CNC takes machine shops to new levels

I had the privilege of learning the machining craft at my family’s machine shop. It was a true mom and pop shop where we made anything that would pay the bills. As orders grew larger and parts became more complex, it was clear that our future would depend on successfully integrating CNC equipment into our shop. In 1995, we purchased our first machining center: a small one without any options.

Buying it launched our shop to the next level. Five weeks after receiving the machine, we ordered another just like it. I programmed them with a pencil, paper and a calculator, typed codes into the controls and stored all programs in the machine tool controls. We used edge finders and indicators to set parts and measured tool lengths by touching parts with each tool. Compared with today’s technology, our methods were crude.

Machining centers and techniques have advanced at a fast pace since I started programming and operating CNC machines. A few significant improvements have transformed the machines into what we use today, enhancing shop and machinist efficiency.

Need for Speed

Our first CNC machine was capable of only a 7,500-rpm spindle speed. Although machines were available with higher-speed spindles, those machines were expensive and rarely found at small shops.

Mitsubishi Hitachi Power Systems Americas has several machining centers (right) with features like high-torque
spindles and through-spindle coolant. Image courtesy of C. Tate

When we bought our original machines, we would have needed to use some type of ancillary device, such as an air spindle or a geared spindle speeder, to achieve higher spindle speeds. In addition to being costly, spindle speeders were often unreliable and underpowered. Today, it is common for machining centers to have 20,000-rpm spindles.

Spindle speed may sound insignificant, but it has a direct impact on the programmed feed rate of a machine tool. High feed rates usually mean high removal rates and reduced cycle times, making a shop more efficient.

Every programmer should know that rpm multiplied by feed per tooth equals inches per minute. So as spindle speeds increased, more dynamic machine tools were needed.