CNC boring and milling machine?

CNC milling machine is developed on the basis of ordinary milling machine. The processing technology of the two machines is basically the same, and the structure is somewhat similar. But the CNC milling machine is an automatic processing machine controlled by the program, so its structure is also very different from the general milling machine.

As shown in the figure, CNC milling machine is generally composed of CNC system, main transmission system, feed servo system, cooling and lubrication system, etc.

1. The headstock includes headstock and spindle drive system, which is used to clamp the tool and drive the tool to rotate. Spindle speed range and output torque have direct influence on machining.

2. The feed servo system consists of a feed motor and a feed actuator, and the relative motion between the tool and the workpiece is realized according to the feed speed set by the program, including linear feed motion and rotary motion.

3, control system CNC milling machine motion control center, the implementation of CNC machining program to control the machine tool for processing.

4, auxiliary devices such as hydraulic, pneumatic, lubrication, cooling system and chip removal, protection and other devices.

5. The basic parts of a machine tool usually refer to the base, columns, beams, etc. It is the foundation and framework of the whole machine tool.

[Edit this paragraph] Process equipment

The technological equipment of CNC milling machine mainly refers to fixtures and cutters.

1。 fastener

CNC machine tools are mainly used to process parts with complex shapes, but the fixture structure used is often not complicated. The choice of fixture for CNC milling machine can be determined according to the batch number of the parts produced first.

For single-piece, small-batch, heavy-workload mold machining, positioning and clamping can be realized directly on the machine tool workbench, and then the position of the parts can be determined by setting the machining coordinate system.

For a batch of parts, you can choose a fixture with simple structure. For example, when machining the cam surface of the cam part shown in figure 1, the cam fixture shown in figure 2 can be used. The two positioning pins 3 and 5 and the positioning block 4 form six-point positioning of the two pins on one surface, and the pressure plate 6 and the clamping nut 7 are clamped. In the figure: 1- cam part, 2- clamp body, 3- cylindrical locating pin, 4- locating block, 5- diamond locating pin, 6- pressure plate and 7- clamping nut.

Figure 1 cam parts drawing

Fig. 2 Cam clamp

2。 cutting machine

According to the material, geometry, surface quality requirements, heat treatment state, cutting performance and machining allowance of the parts to be processed, the tools used in the CNC milling machine should be selected with good rigidity and high durability. See Figure 3 for common tools.

Fig. 3 Common cutting tools

(1) milling cutter type selection

According to the geometric shape of the parts to be machined, the selected tool types are:

1) When machining curved parts, in order to [1] ensure that the cutting edge of the tool is tangent to the machining contour at the cutting point and avoid interference between the cutting edge and the workpiece contour, ball-end end end mills, two-edge milling cutters for rough machining and four-edge milling cutters for semi-finish machining and finish machining are generally adopted, as shown in Figure 4.

Fig. 4 Machining curved milling cutter

2) When milling a large plane: In order to improve the production efficiency and the roughness of the machined surface, a disc milling cutter with an insert is generally used, as shown in Figure 5.

Fig. 5 Machining large plane milling cutter

3) When milling facets or stepped surfaces, a general milling cutter is generally used, as shown in Figure 6.

Fig. 6 Machining step milling cutter

4) When milling the keyway, in order to ensure the dimensional accuracy of the groove, a double-edge keyway milling cutter is generally used, as shown in Figure 7.

Fig. 7 Machining slot milling cutter

5) When machining holes, drill bits, boring cutters and other hole machining tools can be used, as shown in Figure 8.

Drilling tool

Fig. 8 Hole Machining Tool

(2) Selection of milling cutter structure

Milling cutter generally consists of blade, positioning element, clamping element and cutter body. Because there are many ways to position and clamp the blade on the cutter body, and the types of blade positioning elements are different, there are also many structural forms and classification methods of milling cutter. When selecting, it can be mainly based on the arrangement of leaves. Blade arrangement can be divided into two categories: plane structure and vertical structure.

1) paperback structure (blades are arranged radially)

Fig. 9 Milling cutter with paperback structure

The cutter body structure of the paperback structure milling cutter (as shown in Figure 9) has good manufacturability, is easy to process, and can use a non-hole blade (the blade is cheap and can be reground). Because the clamping element is needed to cover a part of the blade, the chip space is small and the cemented carbide section in the cutting force direction is small, so the plane structure milling cutter is generally used for light and medium milling.

2) Vertical structure (tangential arrangement of blades)

Figure 10 Vertical Structure Milling Cutter

The blade of the vertical structure milling cutter (as shown in figure 10) is fixed on the cutter groove with only one screw, which has simple structure and convenient indexing. Although there are few tool parts, it is difficult to process the tool body, which generally requires five-axis machining center. Because the blade is clamped by cutting force, the clamping force increases with the increase of cutting force, so the clamping element can be omitted and the chip space can be increased. Due to the tangential installation of the blade, the section of cemented carbide in the cutting force direction is large, and it can be cut with large depth and large feed. This kind of milling cutter is suitable for heavy and medium milling.

(3) Selection of milling cutter angle

The angle of milling cutter includes rake angle, rake angle, main deflection angle, auxiliary deflection angle, edge inclination angle and so on. In order to meet different processing needs, there are various angle combinations. The main angles are the main deflection angle and the main rake angle (the main deflection angle and the main rake angle of the tool are generally clearly stated in the manufacturer's product samples).

1) main deflection angle Kr

The main deflection angle is the included angle between the cutting edge and the cutting plane, as shown in figure 1 1. The main deflection angles of the milling cutter are 90, 88, 75, 70, 60 and 45.

Figure 1 1 main deflection angle

The main deflection angle has great influence on radial cutting force and cutting depth. The radial cutting force directly affects the cutting power and the anti-vibration performance of the tool. The smaller the main deflection angle of the milling cutter, the smaller the radial cutting force and the better the vibration resistance, but the cutting depth also decreases.

The main deflection angle of 90 is selected when milling the shoulder plane, which is generally not used for pure plane machining. This kind of tool has good versatility (that is, it can process both step surface and plane), so it is selected in single piece and small batch processing. Because the radial cutting force of this tool is equal to the cutting force, the feed resistance is large and it is easy to vibrate, so the machine tool is required to have greater power and sufficient stiffness. When machining a plane with shoulders, you can also choose a milling cutter with a main deflection angle of 88. Compared with the milling cutter with the main deflection angle of 90, its cutting performance has been improved.

The main deflection angle of 60 ~ 75 is suitable for rough machining of plane milling. Because the radial cutting force is obviously reduced (especially at 60), its vibration resistance is greatly improved, and the cutting is smooth and light, so it should be the first choice in plane machining. The 75 main deflection angle milling cutter is a universal tool with a wide range of applications. 60 main deflection angle milling cutter is mainly used for rough milling and semi-finish milling of boring and milling machines and machining centers.

The radial cutting force of the milling cutter with the main deflection angle of 45 is greatly reduced, which is about equal to the axial cutting force. The cutting load is distributed on a long cutting edge, which has good vibration resistance and is suitable for machining occasions where the spindle of boring and milling machine is suspended for a long time. When machining plane with this tool, the damage rate of the blade is low and the durability is high; When processing iron castings, the edge of the workpiece is not easy to collapse.

2) rake angle γ

The rake angle of milling cutter can be divided into radial rake angle γf and axial rake angle γp, and the radial rake angle γf mainly affects the cutting power. The axial rake angle γp affects the chip formation and the direction of axial force. When γp is positive, the chips will fly away from the machined surface. See figure 12 for the positive and negative discrimination of radial rake angle γf and axial rake angle γ p. ..

Figure 12 front angle

Commonly used rake angle combinations are as follows:

Double negative rake angle milling cutter usually adopts square (or rectangular) blades without rake angle, with many cutting edges (usually eight), high strength and good impact resistance, which is suitable for rough machining of cast steel and cast iron. Because the chip shrinkage rate is large and the cutting force is large, the machine tool is required to have high power and high rigidity. Because the axial rake angle is negative, chips cannot flow out automatically, and chip accumulation and tool vibration are easy to occur when cutting ductile materials.

When machining with double negative rake angle milling cutter, in order to make full use of and save blades, it is suggested that double negative rake angle milling cutter should be preferred. When using double positive rake angle milling cutter to produce edge collapse (that is, large impact load), double negative rake angle milling cutter should also be preferred if the machine tool allows.

Double positive rake angle Double positive rake angle milling cutter adopts blade with rake angle, with small wedge angle and sharp cutting edge. Because the chip shrinkage ratio is small, the cutting power consumed is small, and the chips are discharged in a spiral shape, so it is not easy to form chip accumulation tumors. This kind of milling cutter is most suitable for cutting soft materials and stainless steel, heat-resistant steel and other materials. For machine tools with poor rigidity (such as boring and milling machines with extended spindle) and low power, and when processing welded structural parts, double positive rake milling cutters should also be preferred.

Positive and negative rake angle (axial positive rake angle and radial negative rake angle) This kind of milling cutter combines the advantages of double positive rake angle and double negative rake angle milling cutter, and axial positive rake angle is beneficial to the formation and discharge of chips; Radial negative rake angle can improve the strength and impact resistance of the blade. This kind of milling cutter has the advantages of smooth cutting, smooth chip removal and high metal removal rate, and is suitable for large margin milling. The tangential tooth distribution heavy cutting milling cutter F2265 of Walter Company is a milling cutter with positive axial rake angle and negative radial rake angle.

(4) Selection of number of teeth (pitch) of milling cutter

The number of teeth of milling cutter can improve the production efficiency, but due to the limitation of chip space, cutter tooth strength, machine tool power and stiffness, the number of teeth of milling cutter with different diameters is also adjusted accordingly. In order to meet the needs of different users, there are generally three kinds of milling cutters with the same diameter: coarse teeth, medium teeth and dense teeth.

Coarse tooth milling cutter is suitable for large margin rough machining of ordinary machine tools and milling of soft materials or large cutting width; When the power of the machine tool is small, in order to make the cutting smooth, coarse tooth milling cutter is often used.

Medium-tooth milling cutter is a universal series with wide application range, high metal removal rate and cutting stability.

Close-tooth milling cutter is mainly used for AG feed cutting of cast iron, aluminum alloy and nonferrous metals. In specialized production (such as assembly line processing), in order to make full use of equipment power and meet the requirements of production rhythm, dense tooth milling cutters (mostly special non-standard milling cutters at this time) are often selected.

In order to prevent the vibration of the process system and make the cutting smooth, there is also a non-equidistant milling cutter. For example, NOVEX series milling cutters of Walter Company all adopt unequal pitch technology. It is suggested that unequal pitch milling cutters should be preferred in rough machining of large margin steel castings and iron castings.

(5) Selection of milling cutter diameter

The choice of milling cutter diameter varies greatly with different products and production batches, and the choice of cutter diameter mainly depends on the specifications of the equipment and the machining size of the workpiece.

1) face milling cutter

When selecting the diameter of the plane milling cutter, it is mainly to consider that the power required by the cutter should be within the power range of the machine tool, and the diameter of the spindle of the machine tool can also be used as the basis for selection. The diameter of the plane milling cutter can be selected according to d = 1.5d (d is the spindle diameter). In mass production, the tool diameter can also be selected according to 1.6 times the cutting width of the workpiece.

2) End milling cutter

The selection of end milling cutter diameter should mainly consider the requirements of workpiece machining size, and ensure that the power required by the cutter is within the rated power range of the machine tool. If it is a small-diameter end milling cutter, it is mainly considered whether the maximum revolution of the machine tool can reach the minimum cutting speed of the cutter (60m/min).

3) Slot milling cutter

The diameter and width of the slot milling cutter should be selected according to the size of the workpiece to be machined, and the cutting power should be within the power range allowed by the machine tool.

(6) Maximum cutting depth of milling cutter

Different series of indexable surface milling cutters have different maximum cutting depths. The greater the maximum cutting depth, the larger the blade size used by the tool and the higher the price. Therefore, from the perspective of cost saving and cost reduction, the appropriate specifications should be selected according to the maximum machining allowance and maximum cutting depth of the tool. Of course, it is also necessary to consider the rated power and stiffness of the machine tool to meet the needs of the maximum cutting depth of the tool.

(7) the choice of blade brand

The main basis for selecting the cemented carbide brand of the blade reasonably is the properties of the processed material and cemented carbide. Generally, when choosing a milling cutter, the corresponding brand of cemented carbide blades can be equipped according to the processing materials and processing conditions provided by the cutter manufacturer.

Due to the different compositions and properties of similar cemented carbides produced by different manufacturers, the expression of cemented carbide brands is also different. For the convenience of users, the International Organization for Standardization stipulates that cemented carbide used for cutting can be divided into three categories: P, M and K according to its chip removal type and processing materials, and each category is divided into several groups according to processing materials and applicable processing conditions, which are represented by two Arabic numerals. The larger the number in each category, the lower the wear resistance and the higher the toughness.

P-type alloys (including cermets) are used to process metal materials that produce long chips, such as steel, cast steel, malleable cast iron, stainless steel and heat-resistant steel. Among them, the greater the number of groups, the greater the selectable feed and cutting depth, and the smaller the cutting speed.

M-type alloy is used to process black or non-ferrous metals that produce long and short chips, such as steel, cast steel, austenitic stainless steel, heat-resistant steel, malleable cast iron and alloy cast iron. Among them, the greater the number of groups, the greater the selectable feed and cutting depth, and the smaller the cutting speed.

K-type alloy is used to process ferrous metals, nonferrous metals and nonmetallic materials to produce short chips, such as cast iron, aluminum alloys, copper alloys, plastics and phenolic plastics. Among them, the greater the number of groups, the greater the selectable feed and cutting depth, and the smaller the cutting speed.

Although the cemented carbides produced by each factory have their own brands, they all have classification numbers corresponding to international standards, which is very convenient to choose.

Selection of CNC milling machine

1: Select according to the size of the machined part.

The workbench width of CNC milling machine with small lifting table is mostly below 400mm, which is most suitable for contour milling of small and medium-sized parts and complex surfaces. The workbench of large milling machines such as gantry milling machines is mostly 500-600 mm, which is used to solve the processing needs of large-size complex parts.

2. Select according to the accuracy requirements of the machined parts.

China has established the precision standard of CNC milling machine, among which the CNC vertical milling machine has professional standard. The standard stipulates that the positioning accuracy of its linear motion coordinates is 0.04/300mm, the repetitive positioning accuracy is 0.025mm, and the milling accuracy is 0.035mm. In fact, the factory accuracy of the machine tool is quite reserved, which is about 20% lower than the tolerance value of the national standard. Therefore, from the perspective of precision selection, the general CNC milling machine can meet the processing needs of most parts. For parts with high precision requirements, we should consider the precision CNC milling machine.

3. Choose according to the processing characteristics of the parts to be processed.

For frame-shaped plane or unequal-height steps, CNC milling machine with point-and-line system can be selected.

If the machined part is a surface contour, two-coordinate linkage system and three-coordinate linkage system should be selected according to the geometric shape of the surface.

According to the requirements of parts processing, CNC dividing head or CNC turntable can be added on the basis of ordinary CNC milling machine. At this time, the machine tool system is a four-coordinate numerical control system, which can process spiral grooves, blade parts and so on.

4. Choose according to the batch number of the parts or other requirements.

For large quantities, users can use special milling machines. If it is small and medium batch, and it is often put into production periodically, it is very suitable to use CNC milling machine, because many fixtures and programs prepared in the first batch can be stored and reused. In the long run, it is inevitable that the milling machine with high degree of automation will replace the ordinary milling machine, reduce the workload of workers and improve productivity.

borer

Boring machine Boring machine is mainly a machine tool for boring workpieces with boring knives. Usually, the rotation of boring tool is the main movement, and the movement of boring tool or workpiece is the feeding movement. Its machining accuracy and surface quality are higher than that of drilling machine. Boring machine is the main equipment for processing large box parts.

Machining features: during machining, the workpiece is not moving, so the tool moves, the center of the tool is aligned with the center of the hole, and the tool rotates (main movement).

(1) horizontal boring machine

It is one of the most widely used boring machines. Mainly processing holes, the boring accuracy can reach IT7, the surface roughness Ra is 1.6-0.8um, and the main parameter of the horizontal boring machine is the spindle diameter.

(2) Coordinate boring machine

Coordinate boring machine is a high-precision machine tool. Its structural feature is a precise measuring device of coordinate position. Coordinate boring machines can be divided into single-column coordinate boring machines, double-column coordinate boring machines and horizontal coordinate boring machines.

Single-column coordinate boring machine: the spindle drives the cutter to rotate, and the spindle sleeve moves axially. Features: simple structure, convenient operation, especially suitable for machining precision holes of plate parts, but its rigidity is poor, so this structure is only suitable for small and medium-sized coordinate boring machines.

Double-column coordinate boring machine: the cutter is installed on the spindle as the main movement, and the workpiece is installed on the workbench and moves vertically and linearly along the guide rail of the lathe bed with the workbench. Good rigidity. At present, large-scale coordinate boring machines all adopt this structure. The main parameter of double-column coordinate boring machine is the width of table.

Horizontal coordinate boring machine: the worktable can rotate in the horizontal plane, and the feeding movement can be realized by the longitudinal movement of the worktable or the axial movement of the spindle. Its processing precision is high.

(3) Diamond boring machine: It is characterized by small feed and fast cutting speed, so the machined workpiece has high dimensional accuracy (IT6) and the surface roughness can reach 0.2 micron.

To add:

1.

condition

Boring machine refers to a machine tool that mainly uses boring tools to process the existing prefabricated holes on the workpiece. Usually, the boring cutter rotation is the main movement, and the boring cutter or workpiece movement is the feed movement. It is mainly used for machining high-precision holes or finishing multiple holes at one time, and can also be used for machining other machined surfaces related to hole finishing.

2. It varies according to the structure and processing object.

(1) Horizontal boring machine: the boring shaft is arranged horizontally and fed axially. The headstock moves vertically along the guide rail of the front column, and the workbench moves vertically or horizontally for boring. This machine tool is versatile and economical. It is mainly used for hole machining of box (or bracket) parts and other hole-related machining surfaces.

(2) Coordinate boring machine: a boring machine with precise coordinate positioning device, which is mainly used for boring holes with high requirements on size, shape, especially position accuracy, and can also be used for precise coordinate measurement, template marking and calibration.

(3) Fine boring machine: a boring machine that performs precise boring with tools such as diamond or cemented carbide.

(4) Deep hole boring machine: a boring machine for boring deep holes.

(5) Floor boring machine: the workpiece is placed on the floor table, and the column moves longitudinally or transversely along the bed. Used for machining large workpieces.

In addition, there are milling and boring machines that can be used for milling, or deep-hole drilling and boring machines that can be used for drilling.

3. Inspection standard

The inspection standards of boring machines are as complete as those of other metal cutting machines, including relevant standards, special standards and quality grading standards, and the exported products should reach the first-class products. Its special standards mainly include JB2253-85 coordinate boring machine parameters, JB3753-84 vertical coordinate boring machine 3220 cone hole vertical shaft end, JB2255-85, ZBJ54022-89 coordinate boring machine accuracy and technical conditions, JB2254-85 coordinate boring machine accuracy, JB GB/T14660-90. 8-88JB4366. 1-86 "End Dimensions of Boring Shaft of Floor Milling and Boring Machine", JB4366.2-86 "End Dimensions of Milling Shaft of Floor Milling and Boring Machine", JB/GQ 1090-86 "Accuracy of Fixed Platform of Machine Tool", JB4070-85, JB JB/T4289.2-94 Technical specifications of vertical fine boring machine JBJ5 1003. 1-88, ZBJ51003.2-85-85 Boring head parameters and technical specifications of vertical fine boring machine JB/T5765-9 1. JB5564-9 1 horizontal fine boring machine accuracy, JB /T540 10-93 horizontal fine boring machine technical conditions, ZBJ52004-88, ZBJ5 1002-88 horizontal fine boring machine and boring head accuracy and technical conditions, etc.

4. Inspection items

The related standard inspection items are similar to other metal cutting machine tools. The professional standard inspection items are mainly accuracy and performance, which can be summarized as: the accuracy of the power head for installing the tool, the accuracy of the workbench for installing the workpiece, the mutual position accuracy of the two along the lathe bed, the column and the gantry guide rail, and the machining accuracy. And the inspection must also refer to JB2670-82 General Rules for Precision Inspection of Metal Cutting Machine Tools.