Giddings & Lewis G50-T Horizontal Boring Mill
Photos from a FANUC controller retrofit of a Giddings & Lewis G50-T CNC table type horizontal boring mill. Here you can see the covers are removed. Ballscrew Guys have more than quite a few G&L ball screw refurbishment under our belt. This particular one was a challenge, as we rebuilt the vertical-Axis in place. This required use of ladders and a scissor lift.
Vertical-Axis ball screw service on a Giddings & Lewis G50T CNC table type horizontal boring mill. Notice it is a heavy-duty machine center type split nut ball nut. It has an upper and lower half connected together by a spacer shim. This shim, along with the proper sized balls, is what maintains the preload. If the ball screw assembly no longer has adequate preload, the lack of drag torque is looseness. On a vertical-Axis on smaller machines, gravity would assist in helping this axis keep position. But on a monster boring mill like this, it would wiggle. One of the primary causes of wearing out the vertical-Axis of these machines is when the counterbalance system for the unit is not operating properly. Every time we seem to service a vertical-Axis on machines this size, there is almost always a counterbalance and lubrication delivery issue. On this ball nut you can see that it has a rather unique ball return tube design.
Vertical-Axis ball screw service on a Giddings & Lewis G50T horizontal boring mill. We are servicing the ball screw in position. Built a support cradle under the machining head prior to disconnecting the ball nut from the axis yoke. This type of rebuild is challenging. Ideally, the entire ball screw would be pulled from the machine, then refurbished on the ground in a horizontal position. But the location and geometry of the machine prevented these options. Not a job to take lightly. The main issue causing the ball screw issue on this machine was extended operation without the axis counterbalance system functioning properly. This, coupled with insufficient lubrication, is what wore down the ball screw assembly.