CNC Programming Tips the Professional Way

When a program is completed and sent to the Computer Numerical Control Machine, the programming process is over. All calculations were made and the algorithm fully written. But the question is the programmer’s job really finished? When is the programmer’s responsibility really over? And how can we evaluate the type of program that the Computer Numerical Control Machine programmer did?

The fairest and reasonable answer to those questions would basically when a part has been machined under the most optimized working conditions. Therefore the Programmer’s responsibility does not end after he or she finishes the program. We could say that the program at this stage is still very much in the development process, because most of the programming considerations were based on certain assumptions and there are a lot of external factors that may affect the outcome of the product.

Every Computer Numerical Control programmer should have an effort to be in the touch with the actual production. In the field of software development, Constant communication with your colleagues as well as actual machine operators of the CNC will help you to improve your own program. Because most of the time the CNC machine operators are a good source of constructive ideas, improvements and suggestions.

A good CNC programmer should talk, ask questions to them and most importantly listen to what they have to say. Programmers who never put their foot in the actual machining process and think they are always right are all on the wrong track. Exchanging ideas with CNC machine operators, asking questions and seeking answers is the only way to be fully aware of what is going on in the machine.

Whenever you start a Computer Numerical Control Program the first time it is important to check its Program Integrity. A new and unproved program is a potential source of problems. During Manual Programming in CNC, mistakes are more common than when the program is made in a CAM program.

A good way to look at a new program is through the machine operator’s perspective. Experienced Machine Operators take a direct approach when running a program for the first time. That means that they wont take any chances of mistakes with the actual running of a program therefore a good programmer must take note of any comments that the Machine operator will say about the program.

What does an experienced Machine Operator look for in a new part of a program? Most of the Machine operators would say that the first and most important thing to be checked on a Computer Numerical Control Program is its consistency. Therefore a machine operator looks at how a CNC programmer does its own programming, is the way you create your own algorithms the same as the other ones. Machine Operators take note with this kind of Information.

Upgrading your CNC Program

Whenever you upgrade your own program, it means that you are strengthening or enriching it, therefore making it better than it was before. Upgrading would be based on this standard, It is to decrease the production cost without compromising the quality of the part being manufactured or the safety of the Computer Numerical Control Machine Operator.

One of the Most Common forms of Program Optimization is doing some minor changes to the spindle as well as the feed rates of the machines. This process is called cycle time optimization, slightly increasing the spindle speed and feed rates of these machines will decrease the time it takes to finish the part.

And when we compare it to mass production, saving one second for each part in a batch of 3600 pieces would mean an hour saved. Efficiency in the rate of production is a very important aspect in Mass Production.

3 Basic Motion Types in a CNC Machine

A Computer Numerical Controlled (CNC) machine may have more than one motion type that it uses, but there are three most common motion types that are easy to remember. These are the Rapid Motion, the Straight Line Motion, and the Circular Motion.

All of these motion types may seem different but they share two things in common, which would be that they are all modal and the endpoint of each motion is specified in motion command. By being modal it means that the motion type would be in effect until changed otherwise.

3 common motion types:

1.) Rapid Motion Type

Rapid motion type is also called Positioning. The way this motion type is used is through utilizing the fastest rate possible of the command motion of the machine. Example uses of rapid motion are moving to clear obstructions, placing cutting tools to and from the desired position, and any program that provides non-cutting in their schemes.

The command that is usually programmed to a CNC machine is G00 because in this command, the end point for the rapid motion would be specified.

The CNC machine, with most controls given, will be able to move as fast as possible in all commanded axes. In the case of rapid motion, one axis may be able to reach its end point before other axes. Straight line movement will not occur with type of rapid command function and the programmer of the machine must take into account that there are no obstructions to avoid. Straight line motion will happen even during rapid motion commands when done with other controls.

2.) Straight Line Motion

This type of motion would allow the programmer of the machine to command perfectly straight line movements within the machine. Unlike the rapid motion type, the straight line motion would allow the programmer to vary the rate of the motion or feed rate to be used during the movement. Examples of using straight line motion would be turning a straight diameter, taper, when milling straight surfaces, and when drilling for this is because these examples require straight cutting movement.

The common word to specify a straight line motion into a machine would be G01, for within this command the programmer will include the preferred end point within each of the axes.

3.) Circular Motion

This motion type would cause the machine to move in the direction of a circular path and is used to generate the radii in machining. When talking about points on circular motion feed rate, it is equal to that of straight line motion.

Other than that of straight line motion and rapid motion, there are two G codes that are commonly used when programming a circular motion into a machine. These are G02 and G03. G02 is used when the programmer desires a clockwise motion into the machine while G03 is used to make an anti-clockwise motion. To know which of the commands to use, the programmer must view the movement with the same perspective as to what the motion of the machine will be, may it be clockwise or anti-clockwise.

Another requirement that would be programmed into a machine that would be using circular motion is that the programmer must specify the radius of the arc that is to be generated. With brand new technological advances in CNC, an “R” word is now used to specify the radius.

For older controls in CNC machinery, an “I”, “J”, and “K” are used to specify location of the center point of the arc.

Understanding CNC

Have you ever asked yourself how machines in a factory know exactly when to stop making the parts they’re supposed to make? Well, this is all because of Computer Numerical Control (CNC). But to understand CNC, you have to know what Numerical Control (NC) is.

HISTORY

NC machines were first introduced after the 2nd world war as mass production became the trend. These machines were given a set of instructions in punched cards. However, these machines were hard-wired and their parameters were difficult to change.

These NC machines still required a great deal of human intervention. To illustrate this point, try to take a look at a drill press. A lot of actions have to be taken in order to manufacture a product. The process is actually so complicated that a person has to do something almost every step of the production process. This created an avenue for errors to take place as the likelihood of fatigue increased with the quantity growth.

CNC then came into the picture when computers were introduced. Punched cards were replaced by floppy disks, cables, and other software transfer media. This made it easier to manage and edit data.

Production and manufacturing were revolutionized by the increased automation of CNC machines. These machines allowed a degree of added control over the quality and consistency of the components that were manufactured without any additional strain on the operators. This reduced the frequency of errors and allowed the operators time to perform additional tasks. Furthermore, this automation allowed a greater degree of flexibility in the way components are held in the manufacturing process.

With the advent of Computer Aided Manufacturing (CAM), even programming CNC machines is a snap. These programs actually take the bulk of the programming process to make the operation less tedious. However, to be an effective programmer of CNC machines, you have to know what the machine you’re working on will be doing. That is why machinists are often the best people for the job.

The ease that the machines provide is hinged heavily on the quality of the machine. Low-cost CNC machines oftentimes have many functions that have to be manually activated. High-cost machines, however, are almost fully automated. The operator only has to load or unload workpieces. Once the cycle has been initiated, the operator just has to sit back and watch for any malfunctions. The stress on the operator is so low that some even complain of boredom in the middle of a cycle.

CODING

The programming language that CNC uses is called a G-Code. These codes actually position the parts and do the work. To be able to have a machine work properly, you have to input the correct variables such as axes, reference points, the machine accessories, and whatnot. Every machine has a different set of variables so you have to be careful to take note of the differences.

Aside from the G-Code, logical commands or parametric programming can be used to make the process more time-efficient. This type of programming language shortens lengthy programs with incremental passes. A loop can also be programmed thereby removing the need for coding repetitions.

Because of these features, parametric programming is more efficient than CAM. It allows users to directly and efficiently make performance adjustments. It also allows extensions to the functionality of the machine it is running on.

And that makes CNC.