How Does CNC Machining Center Automation Work?

Automation in CNC Machining Centers

In addition to the computer numerical control system, the key automated components of a machining center (BAZ) include the tool magazine, tool-transfer equipment fitted with an automatic tool-changing arm, indexing and rotary tables for milling and turning, and workpiece pallet changers.

Core Components of an Automation System

Why the CNC System Is the Automation Hub

The computer numerical control (CNC) system is the core of machining-center automation. It can control many other components and machining parameters, including:

• Spindle speed
• Traversing linear and rotary axes
• Changing and loading the appropriate tools
• Changing and supplying clamped workpiece pallets
• Hydraulic, electrical, and coolant-lubricant supply equipment

Tool Magazines and Tool-Transfer Equipment

In a tool magazine, the tools required for machining are already mounted in tool holders. A magazine can consist of linear rack arrangements or be built as a disc-type magazine. To save space, tools and their holders, usually hollow-taper shanks, are stored on the racks with snap-in connections. A tool magazine made up of several rack rows or multiple discs can hold up to 200 tools.

An automatic tool-changing arm removes a tool from the spindle head and installs another tool. The removed tool can be returned to the magazine for storage or rejected when it is worn.

Basic Automatic Tool-Change Sequence

The automatic tool-change sequence of a linear robot fitted with a double-arm changer typically includes the following steps:

1. A tool-transfer device, such as a linear robot with a gripper, retrieves the new tool from the magazine and travels to the automatic tool-changing arm.
2. One arm of the double-arm changer receives the new tool and moves to the spindle head. At the same time, the second arm removes the old tool from the spindle head. The changer then rotates and installs the new tool in the spindle head.
3. The other changer arm returns the old tool to an occupied tool-storage location in the magazine.

The process for picking up and changing tools from a disc-type magazine is similar.

How a Five-Axis Table Expands Multi-Side Machining

A CNC machining center can have five axes: three linear axes, X, Y, and Z, plus an A’ tilting axis and a B’ rotary axis. The B’ axis can use angular motion for multi-side machining or continuous rotation at different speeds. This capability allows turning operations to be performed on a machining center.

The work spindle can be arranged vertically or horizontally and can also swivel through 90 degrees. With a horizontal spindle orientation, or when machining begins from below the workpiece, chips fall out of the machining enclosure and coolant-lubricant can flow downward freely.

A rotary or circular table that supports one-time clamping for five-axis machining is an important element for improving automation and productivity. It allows a workpiece to be machined on five axes in a single setup. The five-side machining shown is completed by combining a rotary indexing table with a spindle that can machine in both horizontal and vertical positions. This approach avoids the time lost to repeated clamping and reduces locating errors caused by multiple setups.

How Pallet Changing Improves Cycle-Time Efficiency

Most machining centers are equipped with a workpiece-pallet change preparation station. At this station, a completed workpiece is unclamped and a skilled technician loads a new blank. At the same time, the previous workpiece that has been transferred into the machining station is performing its main machining cycle.