CNC is an acronym for (Computer Numerical Control), topics covered here include, Programming, Mechanics, and Design; with a CNC if you can think of a task, you can automate it, many things are controlled numerically today.
Before CNC it was NC (1940s and 1950s) which stands for numerical control, different from today mainly because of the invention and evolution of IC's (Integrated Circuits).
The Arduino is one very
good example of a Micro-Controller with some very interesting IC's, it has an Atmel chip that functions as a processor and it can store
code, the Arduino board also has an FTDI integrated circuit for USB connection.
MODERN CNC APPLICATIONS
- Rapid Prototyping.
- Repetitive Manufacturing.
- Industrial Automation.
CNC'd devices of today include Drones, Autonomous Robots, SLS and Filament 3D-printers, and a large number of different Cutting machines, Pick and place machines for building circuits, even Vending machines are CNC'd.
Computers today are getting smaller and smaller, but still faster and faster; for example a micro-controller called Arduino can run a 3D-Printer, and the same Integrated Circuit that powers the Arduino also powers a micro sized Computer called the Raspberry PI; Intel even has something small, Intel competing with ARM now has a mini Computer called the Galilao, a 512MHz dual core Credit card sized computer, and yes others can be found.
Stunning advancements are taking place every day because of SMD (Surface Mount Design) Electronic Components, these Components make the computers and controllers much smaller; the ideas generated by driven people with problems, along with new technology like the 3D-Printer make new advancements available to more and more people everyday.
Comprehension of a CNC.
To help understand what a CNC machine is, let's take a look at a Scroll Saw! As you probably know, a Scroll Saw is a Bench Top, manual Machine used to cut detailed parts out of a chosen material, this material is usually Wood but sometimes Plastic, Aluminium, or in very rare cases Mild-Steel, accuracy is sometimes very difficult to achieve with this tool .
To use the Scroll-Saw an Operator has to move the part over a bed and follow a line with precision, one slip and that's it for that part (in most cases), or a blade can break; the more detailed the part, the more risk a slip may happen and all the time spent will be lost by damaging the part, the Scroll-Saw also cuts in 2-D, so profiling is another added factor.
Imagine a Scroll-Saw but instead of a blade oscillating up and down, we have a rotary cutting tool like a Drill-bit, the bed has some clamps to hold the part for you but it moves right to left, forward and backward, the bit can move up and down into the work, this machine would now be called a Milling-Machine.
A Milling-Machine/ Engraver/ Tangential Cutter/ Router/ Plotter, are all devices that move on three or more planes or motion, the Machine above, our modified Scroll-Saw, would have three planes of motion; this machine can cut/ move into the work over a number passes, it can move off the bed incrementally, and can move the bed on two Axis incrementally to create a profile.
With a CNC'd machine and Automation, any part can be cut and profiled accurately
by giving the proper command to some motors that are attached to a machine; an
ATC (Automatic Tool Change) will select the proper Cutting Tool/Bit, PWM (Pulse
Width Modulation) changes the spindle (Shank) speed, Motor Drivers control motor
position and speed, and the Computer runs some algorithms to take care of
feed-rates so no tool gets injured on the job.
DIFFERENT TYPES OF CNC MACHINES AND FUNCTIONS
Not all machines are created equal, some interface in different ways, some Cut material, some Print material and create 3D-Objects, some are Robotic-Arms and are used to assemble things, Pick and Place machines assemble PCB/PBA's (Printed-Circuit-Boards/ Printed Board Assemblies) by the thousands, even millions per day.
CNC is used widely today in manufacturing for many different reasons, the
following are some of the important fields where the manufacturing processes has
improved greatly and continues to improve today:
Machines that perform Drilling operations, Boring, Tapping, Reaming, and Counter tapping, are classed in this category, in addition to turning operations other Material Removal applications include Facing, Knurling, Threading, and Pocketing.
Grinding operations such as ID (Internal Diameter) Grinding and OD (Outside Diameter) are also carried out using Material Removal machines, Contour grinding was an operation that couldn't be done until CNC technology came into play.
An example of where a Material Removal Machine might be used can be found in the Sheet Metal industry where thin sheets of metal is used to produce Cabinets or even a Car Body; holes are drilled at specific locations (Removal of Material), the sheets are then bent and folded to fabricate various finished shapes with varying strengths.
The filing cabinet as noted is an example, in order to fabricate one a CNC aided machines cut sheets of thin steel using Water, Laser cutters, or Plasma cutters, then a Drill press is used for the holes, they are drilled very precisely in predetermined places, finally the sheet is bent to a specific shape and assembled using a Robotic Arm.
Electrical Discharge Machines (Plasma), Machines work by removing metal with
electricity, some even call the process "burning the metal" but
that's not the case, these machines come in two forms.
The Wood Working Industry:
The same way CNC
machines are being used in the metal removal industry they are also used in the
wood working industry, Drilling and Routing are the two most common CNC
operations that are being carried out in this industry.
There are wood working machines that are able to carry out any number of other operations by the use of ATC (Automatic Tool Change) devices, and machines with many axis.
There are various types of engraving machines that use CNC technology, Water jet CNC cutting machines that use Water Streams at very high pressure cuts material, some other CNC machines are used for the manufacture of electrical components, for example a Coil winders, Wire stripper, or advanced Pick and Place machines.
Research and development is pricy business, one off items are very expensive for
a wide range of reasons, from material costs being high from not buying in bulk,
to investing in tooling and the manufacture of some not so common if not never
invented parts, this is why people and companies are investing in, even building 3D-Printers.
CNC COMPONENTS INTRODUCTION:
For use or construction of a CNC machine, it's a good idea to understand what all the different components are, and how they work together, similar to owning a Car; the operator should know how to use it's features, for example turn on the Windshield wipers, turn the lights on, place the car/ truck in gear. Having a good understanding of what's happening under the hood is a good idea also, when you know your machine in and out, you'll be more safe, comfortable, just simply able to get the best out of it.
In order to learn about a particular machine the best thing you could do is to refer to its manual, the manual provides information about the internal parts, it lists specifications such as its maximum values in terms of power consumption, speed, cutting limits, if the machine has an ATC (automatic tool changer) the number of cutting tools it is able to hold, and more.
Knowing what makes up a CNC Machine is helpful if you want to build your own, or if you want to modify a manual machine. The conventional 3-axis machine is the most common for the Do It Yourself project, the 3-Axis machine can be used for 3D-Printing, Laser-Cutting, Spindle-Cutting (milling), Tangential-Cutting, Plasma/ Torch-Cutting, Waterjet-Cutting, or Hotwire-Cutting.
People who assemble their own machines at home often have great success, the online community is very large so support is just around the corner, the components required are few, some technical know how is needed (online community) so some reading, troubleshooting, and parts hunting, will be needed to complete this rewarding project.
The best part, after building your own machine, you'll have that extra know how for other complicated projects, and you'll have the machines to help get those complicated projects finished with extreme accuracy, besides all that, it's easier than one might think, everyone has a hidden skill or two.
In case you decide to perform some modifications to an existing conventional machine some things will need to be determined before it can be converted, like Motor size, the proper Driver for that Motor, the proper Power supply/ supplies for the motor(s), even the kind of motor and driver you want to use, Steppers are common but DC, Servo, or AC-Motors can be used with the proper Driver.
Motors vary, so do the drivers and controllers, the Parallel Driver (DB25 interface) is a common driver for Stepper-Driven machines, Serial Drivers (RS232, USB) Arduino, Gecko, are often used for Servo, DC, Universal and AC motors.
PWM circuits containing TRIAC's with a Micro Controller interfaced via Serial-Port are used to control AC-Motors, and Universal motors can be controlled using any PWM circuit with a Micro-Controller (Serial-Port Communication), an Encoder is used with these motors making a Closed-Loop system for high Accuracy.
Slides/ Drive Screws/ Belts:
The Drive Screw for the CNC consists of some threaded bar stock; known as Ready-Rod, this stock can be found down the Hardware Isle at the local hardware store, good for a small desktop hobby machines. ACME rod is used for industrial applications because of the thread pitch, the coarser the pitch the faster the machine can move with little motor movement, the Nut for industrial machines has anti-backlash properties, a simple spring also used in the Open-Source 3D-Printer builds is used in conjunction with the Nut.
Belts are also used on some applications, but not common for cutting machines due to torque loss and belt stretching, belts also make for a fast moving machine, hence why Belts are used on the common Open-Source 3D-printers where little resistance is placed on any axis and speed is required.
Linear Slide Bearings:
Other (V-Groove, ZZ, ULN):
Controllers interface between the motor-drivers and your Computer. It is not impossible to design and construct your own controller board plans can even be found on the web or included with some PCB/ PBA (Printed Circuit Board/ Printed Board Assembly) design software, for example "Eagle".
As noted above, the controller will interface with the PC in different ways, a Serial-Controller will have Firmware installed, a Parallel-Controller will connect directly to the Motor-Drivers, one being much easier than the other to configure.
A Serial connection:
- Firmware is loaded onto Arduino this is known as a Sketch, information is sent from the computer in the form of a packet to the Arduino, Arduino processes Packets of information based on the instructions written in the Sketch, and electrical Pulses are sent to move the Motor.
A Parallel connection:
- The Computer sends electrical pulses directly threw the Parallel-Port to Motor-Drivers that move the Motors.
In addition to the Motors, the Bearings, Controller, and Power-Supply, the CNC machine also may carry some accessories, among them could be probing systems, pallet changers for automatic removal and reloading of material, adaptive control systems (temperature sensing for example), and other automation systems, the list of accessories could be a very long one.
In the case these accessories are included with a Machine you purchased, details can found in the user manual, if they are aftermarket additions other manuals/ datasheets should be available online.
When it comes to running a machine with the help of CNC software three components are required:
CAD (computer aided design), CAD software is used to draft a part or complete assembly using the computer.
CAM (Computer Aided Manufacturing) is software that programs the machine and plans the cut operation, this software converts the CAD drawing into G code,
Machine Software (compiler), this is the software that converts the G-Code into packets or pulses to control the machine.
Software packages or components can be found online, this website offers Machine-Software for sale with Serial or Parallel control, configuration required for use with some machines, some Drivers are already configured just select the appropriate configuration file.
Spindle direction, speed of the tooling, and coolant changes are some of the things some machines can't be programmed to monitor, in this case the operator has to manually monitor and control these features.
When it comes to programmable functions they vary from machine to machine. Also the commands used for changing them also vary from one manufacturer to another, Post-Processors can be written for CAM software so the outputted G-Code will work with your machine, M codes (miscellaneous commands) are included with the Post-Processor.
Salvaging parts from old electronic devices and toys are great ways to start collecting components and get started if you're a Do-It-Yourselfer and you want to build your own machine. Alternately buying the parts isn't a bad idea either, specially if there's a concern a part or two salvaged won't work properly, or at all.
Collecting a part or two from an old device can be easy... Just smash your way in with a hammer and collect the parts you want, or analyse the construction and learn from it while taking it apart.
Old Printers are a good source
for parts, and Motors, depending on the kind of printer Stepper, Servo, or DC,
motors will be found in Printers, the Dot-Matrix machines have Stepper-Motors.
It's important to consider voltage and amperage values.
BENEFITS OFFERED BY CNC TECHNOLOGY TODAY
Save Time! Save labour! Save Material! Produce goods when you're someplace else, make money at home when you're at work. R&D, and concepts, prove your idea in hours not weeks or months, save on material by having less error.
The following are some of the advantages:
CNC machines do the dirtywork,
If a CNC machine is working properly there's no real need for an operator, the machine can load new parts even package finished ones, just keep providing enough raw materials for the machine to keep running, if the needs of the machine are taken care of it could run uninterrupted for days, even weeks, that way the operator can attend to other important things, since the machine is automated and computer controlled the accuracy of produced parts are of a very high level.
Since the machine is driven by software the operator doesn't have to be a skilled craftsman, even if a CNC workshop has several machines, having just one supervisor is enough to manage high production levels, saving on labour.
When you use a CNC machine you have the option of making a wide range of different products without any problems, it's as easy as changing the program, often this program is a simple text file that can be used time and time again to produce the exact same part, time after time.
Since CNC machines could be adjusted to manufacture different products in short times it's not necessary to have a big inventory, but not a big deal if you do either, machine set up is usually pretty simple, jigs help with complex setups, production runs for new product can be started in limited time, often a new part can be planned, programmed, and produced in one day.
machines are developed so well that they never need an operator to work, they
can be controlled over the web, in cases where raw material has run out, the
machine runs out of oil, or in case of a break down, the machine will send an
alert to the operators mobile phone for attendance.
DISADVANTAGES OF CNC MACHINES
CNC machines are generally more expensive than manually operated machines, however costs are offset by production levels and quality, prices are also coming down, do it yourself builds are inexpensive but still result in high quality production.
Software is expensive for the most part, MasterCAM and others can cost into the thousands of dollars, Solidworks for example could cost as much as ten thousand dollars, machine software often comes with proprietary machines but may not, some Machine software can be found free online (EMC), however Windows versions cost money (Mach3).
Because CNC machines need fewer operators (one operator could look after a number of machines) it contributes to unemployment and deflation of goods, however maintenance people still need to be employed to keep these machines working, and replacement parts still need to be built by someone.
The form of education has changed, with CNC's the present day school curriculum may not include training on manually operated machines, this limits new grads to Computer controlled machines, they may not have the same skill as past graduates, the computer does all the manual work for them.
When you weigh advantages against disadvantages of the CNC machine however, it appears to me that the advantages may outweigh the disadvantages, therefore, the CNC machine is not only going to stay but also develop further in the future.
After the 1970s when computers made their appearance, Conventional and Numerical Control systems were modified for Computer Control, instead of running off a special punched Tape, today Machines are controlled from a file generated from a Computer mathematically.
Today, an Operator has to sit near the machine to monitor the progress and interrupt the process in case anything goes wrong, and the Operator loads the raw material, opposed to physically producing the first example, setting up the machine, loading the raw material, and monitoring/ controlling the machine.