Gantry Type Milling Machine Explained

In 1818, American inventor Whitney created the first horizontal milling machine.

In 1862, American inventor Brown created the first universal milling machine, which was the prototype for the elevator milling machine and was designed to mill the spiral groove of twist drills.

The gantry milling machine appeared in approximately 1884.

In the 1920s, semi-automatic milling machines were developed, featuring workbenches equipped with stoppers that allowed for automatic conversion between “fast feed” and “feed fast.”

Gantry Type Milling Machine

Milling machine

(1) Definition:

The Gantry Milling Machine, referred to as a Gantry Mill, is a type of milling machine with a gantry-style frame and a long, horizontal bed. It is capable of machining surfaces simultaneously with multiple milling cutters, resulting in high processing accuracy and production efficiency. This type of machine is suitable for flat and beveled surfaces on large workpieces in batch and mass production. Additionally, CNC Gantry Milling Machines can also process complex surfaces and specialized parts.

(2) Difference:

The Portal Milling Machine shares a similar shape with a planer, but the main difference lies in the beam and column. Instead of a planer holder, the Portal Mill is equipped with a spindle box and milling cutter. The reciprocating motion of the longitudinal table on a Gantry Milling Machine serves as a feed motion, while the rotary motion of the milling cutter is the main motion.

(3) Structure

The Portal Milling Machine is comprised of a door frame, a bed table, and an electrical control system. The door frame is made up of a column and a top beam, with a beam in the middle that can move up and down along the two column guide rails. There are one or two milling heads with vertical spindles attached to the beam, allowing for lateral movement along the beam guides.

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Additionally, a two-stage milling head with a horizontal spindle can be mounted on the two columns for upward movement along the column guide. These milling heads are capable of machining multiple surfaces simultaneously and each one is equipped with a separate motor (up to 150 kW), shifting mechanism, steering mechanism, and spindle components.

The horizontal long bed has a movable workbench and is covered with a shield. During operation, the workpiece is mounted on the table and then fed longitudinally. There are several variations of the Portal Milling Machine available to accommodate different workpieces, including:

① Gantry Boring and Milling Machine:

The beam is fitted with a milling and boring milling head and has a main shaft (sleeve or ram) for axial motorized feed, along with a fine motion adjustment device that can adjust speeds as low as 5 mm/min. This allows for both boring and milling operations.

② Gantry Drilling and Milling Machine:

The gantry milling machine bed is equipped with an X-axis guide rail, and the gantry milling machine table is secured to the bed. A gantry frame sits on top of the workbench, which includes a gantry carriage clamped on the X-axis rail. The Z-axis guide rail is mounted on the gantry, and a beam is provided with a Z-axis carriage that is movably clamped to the Z-axis guide. A Y-axis guide rail is also mounted on the beam, with the milling device arranged on it. This allows the gantry frame to undergo three-dimensional space milling processing of X, Y, and Z under the control of the numerical control system.

The CNC Portal Milling Machine is capable of high-precision milling, drilling, boring, and cutting operations.

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(4) Key Specifications

The key specifications of the Portal Milling Machine include the width of the work surface and the width of the gantry. For example, a CNC Gantry Milling Machine with the model SK2015-3 has a gantry width of 1.5 meters and a work table length of 3 meters. This means it is capable of processing workpieces that are 1.5 meters wide and 3 meters long.

Classification of gantry type milling machine

(1) Division by Form

Gantry mills are divided into two types based on their mobility: fixed table mobile type (which accounts for 90% or more of the total) and mobile (also known as bridge) type. The mobile type is characterized by its compact size and high load capacity, and it can travel up to 20 meters, making it suitable for machining long or heavy workpieces.

Additionally, gantry mills can be divided into two types based on the movement of the beam: moving beam type and fixed beam type. If the beam moves on the column, it is referred to as an overhead type.

(2) Division by System

Gantry mills can be divided into two categories based on their control system: ordinary type and CNC type. Some manufacturers have also developed digital intelligent gantry mills that can be easily converted between ordinary and CNC modes with the press of a button, making them more flexible and practical.

(3) Division by Capability

Gantry mills are classified into three categories based on their capabilities: light, medium, and heavy (super heavy).

Performance characteristics

The gantry milling machine has a sturdy construction, high efficiency, easy operation, simple design, and overall excellent performance. The specific performance characteristics may vary depending on the type, model, and manufacturer, and are largely influenced by the technology used.

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For instance, the SK series three-axis CNC gantry milling machine has the following performance features:

  • The vertical milling head is equipped with a powerful TX400 heavy-duty gantry milling head and double rectangular guide rails, ensuring high rigidity.
  • The milling head is driven by a ball screw, pneumatic broach device, and servo motor.
  • The side milling head is equipped with a V5 gantry milling head with an independent lubrication system, driven by a reducer and controlled by frequency adjustment.
  • The machine has a three-axis CNC system that can be easily switched between universal milling and CNC milling modes with a single button. The system can be programmed and operated manually using the control panel, making it highly practical for actual machining processes.
  • The bed is driven by a Taiwan ball screw and servo motor, while the beam can be raised and lowered using a timing belt and synchronous wheel.
  • The machine has a hand-held electronic handwheel unit for easy three-axis tool setting.
  • It also features a unique safety interlocking device for the beam lifting mechanism to ensure repeatability of the machine.
  • The machine is continuously lubricated by a standard cycloid pump group with low failure rates.

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