CNC router FAQs: What you need to know

Q What’s the difference between a stepper and a servo?

A The basic difference between a stepper and a servo-based system is the type of motor and how it is controlled. In a servo-based system, there is constant signal feedback from the encoder (or motor) to the servo drive. This feedback tells the servo drive exactly where it is within its move. The servo is much more powerful, has quicker acceleration time and quicker positioning speed.

A stepper based system runs on an open loop meaning it sends out the number of pulses to the proper axis to get to the programmed location. Because of their simplicity, steppers are less expensive than servos, but when configured correctly, they will also produce great cuts on a consistent basis.

Q What’s better, rack-and-pinion or ball screw?

A The short answer is that both are good based on which is best suited for a particular axis or application. Ball screws are best known for being smooth and friction-free. They can be a good choice for the short axis. Over a long axis (4-foot) however, a ball screw-driven system can be susceptible to “screw whip,” which is vibration that worsens the faster a screw rotates. This is because of the critical speed of rotation needed over a long axis.

Rack-and-pinion drives are best known for being rigid and not limited by length, which makes them suited for the long axis. This drive also is geared more aggressively to better utilize the torque of the motors, providing an appreciable difference in speed between the two systems. Rack-and-pinion’s shortcomings include higher friction and potential backlash if the pinion is not properly engaged.

Q Do I need to learn a programming language like G Code to operate a CNC router?

A No you don’t. The design software titles available today allow you to design your files, import pictures and drawings, manipulate them and the software will in turn generate the code that the machine will use to cut out you parts.

Q What size machine is best for me?

A What kind of work do you want to do now? How about 3 years from now? If you are in a small shop and you only want to make small parts, a small machine will likely do you just fine. But if you want to cut full sheets you will do well to look at a 4 x 8 foot or larger machine.

Q What's the difference between a spindle and a router?

A Both tools are similar only in that fact they both hold a router bit and can rotate it to cut material at high speeds. A router is a 110V consumer grade tool that is rated for intermittent use while a spindle is an industrial motor for cutting in production situations. Spindles are more powerful (note that hp ratings between routers and spindles are not comparable) and will maintain their full torque down to much lower RPMs than a router. Spindles also have precision bearings, which means less runout.

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