Machine Base / Gantry Assembly

The machine base and gantry assembly are the two primary CNC router structural elements. They are responsible for supporting the system drive trains, work surface, spindle and so on.

To provide accurate, high quality cutting results, CNC routers rely upon a machine base and gantry assembly that features high level stiffness, effective vibration damping and long-term stability. This is especially true as CNC routers continue to increase their speed and acceleration rates, compelling system structure to absorb ever increasing forces.

Stiffness

Stiffness means a resistance to deforming under load. It is the exact opposite of deflection which means the flexing  of a mechanical or structural component under load. A CNC router is composed of numerous components, including its machine base and gantry assembly, that depending on material characteristics, alignment and jointed conditions can exhibit a lack of stiffness and be subject to various levels of deflection. Deflection carries the penalty of decreased system accuracy, repeatability and is a primary source of increased vibration.

Damping

Damping is any effect that tends to reduce the amplitude and frequency of vibration. Damping in a CNC router is basically derived from two sources--material damping and contacting surfaces damping . Material damping is the damping inherent in the materials of which the machine is constructed. As an example, cast iron features better damping characteristics than steel or aluminum. However, the magnitude of system material damping is generally small compared to the damping contribution from the contacting surfaces at system joints. Meaning stiffer jointed conditions in a machine base and gantry assembly result in better overall system damping.

No machinist or engineer would deny that the biggest challenge in any machining process is eliminating vibration. When vibration is not subject to effective damping, oscillations increase in both magnitude and frequency, which in turn translates into poor cut quality, accelerated tool wear, and premature component failure.

It is worth noting that the quality of machine base and gantry assembly can affect system accuracy, repeatability, and overall operational quality in equal and sometime greater measure than more heralded components, such as: ball screws, rack & pinions, gear reducers and so on.