Colombo USA

Technical Guide – Speed

Incorrect spindle speed is a common error in CNC machining. Generally, each material and cuts has an ideal tool profile and cutting speed. Larger diameter tools require slower speeds.

Spindle speed and feed rate for a given cut must be balanced for best work quality, tool life and spindle life.

Speed is controlled by a FREQUENCY INVERTER connected to the electric spindle. All spindles are 3-phase, cycle with infinitely variable speed from 0 to maximum rpm by correctly programming your
frequency inverter drive for each spindle.

MATERIAL

CHIP LOAD INCHES
Minimum Average
Solid Wood – dense 0.006 0.015
Solid Wood – soft 0.008 0.020
Particle Board 0.010 0.025
MDF 0.008 0.015
Rigid Plastic 0.010 0.020
Flexible Plastic 0.015 0.025
Aluminum 0.002 0.009

Feed Rate
Feed Rate

Formula = (feed speed in/min ¡Â RPM) / ( Number of cutting edges) = chip load

Feed rate must be balanced with spindle speed. Changing one influences the other. Too slow feed rates decrease the tool life due to overheating and may leave bum marks on the workpiece. Heat builds in the tool when not enough material is removed to cool the cut interface. Often, determining the best feed rate can only come from trial and error. General feed rate chart for different materials is shown as a starting point. Your cutting tool suppliers can advise cutting data for various materials.

Cutting Entry Angle

Cutting-Entry-Angle

Keep down-feed rates < 20% for the first 1 mm of depth. Ramp down to full cut depth at an angle less than about 20 degrees. This minimizes axial force.

Above all, avoid “crashes” of the spindle into the table, fixtures and workpiece.