CNC MACHINING CENTERS

                    The machining centre is a machine tool which is capable of doing multiple machining operations on a work part in a single setup. Recent CNC machining centers are equipped with lot of feature which can increase the production and time saving. Time saving on CNC is a huge profit for the company.

The machining center designation refers to the orientation of the machine spindle, and is classified as below:

1. Vertical Machining centers (VMC).
2. Horizontal Machining centers (HMC).
3. Universal Machining centers (UMC).

1. Vertical machining centre (VMC):

These machines have its spindle on a vertical axis relative to the work table and always perpendicular to the machining bed. A vertical machining centre (VMC) is typically used for flat work that requires tool access from top. E.g. mould and die cavities, large components of aircraft. Vertical machining centers are limited for the small type of components. These machines are less expensive compared to the other machining centers.

Axes Designation in vertical machining centers is as shown below:

    2. Horizontal machining centre (HMC):

This type of machines have the Z axis in the horizontal position and the part is loaded on the table vertically in X and Y direction. Horizontal machining centers are used for machining the cube shaped parts where tool access can be best achieved on the sides of the cube. The number of setups can be reduced compared to the Vertical machining centers.  Some horizontal machining centers have their bed in X and Y axis perpendicular to the spindle and some have in X and Z axis parallel to the spindle.

Axes Designation in vertical machining centers is as shown below:

               3.  Universal machining centre (UMC):

These machines are the machines which has 5 or more axis. It has a work head that swivels its spindle axis to any angle between horizontal and vertical making this a very flexible machine tool.  The complex parts like Aerofoil shapes, curvilinear geometries can be machined using these universal machining centers. These machines works on the swivels spindle axis which is called pivot point. Most of these machines are used for finishing of parts due to achieving of high accuracy. 

Advantages of machining centers:

·         Reduced setups which gains the time and saves the machining cost.

·         Reduced part handling by the operator, due to reduced setups.

·         The parts utilize the same fixture throughout their processing which Increases the accuracy and repeatability.

·         Faster process and faster delivery of parts in small lot sizes.

Disadvantages of machining centers:

·         These machines are more expensive compared to other conventional machines.

·         Need highly skilled and trained labors to operate these machines.

·         Needs software’s for DNC, Simulation and CAM programming, which makes the cost higher to use these machines.

Features of CNC machining centers:

Usually the CNC machining centers are designed with many features to reduce non productive time. Some of the features are:

                      1.       Automatic tool changer (ATC).
                2.       Automatic work part positioned.
                3.       Automatic pallet changer.

       1.       Automatic tool changer (ATC):

                        The Cutting tools are stored in the storage unit called the “tool magazine” which is integrated with the machine tool and named with the tool numbers. When a tool number is called by the tool number the magazine rotates to the proper position and an automatic tool changer (ATC) with the program control, exchanges the tool in the spindle for the tool in the tool storage unit. The Capacities of tool magazine commonly range from 16 to 80 cutting tools. These Automatic tool changes save the manual tool changing and the big save on the cycle time or the operation time.

      2.       Automatic work part positioned:

                      Automatic work part positioning acts as rotary axis rotating the part and give access to the cutting to machine, many horizontal and vertical machining centers have the capability to orient the work part relative to the spindle. The table can be oriented at any angle about a vertical axis to permit the cutting tool to access almost the entire surface of the part in a single setup. These automatic work part positions are programmed by the programmer. The positioning of the rotation is very important the tool need to move to safety plane when there is a big rotation in the rapid. With these features we can reduce the number of setups and save huge time and gain increase in productivity.

       3.       Automatic pallet changer:

                    Recent modern Machining centers are equipped with two (or more) separate pallets that can be changed using an automatic pallet changer. While machining is performed with one pallet in position at the machine, the other pallet is in a safe location out of the machine. The operator can unload the finished part and then fixture the raw work part for next cycle with the pallet outside the machine. Using these automatic pallet changers the time of loading and unloading the part can be saved and the machine will be loaded continuously. These featured machines are very helpful in mass production activity.

Enjoy learning CNC Programming.