An evolution of our gantry router platform, the GM-2 Gantry Mill is a large-frame milling machine capable of serious metal removal. Below is a comparison of features that differentiate the GM-2 (gantry mill) from the GR-712 (gantry router).

Gantry Mill Design Improvements:

• Improved Gantry Design
• Twin X-Axis Ballscrews
• GM/UMC Spindle Head Assembly
• Maximum Torque
• Increased Axis Thrust
• Higher Tool Changer Capacity
• More Z-Axis Travel
• Augers For Chip Removal
• Free-Standing Control Pendant

To allow the Gantry Mill to take much heavier cuts, we stiffened the X-axis considerably, and redesigned the columns of the gantry assembly to improve stability and rigidity. The forward-most X-axis linear guide trucks are now well in front of the bridge, moving the center of gravity back, so the X-axis trucks are more evenly loaded. Also, there are now four linear guide trucks per side, and each truck has a higher load rating than those on the gantry router series machines.

To take full advantage of the improved column and bridge design, we improved the X-axis drive system by adding a second X-axis ballscrew/motor assembly. Driving the gantry synchronously from both sides, rather than through a single connection in the center, ensures the gantry remains stable and rigid while in motion, and prevents skewing.

The two X-axis motor assemblies also nearly double the machine’s X-axis thrust, providing more force for heavy cuts and faster material removal.

The highlight of the GM-2 is its powerful 30 hp (22.4 kW) inline direct-drive spindle. This is the same high-performance spindle used in our VF, EC, and UMC Series mills – now available to tackle your biggest jobs on this large, open-frame machine.

The GM-2 comes standard with an 8100-rpm spindle that is outstanding for all-purpose machining work. For high-speed machining operations and high feedrates with small tools, optional 10,000-rpm and 15,000-rpm high-speed spindles are available. These spindles are capable of high rpm operation, without sacrificing low-speed torque or high-speed power.

The GM-2 also incorporates the robust spindle head assembly from our highly successful UMC-1000, which uses linear guide trucks with a much higher load rating for added rigidity, transforming our very successful large-frame gantry router into a high-performance gantry milling machine.

This change also means that high-productivity options like Through-Spindle Coolant and Through-Tool Air Blast are available on the GM-2.

The GM-2’s upgraded spindle/motor combination more than triples the available torque and doubles the power rating of the spindle, compared to our GR-712 gantry router.

You get 90 ft-lb (122 Nm) of torque at 2000 rpm, and a 30 hp (22.4 kW) vector drive system – exactly the same performance you get from our very popular VF and UMC Series models. Now, you don’t have to sacrifice high metal removal rates for a huge work envelope.    

Increased spindle power and rigidity mean nothing if you can’t push the cutter through the material. So, we stiffened the GM-2’s gantry, column, bridge, and spindle head assemblies to handle the additional forces generated during heavy cuts, and then added a second X-axis ballscrew/motor assembly to increase the axis thrust.

The GM-2’s X-axis thrust increased 80% to 4500 lbf (20,017 N), and the Y-axis increased 60% to 1650 lbf (7340 N) – more than enough for heavy cuts and fast material removal.

The GM-2 also features our 30+1 tool side-mount tool changer with high-speed, direct-positioning carousel. This tool changer more than triples the tool capacity compared to our GR series gantry routers, and has the added benefits of providing much faster tool changes, and tool storage outside of the machining envelope.

With the addition of the spindle head casting and spindle motor assembly from the UMC series models, we were able to easily increase the Z-axis travel over the gantry router models.

In fact, we effectively doubled the Z-axis travel from 11" (279 mm) to 22" (559 mm).

Additionally, we increased the spindle nose-to-table dimensions to allow more room for the typical workholding used in milling applications. The minimum nose-to-table dimension increased from 2.5" (63.5 mm) on the GR-712 to 4" (102 mm) on the GM-2. The maximum nose-to-table dimension increased from 13.5" (343 mm) on GR-712 to 26" (660 mm) on GM-2.

More spindle power means you’ll be producing a lot more chips each hour.

The GM-2 comes standard with dual chip augers – one on each side of the table, along the X-axis. The machine also comes with removable splash guard panels, which help constrain most coolant splash to the table, and remove easily, so chips and coolant can be brushed into the auger troughs on either side of the table.

All GM series models also come equipped with travelling enclosures, with flexible chip guards. These overlapping clear plastic strips create a flexible “curtain” that constrains chips and coolant flying off the cutting tool to the area around the spindle within sheet metal enclosure.

The GM-2’s free-standing control pendant on wheels allows the operator to move the control to any convenient position, rather than have it permanently attached to the electrical panel at the end of the machine, like the gantry router models.

The machine also uses more convenient contact safety sensors, rather than the light curtain sensors found on the GR series. Now, you can step close to the machine without triggering a feed-hold condition. You actually have to make contact with the safety sensor to trigger a feed-hold. This allows the operator to safely work on the table away from the machining area, without tripping the sensor.