Horizontal multi-spindle machining center

A horizontal multi-spindle machining center for machining workpieces, the horizontal multi-spindle machining center comprising:

• a base configured to be disposed on a support surface;
• a column configured to be disposed over the base and to be moved in a left-right direction of the workpieces by an X-axis drive unit;
• a ram configured to be disposed in the column and to support spindles into which cutting tools are mounted;
• a Y-axis drive unit configured to move, in an up-down direction, a saddle supporting the ram;
• a Z-axis drive unit configured to move the ram in a front-back direction of the workpieces;
• servomotors configured to rotate the spindles;
• and
• a jig configured to be disposed in front of the spindles and to fasten the workpieces;
• wherein an auto tool changer (ATC), configured to exchange the cutting tools mounted to the spindles, is disposed above the spindles;
• wherein guide rails of the X-axis drive unit are fastened to the base on a top of the base,
• wherein the column is moved along the guide rails,
• wherein the Y-axis drive unit is disposed on one side of the column,
• wherein the ram is equipped with four of the spindles and is disposed in the column,
• wherein transfer of the ram in a Z-axis direction is supported by the saddle,
• wherein the column, the ram and the saddle are moved in the left-right direction of the workpieces by the X-axis drive unit, the ram is moved in the front-back direction of the workpieces by the Z-axis drive unit, and the ram and the saddle are moved in an up-down direction of the workpieces by the Y-axis drive unit;
• and
• wherein the Y-axis drive unit moves the saddle along guide rails fastened to the column, two Y-axis drive motors of the Y-axis drive unit are disposed on opposite sides of the saddle, the two Y-axis drive motors are synchronously controlled, and the two Y-axis drive motors measure loads applied to the respective drive motors, compare the measured loads with each other, and stop operation of the machining center when a difference between the load of one of the drive motors and the load of the other drive motor exceeds a set range.