Application of high-speed five-axis machining center in automobile mold manufacturing

Introduction: Nowadays, automobile molds have increasingly higher requirements for the surface quality and cutting speed of molds. The best cutting state can be achieved when using a five-axis CNC system to process planes with three-dimensional curves. Different geometric shapes can be processed by changing the setting angle of the tool axis at any position within the machine tool processing area.

Three-axis machining center for deep cavity mold processing

The design of automobile parts is mainly completed by CAD systems, reverse engineering and various tests. The processing procedures for the complex surface of the mold come from CAM software. However, how to ensure the accuracy of design and processing depends on CNC machining. Let’s discuss some five-axis processes in mold processing. The relationship between the application of CNC systems and the quality of molds.

Comparative application of three-axis machining and five-axis machining molds

Three-axis machining centers can only process deep-cavity molds by lengthening the tool shank and cutting tools (see Figure 1). However, when processing deeper and steeper cavities, five-axis machining centers can add additional components to the workpiece or spindle head. Rotation and swing create the best process conditions for processing, shorten the tool length appropriately, and avoid collisions between the tool and tool shank and the cavity wall, reduce tool jitter during processing and the risk of tool breakage, thereby improving the surface quality of the mold. , machining efficiency and tool life (see Figure 2).

When using a three-axis machining center to process the side wall of a mold, the depth of the side wall determines the length of the tool. The tool length must be greater than the depth of the side wall. When the tool length increases, the strength of the tool will be reduced. If the tool length exceeds 3 When the diameter is doubled, the tool will give way, making it difficult to ensure the quality of the workpiece (see Figure 3). When using a five-axis machining center to process the side wall of the workpiece, you can swing the workpiece or the spindle to make the tool perpendicular to the side wall of the workpiece, and then use a plane milling cutter to mill the side wall, which can ensure the quality of the workpiece and extend the tool life (see Figure 4).

When using a three-axis machining center to process a relatively flat curved surface, a ball cutter should be used for fine milling to obtain better surface quality, so the tool path should be increased. But as we all know, the linear speed of the tool center rotation of the ball-nose tool is close to zero, so it causes great damage to the tool during processing, shortens the tool life, and worsens the surface quality (see Figure 5). When using a five-axis machining center to process a relatively flat curved surface, in order to increase the relative linear speed between the ball-end cutter and the workpiece, the cutter is machined at a certain angle on the workpiece as shown in Figure 4, so that the distance between the ball-end cutter and the workpiece is increased. The relative linear speed increases, which can not only improve the life of the tool, but also improve the surface quality of the workpiece (see Figure 6).

In addition, when machining a normal hole on an inclined surface in a five-axis machining center, the machining action in a swing-head machine tool is to place the spindle in a direction perpendicular to the slope on the workpiece by swinging the head and then position it to the position of the hole. It is necessary to process the hole. At least two linear axis interpolation movements can be used to process oblique holes, which greatly reduces the accuracy of the holes. When using a swing-table five-axis machining center for bevel hole processing, the action is to place the slope on the workpiece in a direction perpendicular to the spindle through the swing table. During hole processing, only one linear axis movement of the spindle is required, which greatly improves the processing efficiency. Hole accuracy (see Figure 7).

Other advantages of five-axis machining systems

Nowadays, automobile molds have increasingly higher requirements for the surface quality and cutting speed of molds. The best cutting state can be achieved when using a five-axis CNC system to process planes with three-dimensional curves. Different geometric shapes can be processed by changing the setting angle of the tool axis at any position within the machine tool processing area. Irregular curved surfaces with the same shape are usually processed with three axes. The direction of the cutting tool remains unchanged during the movement along the entire cutting path. The cutting state of the tool tip cannot always be perfect in all parts of the entire curved surface.

For deep grooves or surfaces that frequently change curvature, a five-axis CNC system is required for processing. The direction of the tool or the position of the workbench can be changed. The cutting tool can always maintain the best cutting state while moving along the entire processing path. The tool direction can be optimized while the tool moves linearly, so that perfection is achieved in all parts of the entire curved surface. If you want to mill a straight line with no change in direction, just draw a straight line on the tool holder. If the direction changes at the same time, the tool tip draws a curve. If the tool tip can draw the required straight line when the direction changes, this curve must be compensated, which is a crucial point in five-axis machining. The tool rotates around the center of the axis without the control system taking the tool length into account. The tip of the knife will move out of its position and is not fixed. However, a five-axis control function has been added to the control system. The control system only changes the direction of the tool, and the tool tip position remains unchanged. Necessary compensation movements on the X, Y, and Z axes have been automatically calculated to ensure machining accuracy.

Basic shape milling of electrolytic red copper thin-walled electrodes

Curved thin-walled electrodes are widely used in the manufacturing of injection molds and die-casting molds. Their function is to form the sheet shape of products, such as heat sinks in motorcycle engines, aluminum alloy heat sinks in computer cases, and power supply heat dissipation windows in audio products. Shape etc.
1. The general characteristics of curved thin-walled electrodes are:

1. The electrode height is high, and the highest point is 22.0mm from the base plane.

2. The thickness of the electrode sheet is small, 1.5mm.

3. The top of the electrode is curved and must be finished with a spherical knife.

4. The distance between the sheets is 5.0mm. For narrow grooves, only tools with smaller diameters can be used to process the sheet shape.

2. Milling processing requirements for curved thin-walled electrodes:

1. Most of them are composed of narrow grooves and flakes with a certain height and even arrangement, and the top is in the shape of a complex curved surface;

2. Made of electrolytic red copper, the copper material has strong ductility.

3. When using a machining center or CNC milling to process the shape and the top of the curved sheet, it is easy to cause deformation and bending;

4. There are high requirements for process planning, cutting amount, and CAD/CAM programming parameter settings.

Based on the above characteristics, MasterCAM9.1 is used for programming and a machining center is used for milling. The following process steps are applied for CNC machining:

3. Basic shape processing

Because the electrode only needs to process the front side, the blank copper material is directly clamped on the flat-nose pliers (the flat-nose pliers have been calibrated) to start centering and setting the tool. After setting the tool, the first step is to use the pocket plane grooving method to remove the material in the area around the sheet.

Using imported ultra-fine particle full tungsten steel cutters, the amount of tool wear is extremely small, so the tool is not changed after rough machining, but the Contour machining method is directly used to finish the outer shape and lower datum down to size. The tool is φ16mm, the roughing tool speed is n=1200r/min, the cutting amount of each layer is 1.0mm, and the feed speed is νf=1000mm/min. The finishing speed n=1500r/min, the cutting amount on the back of each layer is 11.0mm, and the feed speed νf=300mm/min. The outline has been processed with an electric spark gap of 0.1mm on one side; temporarily retain the thin parts and the materials between the thin parts. The lower base is the reference centering frame during EDM, and the bevel is used to determine the direction of the electrode.

Milling of thin-walled electrode curved surfaces

The curved surface milling process of electrolytic red copper thin-walled electrodes is divided into two parts:

1. Rough milling of electrode surface

Use SurfaceRoughPocket programming, that is, surface roughing, to perform surface rough milling. In order to save time, we continue to use a φ16mm end mill, with a rotation speed of 1200r/min, a feed speed of νf=1000mm/min, and a cutting amount of 0.7mm on each layer.

2. Electrode surface finishing

Use the SurfaceFinishParallel programming method to finish the curved surface, using a two-edged spherical milling cutter with a diameter of φ10mm; the tool speed is 2300r/min; the feed speed is 1000mm/min; the feed angle is 315°; in order to ensure sufficient accuracy and good quality of the curved surface The surface quality of the surface, the Tolerance value of the surface accuracy parameter is set to 0.005, and the infeed distance of each line is 0.15mm.

Tool path simulation effect during machining. If surface rough machining is performed directly (i.e., the second step of SurfaceRoughPocket processing) and surface fine milling is performed directly, the cutting amount of fine milling with a φ10mm spherical cutter will be larger, the tool vibration will be large, and the surface roughness value will be reduced. Increasing the diameter will not achieve the purpose of rapid precision milling and may even cause the tool to break. The purpose of adopting an infeed angle of 315° is to make the spacing between processing rows uniform, to achieve good cutting fluid flushing effect, and to improve the surface quality of the workpiece.

Thin-walled electrode surface finishing

After finishing the curved surface, finish the thin-walled shape. If you machine the outline first and then the top curved surface, the thin-walled shape will be too high at this time. Under the action of the cutting force of the tool, the top of the copper electrode will often deform and bend, causing Processing failure is also the most common problem in sheet electrode processing. At the same time, due to the 5.0mm narrow groove between the sheets, only smaller diameter tools can be used to process the shape of the sheets. Therefore, an end mill with a diameter of 4.0mm is used, the rotation speed is 2000r/min, and the feed speed νf=400mm/min. After processing the curved surface and then processing the electrode shape, it is also necessary to pay attention to the cutting depth each time. The tool diameter is small and the clamping The length is longer (greater than the electrode height, which is 26.0mm). Therefore, it is easy to cause over-cutting by grabbing the knife; the amount of cutting on the back of each layer is only 0.4mm; while the rotation speed and feed speed should be higher to achieve a certain efficiency.

1. Setting of specific paths

Among them, the shape machining allowance parameter (XYstocktoleave) is -0.1mm, which is the spark machining gap reserved for the electrode. The tool lift selection parameter (Keeptooldown) is selected to not lift the tool. Because the tool is cut outside the contour, it has been determined that the tool is cut in a safe empty position, so there is no need to set the tool lift to save tool idle running time and improve efficiency.

2. Process route planning

The process route planning of curved thin-walled electrode processing plays a decisive role in the success or failure of the processing. The same processing method and parameter settings are carried out in different processing sequences, and the results obtained are completely different. Process plan: rough milling of the shape, frame processing → contour roughing of the curved surface → finishing of the curved surface → finishing of the thin-walled shape.

Five-axis high-speed milling of typical aircraft fuselage parts

The structural characteristics of typical aircraft parts are thin-walled structures, complex shapes, large changes in bevel angle, and mostly hyperboloid shapes, which require precise forming. In order to reduce the weight of the aircraft, increase its maneuverability and increase its payload and range, lightweight design is carried out and new lightweight materials are widely used. In order to improve the strength and working reliability of parts, overall blank parts and overall thin-walled structures are mainly used. Nowadays, aluminum alloys, titanium alloys, high-temperature resistant alloys, high-strength steels, composite materials, etc. are widely used. Thin-walled parts and honeycomb parts with complex structures not only have complex shapes, but also have many holes, cavities, grooves, ribs, etc., and have poor process rigidity.

1. Typical parts of fuselage structural parts

Typical parts of aircraft fuselage structural parts include beams, ribs, ribs, frames, wall panels, joints, slide rails and other parts. Mainly flat parts, slender parts, multi-cavity parts and ultra-thin wall partition frame structural parts. The blanks are plates, forgings and aluminum alloy extruded profiles. The material utilization rate is only about 5%-10%, and the amount of raw materials removed is large. At present, more than 90% of domestic aircraft parts are aluminum alloy parts, with a small amount of stainless steel and titanium alloy steel, and there are more and more overall structural parts. The application of composite materials is the future development direction.

2. Structural characteristics of typical parts of fuselage structural parts

1. The outline size of parts is getting larger and larger. For example, the length of some beam parts has reached 13m.

2. The bevel angle of parts changes greatly, and the walls are ultra-thin. The thinnest part is only about 0.76mm, so the processing technology has poor rigidity.

3. The structure of parts is becoming more and more complex, and many parts adopt overall structures.

4. The requirements for dimensional accuracy and surface quality of parts are getting higher and higher. For example, defects such as burrs that appear after processing of some parts are not allowed to be removed manually.

3. Machining center machine tools for milling typical parts of the fuselage

1. Three-coordinate machining center, such as large gantry vertical machining center;

2. Five-axis linkage machining centers, such as large gantry vertical machining centers, should be equipped with A/B swing angle milling heads or A/C swing angle milling heads;

3. From development considerations, a large-scale gantry-type dual-spindle five-coordinate machining center with a workbench size of 5m × 20m is needed for processing beam parts;

4. Processing aluminum alloy parts requires a high-power high-speed machining center with a power of ≥40kW, a spindle speed of more than 20,000r/min, and a two-coordinate swing angle milling head;

5. Due to the large amount of removal in the cutting of integral aluminum alloy parts, in order to facilitate chip removal, it is best to require a horizontal machining center with a worktable that can be turned 90°;

There are many types of aircraft fuselage structural parts with different shapes, and the process rigidity is poor, requiring a large number of fixtures. In order to reduce costs and shorten the production preparation cycle, various flexible fixtures are needed.

High-speed five-axis milling of aircraft engine casings

The key parts of the aircraft engine include the casing, various blades and the blisk.

There are three types of aircraft engine casings:

1. Split ring structure,

2. Overall ring structure,

3. Special-shaped shell.

The casing material is a high-strength titanium alloy material that is difficult to process and resistant to high temperatures. The receiver is a thin-walled, weakly rigid structure with complex shapes, high precision requirements, and difficult processing.

The casing is a large part. The diameter of the casing of an aeroengine with a thrust of 15,000 kg is φ800mm. The overall dimensions of the large fan casing of a large aircraft are φ1823.5mmx546mm, and the wall thickness at the thinnest point is 3mm. Therefore, casing processing requires medium and large multi-functional, high-precision CNC machine tools.

For example, CNC vertical lathes and precision CNC vertical lathes with a diameter of φ2000mm; a gantry-type five-axis linkage machining center with a workbench size of 2400mm × 5000mm must have dual stations, online measurement and simulation functions, and a tool magazine with a capacity of about 60 tools , CNC system with advanced programming functions, a gantry CNC boring and milling machine with a workbench of 3000mm×5000mm.

Application of five-axis high-speed machining center in automobile panel mold

High-speed cutting theory is increasingly accepted with the development of CNC machining equipment and high-speed machining tool technology; high-speed cutting is a comprehensive concept that involves many different technical fields. Its emergence has caused the traditional machining concept to change. Fundamental changes. Faced with such a new processing technology, how to effectively use it is a new challenge for the automotive mold manufacturing process.

1. Automobile panel molds have their own manufacturing characteristics, which are mainly reflected in:

The shape of the working part of the mold is composed of non-mathematical curved surfaces. The surface is required to be smooth, smooth, without ripples, and with clear ridges. Because an automobile panel part usually requires several sets of molds to complete, and each working surface must conform to the same requirements. A mathematical model, therefore, its surface roughness and shape accuracy requirements are very high. There are multiple different punching directions in the wedge type mold, which requires the manufacturing equipment to have the function of any rotation angle.

2. Performance of high-speed milling equipment

The main process performance of our company’s five-axis high-speed milling equipment: the maximum spindle speed is 18000r/min, the maximum spindle feed speed is 25m/min, the A-axis rotation angle is ±110 degrees, the C-axis rotation angle is ±360 degrees, axial and radial directions Depth of cut ≤ 0.3 mm, the length of the installed tool should not be greater than 300mm, the weight should not exceed 5kg, and five-axis linkage is possible

Features of high-speed milling: Due to high speed, fast feed, and small cutting volume, the cutting force is small, the cutting temperature is low, and the tool deflection is small. It can obtain a high processing surface finish and high processing efficiency; but it requires uniform cutting load.

3. Design of high-speed milling process

The processing of automobile panel mold parts is mainly based on the profile, and is divided into three stages: rough machining, semi-finishing and finishing according to different processing purposes.

1. Rough machining

Aiming at the maximum amount of material removal per unit time, the surface quality and shape accuracy requirements are not high. Since most of the workpieces are castings, the machined surface layer has many hard points and is uneven, and the company has few high-speed milling equipment. We use powerful milling CNC equipment for rough machining, and choose Φ63R8 ring milling cutter for contour cutting.

2. Semi-finishing

Eliminate the errors left by rough machining, achieve a certain degree of accuracy in shape, make the finishing allowance more uniform, and prepare for high-speed finishing. Since the margin left after rough machining is a zigzag shape, especially the margin at the corners, conventional CNC equipment is still used and a Φ30 ball end milling cutter is selected for semi-finishing. The process method is: first use a small-diameter ball-end milling cutter to evenly clean the margin at the corner, and then use a Φ30 ball-end milling cutter to perform combined processing on large surfaces.

3. Finishing

Remove the semi-finishing allowance to make the surface accuracy meet the technical requirements. High-speed milling equipment is used for finishing, and a Φ20 ball-end milling cutter is selected for parallel line cutting to obtain a high-quality working surface and reduce the amount of grinding and preparation required by the fitter.

The choice between three-axis linkage milling and five-axis linkage milling in finishing: Since curved surface processing is a point contact milling method, and the curvature of the mold surface changes greatly, when using a ball-end milling cutter for three-axis linkage milling, the tool and the workpiece The contact point changes with the change of curvature. The cutting speed at the tool tip point is zero and the cutting force is minimum. The participation of this point in cutting will reduce the quality of the machined surface and increase the wear of the blade. At the same time, the Z-direction stress on the machine tool spindle will increase. . The cutting speed is the largest at the radial point of the tool, and its cutting force is the largest. Participating in cutting at this point will also accelerate the wear of the blade there. (The picture shows the failure mode of the blade during three-axis linked cutting) In other words, the cutting force is constantly changing during the entire cutting process. The larger the tool diameter, the greater the change in cutting force. Therefore, small-diameter ball-nose tools should be selected as much as possible to reduce changes in cutting force. However, for steep wall machining, small diameter and long tool shank are not conducive to high-speed machining.

Compared with three-axis linked milling, five-axis linked milling has certain advantages. It can always maintain a certain angle (or a certain range) between the tool axis and the workpiece surface through the movement of the two rotating axes, avoiding the maximum cutting speed point and the cutting speed zero point, so that the cutting force can maintain a certain stability, and the machining of steep walls can be maintained. There is no need to lengthen the tool holder. For contour surfaces and holes with multiple different punching directions on the mold, using five-axis linkage milling can also simplify the processing process and reduce auxiliary time such as tool alignment. However, the spindle of the five-axis linkage equipment is too large, and the diameter of the clamped tool is small and short, which may interfere with the workpiece during processing, which limits its rotation angle. It is difficult to process parts such as narrow and deep valleys and deep cavities. .

Therefore, the five-axis linkage milling method in the manufacturing of automobile exterior panel molds is currently mainly used in mold parts with relatively flat surfaces, small curvature and little change, such as automobile exterior panel molds. However, many automobile exterior cover parts have complex shapes and large changes in curvature.

Process arrangement of five-axis milling of square steel blades

Leaves can basically be divided into three parts: root, body and crown.

Generally, square steel blades have single T or double T-shaped blade roots, with at least two or more blade root grooves, as well as the inlet and outlet side planes and the inner back radial plane;

The blade body is composed of several profile lines, which are divided into four parts: inner arc, back arc, steam inlet edge, and steam outlet edge;

The uppermost part is the blade crown. Like the blade root, the two sides and the inner and back radial surfaces must also be processed; the area where the profile and the blade root and blade intersect is transitioned by a rounded corner, which is called a turn. catch.

When preparing a blade, the first thing to consider is the formulation of a process plan. Based on the structural characteristics of the product as well as the accuracy level and technical requirements, the most stable clamping method and the most reasonable processing method are determined, such as the high-pressure of a combined cycle unit. For moving blades, the most demanding requirements should be the size of the two sides and the pitch between the inner radial surfaces, as well as the position between the blade root and the blade crown. The most basic clamping method is one clamp and one top. However, in order to ensure the consistency of the process datum, the positioning process boss and center hole are first processed on the vertical machining center, and then the entire process is carried out based on the processed positioning datum. Processing of blades. In order to ensure the accuracy of both sides and pitch, these parts are processed with the same precision milling cutter, and online measurement is used. The two sides of the blade root or blade crown are processed first, measured online, and the tool length is adjusted. Align the two sides, and then use the adjusted tool length to process the inner radial surface of the corresponding part to ensure the pitch requirements.

The entire process is arranged as follows:

1. On the five-axis vertical machine tool, in one clamping process, the clamping process boss of the square steel is first processed, and then the center drill is used to process the center holes for positioning at both ends. This fully ensures the consistency of all process benchmarks;

2. Position the process boss and the center hole, and clamp it on the five-axis machine tool by pressing one end and tightening the other;

3. After the clamping is firm, first clear up the entire wasteland to remove a large area of margin;

4. Rough machine the two sides of the tip of the tailstock and the inner back radial surface, then use a fine milling cutter to finish machining the two sides at a slightly larger amount, measure online, compare it with the nominal size after the increased amount, and adjust the tool length accordingly. Then process until the two sides are accurate; then use the last adjusted tool length to finely mill the inner back radial surface of the tailstock side;

5. Repeat the above steps and the method of online measurement and adjustment of the knife length to accurately determine the two sides of the drive end clamp and the inner radial surface of the part;

6. Then rough mill the profile and transfer the two transition fillets, leaving a margin of 0.5 to 1MM on one side;

7. Then rough and fine mill to process the blade root groove and steam seal as well as each chamfer and process groove;

8. Rotary machining and fine milling of the profile, as well as two transfers; if the margin is large, you can also add one step of semi-finishing;

9. Finally, mill out the blade top and blade root bottom surface, and use a keyway milling cutter to drill out the semicircular groove on the blade root bottom surface to complete the processing of all parts.

For large-area land reclamation, rough milling of both sides, radial surfaces and rough milling profiles, the same φ40MMR6 rough milling fillet blade is used. The blade is a φ12MM round blade, with low speed and large feed. method for processing. The fine milling cutter for fine milling both sides and the radial surface is a φ63MM insert cutter, using an R0.5 square shoulder insert. The fine milling cutter for fine milling the profile is a φ20MMR4 insert cutter, using a φ8MM round insert. The transfer part uses a 4° taper ball nose cutter. As for the rest of the root groove and other parts, solid carbide end mills are used. According to different groove widths, different diameters and R angles are selected, as well as different processing parameters.

The initial process plan is to process all parts on a five-axis machine, regardless of rough and finish machining, and place the process boss on the side of the blade crown. Then when clamping, the blade crown is pressed at the fixture and the blade root is It was placed at the tip of the tailstock, and a large number of vibration patterns appeared in the inner and back radial surfaces of the blade root processed in this way. No matter how the processing parameters were adjusted, the results were not ideal, and the longer the blade, the more serious the vibration patterns were. Later, the process plan was changed. The process boss is placed at the blade root and pressed tightly against the blade crown side, which solves the problem of radial vibration marks. Another problem that troubled us was the processing of the semicircular groove on the bottom surface of the blade root. Because it was not perpendicular to the radial surface, the left and right position tolerance requirements could not be guaranteed. For this, a lot of time and blanks were wasted. In the end, after communicating with the craftsmen, we had to Put the semicircular groove on the three-axis equipment to make it.

Five-axis machining process route of titanium alloy fan blade profile

Large bypass ratio turbofan engine fan blades basically reach more than 500MM in length and size. This large-scale structural feature makes it endure very large centrifugal force and vibration stress during operation, so it has also become the first choice for large turbofan engines. Very important parts. At present, many turbofan engines still use technically mature titanium alloy damper fan blades. The narrow and long structure of this blade profile makes its weak rigidity in the form of a thin-walled structure in the back direction of the basin more prominent. This poor structural rigidity, the large overall area of the profile, and the difficult-to-process nature of the material have brought adverse effects to its use of traditional machining processes. This is intuitively reflected in the profile dimensional accuracy and position accuracy of the profile. It is difficult to ensure that manual polishing is inefficient and labor-intensive, and the leaf shape is prone to burns and ablation. The existence of the above problems constitutes a bottleneck in blade production. With the development and application of multi-axis CNC machining technology and research on this type of blade profile processing technology, the difficulties in processing this type of blade profile have been gradually broken through, and the processing quality and efficiency levels have reached a relatively ideal state.

In view of the difficult factors in surface processing of large titanium alloy fan blades, based on the comprehensive processing advantages of multi-axis linkage CNC machining technology, the main processing process routes determined are:

1. Processing of blade tenon and auxiliary positioning datum

2. CNC rough milling of blade profile

3. Stress relief annealing

4. Positioning benchmark repair

5. CNC precision milling of blade profile

6. Surface finishing.

The overall process idea established by the above process route is: CNC rough milling of the profile removes most of the margin and makes the fine milling process have an ideal margin distribution; CNC fine milling of the blade profile ensures the geometric dimensions of the profile and position accuracy basically meet the final accuracy requirements of the blade; the light finishing of the blade profile ensures that the surface layer quality of the profile meets the requirements.

Five-axis linkage machining center milling titanium alloy fan blade profile

According to the overall process requirements of the blade profile, the milling process of the blade profile must ensure that the geometric position accuracy of the profile basically meets the design requirements and has a certain surface roughness quality. At the same time, improving the efficiency during processing is also the focus of profile milling. One of the jobs. Based on the understanding of the processing characteristics of large titanium alloy fan blades, it is necessary to comprehensively consider the influence of various factors such as equipment, cutting tools, and processing positioning.

For the milling of large titanium alloy fan blade profiles, it is very necessary to choose a five-axis linkage machining center. Choosing a mature five-axis linkage blade machining center involves both efficient processing and machining accuracy assurance capabilities. For the processing of profiles with large curvature changes, the swing angle function of the machine tool spindle can well adapt to the requirements for consistent cutting stress corresponding to changes in profile curvature. The high-pressure cooling system of the machine tool greatly reduces the cutting temperature and avoids rapid tool wear. , so that the profile processing can obtain good processing accuracy and surface processing quality.

1. Blade clamping method

In order to prevent and reduce the torsional deformation produced during the clamping and cutting of long blades, it is necessary to ensure that the rotary shafts for clamping the blades at the front and rear ends of the equipment have synchronous rotation functions. The purpose is to change the traditional blade processing technology of one end clamping and one end pushing. The tight positioning and clamping method avoids the bending deformation caused when the blade is clamped and the torsional deformation of the blade profile in the length direction caused by one end rotating and the other end following the blade rotation processing. To adapt to the requirements of blade positioning and clamping, the auxiliary positioning part at the tail end of the blade must have strict position accuracy requirements relative to the tenon positioning datum at the front end. After the rough machining of the profile is completed, the front and rear parts of the blade caused by stress deformation must be The position accuracy error between the end positioning datums must be repaired.

After the fixture for blade profile processing is installed on the rotary axes at the front and rear ends of the machine tool, and after confirming that there is no concentricity error in the rotary axes at the front and rear ends of the machine tool, a special mandrel is used to detect and adjust the installation accuracy of the front and rear fixtures. Ensure that the clamps at both ends have an accurate positional accuracy relationship to prevent the synchronous rotation function of the front and rear rotary axes of the machine tool from generating additional torsional stress due to poor clamping accuracy.

2. Rough milling of blade profile

In order to remove a large allowance and leave a uniform machining allowance for finishing, under this premise, the processing of this process should ensure high processing efficiency. The five-axis linkage blade machining center has a wide-row machining function. The principle is that when milling blades, the center line of the tool is not perpendicular to the tangent line of the point or surface to be milled, but is in line with the point or surface to be milled in the direction of tool movement. The normal direction is at a certain angle. This type of milling uses a cylindrical end mill, and the milling trajectory is a wider elliptical arc. Compared with the milling of a ball-nose cutter, the same profile crest height or surface can be milled. Quality-wise, the resulting toolpaths are much more widely spaced. Therefore, this kind of processing has high processing efficiency. In actual processing, the rotary processing method is used to move from one end to the other end along the length of the blade, that is, the spiral milling method. From an efficiency perspective, the spiral milling method also has higher processing efficiency than the longitudinal milling method.

3. Fine milling of blade profile

In order to obtain higher geometric and positional accuracy, and at the same time make the roughness level of the profile meet certain requirements. In order to reduce the “springback” effect caused by titanium alloy material processing and the impact of tool wear on processing accuracy when processing large-area profiles, the tool must be sharp and avoid long-term processing of one tool. For this reason, when possible, try to use end mills for longitudinal milling of the profile. For longitudinal milling, several tools can be used to mill the blade back surface, blade basin surface, intake edge, and exhaust edge to avoid the wear caused by large-area processing with one tool, which will affect the accuracy of the processing of various parts of the blade. The phenomenon of inconsistency is beneficial to the final finishing of the profile.

In order to improve cutting conditions when milling large titanium alloy fan rotor blades, all measures to avoid tool wear are necessary. In terms of the selection of tool materials and specifications, a solid carbide coated cylindrical ball milling cutter is selected to process the inner surface of the blade edge plate, the transition arc between the inner surface of the edge plate and the profile, and the transition profile close to the edge plate. , at the edge of the intake and exhaust, choose an end mill with a cylindrical carbide-coated blade to process the large surface of the blade basin and blade back. The selection of coating materials for machining titanium alloy tools is very important. Avoid using coating materials that have affinity with titanium alloys. At present, PVD-coated tools are commonly used for machining titanium alloys. The PVD coatings are thin and smooth. When they adhere to the carbide substrate of the tool, they also generate a residual stress. This stress is conducive to improving the damage resistance of the tool. PVD It can be closely attached to the tool, which is helpful to maintain a sharp cutting edge shape. PVD tools have good wear resistance, stable chemical properties, and are not prone to built-up edges. During processing, it is necessary to use sufficient coolant to cool the tool and improve the friction effect, select reasonable cutting processing parameters, and improve the effect of cutting force.

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