have a robust; yet user friendly solution across the spectrum of CNC applications. In addition, MachMotion has a switch panel, handwheel, E-stop, Cycle Start/Stop, Feed-rate Override features.

Thus, MachMotion is both closing the gap and bridging the CNC gap between the hobbyist and CNC industrial user, since their universal, non-propriety, high quality, but inexpensive, alternatives have enabled the CNC user across the CNC industry to be empowered and provide the means for anyone to obtain and operate their own CNC system at home or in the factory.  For many machinists who’s older Fanuc, Allen Bradley, GE, Siemens, or Cincinnati control has failed in the middle of a production run, the purchase and installation of a Machmotion control is the fastest way to get their machine back up and running again. 

Due to MachMotion’s CNC universality, Mach Motion can implement turn key CNC solutions with drives and motors from the following manufacturers (not an inclusive list), Danaher, Gecko, and Servo Dynamics, is currently working with Mitsubishi to provide a greater range of powerful drives to meet the needs of many CNC applications.  In addition, MachMotion has the capability to provide CNC upgrades, CNC kits, and CNC retrofits tailored to the needs of the particular customer to include CNC applications with CNC mills, CNC lathes, CNC Routers, CNC Plasma cutters, CNC lasers, CNC grinders, CNC engravers and CNC gear cutters.  MachMotion has machine retrofits for machines manufactured by many CNC Machine Manufacturers including: Allen-Bradley, Anilam, Bridgeport, and Sherline, just to mention a few, have been retrofitted with MachMotion’s CNC systems.

The Mach3 CNC software within MachMotion’s CNC PC based packaged console enclosure includes an integrated opto-isolated universal breakout board (I/O board) that is standard with MachMotion’s CNC turn key system in order to suit most CNC application needs without being restricted to any particular CNC OEM’s service or propriety parts.

For more information visit MachMotion’s products link:
CNC Controls