The Y axis rails are the backbone of a CNC router.  In addition to defining the size of the work area, these rails must support the full weight of the rest of the machine.  They need to be strong enough to support the gantry and spindle.  And they need to be rigid enough to remain stable during heavy cutting and rapid movements.

The primary structural members for these rails are a pair of heavy-duty “15-Series” aluminum extrusions from 80/20.

To these, we’ve bolted some precision-ground linear guide rails, with matching recirculating ball slides to create a rugged, yet precise low friction linear slide.

The front and rear cross-members are cut from 3/8” aluminum plate.

The vertical members in the corners are pre-drilled to accept the bearings for the ball screws that will drive the gantry.

The rear vertical members are also pre-drilled for the NEMA-23 motor mounts.  The whole assembly is then squared up and securely bolted to the base.

Next 3D Thursday:  The Gantry.