Metal Cutting Processes - Milling

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. Types of Milling Machine




Horizontal Milling Machine
[FONT=Arial, Helvetica, sans-serif]Figure1 shows the main features of a Plain Horizontal Milling Machine. [/FONT]
[FONT=Arial, Helvetica, sans-serif]Their functions are :- [/FONT]
[FONT=Arial, Helvetica, sans-serif]a. Column[/FONT]
[FONT=Arial, Helvetica, sans-serif]The column houses the spindle, the bearings, the gear box, the clutches, the shafts, the pumps, and the shifting mechanisms for transmitting power from the electric motor to the spindle at a selected speed.[/FONT]
[FONT=Arial, Helvetica, sans-serif]b. Knee[/FONT]
[FONT=Arial, Helvetica, sans-serif]The knee mounted in front of the column is for supporting the table and to provide an up or down motion along the Z axis. [/FONT]
[FONT=Arial, Helvetica, sans-serif]c. Saddle [/FONT]
[FONT=Arial, Helvetica, sans-serif]The saddle consists of two slideways, one on the top and one at the bottom located at 90º to each other, for providing motions in the X or Y axes by means of lead screws. [/FONT]
[FONT=Arial, Helvetica, sans-serif]d. Table[/FONT]
[FONT=Arial, Helvetica, sans-serif]The table is mounted on top of the saddle and can be moved along the X axis. On top of the table are some T-slots for the mounting of workpiece or clamping fixtures. [/FONT]
[FONT=Arial, Helvetica, sans-serif]e. Arbor [/FONT]
[FONT=Arial, Helvetica, sans-serif]The arbor is an extension of the spindle for mounting cutters. Usually, the thread end of an arbor is of left hand helix.[/FONT]

03_f2.jpg

[FONT=Arial, Helvetica, sans-serif]. Horizontal Milling Machine[/FONT]








[FONT=Arial, Helvetica, sans-serif]Vertical Milling Machine [/FONT]
[FONT=Arial, Helvetica, sans-serif]Figure 2 shows a vertical milling machine which is of similar construction to a horizontal milling machine except that the spindle is mounted in the vertical position. [/FONT]
[FONT=Arial, Helvetica, sans-serif]Its additional features are :-[/FONT]
[FONT=Arial, Helvetica, sans-serif]a. Milling head[/FONT]
[FONT=Arial, Helvetica, sans-serif]The milling head consisting the spindle, the motor, and the feed control unit is mounted on a swivel base such that it can be set at any angle to the table. [/FONT]
[FONT=Arial, Helvetica, sans-serif]b. Ram[/FONT]
[FONT=Arial, Helvetica, sans-serif]The ram on which the milling head is attached can be positioned forward and backward along the slideway on the top of the column. [/FONT]

03_f3.jpg

[FONT=Arial, Helvetica, sans-serif]. Vertical Milling Machine[/FONT]




[FONT=Arial, Helvetica, sans-serif]Cutting Tools [/FONT]
[FONT=Arial, Helvetica, sans-serif]3.1. Cutting Tools for Horizontal Milling[/FONT]
[FONT=Arial, Helvetica, sans-serif]a. Slab Mills[/FONT]
[FONT=Arial, Helvetica, sans-serif]For heavy cutting of large and flat surfaces. [/FONT]

03_f4.jpg

[FONT=Arial, Helvetica, sans-serif]Slab Mill[/FONT]​


[FONT=Arial, Helvetica, sans-serif]b. Side and Face Cutters [/FONT]
[FONT=Arial, Helvetica, sans-serif]This type of cutters has cutting edges on the periphery and sides of the teeth for cutting shoulders and slots.[/FONT]

03_f5.jpg

[FONT=Arial, Helvetica, sans-serif]. Side and Face Cutter[/FONT]



[FONT=Arial, Helvetica, sans-serif]c. Slitting Saws [/FONT]​

[FONT=Arial, Helvetica, sans-serif]For cutting deep slots or for parting off. [/FONT]
03_f6.jpg

[FONT=Arial, Helvetica, sans-serif]. Slitting Saw[/FONT]


[FONT=Arial, Helvetica, sans-serif]Note: Horizontal milling cutters are specified by the name, the material, the width, the diameter, and the hub size of the cutter. [/FONT]

[FONT=Arial, Helvetica, sans-serif]Example ---[/FONT]​

[FONT=Arial, Helvetica, sans-serif]Side and face cutter,[/FONT]
[FONT=Arial, Helvetica, sans-serif]High Speed Steel, [/FONT]
[FONT=Arial, Helvetica, sans-serif]Cutter size : 10 X ø 100 [/FONT]
[FONT=Arial, Helvetica, sans-serif]Hub size: ø 25 [/FONT]




[FONT=Arial, Helvetica, sans-serif]3.2. Cutting tools for Vertical Milling[/FONT]
[FONT=Arial, Helvetica, sans-serif]a. End Mills[/FONT]
[FONT=Arial, Helvetica, sans-serif]Commonly used for facing, slotting and profile milling. [/FONT]

03_f7.jpg

[FONT=Arial, Helvetica, sans-serif]. End Mill[/FONT]


[FONT=Arial, Helvetica, sans-serif]b. Rough Cut End Mills[/FONT]
[FONT=Arial, Helvetica, sans-serif]For rapid metal removal.[/FONT]

03_f8.jpg

[FONT=Arial, Helvetica, sans-serif]. Rough Cut End Mill[/FONT]


[FONT=Arial, Helvetica, sans-serif]c. Slot Drills [/FONT]
[FONT=Arial, Helvetica, sans-serif]For producing pockets without drilling a hole before hand. [/FONT]

03_f9.jpg

[FONT=Arial, Helvetica, sans-serif]Slot Drill[/FONT]


[FONT=Arial, Helvetica, sans-serif]d. Face Milling Cutters[/FONT]
[FONT=Arial, Helvetica, sans-serif]For heavy cutting. [/FONT]

03_f10.jpg

[FONT=Arial, Helvetica, sans-serif]Face Milling Cutter[/FONT]
 

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يتبع

Milling Processes
[FONT=Arial, Helvetica, sans-serif]Milling is a metal removal process by means of using a rotating cutter having one or more cutting teeth as illustrated in figure 13. [/FONT]
[FONT=Arial, Helvetica, sans-serif]Cutting action is carried out by feeding the workpiece against the rotating cutter. Thus, the spindle speed, the table feed, the depth of cut, and the rotating direction of the cutter become the main parameters of the process. Good results can only be achieved with a well balanced settings of these parameters. [/FONT]

03_f13.jpg



Depth of Cut
[FONT=Arial, Helvetica, sans-serif]Depth of cut is directly related to the efficiency of the cutting process. The deeper the cut the faster will be the production rate. Yet, it still depends on the strength of the cutter and the material to be cut.[/FONT]
[FONT=Arial, Helvetica, sans-serif]For a certain type of cutter, a typical range of cut will be recommended by the supplier. Nevertheless, it should be noted that a finer cut is usually associated with a better surface finish as well as a long tool life.[/FONT]




[FONT=Arial, Helvetica, sans-serif]Direction of Cutter Rotation[/FONT]
[FONT=Arial, Helvetica, sans-serif]a. Up Cut Milling[/FONT]
[FONT=Arial, Helvetica, sans-serif]In up cut milling, the cutter rotates in a direction opposite to the table feed as illustrated in figure 14. It is conventionally used in most milling operations because the backlash between the leadscrew and the nut of the machine table can be eliminated. [/FONT]

03_f14.jpg

[FONT=Arial, Helvetica, sans-serif]. Up Cut Milling[/FONT]



[FONT=Arial, Helvetica, sans-serif]b. Down Cut Milling[/FONT]
[FONT=Arial, Helvetica, sans-serif]In down cut milling, the cutter rotates in the same direction as the table feed as illustrated in figure 15. This method is also known as Climb Milling and can only be used on machines equipped with a backlash eliminator or on a CNC milling machine. This method, when properly treated, will require less power in feeding the table and give a better surface finish on the workpiece.[/FONT]

03_f15.jpg

[FONT=Arial, Helvetica, sans-serif]. Down Cut Milling[/FONT]








Typical Milling Operations
[FONT=Arial, Helvetica, sans-serif]6.1. Plain Milling [/FONT]
[FONT=Arial, Helvetica, sans-serif]Plain milling is the milling of a flat surface with the axis of the cutter parallel to the machining surface. It can be carried out either on a horizontal machine or a vertical machine as shown in figure 16.[/FONT]
03_f16.jpg

[FONT=Arial, Helvetica, sans-serif]. Plain Milling [/FONT]




[FONT=Arial, Helvetica, sans-serif]6.2. End Milling[/FONT]
[FONT=Arial, Helvetica, sans-serif]End Milling is the milling of a flat surface with the axis of the cutter perpendicular to the machining surface as shown in figure 17. [/FONT]
03_f17.jpg

[FONT=Arial, Helvetica, sans-serif]End Milling[/FONT]




[FONT=Arial, Helvetica, sans-serif]6.3. Gang Milling[/FONT][FONT=Arial, Helvetica, sans-serif]Gang milling is a horizontal milling operation that utilises three or more milling cutters grouped together for the milling of a complex surface in one pass. As illustrated in figure 18, different type and size of cutters should be selected for achieving the desire profile on the workpiece. [/FONT]

03_f18.jpg

[FONT=Arial, Helvetica, sans-serif]. Gang Milling[/FONT]







[FONT=Arial, Helvetica, sans-serif]6.4. Straddle Milling [/FONT][FONT=Arial, Helvetica, sans-serif]In straddle milling, a group of spacers is mounted in between two side and face milling cutters on the spindle arbor as shown in figure 19. for the milling of two surfaces parallel to each other at a given distance. [/FONT]

03_f19.jpg

[FONT=Arial, Helvetica, sans-serif]. Straddle Milling[/FONT]




 

eng. ahmed elkady

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