Used as term for a design of CNC-machining centres. It is a special form of portal machines.

Also, the term "real moving gantry" is used to differentiate from machines driven on both sides.

In moving gantries a linear axis is realized by a portal, driven on both sides, moving above a fixed table (mostly the X-axis).

At the portal an aggregates support is mounted that is driven by an additional linear axis (mostly Y).

In "real moving gantries" both sides of the portal are driven by synchronized motors. There are cheaper possibilities, where only one single motors drives the protal by gearboxes or belts. This may cause transmission losses.

There is a special variation based on the design of a cantiliver machine. Thereby the cantilever is ride-stabilized by a support. But this is not a driving portal in the real sense.

Advantages

• Gantry machines need much less space for equal working ranges than standing portal machines.
• Especially with long and relatively narrow tables there is an advantage in the design in comparison to cantilever machines, since the cantilevered portion of the portal is relatively small, and thus, this is the design with the lowest vibrations. The gantry design can be frequently found in the component industry.

Disadvantages

In a real gantry machine, both sides of the portal are driven synchronized and by separate motors to achieve the best possible positioning accuracy. This is relatively complex and therefore expensive. Some manufacturers solve this in a more inexpensive way using a central drive, which is transferred to both sides of the portal. However, this includes the risk of transmission losses and inaccuracies.

Alternative terms

• Driving portal
• Moving gantry machine
• Gantry
• Gantry machine