CNC machining centers
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CNC machining centers are machine tools that can perform multiple machining operations on a workpiece in a single setup under numerical control. They are classified as vertical, horizontal, or universal depending on the orientation of the machine spindle. Vertical machining centers have a vertically oriented spindle and are used for flat parts, while horizontal machining centers have a horizontally oriented spindle and are suitable for cube-shaped parts. CNC machining centers feature automatic tool changers, workpiece positioning systems, and automatic pallet changers to reduce non-productive time during machining operations.
CNC machining centers
- 2. CNC MACHINING CENTERS: The machining centre, developed in the late 50’s is a machine tool capable of multiple machining operations on a work part in one setup under NC program control.
- 3. Classification : Machining centers are classified as vertical, horizontal, or universal. The designation refers to the orientation of the machine spindle. 1. A vertical machining centre has its spindle on a vertical axis relative to the work table. 2. 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 3. A horizontal machining centre (HMC) is used for cube shaped parts where tool access can be best achieved on the sides of the cube. 4. A universal machining centre (UMC) has a work head that swivels its spindle axis to any angle between horizontal and vertical making this a very flexible machine tool. E.g.: Aerofoil shapes, Curvilinear geometries.
- 4. The term “Multi tasking machine” is used to include all of these machine tools that accomplish multiple and often quite different types of operations. The processes that might be available on a single multi tasking machine include milling, drilling, tapping, grinding and welding. Advantage of this new class of highly versatile machine compared to more conventional CNC machine tolls include: Fewer steps, Reduced part handling Increased accuracy and repeatability because the parts Faster delivery of parts in small lot sizes.
- 5. Features of CNC machining centers: CNC machining centers are usually designed with features to reduce non productive time. The features are: • Automatic tool changer : The tools are contained in a storage unit that is integrated with the machine tool. When a cutter needs to be changed, the tool drum rotates to the proper position and an automatic tool changer (ATC) operating under program control, exchanges the tool in the spindle for the tool in the tool storage unit. Capacities of tool storage unit commonly range from 16 to 80 cutting tools.
- 6. • Automatic work part Positioned: Many horizontal and vertical machining centers have the capability to orient the work part relative to the spindle. This is accomplished by means of a rotary table on which work part is fixture. 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. • Automatic pallet changer: Machining centers are often equipped with two (or more) separate pallets that can be presented to the cutting tool 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 away from the spindle. In this location, the operator can unload the finished part and then fixture the raw work part for next cycle.
- 9. Vertical Machining: known as milling, relies on rotary cutters to remove metal from a work piece. Vertical machining occurs on a vertical machining center (VMC), which employs a spindle with a vertical orientation. With a vertically oriented spindle, tools stick straight down from the tool holder, and often cut across the top of a work piece.
- 10. Horizontal Machining: A horizontal machining center (HMC) is a machining center with its spindle in a horizontal orientation. This machining center design favors uninterrupted production work. One reason for this is that the horizontal orientation encourages chips to fall away, so they don’t have to be cleared from the table. More significantly, the horizontal design allows a two-pallet work changer to be incorporated into a space-efficient machine. To save time, work can be loaded on one pallet of an horizontal machining center while machining occurs on the other pallet.
- 12. Vertical and Horizontal Machining Application: Horizontal machining centers are often used to mill grooves and slots. It may also be used to shape flat surfaces. Vertical machining centers have its spindle axis vertically oriented. Its milling cutters are held in the spindle and it rotates on its axis.
- 13. SOLUBLE OILS: Contain no petroleum or mineral oil , composed of alkaline inorganic and organic compounds SEMISYNTHETIC FLUIDS: Emulsion when mixed with water ( LEAST EXPENSIVE ) SYNTHETIC FLUIDS: Combination of synthetic and soluble oil fluids
- 14. Lubricating during cutting process Cooling the workpiece at high cutting speeds Improving tool life, Improving surface finish Flushing away chips from the cutting zone Corrosion protection of the machined surface
- 15. High Accuracy e.g. Aircraft parts Production rate is very high Complex surfaces need to be machined Flexibility in job change , automatic tool settings More safe , higher productivity , better quality Less paper work , faster prototypeproduction
- 16. Costly setup Skilled operators Computers , Programming knowledge required Maintenance is very difficult
- 18. Thank You.