What Is a Gantry Type Machining Center?
A gantry-type machining center is a type of machining center that is automatically controlled by CNC (computer numerical control) commands.
It is classified as the largest machining center and consists of a spindle, table, column, NC unit, and automatic tool changer (ATC). It is so called because the structure supporting the spindle, which rotates the cutting tool, is gantry-shaped when viewed from the front of the machine.
Because of its structure which allows for a large width and length of the table for loading the cutting workpiece, it is used for heavy-duty cutting of large products. Because it is a very large facility, it is used only in a limited number of processing plants.
Because of the large size of double-column machining centers, there are only a limited number of domestic manufacturers of these machines. On the other hand, the demand for double-column machining centers is increasing for use in larger semiconductor facilities and in the production of molds for electric vehicles.
Uses of Gantry-Type Machining Centers
The gantry-type machining centers currently in operation in Japan are capable of machining workpieces up to 12 m or more in length, 4 m or more in width, and 1 m or more in height, so their main applications are for large products.
Because of their extremely precise positioning and cutting accuracy, they are used in the machining of rotating parts for wind and hydropower generation equipment, nuclear power generation equipment, structural parts for aircraft, and large vacuum chambers for semiconductor manufacturing equipment. They are also used for chambers for FPD manufacturing equipment such as liquid crystal and organic EL, parts for large ship motors, and parts for the automotive and aerospace industries. The principle of the double-column machining center is as follows.
Principle of Gantry Type Machining Centers
The structure of a gantry-type machining center consists of a table on the floor for loading the workpiece to be machined, columns on either side of the table (the vertical pillars of the “gantry”), cross-rails connecting the columns above the floor, and a spindle that moves on the cross rails.
Although large, it is suitable for precision cutting because of its high-precision positioning of around 2μm and can be used for a variety of machining operations by changing the spindle attachment. However, the equipment itself is very expensive and the machining cost is also high.
Types of Gantry Type Machining Centers
Gantry-type machining centers are classified into the following types according to the way each part moves. Each of the following types has a different rigidity, or direction to improve accuracy, and is selected mainly according to the axial direction in which accuracy is desired.
1. Fixed Crossrail Type
The column is fixed, and the spindle moves left and right on the Crossrail. The spindle itself moves up and down, and the table moves in a direction perpendicular to the Crossrail.
2. Crossrail Moving Type
The column is fixed; the spindle moves left and right on the crossrail, and the crossrail moves up and down. The table moves in the same way as in the fixed crossrail type.
3. Gantry Type
The table is fixed, and the column moves along the table. There are two types of crossrail movement: fixed type and movable type.
