Have you ever heard of the term “machinist’s ear”? It’s one of the most important things in CNC machining. You need your eyes, of course, but your ear might be just as important or even more when operating a CNC machine. Coolant is blasting, chips are flying, and you can’t even see what’s happening in the CNC machine. That’s where the ears come in handy.
I’ve visited many machine shops across the country and seen countless parts made on CNC Machines. I can’t tell you the number of times I’ve been in a machine shop and heard sounds similar to an alley cat. High-pitched screeches that are deafening. Everyone in the machine shop is probably used to it and goes about their day like it’s normal. It’s not normal. CNC machines should be humming, not screeching.
This is where rigidity comes in. Rigidity is the most underrated aspect of CNC machining, in my opinion. Very few people talk about it, but it is so important. I need to make a part as fast and precise as possible, not to mention cosmetically beautiful. If you don’t have rigidity, you’ll struggle to do any of these things. I’m talking about rigidity in holding both your part and tool.
You’ll maximize rigidity by limiting vibration. Vibration is the enemy in machining. That’s where you run into chatter and screeching. Sometimes you’ll even find a tool sounding like it’s bouncing off the part because there’s so much vibration.
Machinists can have an advantage over most just by keeping rigidity in mind. Find ways to hold as much of a part as possible. Get creative and think outside the box. Keep tools as stubby as possible. You want your part as close to the table as possible and your tool as near the spindle as possible. The further they hang out, the more vibration there’ll be. If setups lack rigidity, speeds and feeds should adjust to the current setup. These simple things will help turn an alley-cat-sounding machine into good machinist music.
I never understood why rigidity isn’t talked about more in this industry. It’s not the coolest thing to discuss, but it makes a huge difference.
- Christian Gilroy - Machinist/Programmer/CNC Mill Foreman at Titans of CNC (2008-2018)