On every CNC shop floor you’re likely to run into the same rookie mistakes. The learning curve for operating a CNC machine skillfully is steep, and beginners can benefit from some good pointers at the outset. Knowing what to do—and, more importantly, what not to do—will save time and money.
At Diversified Machine Systems (DMS), we are in the business of turning beginners into experts. After all, every professional CNC operator once started out as an amateur. Fortunately, all it takes to level-up is some time, experience, and helpful advice along the way. To that end, here are five common mistakes that rookies tend to make—and how you can get ahead of the curve by avoiding them.
1. Setting Offsets Improperly
Offsets are a big deal. If you set any of your machine’s offsets improperly, you run the risk of crashing the machine and causing significant and expensive damage. When using an edge finder, remember to compensate for half the diameter of the edge-finder tip. A lot of positional errors stem from forgetting to account for the edge-finder, a mistake which becomes obvious when all positions are off by that specific amount.
While we’re on the topic of offsets: on the control display, make sure that there are no offset shifts in the work offset page. For example, during setup any value in the global work shift offset should be fixed at “zero.” A global work shift would result in every cutter moving stock in the wrong position. These are small details, but they can make all the difference in your final product.
2. Selecting the Wrong Tool for the Job
When starting a new project, selecting the right tool can be a process of trial-and-error. It pays to be attentive to the result, especially in initial stages. If you’re using the wrong tool, you may notice scratches, burn marks, or edge distortion. These can be signs of “chatter,” or machine vibration that decreases the quality of your work, and can dramatically reduce your tool and machine life.
To mitigate these problems, choose the right cutting tool for each particular job. You can perform trial runs to dial in your tooling when working with a new material. You can also consult a DMS staff member for tooling tips.
3. Setting Cutter Height Inconsistently
One mistake that rookies tend to make is to be sloppy with their cutter height. Setting your cutter height is an initial step that demands precision. Check that the tools don’t have excessive runout and that enough cutter length is protruding from the holder so that the cut depth is less than the protruding length of the tool. If you neglect this crucial step it’s possible that the holder will crash the workpiece.
4. Not Knowing the G-Code
Programming a CNC machine can feel intimidating, and beginners are prone to unnecessary mistakes in the G-code. Taking the extra time to familiarize yourself with the G-code will help you verify that the correct cutters are cutting in the correct sequence. You will also want to verify that the programmed work offsets correspond to the intended work offsets and that all retracts are high enough to avoid any clamps that may be in use for work-holding. Inadequate retracts can result in damage to cutters, product, and the machine itself. A familiarity with your G-code can help you avoid these damages.
5. Poor Maintenance
Maintenance may sound unimportant to the beginning CNC operator, but over time it directly affects the function of your machine. A CNC machine that is poorly maintained will accumulate debris and may block your filters, resulting in overheating and significant damage over time. Your product can also suffer from accuracy and precision problems.
Make a maintenance schedule that includes lubrication, cleaning filters, checking coolant levels, and wiping or vacuuming debris. Getting in the habit of regular maintenance will ensure the longevity of your machine and the quality of your product. Preventative maintenance like this doesn’t take much time if you practice it regularly, but it will save you time and money in the long run.
In most CNC shops you will find some iteration of these common rookie mistakes. Operators who do a little research can avoid these costly and time-consuming errors. They can also earn a reputation for excellence in their work.