Top 11 Myths Of CNC Machining


Manufacturing can be an intimidating space for the uninitiated. With new machining processes and technology springing up on the market, it’s easy to become lost in the weeds and get scared off by the sheer volume of information available.

CNC machining, in particular, can leave folks scratching their heads. Many believe that CNC is a piece of cake, and will dive into uncharted waters without the proper research and training. Others will steer clear of CNC machining entirely for fear that it is too large of an undertaking. The truth is, CNC machining can be extremely accessible, but it is helpful to understand what it is and is not before you get started. Below, we’ll dispel some common myths. 

Myth #1: No Experience Necessary

Machine manufacturers throughout the industry will all make claims about how user-friendly their CNC is. The latest machining centers come equipped with visual programming systems, automatic tool presetters, high-tech work probes and a wide variety of tools and add-ons to simplify the machining process. But at the end of the day, a machine is only as good as its operator, and it takes time to build up a familiarity with the CNC process and the tools and procedures required to effectively produce quality parts on a consistent basis.

For anyone new to CNC machining, it’s always best to seek help from those with more experience. Training is available online and in-person through most machine retailers. Tooling and material vendors can help educate users on proper cutters, feeds/speeds, work holding, etc. Online forums are a great resource to post problems and seek solutions to challenges you may be facing. There is always something new to learn in the world of CNC machining. 

Myth #2: “Set it and Forget it”

There is a common misunderstanding that once you run a part on a CNC, it will continue churning out high-quality components without issue. It is true that there have been significant advancements in machine automation: Modern technology (bar feeders, part loaders, pallet systems and more) have made “lights-out manufacturing” more accessible. Still, issues will always arise. Tools break. Parts shift. Inserts wear down. Sooner or later, it will become necessary for operators to intervene in order to maintain part quality and correct or prevent problems on the machine. 

Myth #3: Predictability of Production Time

With the advent of modern CAD/CAM systems, it has become increasingly simple to calculate production time for a given component. You can track cycle time for any number of parts, and you can even determine the run time for specific tooling operations. All of that information is fantastic for quoting and estimating how much machine time will go into a particular order. That said, CNC machining is never perfect. It can be difficult to anticipate when a certain tool will fail, or when a piece of equipment will break down and require maintenance. There are numerous ways to incur production delays, so it is always best to err on the side of caution when attempting to predict production time on your CNC.

Myth #4: G/M Code is a Thing of the Past

To machine a part, a CNC needs to know what operations to perform and how to perform them. To accomplish this, operators used to type in a lengthy series of numbers and letters (known in the industry as G Code or M code) which were used to communicate with the machine and get it to execute its functions. Today, the vast majority of shops rely on 3D CAM systems (computer-aided manufacture) to define their tools, workpiece, cutting paths, drill cycles and more. Similarly, many machines rely on visual programming systems that allow operators to program parts by simply adding a few dimensions to a library of stock machining operations.

Given these advanced programming tools, G/M Code should be obsolete, right? Wrong. Whether it’s a visual system at the machine, or the latest CAM software, they all are outputting code. The same G and M code that operators have been using for decades, just without the headache of manually typing it in. This code can still be edited and tweaked by operators to improve cutting efficiencies, adjust offsets, change tool paths and more. Even a skilled CAM programmer would benefit from a basic understanding of the raw code, as it can be essential when troubleshooting errors and identifying problem areas during machining.

Myth 5: Everything is Automated

We have seen incredible advancements in the world of machine automation. Many of these technologies have been adopted by large manufacturing outfits to increase capacity and speed up production. That said, even the most robust system of automation technology would not function without skilled operators and programmers.

Machines fail, and it takes a human to get the system back up and running. It would be unwise to invest a great deal of time and money into the latest and greatest tech without a team of experienced CNC professionals overseeing the operation. While the automation equipment available today is impressive and exciting, the majority of shops are nowhere near full automation, relying on talented machinists and programmers to design and manufacture their parts. 

Myth #6: CNC Machining is Expensive

CNC machining is becoming more and more affordable. The combination of CAD/CAM software and modern machining centers has made it easier than ever to take a part from conception to production. Built-in CNC features allow operators to setup parts faster than ever, and today’s cutting tools and high-speed machining operations have significantly reduced cycle times. It can still be quite costly to run parts in small quantities, due to shop minimums and the operator/programmer time involved in each CNC job, but as production numbers increase, part prices can drop exponentially. 

Myth #7: CNC isn’t for the Little Guys

This is just plain wrong. With more and more machine manufacturers competing in the space, CNC equipment has never been more accessible. Machining centers come in every shape and size, so smaller shops are not limited by floor space. Most equipment providers offer machines in a variety of models with a wide range of optional features, which means customers can custom-order a CNC to meet their exact budget and specifications. Though still in its infancy, we have seen a growing market for desktop CNC machines as well. You could literally have a water jet or CNC mill running in a small office or classroom. 

Myth #8: CNC Programmers Don’t Need to Know How to Machine

The best programmers work closely with operators to understand the ins and outs of the machining process. Many programmers start out as machinists themselves. The information gleaned from time on the machine proves invaluable when sitting down to work in a CAM environment. While creating a program, there are a number of factors to account for including work holding, tool lengths, cutter types, speeds/feeds, machining paths and so much more. It is not uncommon for new programmers to generate a program that runs beautifully in their CAM software, only to watch it fail miserably when it reaches the machine. While you can learn to program successfully without a background in machining, it will be a long and challenging road. 

Myth #9: A CNC Machine Can Make Anything

There are no shortage of mind-blowing videos online highlighting the latest features of modern machining centers. Multi-axis mills and live-tooling lathes will produce some of the most beautiful and complex components you’ll ever see. That said, even the most advanced piece of CNC equipment has its limitations. Understanding a CNC’s capabilities is critical when designing and manufacturing parts. Some features simply cannot be machined. This could be due to a particular machine restriction, such as range of motion or cutting envelope. It could also be dependent on factors that go beyond the CNC itself such as tooling, material type, part geometry and more. Modern CNC machining centers can do amazing things, but there can always come a point when their limits will be reached.

Myth #10: CNCs are Built to Last

Like it or not, CNC machines will break down. They operate under a great deal of stress and are subject to incredible amounts of wear and tear. Executing complex machining operations at high speeds will eventually take its toll, and sooner or later machine maintenance becomes a necessity. A skilled operator will not only be able to run the machine, but they will also be able to fix it when failures inevitably occur. A preventative maintenance schedule is highly encouraged to limit machine downtime and avoid unnecessary stoppages. 

Myth #11: We’ve Seen it All in the World of CNC

The manufacturing industry is constantly growing and evolving. Advancements in CNC machining have made technology that once seemed futuristic easily accessible for small shops, hobbyists and educators. Additive manufacturing has taken off, and we’ve only just begun to capitalize on all that 3D printing has to offer. There has never been a better time to get involved in the world of CNC machining, and it will be exciting to see what new products and equipment become available in the years to come.

Bryan Rosenberger, a lifelong Oregonian, helps run R&R Manufacturing, a family-owned machine shop that specializes in waterjet cutting and CNC machining.



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