Doosan DNM 500 II Vertical Machine Center
Servicing the X-Axis ball screw on a Doosan DMN 500 II vertical machine center (VMC). This CNC machine uses PMI ball screws. This particular model had a failure in its lubrication delivery system. They started noticing issues when the machine made a horrible cement mixer noise when in rapid traverse. Ballscrew Guys were called, and we were able to get them figured out.
Looking along the X-Axis table ball screw on a Doosan DNM 500 II VMC. Picture is taken right about the angular contact end mount to the screw. Here the covers have been disconnected and removed to get access to the ball screw shaft and linear way guide rails. You can see the ball nut flange where it connects to the table yoke. The linear way guide slide blocks or “skates” are on either side of the table. You can see the red seal covers of the blocks. This is a PMI brand ball screw.
A view of the PMI ball screw assembly found in a Doosan DMN 500 II vertical machine center or VMC. Here you can see the brass elbow lubrication fitting as it fits into the ball screw flange. This is the only place the ball nut is lubricated. So if the lubrication line feeding this ball nut gets pinched, bent, or broken, the ball nut becomes starved for lubricant. In time it will start to make noise and howl at high speeds. This is the sound of internal component wear. Ball bearings become smaller due to metal-on-metal friction. If even more time passes without service, you will begin to have positioning issues and lost motion. Worst case is the ball nut itself can seize up. This PMI ball screw is part S3130065126060. Ballscrew Guys specializes in refurbishment and repair of your existing ball screw. If you have one of these that is loose or damaged, give us a call.
A very interesting picture of a PMI ball screw (Part S3130065126060) found in a Doosan DNM 500 II Vertical Machine Center. What is unusual is the ball bearing circulation inserts on the ball nut. These are plastic molded parts which help the ball nut circulate ball bearings as it rotated along the raceway helix on the ball screw shaft. Ballscrew Guys does not encounter this design very often. Typically it is a collection of ball bearing guide inserts on either end of the ball nut. Or external return tubes kept in place on the outside of the ball nut. Ballscrew Guys can refurbish and repair your existing ball screw if it is in good shape without excessive damage or corrosion.