How Hard Is It to Learn CNC Machining or Programming?

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In the modern manufacturing field, the use of Computer Numeric Control (CNC) is considered the norm rather than the exception. CNC processes are faster, safer, and have better repeatability compared to their manual counterparts. They are also a lot more practical for high-volume production. For these reasons and many others, skills in CNC machining and programming are highly valued in many industries.

If this is a field you’re interested in getting into, then you might ask – how hard can it be? As with any topic worth discussing, there is no straightforward answer to that question.

Why learn CNC machining?

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No matter the level of CNC machining you wish to learn, it’s going to take a serious amount of effort and time. While there is no doubt that CNC machining is a valuable skill to have, ask yourself first – is it the skillset for you?

For most modern manufacturing processes, CNC machining has largely overtaken manual machining methods. Through CNC, cutting and machining tools can be programmed to execute commands automatically based on a prescribed algorithm. This allows for repeat operations to be executed at a high level of precision, ensuring that each piece is finished according to standards of quality and accuracy.

The reduction of dependence on manual labor has made CNC machining more appropriate for processes that require continuous output. CNC machines suffer no fatigue and can sustain an acceptable level of quality and efficiency even when they have to run 24 hours a day and 7 days a week. They are also less prone to product inconsistencies based on an operator’s level of skill. By reducing the exposure of workers to sharp moving parts, the use of CNC machines has also resulted in a drastic drop in work-related accidents and injuries.

For most industrial machines, a CNC system is merely an upgrade to previously existing mechanical parts. This makes CNC technology incredibly versatile. CNC technology can be integrated into just about any machinery in the shop floor – from old-fashioned ones like mills and lathers to more novel technologies like plasma cutters.

All this discussion of the advantages of CNC machines belabors our point – that learning how to use or program CNC machines is an incredibly valuable skill that can be used across several industries and manufacturing settings. No matter what level your CNC machining skills become, there is no doubt that this versatile skillset is one you can leverage to advance a professional career.

G-Code: the language of CNC machining

Before going to the specifics of the essential skills in CNC machining, we need to make a detour and look at the programming code that controls CNC machines. Known as G-code, this programming language consists of several simple commands that direct the movement and operations of the various parts of a CNC machine assembly. Compared to other programming languages, G-code is very simple. A G-code algorithm contains only commands that the machine follows in sequence – it has no variables, no logic relationships, and possibly no feedback loops.

However, most manufacturing floors and shops don’t have an army of programmers running CNC machines. This is possible because a G-code algorithm does not need to be created from scratch. Rather, the starting point of most CNC machining processes is a 3D model designed in a Computer-Aided Design (CAD) software platform. The proverbial industry-standard, CAD is widely used not just in manufacturing but also in engineering, architecture, product design, and construction.

There is one crucial step that lies between a 3D CAD design and the G-code for a CNC machine. This step is performed by the appropriate Computer-Aided Manufacturing (CAM) software. The bridge between CAD and CNC machines, the purpose of the CAM software is to convert a 3D design into the corresponding G-code algorithm.

CAM software is typically specialized in the specific CNC equipment, as it needs to take into account parameters such as the type of tool to be used and the size of the build platform. The automatically generated G-code is typically good enough to recreate any 3D model, although tweaks to the algorithm can also be made for optimization.

What skills do you need for CNC machining?

With what we know now about how CNC machines work, there are seemingly two disciplines that one must learn to be truly knowledgeable about CNC machining – the mechanical function of the CNC machine, and how they can be programmed using G-code. Although related, we consider these two as distinctly unique bodies of knowledge.

Shop knowledge

As industries move towards automation, knowledge of the mechanical parts of a CNC machine seems to have become less common. According to a survey of 200 CNC machine users, most of the responders said that the hardest part of learning CNC was determining which tool had to be used, the proper tool and feeding speeds, and the width and depth needed for the cuts. Although some of these parameters can be set via G-code, setting the right values to get the desired output can take a bit of trial and error.

Responders also cited difficulties with learning which tool lengths and tool tables to use, as well as how to home or calibrate their machines prior to starting operations. A major struggle for most users was the process of work-holding or fixturing. This is the practice of holding the workpiece in place to prevent it from moving around while it is being cut by the tool. This involves careful selection of the vises to use, how many of them you should use, and how they should be positioned.

Interestingly, all these factors are deemed by more responders to be more difficult than using CAM software to create G-code. There are still certain complications related to the use of CAM software (which we’ll get to later), but most people consider these to be less important than difficulties of the mechanical kind

CNC programming

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The development and evolution of CAM software have been instrumental in the growth of CNC technology. CAM allows for standard 3D models to be reproduced and distributed across different CNC machines, with each one able to come up with the G-code algorithm appropriate for the tools available. However, this description several understates the complexity of using CAM software – it takes more than a single button press to create G-code out of a 3D model.

In most cases, using CAM software will require the operator to have ample knowledge of the CNC machine to be used. The software will typically ask a series of questions involving the processes and tools to be used, the size of the workpiece, and how it is fixed to the build platform. This process is complex enough that jumping from one CAM software to another can be a frustrating experience with its own steep learning curve.

There’s also the matter of the G-code itself. Relying on the CAM software solely to create the G-code is fine, but what if you’re not satisfied with the results? You can either try wrangling around with the CAM software but getting it right in this manner can involve a lot of wasteful trial and error. A more reliable way is to understand G-code commands, dive right into the program, and make those small changes yourself.

The ability to do manual G-code programming is a highly valued skill in any industry. It isn’t even all that hard – as we’ve said, G-code is magnitudes simpler than any standard programming language.

If there are minor errors or adjustments to be made, it is simpler and faster for an operator to make changes to the G-code rather than run the CAM software with different parameters. However, this is impossible to do without an intimate knowledge of how the CNC machine works – the cutting tools, the machining operations, and how workpieces are set up are all skills that a CNC operator will need to know.

The need to make small changes to a G-code algorithm does not diminish the value of the CAM software. As stated, the default G-code created by the CAM can be used with no revisions and often can yield acceptable results. It’s also rare and very impractical for a CNC programmer to build an entire program from scratch. Even for a skilled CNC programmer, the G-code generated by the CAM software provides a good starting point to which refinements can be made.

How much time will it take to be an expert in CNC machining?

One of the major strengths of CNC machining is that it represents a big step up in terms of being user-friendly and easy to learn. This affirmation still holds, especially compared to old-fashioned manufacturing methods. A reasonably skilled worker with basic skills in machining, math, and logic can pick up enough skills to use a CNC machine and even make minor G-code changes in as little as ten days. However, there are also tiers of expertise in CNC machining. It can take several years to become a true expert.

The complexity of a CNC machine also needs to be considered in assessing how difficult it would be to master. The number of dimensions that the tool moves in is a major determining factor. For instance, a CNC lathe is considered a machine that uses only 2.5 dimensions – the cutting tool only rotates and moves in both the lateral and transverse directions.

The next step in complexity has the tool moving across 3 dimensions. The basic CNC mill is a class example of a 3-dimensional CNC process. The most complex type of CNC machine is known as a “five-axis” machine as it combines movement in 3 dimensions with 2 additional rotational aspects. Five-axis machines are incredibly complex to operate and often involve G-code programs that can have more than a million lines of code. Programming for five-axis CNC machines is virtually impossible without a CAM.

Is machine shop and/or programming experience required for CNC machining?

CNC programming may not be as high-profile a career as a web developer or a programmer for mobile apps, but it’s certainly a career that’s highly valued and pays well. Anyone can tell that getting into CNC programming will take a good deal of experience. The only question is – what type of experience is more useful?

A traditional programmer will probably find no difficulty in learning G-code. All you really need to learn are the standard G-code commands, their relevant parameters, and how they translate into real-world movement of the tools and machines. It typically requires no loops, has no complex logical functions, and does not even have a provision for declaring variables.

However, a programmer with limited machine shop experience may have a limited perspective of what CNC machines can do. As we have stressed, the mechanical part of CNC machining is often the more difficult half of it. The knowledge of which tools to use and how to set up the workpiece is something that takes time and experience to develop. More often, a CNC machine operator will have to go through several errors before they can learn how to do things correctly.

This shows the value of machine shop experience in developing the skills necessary for CNC machining. An experienced machinist will be able to explore more ways to use a CNC machine and maximize its capabilities, even if they only have basic G-code programming skills. This does not discount the complexity of G-code programming – it is also a skill that can take several years to master.

Final thoughts

CNC machining is a technology that’s here to stay and will only continue to become a more pervasive part of modern manufacturing practice. Given this fact, it’s easy to see how a career as an expert CNC machinist or programmer could be both sustainable and lucrative. If you’re looking to develop a skill that can lead to a high-paying job, then CNC machining is something worth exploring.

As we have demonstrated, there are two aspects of becoming an expert in CNC machining – knowing how the machines work and knowing how the G-code program works. Of the two, machine shop experience is undoubtedly more important. In any case, being an expert in CNC machines will takes years of working with them, diving deep into the code, and probably making hundreds of mistakes along the way.