chapter 13 milling methods & machines.

by:Lxshow     2020-03-09
Modern Milling machines look similar to 25 years ago.
However, they now have to cut super alloys, titanium and high
Stretch the steel at a much closer tolerance and faster speed than before.
To deal with these requirements, the new milling machine provides higher horsepower, greater stiffness and wider speed and feed range than before.
In addition, more accurate lead screws, closer alignment, numerical control (NC)
And computer numerical control (CNC)
All of this leads to faster work than ever before, better completion and higher accuracy.
Modern CNC vertical milling machine as shown below. 13.
Many types of milling machines used for manufacturing are divided into three general categories.
* Bed and knee Machine * bed-
Type milling machine * Special Machine tool 13. 2.
1 column and knee machine column and knee milling machine are of two types, vertical and horizontal.
The schematic diagram below shows two types of machines.
Versatility is a major feature of knee and column milling machines.
On this type of basic machine, tables, saddles and knees can be moved.
Many accessories such as universal vises, rotary tables and dividing heads further increase the versatility of such machines.
Regardless of whether the machine is vertical or horizontal, several components on all columns and knee milling machines are similar, except for minor changes in size and due to the manufacturer\'s preferences.
These similarities are described in terms of general shapes, geometric relationships with the rest of the machine, functions, and materials for manufacturing components.
Column: The column usually combined with the base into a single casting is cast iron or ball iron.
The column holds the spindle and bearing, as well as the necessary gear, clutch, shaft, pump and shift mechanism to transmit the power from the motor to the spindle at the selected speed.
The gear is usually run in oil and has a long life and is made of a carbide alloy steel.
Some necessary controls are usually installed on the side of the column.
The base is usually hollow, and in many cases it is the bottom slot of the cutting fluid.
The pump and filtration system can be installed on the base.
The hole in the center of the base holds the support of the screw, which can lift and lower the knee.
The mechanical processing vertical sliding at the front of the column can be square or tuxedo.
The knee moves up and down on this slide.
Slides must be in 90-
The degree angle with the cylinder on the horizontal and vertical planes.
The tolerance is very close, usually in minutes or seconds of an arc.
The large hole on the surface of the column casting is for the spindle.
The hole is perpendicular to the front slider on both planes and parallel to the upper slider to drill very precisely.
Spindle: on a horizontal milling machine, the spindle is one of the most critical components.
It is usually forged from alloy steel and is hot.
Treated to resist wear, vibration, thrust and bending loads.
The spindle is usually supported by a combination of ball and straight roller bearings, or by cone roller bearings that absorb radial and end thrust loads.
The spindle is hollow, so the arb can be firmly fixed in the appropriate position using a tie rod.
The front of the spindle is processed to accept the standard arbors.
The two keys installed in the corresponding position of the tree planting pole can complete the actual driving of the tree planting pole.
Precise grinding makes it an internal tapered positioning Rod concentric with the spindle.
Knee: The knee is a casting that moves up and down the slide at the front of the post by lifting screws.
Two tuxedo or square sliders are processed to 90 degrees each other.
The vertical sliding is combined with the sliding at the front of the post, and the horizontal sliding carries the saddle.
It contains the necessary gears, screws and other mechanisms to provide a full range of power supplies.
The operator can select various feed speeds by means of the controller installed on the knee.
Saddle: the saddle of a normal milling machine is a casting with two slides to exact 90-
Angle of each other.
The lower slide coincides with the slide at the top of the knee, and the upper slide accepts the slide at the bottom of the table.
The slide surface in contact with the knee and table is parallel to each other.
The lock of the cross slider and table is mounted on the saddle, as well as the nuts engaged with the cross feed and table feed screws.
In the universal milling bed, the saddle is made of two pieces, which is more complicated, because it must allow the table to rotate through a limited arc.
Tables: milling machines tables vary greatly in size, but they usually have the same physical properties.
At the bottom of the table there is a tuxedo slider that can be placed in the slider at the top of the saddle.
It also has bearings at each end to carry the table feed screws.
The top of the table is machined parallel to the slider at the bottom, with several full length T-
Slots for mounting vises or other workpiece fixtures.
A dial of a few inches per inch is provided to move and place the table accurately.
The table feed screw usually has an Acme thread.
Vertical spindle milling machines are available in a variety of types and sizes.
The head that holds the spindle, motor and feed control unit is fully versatile and can be placed at a composite angle with the surface of the table.
The head-connected ram can be moved forward and backward and locked in any position.
The turret at the top of the column allows the head and ram assembly to swing sideways, thus increasing the contact range of the Machine Head. Some ram-
Both vertical and horizontal milling machines can be used. On ram-
There is a vertical rolling mill with a motor in the column, and the power is transmitted to the spindle through the gear and the key shaft. 13. 2. 2 Bed-
The high output of type milling machines requires a large amount of cutting, and the stiffness of knee and column type milling machines may not be enough to withstand high pressure. A bed-
Type milling machines are usually ideal for this kind of work.
In this machine, the table is supported directly on a heavy bed, while the pillars are placed behind the bed.
There are several advantages to the bed-
Especially the type machine used for production operation.
It is possible to feed the hydraulic workbench;
Hydraulic components are installed in bed castings.
This allows a very high feed force;
Variable feed rate during any given cutting and automatic cycle.
The spindle can be lifted by arrangement of the Cam and the template to produce a special profile.
Essentially heavier construction allows more power to be provided to the spindle, which increases productivity by faster metal removal. Duplex bed-
The type milling machine has two columns and a spindle for milling the two surfaces on the part at the same time.
Main disadvantages of the bed-
Compared to the knee and column type, the type milling machine is less useful.
Its advantages are high productivity, strong adaptability to large machines, and easy to modify special applications. 13. 2.
As industrial products become more complex, new and unusual changes to the more common milling machines have been developed.
The goal is to adapt to larger work, to make many repetitive parts, to locate holes and surfaces precisely, or to do other unusual machining work. Planer-
Type milling machine: the general arrangement of these types of machines is similar to that of a planing machine (Chapter 7)
, In addition to replacing a single cutter bit, a milling head is installed. Planer-
Type machines are mainly used to process parts such as beds for large machine tools and other long work pieces that require precise plane and angular surfaces or grooves.
Profile milling machine: two sets
The dimension profile can be done by using a template or CNC vertical milling machine.
Some contour meters have several spindles that can produce some repetitive parts per cycle. Hydraulic-
The type analyzer has a stylus that touches the template to start the operation.
The operator then moves the stylus along the template, causing the hydraulic fluid under pressure to flow to the correct drive cylinder.
The table moves the work to the tool and copies the shape of the template.
Mold sinking and other processes involving cavity processing can be done on a 3D contour meter.
The precise pattern of the cavity is made of wood, plaster or soft metal.
The stylus follows the outline of the pattern when guiding the tool to process the cavity.
This type of work also uses CNC milling machines. 13. 3 Computer-
The controlled machining system several standard machines discussed in the previous chapters of this paper can perform multiple operations.
For example, the lathe can turn, face, drill, thread, etc.
A drilling rig that can drill holes, expand holes, drill holes, attack teeth, etc.
However, when the increase in productivity requires the purchase of additional processing capacity, it is almost always more economical and feasible to purchase multi-functional machines that can be rapidly changed, processed and automatically processed at the same time. 13. 3.
A machining center was designed and built to provide flexible manufacturing.
They can be used to process several parts or large production runs.
Programming can be relatively simple, and the use of \"canned\" loops provides a lot of versatility.
By definition, the NC machining center is capable of milling, drilling and drilling, and has an index turret tool holder or provides automatic tool change.
The machining center is configured horizontally or vertically.
The relative advantages of each method will be briefly discussed.
Horizontal machine: for heavy-duty boxes, horizontal machine is often advantageous
Parts of the shape such as gear housing have many features that need to be machined on the side.
The horizontal machine is easy to support this type of heavy-duty workpiece.
If the rotary index Workbench is added, there is no need to re-process the four sides of the workpiecefixturing.
Pallet systems used to get parts in and out of workstations tend to be easier to design for horizontal machines where everything in front of the main post is open and accessible.
A horizontal machining center with a pallet shuttle system is shown below.
Vertical machine: for flat parts that must have holes, the vertical machining center is usually the first choice.
The fixtures of these parts are easier to design and manufacture for the vertical spindle.
In addition, the thrust of the cut developed in drilling or milling pockets can be directly absorbed by the machine\'s bed.
3-Sportsand 5-
The axis CNC vertical machining center is displayed on page 26.
3-the first choice of vertical machines in the place
Like mold and mold work, shaft work is done on a surface.
The weight of the head of the vertical machine when it is away from the column, especially on large machines, may be a factor in maintaining accuracy, as it may have some tendency to drop and lose accuracy and cause chatter. 13. 3.
2 flexible machining systems usually use one or more machining centers with other equipment to generate production-
Volume workpiece. A workpiece-
The processing system is required and the central computer usually controls the entire arrangement.
Material Handling: parts move from warehouse to machine components through one of several different types of systems. The material-
The selected processing system must be able to transfer any part to any machine in any order and provide a set of parts before each machine for maximum productivity.
Parts are usually loaded and unloaded manually.
Materials of various types
The handling system used includes: automatic guide car, towing system, roller conveying system, elevated conveying system, monorail, Crane and robot.
Control system: there are three functional levels of computer control of flexible machining system: Main control--
The master controller monitors and controls the entire system, including transferring artifacts to the right machine, scheduling work, and monitoring machine functions.
Direct CNC--
DNC computers distribute appropriate programs to individual CNC machines and supervise and monitor their operations.
Element control--
The third and lowest level of control is computer control over a single machine processing cycle. 13.
Milling Machine accessories and accessories many accessories have been developed for milling machine.
Some are specialized and can only be used for a few operations.
Almost all milling operations use other tools such as vises, arbors, and collets. 13. 4.
1 special milling head developed several types of special milling heads for horizontal or vertical milling machines.
These accessories add to the versatility of the machine.
For example, a vertical head can be installed on traditional horizontal columns and knee milling machines, which greatly increases its practicality, especially in small shops with a limited number of machines. 13. 4.
In all milling operations, the work is maintained by fixtures, fixtures, or clamping devices.
In most cases, when machining, the work remains stationary relative to the table, however, when the machining operation is in progress, the work located in the dividing head and the turntable can be moved on both planes. 13. 4.
3 arb, colle, and several basic types of arb and colle are used to keep the milling tool and pass the power from the spindle to the tool.
They are usually made of alloy steel regardless of type, and are heat treated to obtain wear resistance and strength.
Vertical bar: There are three basic types of vertical bar of horizontal milling machine: Type A, type B and Type C.
Through the tensile bolt of the spindle of the machine tool, screw the screw into the small end of the cone, and pull the knife lever tightly into the cone hole of the spindle of the milling machine.
The power is transmitted from the spindle through two short keys to the knife bar, which engage with the slot on the knife bar flange.
Colleague: on some vertical milling machines, the spindle is drilled to accept collet with a partial straight handle and a partial taper handle.
Collet is secured by a tie rod that is screwed into the threaded hole on the back of collet and tightened from the top of the spindle.
Some milling machine manufacturers offer sleeve arrangements that do not require tie rods.
This type of Collets can be turned off with leverage
Operate the cam or with a large locking nut.
Tool rack: The End Mill and shell mill can provide standard tool rack.
For some operations that require the use of non-tools
The tool can be fixed using a chuck of standard handle size.
These chucks have a Mohs cone or straight handle.
When there is a suitable adapter or joint, both types can be used in the milling machine. 13.
5 Types of milling operations milling cutters can be used separately or in combination to process the various surfaces as shown below.
Plane milling: plane milling is the process of surface milling that will be parallel to the tool axis and basically flat.
It is done on a common or universal horizontal milling machine with different tool widths and teeth only on the periphery.
Side Milling: used for side milling, using tools with teeth on the periphery and one or both sides.
When a single cutter is used, the teeth on the periphery and sides may be cut.
The machined surface is usually perpendicular or parallel to the spindle.
The angle cutter can be used to produce an angle surface with the spindle to perform operations such as external fit or groove in reamers.
Cross-milling: In a typical cross-milling group-up, two-
Use side Mills.
The tool is half
Side or ordinary side milling tools with straight or spiral teeth. Stagger-
The tooth side milling tool can also be used.
Just milling: in just milling, install three or more knives on the knife bar to process several horizontal, vertical or angular surfaces at a time.
When doing steel milling-
Depending on the work to be done, several different types of knives can be used.
The tool used to produce a vertical or angular surface must be side by sidecutting type;
Ordinary milling machines of appropriate width can be used for horizontal plane.
In some cases, the internal face grinding of the teeth can be used at one or both ends of the just grinding device.
Forming milling: the number of parallel surfaces and angle relationships that can be machined through peripheral milling is almost limited by the design of the tool.
The forming tool is expensive, but there is usually no other satisfactory way to produce complex profiles.
Slotting and slitting operation: milling tool for normal or side
The cutting type is used for slotting and slitting operations.
Slotting and slitting are usually carried out on horizontal milling machines, but can also be done on vertical milling machines by using suitable adapters and accessories.
Face milling: face milling can be carried out on vertical and horizontal milling machines.
It produces a flat surface perpendicular to the spindle where the tool is installed.
Tool size and complexity from a simple single
Tool flying knife inserted-
There are many teeth knives with cutting edges.
Large face grinding is usually strictly installed on the nose of the spindle.
They are very effective for removing a large amount of metal and the workpiece must be firmly held on the milling table.
End milling: end milling is probably the most common milling operation.
Both vertical and horizontal milling machines can use multiple types of end mills.
The sizes of end mills range from 1/32 \"to 6 (
For Shell end Mills)
Almost any shape needed. 13.
Turn-milling includes many different processing methods, in which the milling machine processes the rotating workpiece.
These methods are mainly used to process parts of various eccentric shapes;
Flat, tapered and cylindrical surfaces;
Groove and inner hole.
Turning and milling requires that the machine tool has certain functions and several axes.
Machining Center, machining center, special lathe, milling machine and special lathe
Use the purpose machine.
When other operations of turn milling are combined in the machine, a single unit-
The advantage of fast passing through upward machining
Input time and flexibility in production.
The advantages related to turn milling are: the ability to process large unbalanced parts that cannot be rotated at high speed;
Complex surface shapes, eccentric parts and components with outstanding additional elements;
Log, unstable shaft or thinwalled parts.
Complete sections, along with all the accompanying illustrations, can be found on the T & P website www.
Tools and production.
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Hall of Edou Prenticewww. prenhall.
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