The technological process of milling should provide the ability to process on a given machine, under given operating conditions, the largest number of high-quality parts with the best possible use of equipment and tools, as well as at the lowest cost.
The technological process should be built in the most appropriate sequence of operations and transitions using the most rational milling methods.
The sequence of processing depends on many factors: the nature of milling operations, the size and shape of parts, technical conditions for the relative position of individual surfaces, the available equipment park, etc. However, in most cases, the sequence of processing depends on the choice of installation bases.
Selecting installation bases
The order of machining a part depends primarily on which surfaces are selected as mounting bases during machining. Therefore, the installation bases should be planned in advance, before the start of processing.
There are the following main cases of choosing installation bases:
1. The workpiece to be machined does not have pre-machined surfaces. Then the basing has to be carried out on the black surface of the workpiece ( rough base). In this case, at the first installation, it is necessary to process that black surface, which is intended as an installation base for the subsequent processing of other surfaces, that is, to prepare finishing installation base for the following installations.
So, we did when processing a rectangular bar (see Fig. 101). During the first installation, the black surface of the workpiece was taken as the base. This made it possible to process a wide plane 1
, which later served as a fine installation base for subsequent installations.
2. The workpiece to be processed in this operation has planes that have been processed in the previous operations. In this case, basing is done on pre-treated surfaces.
So, for milling a prism (see Fig. 147), the workpiece is a rectangular bar, milled clean on all edges. Any two faces can be taken as a base for processing this block. When milling grooves a and b the edge is taken as the base 1
(fig. 344). When milling grooves v and G edge 1
can no longer serve as a base, therefore, the facet is accepted as a new base 2
(Figure 345).
3. The workpiece to be processed in this operation has external or internal surfaces of revolution, processed in previous operations. In this case, basing is performed on these surfaces.
So, when processing a contour template (see Fig. 161), a central hole with a diameter of 30 mm; when milling a square (see Fig. 210), center holes (centers) were taken as the installation base; when milling the edges of the nut (see Fig. 213), a hole with a diameter of 11.7 served as the installation base mm; when milling the end grooves in the bead (Fig. 215), the external turned surface with a diameter of 34 mm etc.
Choice of milling methods
Depending on the number and order of fixing the workpieces to be machined, milling can be performed using the following methods.
Milling one piece at a time(Fig. 346, a) is mainly used in a one-off production or when processing large-sized workpieces, when more than one workpiece cannot be fixed on the machine table or in the fixture.
At sequential milling method one cutter or set of cutters processes workpieces sequentially clamped in a vice or multiple fixtures.
Sequential milling can be done in an open box, when the workpieces are fixed sequentially at some distance from each other, as shown in Fig. 346, b. To reduce losses due to idle run of cutters, modern milling machines have the ability to adjust table movements according to the principle of alternating feed (see Fig. 291).
A more productive way of sequential milling is to milling workpieces installed package(see Fig. 214, b). With this method of milling, losses during idle run of the cutter in the intervals between the workpieces are excluded, since they are adjacent to each other. Therefore, if the processing conditions and the configuration of the workpieces allow it, then it is always advantageous to secure the workpieces in a package.
At parallel method milling, two or more workpieces, fixed in a vice or multi-seat device, are processed simultaneously with one cutter or a set of cutters (Fig. 346, c).
With the parallel milling method, the machine time is reduced by as many times as there are workpieces in a row. The parallel method is mainly used in the manufacture of large batches of small-sized workpieces. In fig. 347 shows the installation of four screws for parallel milling of their heads with four pairs of three-sided disc cutters.
Parallel - sequential method milling refers to a combination of parallel and sequential milling methods. With this method, you can achieve the highest productivity, which is often used by milling innovators in production.
In fig. 348 shows a productive attachment for slotting castellated nuts. It consists of a foundation 1
and two round plates 2
and 3
.
Base 1
fixed with slot bolts on the table of a horizontal milling machine. On the base, install and fix the lower 2
and the top 3
plate assembly. Top plate 3
connected to the bottom 2
seven bolts 4
with quick release washers 7
.
The bottom plate has 54 cut holes into which the clamps are screwed 8
with an internal hexagon. At the upper end, the clamps have a round disc that freely fits into the hole in the top plate and supports the blanks of the nuts. There are also 54 such holes in the upper plate. Nut blanks are laid in them when the upper plate is overturned. A lower plate is placed on top of it, fixing it with two pins, and tightening seven bolts 4
and all 54 clips. Then a set of plates with 54 blanks embedded in them is turned over and installed on the base, securing it with four swing bolts.
On the upper plane of the top plate 3
there is a system of grooves intersecting each other at an angle of 60 °. Groove width (3.5 mm) corresponds to the width of the slot in the nut.
Milling of a set of 54 nuts embedded in the device is performed by a set of nine disc cutters installed at equal distances on the mandrel. After the first pass, both top plates are turned 60 °, a second pass is made and in the same way a third pass.
With two sets of plates, the filling of the second set with blanks is carried out in the process of milling the slots in the nuts of the first set of plates, thus saving auxiliary time.
When developing a technological process for milling a batch of identical parts, it is necessary to strive for the use of parallel-sequential processing methods.
Process design
The operation of the technological process of machining the parts are entered in sequential order in the process map. The technological process map differs from the operational map in that it is used to establish the part processing process for all operations.
In the technological process map, the sequence numbers of operations are indicated by Roman numerals (I, II, III, IV, etc.). The serial numbers of the installations are designated by Russian capital letters (A, B, C, D, etc.). Sequential numbers of transitions are indicated by Arabic numerals (1, 2, 3, 4, etc.).
The names of installations and transitions are recorded in the form of an order. This emphasizes the strict imperative of the manufacturing process.
The column "Name of installations" indicates the nature and methods of fixing the workpiece, as well as the surface with which it touches the mounting element, fixture or table surface. For example, in the technological plan, the installation shown in Fig. 349, is formulated as follows: "Set the workpiece in a vice with a milled surface 1
to the fixed jaw and fix. "
Milling- the process of processing planes, shaped and helical surfaces, cutting threads and gears, obtaining helical grooves using a rotating cutting tool called a milling cutter.
Milling occurs with a simultaneous rotational movement of the cutter and, usually, a translational movement of the workpiece.
Depending on the direction of rotation of the cutter and the translational movement of the workpiece, there are: 1) counter milling, when the workpiece is fed against the rotation of the cutter; 2) climb milling, when the direction of feed of the workpiece coincides with the direction of rotation of the cutter.
At oncoming When milling, the load on each cutter tooth increases gradually and reaches its maximum value at the exit. This ensures smooth operation of the machine. At the same time, the quality of the processed surface with this milling method is lower, as a result of which it is used for roughing.
At incidentally When milling, the cutter tooth must immediately remove thick chips, so the tool is subjected to maximum stress. This degrades the working conditions of the tool and machine.
The main elements of the cutting mode when milling are: 1) cutting speed; 2) submission; 3) depth and width of milling; 4) cross-sectional area of the cut; 5) machine time.
Cutting speed V when milling, it is the peripheral speed of the cutter, measured by its outer diameter.
The choice of cutting speed depends on the properties of the metal of the workpiece being processed and the material of the cutting part of the cutter, the diameter and durability of the cutter, feed, depth of cut and width of cut, as well as on the number of teeth of the cutter, cooling, etc.
FeedS when milling, the value of the relative movement of the workpiece and the cutter is called (Fig. 52), expressed by the corresponding dimension, mm / tooth. mm / rev, mm / min.
For rough milling, the feed rate is selected as large as possible; So, for cylindrical high-speed cutters, the feed is up to 0.2 mm / tooth for steel, and up to 0.4 mm / tooth for cast iron.
In semi-finishing and finishing milling, the feed rate is limited by the required surface finish, cutter design, strength of the feed mechanism and other factors; for example, for semi-finishing milling, the feed is: for steel - in the range of 0.08–0.05 mm / tooth, for cast iron - 0.15–0.1 mm / tooth.
Milling deptht, or the depth of cut during milling, is the thickness of the metal layer, mm, removed from the workpiece in one pass of the cutter (Fig. 52, a). The milling depth for roughing is 3–8 mm, for finishing - 5–1.5 mm.
Milling widthV called the width of the workpiece surface to be machined in a direction parallel to the axis of the cutter (Fig. 52, a).
Cross-sectional area of cut removed with one tooth of a cutter (for example, cylindrical), is the product of the milling width V and chip thickness a, mm 2:
f = B · a.
Chip thickness during milling is a variable value and changes during counter milling from zero at the moment the tooth enters the part to the maximum value a 1 at the moment the tooth leaves the workpiece (Fig. 52, b).
Since not one, but several teeth are in contact with the part at the same time, it is necessary to deal with the total section of the cut, removed by several teeth, in which, for the case shown in Fig. 52, b, the thickness of the cut layer will be: for the first tooth a 1 for the second a 2 , for the third a 3 and for the fourth a 4 = 0.
The total cross-sectional area of the cut taken during milling at a given time with all teeth affects the value of the cutting force during milling.
Machine time machining a part during milling is the time spent on the process of cutting metal with a milling cutter in one pass. When calculating the machine time, the length of the path of movement of the cutter relative to the part, the feed and the number of passes are taken into account.
The power consumed for the milling process is determined based on the circumferential cutting force and the cutting speed.
Milling machines, depending on the work performed and design features, can be divided into general-purpose and specialized machines.
The first type of milling machines usually includes horizontal milling and vertical milling, so named depending on the horizontal or vertical arrangement of the spindle axis with the cutter in them. The workpiece to be machined in these machines is fixed on the machine table and moves most often in the longitudinal direction.
On milling machines, you can process planes, shaped and screw surfaces, cut gear wheels and perform other work. Depending on the purpose, milling machines are subdivided into single-spindle - horizontal and vertical in the usual design; single-spindle universal milling in horizontal design. There are also specialized and special milling machines available. Specialized milling machines include: longitudinal milling machines with spindles in different planes; face-milling for processing planes; carousel-milling with rotating tables; drum-milling with a rotating drum and copy-milling for processing shaped surfaces. Special machines include thread milling, keyway milling, aggregate milling and rack-and-pinion.
In fig. 53 shows a general view of a horizontal milling machine. On the bed 2 the console can be moved vertically 12 , along the guides of which the cross slide moves 11 in a direction parallel to the spindle axis 5 ... Along the guides of the turntable 10 related to skids 11 , table can move 9 in a direction perpendicular to the spindle axis. The machine has a gearbox 3 and feed box 1 ... Mandrel 4 with cutters 6 one end is fixed in the spindle, and the other rests on an additional support 8 (earring) tied to the trunk 7 .
Tail mills are mounted in the tapered bore of the spindle end of the machine, in which they are clamped with a long bolt passing through the spindle bore. In a vertical milling machine, the spindle is located vertically; Otherwise, the device of the machine does not fundamentally differ from the horizontal milling one. Vertical milling machines are equipped with both rectangular and round tables. Universal milling machines differ from those described in that they have a rotary table that allows you to perform operations for milling helical grooves (for example, for twist drills) and helical gears. Bed type milling machine is characteristic of a group of specialized milling machines. Such machines are manufactured with one or more vertical and horizontal spindles; in the latter case, the workpiece can be processed simultaneously from several sides.
In fig. 54 shows a general view of a four-spindle bed-type milling machine. Along the guides of the bed 1 can move table 2 , on which the workpieces are fixed. Processing is done with cutters fixed in the spindles located in the spindle heads. 3 , 5 , 6 and 7 ... Since the table cannot rise and move in the transverse direction, the tool to obtain the required processing dimensions is set by extending the spindles along their axis and moving the spindle heads 5 and 6 along the guides of the cross member 4 perpendicular to the spindle axes of these headstocks.
In fig. 55 shows a simplified kinematic diagram of a wide-universal console-milling machine model 6M82SH. The choice of the most advantageous cutting speed during milling is achieved by changing the gear ratio of the gearbox i cop by switching the movable unit 20 gear wheels located on the shaft II, and block 21 as well as cogwheels 22 and 23 located on the shaft IV... Thus, 18 spindle speeds can be obtained. V in the range from 31.5 to 1600 rpm transmitted to the mandrel 9 with a cutter.
Knowing the number of revolutions n ed electric motor D 1 , the general formula for setting the speed of the main spindle n shp can be expressed as, rpm,
n shp = n ed · i cop .
The feed mechanism drive receives rotation from the electric motor D 2 ... The choice of longitudinal, transverse or vertical feed is made by switching a number of gear blocks and couplings of the feed box, covering the shafts XIV-XXII... By means of these switchings, 18 feed rates can be obtained (longitudinal and transverse in the range of 25-1250 mm / min, vertical - 8-400 mm / min), which are then transferred to the screws of the longitudinal, transverse and vertical feed (respectively, screws Xxiv, XXIII and Xxv).
Ministry of Education and Science of the Russian Federation
Saratov State Technical University
Methodical instructions
on the course "Technology of structural materials"
for mechanical students
Approved
editorial board
Saratov State
technical university
Saratov 2010
Purpose of work: to study the device of the 6P80G horizontal milling machine, the design of cutters and processing methods on milling machines.
1. Basic concepts
1.1. General characteristics of the machine model 6P80G
The horizontal milling machine is designed for milling the surfaces of various parts made of steel, cast iron and non-ferrous metals of relatively small dimensions in terms of individual and serial production.
Technical characteristics of the machine:
Table working surface, mm ……………………. 200x800
The number of speeds of rotation of the spindle ………………. 12
Limits of spindle revolutions per minute ……… 50-2240
Number of speeds of table feeds ……………………… .. 16
Limits of table feed speeds, mm / min.
longitudinal (Spr) …… ... …………………… .. 22.4-1000
transverse (Sп) ………………………………
vertical (Sв) ……………………………
Speed of rapid movement of the table, mm / min
longitudinal ………………………………… .. 2400
transverse ………………………………… .. 1710
vertical ……………………………… .. 855
Main electric motor power, kW ………… 2.8
The main units of the machine (fig. 1):
A - bed with gearbox and spindle assembly;
B - trunk with suspension; B - additional connection of the console with the trunk; Г - rotary part of the table; D - cross slide;
E - table; F - console with a feed box; З - machine base.
Governing bodies (fig. 1):
1 - handle for gearbox switching; 2 - handle for switching over the spindle; 3 - handle for manual longitudinal movement of the table; 4 - control handle for longitudinal table feed; 5 - handle for controlling the transverse table feed; 6 - vertical feed control handle; 7 - handle for manual vertical movement of the console; 8 - handwheel for switching the feed box; 10 - handle for switching over the feed box.
Machine movements:
Cutting movement (main movement)- rotation of the spindle with a cutter.
Feed movement- moving the table with the workpiece in the longitudinal, transverse and vertical directions.
Auxiliary movements- all specified table movements, performed at high speed.
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Rice. 2. Schemes for milling horizontal surfaces
Milling vertical surfaces is carried out on horizontal milling and longitudinal milling machines with end milling heads (Fig. 3, a), and on vertical milling machines - with side teeth of the end mill (Fig. 3, b).
Rice. 4. Schemes for milling inclined surfaces
Milling grooves: angular (Fig. 5, a), rectangular (Fig. 5, b), T-shaped (Fig. 5, c), dovetail type (Fig. 5, d), shaped (Fig. 5, e), keyed (Fig. 5, e) produced on horizontal and vertical milling machines.
Rice. 6. Scheme of milling combined surfaces
Milling shaped surfaces produced with shaped cutters of the corresponding profile (Fig. 7).
 |
Rice. 7. Scheme of milling shaped surfaces
Gear milling produce modular disk cutters (Fig. 8, a) on horizontal, as well as modular finger cutters (Fig. 8, b) on vertical milling machines.
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a a
Rice. 9. Cutter tooth designs
Pointed cutters are the simplest and are used for processing flat surfaces. The posterior surface of the tooth is delineated in a straight line m... The back surface of cutters with a relief tooth is outlined along the Archimedean spiral. A recessed tooth is used for router bits.
- in the direction of the tooth : straight, screw and multidirectional;
- by general design: solid, snap-on and prefabricated. Solid cutters are made from tool steels. In prefabricated cutters, the teeth (knives) are made of high-speed steel or equipped with plates of hard alloys and fixed in the cutter body by soldering or mechanically.
- by form and purpose: cylindrical, end, end, keyway, disc, angular, threaded, shaped and others.
- by fastening method: end and mounted;
- by appointment: for machining planes, for machining ledges, grooves and grooves, for making threads, for making gears.
1.5. Helical cutter elements
A cylindrical cutter is a multi-tooth cutting tool in the form of a body of revolution, on the generating surface of which cutting teeth are located. Each cutter tooth consists of (Fig. 10):
Front surface (1), along which the chips come off;
The back of the tooth (2), which can be rectilinear (Fig. 10, b), arc (Fig. 10, c) or curvilinear (Fig. 10, d);
The main cutting blade (3), which performs the main cutting work and can be straight, oblique or helical;
Back surface (4) wide f= 1-2mm;
Ribbons (5) wide To= 0.05 - 0.1 mm (left when sharpening for a more accurate manufacture of cutters in diameter).
1.6. Geometrical parameters of a cylindrical cutter with helical teeth
To consider the geometric parameters of a cylindrical cutter, we draw the main cutting plane N-N (Fig. 10), a plane perpendicular to the main cutting edge at the point in question. The profile of the tooth and its geometric parameters are considered in the N-N plane.
Front corner g is the angle between the front surface of the tooth and the plane passing along the radius.
Back angle a - formed by a back surface and a tangent plane drawn through the cutting edge.
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2.2.2. Get acquainted with the design and controls of the horizontal milling machine. Examine the main types of work performed on it. Perform milling schemes.
2.2.3. Get an individual assignment.
2.2.4. Assign the types of cutters taking into account the surface profile of the part of the individual task. Develop sketches of adjustments.
2.2.5. Assign the type of fixture for fixing the individual task on the machine.
2.2.6. Sketch a cylindrical cutter, specifying its constituent elements and geometric parameters.
2.2.7. Draw up a report on the work.
2.3. Materials and equipment
1. Horizontal milling machine model 6P80G.
3. Devices for fixing workpieces: clamping bars, clamps, rotary machine vices, prisms.
4. Drawing details of the individual task.
5. Posters.
Control questions
1. The main units of the machine model 6P80G and their purpose.
2. Classification of movements in the machine.
3. The main types of work performed on milling machines.
4. The main devices used when performing work on milling machines.
5. The main types of cutters.
6. Elements and geometrical parameters of cylindrical cutters.
LITERATURE
1. Dalsky A. M. Technology of structural materials. /, etc. - M .: Mechanical Engineering, 2008 - 560 p.
2. Fetisov and metal technology /, et al. - M .: Higher school, 2008. - 876 p.
MACHINING OF PARTS ON MILLING MACHINES
Methodical instructions
to laboratory work
Compiled by: ARTEMENKO Alexander Alexandrovich
BASKOV Lev Vasilievich
KONOPLYANKIN Sergey Vladimirovich
Reviewer
Editor
Signed for printing Format 60x84 1/16
Boom. type of. Service-print l. 1.16 (1.25) Uch.-ed. l. 1.1
Circulation 100 copies. Order Free
Saratov State Technical University
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Milling has been gaining in popularity lately, therefore it is just as in demand as drilling and turning. Its essence lies in cutting off a layer of metal using a rotating, gear cutter. Milling can be performed on workpieces made of different materials, and this is done both on special machines and manually.
Purpose of milling
With the help of various types of cutters, you can more accurately and efficiently milling parts. These can be of different materials, but the most common processing is on metals. And with the help of modern machine tools equipped with CNC systems, it is possible to reduce the number of rejects, as well as manage using simple numerical programs. Now the cutter has been replaced with a blade as a working tool, which made it possible to reduce the likelihood of rejects, making the workpieces as accurate as possible.
What is milling for processing? With its help, you can cut in metals, grind, apply special patterns, engrave, as well as do turning and other work in various activities. The set includes several multi-tooth cutting cutters, and their fastening in the machines determines the horizontal or vertical type of work. In production, milling at a certain angle can also be used, for which the cutter is pre-installed in the required direction. Depending on the type of processed product, such milling has several methods. But it is worth noting that a considerable number of various cutters are used, in particular, these are cylindrical, end, end, gear, shaped, and also more complex ones.
The spheres of application of milling are quite diverse; it can be used in metalworking, mechanical engineering, jewelry production, woodworking, and even in design and architecture.
Metal processing by milling is carried out regardless of its strength. Cutters are selected based on what kind of processing is needed, cylindrical or end types of cutters are used for planes, in the latter, asymmetric cutting patterns are selected. That is, if the parts are of the correct rectangular, square and similar shape, then these two methods are most often used. The same profile part can be made with a cylindrical cutter or from the end.
Milling cutting of aluminum is considered quite popular in our time, since aluminum is widely used in exclusive design, interiors, for advertising elements, camera equipment, etc. Due to its lightness, strength and low melting point, it is widely used and it is not difficult to cut various products. On the details of souvenirs, marketing and kitchen products on modern high-tech machines, you can make inscriptions, patterns, relief, etc. At the same time, they are obtained without burrs, the correct size and shape, as well as with perfect edges.
Volumetric milling of plastic, especially in 3D, has gained considerable popularity in our time. These are quite popular services that are used for industrial products, enclosures. Moreover, the details are quickly made, since the milling and engraving type machine works quite quickly, and the price for the work performed is low. Both spline and shaped and gear parts are processed, as well as processing of holes, ends, grooves. From plastic in 3D form, you can mill decorative and other parts, casting molds, polymer cases and much more, creating original and desired product shapes.
Classification of milling work
As already mentioned, depending on the cutter used, there are several types of milling, namely:
- Face milling, the essence of which is to obtain a certain shape of parts using an end mill. This is necessary in most cases for cutting undercuts, grooves, a window, as well as a "well", a groove, etc. in products. With its help, reverse milling of the end face from the inside of a different plan of products is also performed. End milling is needed to obtain parts with more accurate dimensions, ease of installation, and, in fact, cut ends serve to transmit compressive forces.
- End, which are needed for the formation of ledges in planes of a vertical or horizontal shape.
- Cylindrical, characterized by the production of products in planes with the corresponding milling cutter in the opposite position.
- Serrated.
- Shaped, which consists in creating shaped (spheres, ellipses, etc.) parts of irregular shape. This is milling with special cutters, resulting in shaped products.
Many other types of cutters are also common in different areas of activity, which are distinguished by their versatility, great capabilities and accuracy in performing work. Helical grooves are used to create countersinks, drills, etc. It is worth noting the difference between milling with double discs, a slotted blade for creating grooves in parts, as well as their more complex shapes. You can also create a specific shape with a short application of milling types.
In addition to the classification of milling by types of cutters, there is also a distribution of them into vertical arrangement in the machine, horizontal and at an angle.
Machine tools for such work, in turn, are divided into mechanical and laser. There is a direction of the cutting, driving element together with the product, which is called a passing type of processing. If the product moves towards the cutter, then it is considered to be counter milling.
It is also worth noting the profile milling of parts, both wood and metal, etc. This differs in products that are convex or concave. In this case, it is necessary to more carefully approach the choice of the technological type, which depends mainly on the size of the part and the complexity of the profiling. This type of process takes place in three stages: preliminary rough and partially clean milling, semi-clean and finally final clean. Often, to obtain high quality parts, finishing is performed with high feed rates, and the previous operations are performed separately on different machines.
Since for milling parts in a cylindrical way, it is performed with not so good fastening, then most often profile milling of products is done in an end way. Basically, it is a universal method for multi-batch industrial production. In this case, it is possible to use several methods of milling different flat surfaces. This is the use of two chisels, large diameter cutters and several chisels at the same time.
Work in this mode can be much faster and more relaxed, especially when using several cutters at once, located on different sides of the product. For this reason, surface milling with face mills is more commonly used in production.
Milling is carried out, in addition, also with the help of an ion beam. This is a relatively new and high-tech process that allows you to remove the most accurate metal layer. Ionic milling is carried out by the action of a helium atom on the surface, the main condition is the control of voltage and energy. In other words, today it is not necessary to polish or grind parts, it can be done at the atomic level, and additional parts can be inserted onto the hot metal.
Technological stages of the process
As for the technological process of milling, it consists of several sequences that must be followed:
- The product is carefully brought from the side of the surface required for processing to the router, which is rotating at this time.
- Having taken the table away, the spindle is turned off so that it does not rotate.
- After that, you need to set the required cutting depth.
- The spindle is started.
- The product, located on the table, is brought along with it to the docking with the cutter.
The processing of metal parts with a cylindrical cutter is carried out with a cutter length 10-15 mm more than the product is, and its diameter is selected based on the cutting thickness and width. Choosing end mills will make the job less noisy because the parts are more securely attached. The productivity of the enterprise will be high when using a set of cutters, since the task is greatly simplified. It all depends on the cutters used, and these are: joint cutters, chisels, with two discs at the same time, a set of cutters located on different sides of the workpiece, etc. Milling planes with several end mills makes several cuts at once, and also eliminates impacts during work.
Modern technologies make it possible to carry out safe and with a lower percentage of rejects processing on machines equipped with CNC systems. In some cases, as in the processing of parts of increased hardness, you can grind them on them. They guarantee products with the maximum exact geometrical shape as well as productivity. There are both special-purpose and general use, but small parts of the house can be processed with a hand-held electric router. Computer control allows you to set all the parameters and perform as accurately as possible, in addition, it is possible to calculate and create 3D models directly on the machine.
Thanks to modern technologies, milling is gaining great popularity in various industries. As for metal, it is possible to make both aluminum and steel, titanium products on machines. Regardless of the material, milling can be used to make special-purpose parts, exclusive, jewelry, etc. And only on machines equipped with CNC systems, it is possible to perform laser milling of complex-shaped parts. It is expensive, but high-quality processing is possible without preliminary grinding.
Processing workpieces on milling machines
Milling - blade cutting by cutting ruled surfaces with a multi-flute tool- milling cutter; the main movement, rotary, is imparted to the tool, the feed movement, rectilinear, is imparted to the workpiece in the direction of any of the coordinate axes.
The surface is called ruled, if it can be described by the motion of the straight line(generatrix) along some line (guide). It is a collection of straight lines depending on one parameter.
A milling cutter is a cylindrical multi-tooth tool with teeth at the end and / or generatrix.
Consider surface treatment schemes on universal horizontal milling (GFS; has a horizontal axis of rotation of the cutter) and vertical milling (VFS; has a vertical axis of rotation of the cutter) machines.
Horizontal planes are milled with cylindrical cutters on GFS(fig.10.40, a) or end mills on the VFS (Fig.10.41, a). Horizontal planes are more often processed with end shell cutters, since they have a more rigid fixation and provide a smooth, vibration-free cutting. With a large width of the processed plane, end mills are used and the processing is carried out in several successive working strokes. Narrow horizontal planes are convenient to machine with end mills.
Vertical planes on the GFS are processed with end shell cutters(fig.10.40, b) or milling heads, and on VFS - end mills (Fig.10.41, b). It is more convenient to process vertical planes large in height on the GFS using vertical feed. The processing of vertical planes of small height can be processed on the GFS using end or disc mills. Inclined planes of small width are processed on the GFS with a single-angle mill (Figure 10.40, v).
Wide inclined planes are processed on VFS with a turn of the spindle head(fig.10.41, v) with front attachment or end mills. Simultaneous processing of several surfaces (vertical, horizontal and inclined) is carried out at the GFS (Figure 10.40, G) by installing a set of cutters on the mandrel.
Horizontal ledges and grooves are processed with disc one-sided (Figure 10.40, d) and three-sided (Fig.10.42, a) with cutters on GFS or end mills (Fig.10.41, G; 10.42, b) at the VFS. Shaped grooves with a curved generatrix are processed on GFS with shaped disc cutters(fig.10.42, v). Dovetail or T-shaped grooves are processed on the VFS (Fig. 10.42, G, d). First, a rectangular slot is made with an end mill, then a single angle end mill or a special T-slot end mill is used. Keyways for segment keys are milled on GFS with a three-sided disc cutter (Fig.10.42, e), for rectangular keys - on the VFS with an end mill (Fig.10.42, f).
Rice. 10.40. Processing of planes on GFS: a- horizontal; b- vertical; v- inclined; G- several planes at the same time; d- ledges
Rice. 10.41. Processing of planes on VFS: a- horizontal; b- vertical; v- inclined; G- ledges
Rice. 10.42. Milling grooves: a, b- rectangular; v- semicircular; G- “dovetail” type; d- T-shaped; e, f- keyway
Rice. 10.43. Milling shaped surfaces: a, b- by copying with a cylindrical and end (finger) cutter, respectively; v- by copy
Shaped surfaces are processed by copying using shaped cylindrical(fig.10.43, a), disk or end (Fig.10.43, b) cutters, according to a copy on special copy milling machines (Fig.10.43, v) and by the rolling method on special machines.
