Learn CNC Basics

important CNC feature can be applied in at least two ways. For example, program zero can be assigned in the program or through some form of offset. Tool length compensation offsets can be specified as the tool's length or the distance from the tool tip to program zero in Z. Cutter radius compensation offsets can be specified as the cutter radius or the deviation from the planned cutter size. And many CNC words can be specified with or without a decimal point.

Additionally, there are those CNC features that have been developed for a niche market. Conversational CNC controls that are programmed on the shop floor make it easy to develop programs when programming must be done during setup. Tool length measuring probes are designed to measure tool lengths during setup for those applications when tool lengths cannot be measured off-line. Apparatus such as bar feeders, automatic loading systems, in-process and post-process gaging systems, and tool breakage detection systems all facilitate unattended operation.

The choices related to each CNC feature make for a great deal of flexibility. The same CNC machine tool and/or control can be applied to a variety of applications. However, with flexibility comes the potential for confusion, controversy, and misapplication. During my CNC courses, students often get into heated discussions regarding the pros and cons of even the most common CNC features. What makes perfect sense to one person seems wasteful or unfeasible to another.

The most basic reason for the controversies that surround certain CNC features has to do with company type. Knowing the subtle differences among company types will help you understand why there are so many ways of handling certain CNC features and will give you an appreciation for another company's differing ways of handling applications.

Product producing companies get their revenue from the sale of a product. In almost all cases, the actual cost of operating CNC machines is one step removed from how the company makes money. In fact, it may be difficult for manufacturing people in some product producing companies to determine each CNC machine's shop rate (the hourly cost for machine usage). Product producing companies commonly have the luxury of adequately tooling up for the component workpieces they run. Most perceive machine up-time (productivity time) as the highest priority. For this reason, they commonly staff their CNC environments with enough people to ensure that their CNC machines run workpieces for as great a percentage of time as possible. Product producing companies tend to have the most complicated CNC environments since they often employ a wide range of CNC machine types for a variety of processes. Many also have CNC machine tools in their toolrooms and research and development departments.

Companies that produce production workpieces for other companies, commonly called contract shops or job shops, generally get their revenue from product producing companies. Manufacturing costs are directly tied to the workpieces being machined, and job quotes are based on the shop rate for the specific CNC machine tools to be used. While up-time is still important, most job shops have a slightly different set of priorities. Since most are quite small (under 50 people), they tend to expect their CNC people to perform many tasks required to get and keep their CNC machines running. It is not uncommon for the person operating a CNC machine to program, set up, verify the program and run every workpiece in the lot. Since they tend to specialize in specific machining operations, job shops often have simpler CNC environments made up of but a few different machine types.

Tooling producing companies specialize in the manufacturing of tooling needed for all forms of production machinery. Die shops, mold shops and companies that produce cutting tools and fixturing are among the tooling producing companies. Like job shops, since tooling producing companies tend to specialize in a certain kind of tooling, they commonly have simple CNC environments made up of only a few different machine types. Also like job shops, they tend to expect their people to perform many CNC related tasks. Many do not place near the emphasis on machine up-time as job shops and product producing companies. It is not uncommon to see expensive CNC machines sitting idle for days if they are not currently required.

Prototype producing companies relieve product producing companies of the need to permanently staff a research and development department to make the prototype component workpieces and assemblies needed to test a new product design. For this reason, more and more companies are specializing in the production of prototypes.

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Learn About CNC

Little Did I know…

There was a steep learning curve with CNC. Building a frame for the machine is only a small part of the project. Today it is much easier. The software, components and suppliers are better. There is an entire cottage industry that has sprung up around CNC to support it. Some of the best people in the world make their livings servicing CNC Hobbyist needs.
For some reason I figured if I just build this machine it would spit out parts whenever I wanted it to. Simple, Simple, Simple ran through my head. Over time, I started to get it. I didn't have a teacher, but I started to learn the ins and out of what I was doing.
Other things I had to learn along the way:
CAD Software
Designing Parts
CAM Software
Preparing parts for machining
Simulating Machining
Machining Basics
Cleaning parts
So, where am I at today?
Today I have multiple CNC machines that I work with. Each have their own nuances, software, capabilities and functions. The point of it is that they are all CNC. They all follow the same basic process. That process is pure gold if you know it. You can move from machine to machine and know what is going on. That is what I want to teach you.

Computer Aided Design by Solidworks

Solidworks is the main 3D CAD software used by our lab. It is mainly used in mechanical design and is the most popular CAD software on the market. Three main file types are used in Solidworks; Part files, Assembly files and Drawing files. Part files are a 3D representation of a single component. Assembly files are a 3D arrangement of Parts or other Assemblies. Drawing files are 2D engineering drawings of Parts, Assemblies or custom drawings. Solidworks also comes with some free analysis software, listed below.
1. COSMOSXpress is a limited static FEA solver that can be used on single part files. The full featured version is COSMOS.
2. COSMOSFloXpress is a limited computation flow dynamics (CFD) solver. The full featured version is COSMOSFloWorks.
3. DFMXpress is a design for manufacturing (DFM) program that checks if a part can be machined.
4. DriveWorksXpress is a rules-based design automation tool that allows creation of multiple variations of parts, assemblies and drawings quickly and accurately.
Learning Solidworks is beyond the scope of this guide, please consult the Solidworks help and tutorials if you would like to learn more.


Almost all CNC machine are controlled by a common programming language called G-code. Even though this standard language exists, not all machines can perform every G-code command. The list of G-code commands that our machine is capable of performing is located on the CNCMill wiki page. For simple parts it is not hard to manually write all of the G-code, but for complex parts, the number of lines of G-code can be in the millions. Fortunately, computer aid manufacturing (CAM) software can generate G-code based on a drawing or solid model eliminating the need to write the G-code manually. But, to further your understanding of CNC machining, you should review the G-code commands to get a sense for how the machine operates. Also, in some cases, the G-code generated by the CAM software is not perfect and has to be edited manually. This is particularly true for the canned drill commands.
Only a few commands are needed to make your logo. Please consult the CNC manual for all of the G codes available. An example G-Code program is listed below that cuts a square with an inscribed half circle shown as shown in Figure 1. The top of the part is assumed to be at a Z depth of 0.000in. The program will cut the shape 0.020in deep. Use notepad to write your G-Code and save it as a text file.


Computer Aided Manufacturing (CAM) LazyCAM

Links to video tutorials for this software are located on the CNCMill wiki page. The only file type that can be imported into LazyCAM is a DXF file. Even if a drawing program is able to generate DXF files, it might not import properly into LazyCAM. For example, DXF files made with CorelDraw 12 will not import circular features into LazyCAM. The lines of a DXF file are interpreted as the toolpaths the CNC machine will follow. This means that the diameter of the tool should be know before starting on your DXF toolpath drawing


MeshCAM has the ability to generate true 3D toolpaths from CAD files. It is fairly easy to use, but does not give as much control over the toolpaths as LazyCAM. If this program is used, please do a dry run to insure the toolpaths are what you intended. If program opens up as a demo version, enter the username: Mark Merlo and registration code as: 0201-02C8-0658-0000-8DAE

CNC Foam Cutter

The CNC Foam Cutter consists of an electrically heated wirer that cuts (melts) through Expanded Polystyrene (EPS, XPS), Expanded Polypropylene (EPP), Expanded Polyethylene (EPE), and Semi-rigid polyethylene foam (XPE). The wire is guided by two XZ computer controlled traverses at each end of the wire. Any 3D object that can be defined by straight lines can be cut out. This includes rectangular, tapered and swept wings.

How To Work With CNC Equiment

A CNC machine is used in woodworking shops and some other industrial settings. They are very expensive, so most individuals do not buy them, although used ones can be obtained more cheaply. They are important for speed and accuracy in large, repetitive tasks.

There are many uses in industry for CNC machines. Routers drill holes, for example. Many CNC machines can perform a number of tasks at once, improving efficiency in the manufacturing process.

The technology behind these machines is Computer Numerated Control. This technology was developed in the seventies and it allows for a machine to be programmed in advance so the operations are set up to work almost automatically. The initial setup is a little complicated, but once that is done the machine is easy to operate.

A CNC router would be programmed to drill a hole repeatedly at certain intervals. This is much more efficient than manual calculation and drilling and eliminates inconsistency due to human error or fatigue.

A CNC lathe would be used to cut pieces of wood of uniform size and shape. Lathes can have horsepower ranging from 15 to 40 HP, and how much power is needed depends upon the job being done. A good CNC lathe will allow you to work at various levels of automation, so that you can work all manual, or all automated, or any combination in between.

The best mill available is the Bridgeport mill. Mills are designed to be used in both large industries and small milling shops, and the Bridgeport mill is built to last in any situation. The price is prohibitive, however, for individual use.

A CNC mill is considered specialty equipment. The concept is to use computer programming and robotic operation for speed and accuracy. This kind of speed and accuracy would be impossible to achieve for an individual. The airline industry frequently uses the CNC technology of Bridgetown mills; specifications are entered, and the mill automatically determines which functions to perform and how.

Engravers can also be CNC machines. Engraving can be done on many materials, including wood or wood composite, metal, stone or glass. These machines can do very exact engraving on materials from the smallest to the largest, and have the same result over and over.

Since CNC machines are so expensive most individuals cannot afford them, there may be individuals who do a lot of repetitive machine work and would like to obtain one. An option in this case is a used CNC machine, which can be as low as half the price of a new one. It is important to make sure the used machine is in good condition, so you may be better off looking for a rebuilt machine. This is one that has had the major components replaced so it is almost a new machine. Frequently, rebuilt machines have a warranty of at least one year, so that you can be assured that it will be working, or you can get it repaired if it does not.