A small single-pendulum-head five-axis machining center capable of realizing liquid nitrogen internal spraying type cooling machining

Abstract

A small single pendulum head five-axis machining center capable of realizing liquid nitrogen internal spraying type cooling processing includes a small rotary table type machining center main machine, a liquid nitrogen heat insulation transmission control system and a liquid nitrogen internal spraying type single pendulum milling head. The liquid nitrogen heat insulation transmission control system is integrated in the small machining center to realize stable transmission and state adjustment of liquid nitrogen during processing. The liquid nitrogen internal spraying type single pendulum milling head is provided with multiple sections of static and rotating vacuum heat insulation pipelines and low-temperature resistant rotating sealing joints therebetween to realize heat insulation and rotating dynamic sealing during the transportation of liquid nitrogen with extremely low temperature, thereby ensuring normal operation of the small size single pendulum milling head. Through the application of different structure internal cooling cutters, the machining modes of liquid nitrogen direct cooling cutting edge and liquid nitrogen indirect cooling cutting edge are realized, cutting processing options are provided for material parts with different cooling temperature adaptability, and the machining center has potential to become one of the important equipment for high-quality and high-efficiency clean machining of small-size complex structure difficult-to-machine material parts such as human implants.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of numerical control machine tool design, and relates to a small single-swing-head five-axis machining center capable of realizing liquid nitrogen internal spraying type cooling machining. BACKGROUND

[0002] Liquid nitrogen cooling machining is a new green machining technology, which can greatly reduce the cutting temperature and improve the surface integrity of difficult-to-machine material parts. Meanwhile, liquid nitrogen is a clean and non-polluting cooling medium, and there is no residue on the surface of the parts after machining, and no cleaning is required. For drilling or complex curved surface milling machining, compared with external spraying cooling, internal spraying cooling in the tool can more accurately enter the cutting area, so the liquid nitrogen internal spraying cooling is very suitable for machining of difficult-to-machine material parts with extremely high surface cleanliness requirements. For titanium alloy artificial joints, titanium alloy interbody fusion cages, titanium alloy abutment teeth, polyether ether ketone orthopedic stents and other human implants, there are problems of insufficient conventional cooling or insufficient cleanliness in cutting machining, which leads to rough machining surface of the parts, significant edge burrs and subsequent finishing and cleaning process is complicated. Therefore, for such small size difficult-to-machine material human implants with complex surface shape, liquid nitrogen internal spraying type cooling multi-axis linkage machining has unique advantages.

[0003] Therefore, the liquid nitrogen internal spraying small single-swing-head five-axis machining center can be one of the equipment for high-quality and efficient clean drilling and milling machining of human implants. However, in the compact space of the small machining center, the liquid nitrogen passes through the single-swing-head, the electric spindle and the tool inner cavity to realize the controllable liquid nitrogen internal spraying cooling function, and the conventional machine tool structure obviously cannot work. For example, different materials of human implants or different machining features have different requirements for the liquid nitrogen flow, pressure or cooling temperature, so it is necessary to reasonably arrange the liquid nitrogen transmission and control system in the limited machine tool space, and the system should also have good heat insulation capacity. Since the temperature and flow of liquid nitrogen are often closely related, the temperature cannot be adjusted independently, and for this purpose, different cooling processes during cutting can be used to change the temperature. Finally, the most difficult one is how to pass the liquid nitrogen through the single-swing milling head without affecting its normal operation. The heat insulation during the transmission of liquid nitrogen near-196 DEG C, the ultra-low temperature dynamic sealing at the junction of the static pipeline and the multi-degree-of-freedom rotating pipeline, and the automatic tool changing of the liquid nitrogen internal spraying electric spindle are all extremely challenging.

[0004] At present, in order to realize the liquid nitrogen internal spraying type cooling processing, some processing devices are invented by domestic and foreign institutions. In 2010, the company limited in invention patent 201080018034.3 discloses "a device for conveying low temperature fluid through machine tool spindle axis", which transmits liquid nitrogen in the spindle by using static vacuum pipeline, but the spindle is a mechanical spindle, and the multi-degree-of-freedom swing head structure is not involved. In 2018, Dalian University of Technology discloses "a super low temperature medium internal spraying type numerical control machine tool" in invention patent 201810144333.X, which has the function of liquid nitrogen internal spraying type cooling through the spindle, and can control the liquid nitrogen transmission parameter, but the machine tool is a three-axis vertical milling machine using mechanical spindle, and its technical features cannot realize the single swing head connected electric spindle and internal spraying of liquid nitrogen. In 2019, Dalian University of Technology discloses "a honeycomb sealing structure tool holder for liquid nitrogen hollow conveying" in invention patent 201911212427.7, which can also realize the liquid nitrogen internal spraying type cooling processing of the tool, but the liquid nitrogen enters from the outside of the tool holder and does not pass through the spindle. If the tool holder is installed in the single swing head five-axis machining center, the external connected liquid nitrogen conveying pipeline will move with the swing of the spindle, which not only interferes with the cutting processing, but also easily breaks the connection. SUMMARY

[0005] The present application is directed to the deficiencies of the prior art or the demand for improvement, and proposes a small single swing head five-axis machining center which can realize liquid nitrogen internal spraying type cooling processing, and overcomes the technical problems such as liquid nitrogen heat insulation transmission in the limited space of small size single swing milling head, continuous multi-degree-of-freedom rotary dynamic sealing of super low temperature fluid in the single swing milling head, and coordinated arrangement of reliable liquid nitrogen transmission and stable control system in the compact space of machine tool.

[0006] The technical scheme of the present application is:

[0007] A small single swing head five-axis machining center which can realize liquid nitrogen internal spraying type cooling processing, mainly composed of a small rotary table type machining center main machine, a liquid nitrogen heat insulation transmission control system and a liquid nitrogen internal spraying type single swing milling head.

[0008] Small rotary table type machining center main assembly: pedestal 1.2 is installed on the bed seat 1.1, and two Y-axis guide rails 1.3 are fixed on the pedestal 1.2; four Y-axis sliders 1.4 are installed on the lower surface of the workbench base 1.7, and the Y-axis slider 1.4 is in sliding cooperation with the Y-axis guide rail 1.3, and the power is derived from the transmission of the Y-axis motor 1.5 and the Y-axis screw 1.6; the C-axis guide rail 1.8 is fixed on the upper surface of the workbench base 1.7, the C-axis slider 1.9 is installed at the bottom of the rotary table 1.10, the C-axis slider 1.9 is in sliding cooperation with the C-axis guide rail 1.8, and is directly driven by the C-axis motor 1.11; the bed double-side column 1.12 is installed on the bed seat 1.1, the top front side of the bed double-side column 1.12 is provided with two X-axis guide rails 1.13, four X-axis sliders 1.14 are installed on the back of the X-axis slide block 1.17, the X-axis slider 1.14 is in sliding cooperation with the X-axis guide rail 1.13, and the power is derived from the transmission of the X-axis motor 1.15 and the X-axis screw 1.16; two Z-axis guide rails 1.18 are installed on the front of the X-axis slide block 1.17, four Z-axis sliders 1.19 are installed on the back of the Z-axis slide block 1.22, the Z-axis slider 1.19 is in sliding cooperation with the Z-axis guide rail 1.18, and the power is derived from the transmission of the Z-axis motor 1.20 and the Z-axis screw 1.21; the head box 1.23 is fixed on the lower end of the Z-axis slide block 1.22, the milling head box 1.24 is connected to the right side of the head box 1.23, and the liquid nitrogen internal spraying type single pendulum milling head is installed in the head box 1.23 and the milling head box 1.24; the tool magazine 1.27 and the tool changing robot 1.28 are installed on the right side of the machine tool, the chip groove 1.29 is installed on the lower side of the bed seat 1.1, and the bed seat 1.1 is horizontally placed on the ground by four bed feet 1.30;

[0009] The liquid nitrogen heat insulation transmission control system is assembled: the self-pressurized liquid nitrogen tank 2.1 is placed at the left rear of the machine tool, the liquid outlet valve 2.2 on the self-pressurized liquid nitrogen tank 2.1 is connected with the input vacuum hose 2.4 through the nut 2.3, and the input vacuum hose 2.4 is connected with the stainless steel hard pipe 2.6 through the nut 2.5; the stainless steel hard pipe 2.6 is sequentially connected with the pressure reducing valve 2.7, the flow meter 2.8, the safety valve 2.9, the adjusting valve 2.10, the temperature sensor 2.11 and the pressure sensor 2.12 through the threaded and flange connection mode, and the stainless steel hard pipe 2.6 is heat-insulated by the polyurethane foam wrapping mode; the stainless steel hard pipe 2.6 is connected with the vacuum hard pipe 2.15 through the nut 2.14, and the vacuum hard pipe 2.15 is connected with the middle vacuum hose 2.17 through the nut 2.16, and the middle vacuum hose 2.17 is connected with the output vacuum hose 2.19 through the nut 2.18; the stainless steel hard pipe 2.6, the vacuum hard pipe 2.15 and the middle vacuum hose 2.17 are fixed on the machine tool protection panel 2.23 by the fastening clamps 2.13; in addition, the valve actuator 2.20 of the adjusting valve 2.10 is reinforced on the machine tool protection panel 2.23 through the bracket 2.21, and the data acquisition and transmission module 2.22 is adhered on the machine tool protection panel 2.23;

[0010] The single pendulum head part in the liquid nitrogen internal spraying type single pendulum milling head is assembled: the pendulum head box body 1.23 is fixed on the lower end of the Z-axis ram 1.22 through bolt connection, the pendulum head bearing 3.6 is installed in the pendulum head box body 1.23, and the pendulum head bearing 3.6 outer ring is pressed by the bearing gland 3.5; the pendulum motor stator 3.3 is installed on the inner surface of the pendulum motor shell 3.2; the pendulum shaft core 3.7 is installed into the pendulum head box body 1.23 along the inner ring of the pendulum head bearing 3.6, and a gap is left between the pendulum shaft core 3.7 and the pendulum head box body 1.23, and the pendulum motor rotor 3.4 is installed on the outer surface of the pendulum shaft core 3.7; the pendulum motor shell 3.2 provided with the pendulum motor stator 3.3 is installed into the inner cavity of the pendulum head box body 1.23 and fixed by bolt connection; the pendulum vacuum spindle 3.8 is installed in the pendulum shaft core 3.7 by interference fit, and the pendulum rotary sealing joint movable ring 3.10 is screwed into the left end of the pendulum shaft core 3.7 by screw thread; the free end of the output vacuum hose 2.19 passes through the Z-axis ram center hole 3.12 and the L-shaped hole 3.13 of the pendulum installation cover 3.1 in sequence, and is inserted into the inner hole of the pendulum rotary sealing joint static ring 3.9 in transition form, and the pendulum rotary sealing joint static ring 3.9 is screwed into the outlet of the L-shaped hole 3.13 by screw thread; the pendulum installation cover 3.1 is fixed on the outer side of the pendulum motor shell 3.2 by bolt connection, and at this time, the pendulum rotary sealing joint movable ring 3.10 and the pendulum rotary sealing joint static ring 3.9 end surfaces are in precise contact, and play a rotary dynamic sealing role; the pendulum head box body 1.23 open side is covered by the pendulum head box body side cover 1.26 through bolt connection;

[0011] The assembly of the milling head part in the liquid nitrogen internal spraying single pendulum milling head: the milling head box 1.24 is fixed to the right side of the pendulum head box 1.23 by bolts, the fixed joint 3.11 is screwed into the right end of the pendulum head shaft core 3.7 in the form of threads until it abuts against the pendulum vacuum core 3.8; the broach disc spring 4.9 is installed on the vacuum interlayer broach rod 4.8, the vacuum interlayer broach rod 4.8 is installed in the main shaft core 4.10; the main shaft rotary sealing joint moving ring 4.6 is screwed into the tail end of the vacuum interlayer broach rod 4.8 in the form of threads, the broach cylinder 4.7 is integrally installed at the tail end of the main shaft shell 4.21; the main shaft rotary sealing joint static ring 4.4 is screwed into the terminal 4.3 in the form of threads, the terminal 4.3 is installed on the broach cylinder 4.7, the connecting pipe 4.2 is screwed into the outside of the terminal 4.3 until it abuts against the main shaft rotary sealing joint static ring 4.4; the broach claw 4.11 is interference fitted into the inner cavity of the main shaft core 4.10 at the head end, the broach wedge 4.12 is connected with the vacuum interlayer broach rod 4.8 by threads; a through air exhaust hole 4.20 is processed on the main shaft shell 4.21 and the main shaft shell head cover 4.22, and the air suction pipe 4.19 is sealingly connected; the assembled milling head part is installed in the milling head box 1.24, and is fixed by bolts, so that the air suction pipe 4.19 extends out of the milling head box 1.24; a gas exhaust pipe 4.23 is inserted into the gas exhaust port 4.5 on the broach cylinder 4.7 through the milling head box 1.24; a pendulum internal vacuum hose 4.1 is selected, one end of which is threadedly connected with the fixed joint 3.11, and the other end is threadedly connected with the connecting pipe 4.2, the milling head box top cover 1.25 is used to seal the open end of the milling head box 1.24 and is bolted.

[0012] During the liquid nitrogen internal spraying cooling processing, first, the heat insulation sleeve 4.17 is screwed into the tool shank 4.13 in the form of threads, then the internal cooling tool 4.15 is inserted into the spring chuck 4.14, and the spring chuck 4.14 is installed in the tool shank 4.13, and then the tool shank 4.13 is locked by the lock nut 4.16; next, the tool shank 4.13 is inserted into the taper hole of the main shaft core 4.10, at this time, the heat insulation sleeve 4.17 is interference fitted with the annular sealing ring 4.18 in the broach wedge 4.12; finally, the broach cylinder 4.7 loads hydraulic pressure to pull the vacuum interlayer broach rod 4.8 by the liquid nitrogen, the broach wedge 4.12 moves, and then the broach claw 4.11 is opened and the tool shank 4.13 is pulled tight, at this time, the main shaft rotary sealing joint static ring 4.4 contacts with the main shaft rotary sealing joint moving ring 4.6 at the end surface, and the liquid nitrogen fluid rotary dynamic sealing is realized; the annular sealing ring 4.18 realizes the liquid nitrogen fluid static sealing between the vacuum interlayer broach rod 4.8 and the heat insulation sleeve 4.17; when the tool is changed, the main shaft rotary sealing joint static ring 4.4 is separated from the main shaft rotary sealing joint moving ring 4.6 at the end surface, at this time, the liquid nitrogen is discharged through the exhaust pipe 4.23 from the exhaust port 4.5.

[0013] The liquid nitrogen is sequentially passed through the input vacuum hose 2.4, the stainless steel hard pipe 2.6, the vacuum hard pipe 2.15, the middle section vacuum hose 2.17, the output vacuum hose 2.19, the swing rotary sealing joint static ring 3.9, the swing rotary sealing joint dynamic ring 3.10, the swing vacuum mandrel 3.8, the fixed joint 3.11, the swing inner vacuum hose 4.1, the connecting pipe 4.2, the main shaft rotary sealing joint static ring 4.4, the main shaft rotary sealing joint dynamic ring 4.6, the vacuum interlayer broach rod 4.8, the broach wedge 4.12, the heat insulation sleeve pipe 4.17 and the inner cavity channel of the inner cooling cutter 4.15.

[0014] When the metal parts such as titanium alloy are machined, the inner cooling cutter 4.15 is used, and the cutting edge cooling jet port 5.2 exists along the cutter inner cooling channel 5.1, so that the liquid nitrogen can directly cool the cutting edge 5.4; when the polymer material parts such as polyether ether ketone are machined, the inner cooling cutter 4.15 is used, and the jet port 5.3 is located at the root of the cutting edge 5.4 and close to the cutter rod of the inner cooling cutter 4.15, so that the liquid nitrogen can only indirectly cool the cutting edge 5.4; the nitrogen gas diffused in the cutting adjacent area can be sucked away by the suction pipe 4.19.

[0015] The beneficial effects of the present application are that the liquid nitrogen passes through the single swing head and the vacuum heat insulation pipeline in the electric spindle, which prevents the internal structure from being damaged at extremely low temperature, and is combined with the small rotary table type machining center to form a liquid nitrogen internal spraying type small five-axis machining center, which can provide a valuable machining equipment for high-quality and efficient clean machining of small-size complex structure parts such as human implants; the low-temperature resistant rotary sealing joint form is used between the multi-section static-rotary vacuum heat insulation pipelines, which not only realizes the connection between the static pipeline and the rotary pipeline during the working of the single swing milling head, but also prevents the liquid nitrogen fluid from leaking at the dynamic-static gap, and in combination with the effective heat insulation effect of the vacuum heat insulation pipeline, the reliable operation of the single swing milling head is ensured; the liquid nitrogen transmission and control system is almost integrated in the small machining center in the shortest pipeline and the most space-saving connection mode, which realizes the stable transmission and state adjustment of the liquid nitrogen during the machining process; through the replacement of different forms of cutters, the liquid nitrogen direct cooling cutting edge and the liquid nitrogen indirect cooling cutting edge two cooling machining modes are realized, which avoids the problem of material freeze cracking caused by the direct cooling of liquid nitrogen during the machining of polymer materials such as polyether ether ketone. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 It is a front view of the liquid nitrogen internal spraying type cooling small single swing head five-axis machining center.

[0017] Figure 2 It is a right view of the liquid nitrogen internal spraying type cooling small single swing head five-axis machining center.

[0018] Figure 3 It is a left view of the liquid nitrogen internal spraying type cooling small single swing head five-axis machining center.

[0019] Figure 4 The top view of the liquid nitrogen internal spray cooling small single pendulum head five-axis machining center;

[0020] Figure 5 The schematic diagram of the liquid nitrogen internal spray single pendulum milling head structure;

[0021] Figure 6 The schematic diagram of the liquid nitrogen direct cooling cutting edge and the liquid nitrogen indirect cooling cutting edge.

[0022] In the figure: 1.1-bed base; 1.2-stand; 1.3-Y-axis guide rail; 1.4-Y-axis slider; 1.5-Y-axis motor; 1.6-Y-axis screw; 1.7-workbench base; 1.8-C-axis guide rail; 1.9-C-axis slider; 1.10-rotary table; 1.11-C-axis motor; 1.12-bed double-side column; 1.13-X-axis guide rail; 1.14-X-axis slider; 1.15-X-axis motor; 1.16-X-axis screw; 1.17-X-axis ram; 1.18-Z-axis guide rail; 1.19-Z-axis slider; 1.20-Z-axis motor; 1.21-Z-axis screw; 1.22-Z-axis ram; 1.23-swing head box; 1.24-milling head box; 1.25-milling head box top cover; 1.26-swing head box side cover; 1.27-tool storage; 1.28-tool changing robot; 1.29-chip pocket; 1.30-bed foot; 2.1-self-pressurized liquid nitrogen tank; 2.2-liquid outlet valve; 2.3-nut one; 2.4-input vacuum hose; 2.5-nut two; 2.6-stainless steel hard pipe; 2.7-pressure reducing valve; 2.8-flow meter; 2.9-safety valve; 2.10-regulating valve; 2.11-temperature sensor; 2.12-pressure sensor; 2.13-fastening clamp; 2.14-nut three; 2.15-vacuum hard pipe; 2.16-nut four; 2.17-middle section vacuum hose; 2.18-nut five; 2.19-output vacuum hose; 2.20-valve actuator; 2.21-bracket; 2.22-data acquisition and transmission module; 2.23-machine tool protection panel; 3.1-swing head installation cover; 3.2-swing head motor shell; 3.3-swing head motor stator; 3.4-swing head motor rotor; 3.5-bearing gland; 3.6-swing head bearing; 3.7-swing head shaft core; 3.8-swing head vacuum spindle; 3.9-swing head rotary seal joint static ring; 3.10-swing head rotary seal joint dynamic ring; 3.11-fixed joint; 3.12-Z-axis ram center hole; 3.13-L-shaped hole; 4.1-swing head inner vacuum hose; 4.2-connection pipe; 4.3-terminal; 4.4-main shaft rotary seal joint static ring; 4.5-exhaust port; 4.6-main shaft rotary seal joint dynamic ring; 4.7-tool breaking cylinder; 4.8-vacuum layer broach rod; 4.9-broach disc spring; 4.10-main shaft shaft core; 4.11-broach claw; 4.12-broach wedge; 4.13-tool holder; 4.14-spring collet; 4.15-internal cooling tool; 4.16-locking nut; 4.17-heat insulation sleeve; 4.18-ring-shaped sealing ring; 4.19-air suction pipe; 4.20-air suction hole; 4.21-main shaft shell; 4.22-main shaft shell head cover; 4.23-exhaust pipe; 5.1-tool internal cooling channel; 5.2-cutting edge cooling jet port; 5.3-jet port; 5.4-cutting edge. DETAILED DESCRIPTION

[0023] The specific embodiments of the present application will be described in detail below with reference to the accompanying drawings and technical solutions.

[0024] In the embodiment, the minimum cooling temperature of the liquid nitrogen is-196℃; the outer dimensions of the small machining center are 1560*1100*1800mm; the size of the rotary table is φ400mm, the C-axis rotation range is n*360°; the A-axis rotation range is ±130°; the maximum travel of the X / Y / Z axes is 350 / 300 / 250mm, the positioning accuracy of the X / Y / Z axes is 0.004mm, the repeat positioning accuracy is 0.002mm, the positioning accuracy of the A / C axes is 4'', the repeat positioning accuracy is 2''; the maximum outer diameter of the milling head is φ160mm, the axial length is 320mm, the highest rotation speed is 24000rpm, the rated power is 2.2kW, and the rated torque is 3.2Nm; the minimum diameter of the vacuum barrier broach rod 4.8 is φ16mm; the diameter of the vacuum pipeline is in the range of φ20-φ25mm; the capacity of the tool magazine 1.27 is 10, and the tool changing time is less than 3s; the nominal volume of the self-pressurized liquid nitrogen tank 2.1 is 175L, and the maximum working pressure is 2.2MPa; the adjustable range of the liquid nitrogen flow of the regulating valve 2.10 is 0-50L / h, and the adjustment accuracy is ±1L / h; the adjustable range of the liquid nitrogen pressure of the pressure reducing valve 2.7 is 0.1-1.5MPa, and the adjustment accuracy is ±0.1MPa; the set pressure of the safety valve 2.9 is 2.4MPa; the thermal conductivity of the vacuum structure is approximately 0; the heat insulation sleeve 4.17 is made of modified polyimide material, and the thermal conductivity is less than 0.15W / (m*K); the end face material of the swing head rotary sealing joint static ring 3.9, the swing head rotary sealing joint dynamic ring 3.10, the main shaft rotary sealing joint static ring 4.4, and the main shaft rotary sealing joint dynamic ring 4.6 is silicon carbide; and the minimum inner diameter of the liquid nitrogen transmission channel is φ2mm.

[0025] The assembly process of the small single swing head five-axis machining center capable of realizing liquid nitrogen internal spraying type cooling machining is as follows: as shown in FIG. 1, the main shaft 4.1 is first installed on the rotary table 1.10, and then the main shaft rotary sealing joint static ring 4.4 and the main shaft rotary sealing joint dynamic ring 4.6 are installed on the main shaft 4.1. Figure 1 , 2, 3, 4, 5 and 6, the first step, the bed seat 1.1 on the installation of the pedestal 1.2, the Y-axis guide rail 1.3 is fixed on the pedestal 1.2; Four Y-axis slider 1.4 is installed at the bottom of the workbench base 1.7, Y-axis slider 1.4 and Y-axis guide rail 1.3 sliding fit, by Y-axis motor 1.5 and Y-axis screw 1.6 to provide and transfer power; On the surface of the workbench base 1.7 fixed C-axis guide rail 1.8, and C-axis slider 1.9 is installed at the bottom of the rotary table 1.10, C-axis slider 1.9 and C-axis guide rail 1.8 sliding fit, and by C-axis motor 1.11 directly driven; The bed double side column 1.12 is installed on the bed seat 1.1, the X-axis guide rail 1.13 is installed at the top of the bed double side column 1.12 front side, four X-axis slider 1.14 is installed at the back of the X-axis slide 1.17, X-axis slider 1.14 and X-axis guide rail 1.13 sliding fit, by X-axis motor 1.15 and X-axis screw 1.16 to provide and transfer power; The Z-axis guide rail 1.18 is installed on the front of the X-axis slide 1.17, and four Z-axis slider 1.19 is installed at the back of the Z-axis slide 1.22, Z-axis slider 1.19 and Z-axis guide rail 1.18 sliding fit, by Z-axis motor 1.20 and Z-axis screw 1.21 to provide and transfer power; The swing head box 1.23 is fixed at the lower end of the Z-axis slide 1.22, the milling head box 1.24 is connected to the right side of the swing head box 1.23, wherein the swing head box 1.23 and the milling head box 1.24 are installed in the liquid nitrogen inside spray type single pendulum milling head; The tool magazine 1.27 and the tool changer 1.28 are installed on the right side of the machine tool, the chip pocket 1.29 is installed under the bed seat 1.1, the bed seat 1.1 is placed horizontally on the ground by four bed feet 1.30, the whole machining center weight is about 700 kg; Thus, the small rotary table type machining center main machine assembly is completed;

[0026] Secondly, the 175L self-pressurized liquid nitrogen tank 2.1 is placed at the left rear of the machine tool, and its liquid outlet valve 2.2 is connected with a 1.5m long input vacuum hose 2.4 through a nut 2.3, and the input vacuum hose 2.4 is connected with a stainless steel hard pipe 2.6 through a nut 2.5; a pressure reducing valve 2.7, a flow meter 2.8, a safety valve 2.9, an adjusting valve 2.10, a temperature sensor 2.11 and a pressure sensor 2.12 are sequentially connected through screw thread and flange connection, and the stainless steel hard pipe 2.6 is heat-insulated by being wrapped with polyurethane foam throughout; the stainless steel hard pipe 2.6 is connected with a vacuum hard pipe 2.15 through a nut 2.14, and the vacuum hard pipe 2.15 is connected with a middle section vacuum hose 2.17 through a nut 2.16, and then the middle section vacuum hose 2.17 is connected with an output vacuum hose 2.19 through a nut 2.18; the stainless steel hard pipe 2.6, the vacuum hard pipe 2.15 and the middle section vacuum hose 2.17 are fixed on the machine tool protection panel 2.23 by using a plurality of fastening clamps 2.13; the valve actuator 2.20 of the adjusting valve 2.10 is reinforced on the machine tool protection panel 2.23 through a support 2.21, and a data acquisition and transmission module 2.22 is bonded on the machine tool protection panel 2.23; thus, the liquid nitrogen heat-insulated transmission and control system inside the machining center is assembled and completed.

[0027] Thirdly, the wobble box 1.23 is fixed on the lower end of the Z-axis ram 1.22 by screw connection, and then the wobble bearing 3.6 is installed in the wobble box 1.23 in transition fit, and the outer ring of the wobble bearing 3.6 is pressed by the bearing gland 3.5; the wobble motor stator 3.3 is installed on the inner surface of the wobble motor shell 3.2; the wobble shaft core 3.7 is installed into the wobble box 1.23 along the inner ring of the wobble bearing 3.6 in transition fit, and has a gap with the wobble box 1.23, and then the wobble motor rotor 3.4 is installed on the outer surface of the wobble shaft core 3.7; then the wobble motor shell 3.2 with the wobble motor stator 3.3 is installed into the inner cavity of the wobble box 1.23 and fixed by screw connection; the wobble vacuum spindle 3.8 is installed in the wobble shaft core 3.7 in interference fit, and then the wobble rotary seal joint movable ring 3.10 is screwed into the left end of the wobble shaft core 3.7 by screw thread; the free end of the output vacuum hose 2.19 is sequentially inserted through the Z-axis ram center hole 3.12 and the L-shaped hole 3.13 of the wobble mounting cover 3.1; the free end of the output vacuum hose 2.19 is first inserted into the inner hole of the wobble rotary seal joint stationary ring 3.9 in transition fit, and then the wobble rotary seal joint stationary ring 3.9 is screwed into the outlet of the L-shaped hole 3.13 by screw thread; the wobble mounting cover 3.1 is fixed on the outer side of the wobble motor shell 3.2 by screw connection, and at this time the wobble rotary seal joint movable ring 3.10 is in precise contact with the end surface of the wobble rotary seal joint stationary ring 3.9; the wobble box 1.23 is covered by the wobble box side cover 1.26 by screw connection; at this time, the wobble head part of the liquid nitrogen internal spray type single wobble milling head is assembled.

[0028] Fourthly, the milling head box 1.24 is fixed to the right side of the swing head box 1.23 by bolts, then the fixed joint 3.11 is screwed into the right end of the swing head shaft core 3.7 until it reaches the swing head vacuum core 3.8, the broach disc spring 4.9 is installed on the self-made vacuum interlayer broach rod 4.8, then the vacuum interlayer broach rod 4.8 is installed into the main shaft core 4.10, the main shaft rotary sealing joint moving ring 4.6 is screwed into the tail end of the vacuum interlayer broach rod 4.8, then the broach cylinder 4.7 is installed into the tail end of the main shaft shell 4.21, the main shaft rotary sealing joint static ring 4.4 is screwed into the terminal 4.3, and the terminal 4.3 is installed on the broach cylinder 4.7, then the connecting pipe 4.2 is screwed into the outside of the terminal 4.3 until it reaches the main shaft rotary sealing joint static ring 4.4, secondly, the broach claw 4.11 is interference fitted into the inner cavity of the main shaft core 4.10, and the broach wedge 4.12 is connected to the vacuum interlayer broach rod 4.8 by threads, a through air hole 4.20 is processed on the main shaft shell 4.21 and the main shaft shell head cover 4.22, and the air suction pipe 4.19 is sealed and connected, the assembled milling head part is installed into the milling head box 1.24 and fixed by bolts, and the air suction pipe 4.19 extends out of the milling head box 1.24, an exhaust pipe 4.23 is inserted into the exhaust port 4.5 on the broach cylinder 4.7 through the milling head box 1.24, a swing head inner vacuum hose 4.1 is selected, one end of which is threadedly connected to the fixed joint 3.11, and the other end is threadedly connected to the connecting pipe 4.2, then the milling head box top cover 1.25 is used to seal the open end of the milling head box 1.24 and fix it by bolts, thus the milling head part of the liquid nitrogen internal spraying type single pendulum milling head is assembled;

[0029] In the process of liquid nitrogen internal spraying cooling, the heat insulation sleeve 4.17 is screwed into the tool holder 4.13, then the internal cooling tool 4.15 is inserted into the spring chuck 4.14, and the spring chuck 4.14 is installed into the tool holder 4.13, then the lock nut 4.16 is used to lock it, the tool holder 4.13 is inserted into the taper hole of the main shaft core 4.10, at this time the heat insulation sleeve 4.17 is interference fitted with the ring type sealing ring 4.18 in the broach wedge 4.12, after the broach command is issued, the broach cylinder 4.7 loads hydraulic pressure to pull the vacuum interlayer broach rod 4.8, the broach wedge 4.12 moves, then the broach claw 4.11 is opened and the tool holder 4.13 is pulled tight, at this time the main shaft rotary sealing joint static ring 4.4 and the main shaft rotary sealing joint moving ring 4.6 are in contact with the end face, realizing the rotary dynamic sealing of the liquid nitrogen fluid, at the discontinuity between the vacuum interlayer broach rod 4.8 and the heat insulation sleeve 4.17, the ring type sealing ring 4.18 realizes the static sealing of the liquid nitrogen fluid, when changing the tool, the vacuum interlayer broach rod 4.8 retreats, the end face of the main shaft rotary sealing joint static ring 4.4 and the main shaft rotary sealing joint moving ring 4.6 are separated, and the liquid nitrogen is discharged through the exhaust pipe 4.23 from the exhaust port 4.5;

[0030] In the machining, the liquid nitrogen passes through the inner cavity channel of input vacuum hose 2.4, stainless steel hard pipe 2.6, vacuum hard pipe 2.15, middle section vacuum hose 2.17, output vacuum hose 2.19, swing rotary sealing joint static ring 3.9, swing rotary sealing joint dynamic ring 3.10, swing vacuum mandrel 3.8, fixed joint 3.11, swing inner vacuum hose 4.1, connecting pipe 4.2, main shaft rotary sealing joint static ring 4.4, main shaft rotary sealing joint dynamic ring 4.6, vacuum interlayer broach rod 4.8, broach wedge 4.12, heat insulation sleeve pipe 4.17 and inner cooling cutter 4.15 in sequence;

[0031] In an embodiment, when machining a metal material part with high strength such as titanium alloy, the inner cooling cutter 4.15 is used, and the cutting edge cooling jet port 5.2 exists along the cutter inner cooling channel 5.1, so that the liquid nitrogen can directly cool the cutting edge 5.4, i.e. directly cool the contact area of the cutting edge 5.4 and the material, and at this time, the nitrogen gas diffused in the cutting adjacent area can be sucked away by the suction pipe 4.19;

[0032] In another embodiment, when machining a polymer material part with low strength such as polyether ether ketone, the inner cooling cutter 4.15 is used, and the jet port 5.3 is located at the root of the cutting edge 5.4, close to the cutter rod of the inner cooling cutter 4.15, so that the liquid nitrogen can only indirectly cool the cutting edge 5.4, and cannot directly cool the contact area of the cutting edge 5.4 and the material, and at this time, the nitrogen gas diffused in the cutting adjacent area can be sucked away by the suction pipe 4.19;

[0033] The present application overcomes the problem of heat insulation and dynamic sealing of liquid nitrogen fluid with extremely low temperature in the limited space of single pendulum head and electric spindle, realizes the effective integration of liquid nitrogen internal spraying cooling function and small size single pendulum milling head, and also has the function of automatic tool changing; The pipeline and valve element of the liquid nitrogen transmission and control system inside the machine tool are arranged reasonably, which not only realizes the heat insulation transmission and accurate regulation of liquid nitrogen, but also does not excessively increase the size of the five-axis machining center; The machine tool combined with the use of different types of cutters can provide an optional device and method for high-quality, efficient and clean machining of different material parts with different cooling temperature requirements.

Claims

1. A small size single swing head five axis machining center capable of realizing liquid nitrogen internal spray type cooling machining, characterized in that, The small single pendulum head five-axis machining center capable of realizing liquid nitrogen internal spraying type cooling processing is mainly composed of a small rotary table type machining center main machine, a liquid nitrogen heat insulation transmission control system and a liquid nitrogen internal spraying type single pendulum milling head. The small rotary table type machining center main machine is assembled as follows: the base (1.2) is installed on the bed body base (1.1), two Y-axis guide rails (1.3) are fixed on the base (1.2), four Y-axis sliding blocks (1.4) are installed on the lower surface of the workbench base (1.7), the Y-axis sliding blocks (1.4) are in sliding fit with the Y-axis guide rails (1.3), the power is transmitted by the Y-axis motor (1.5) and the Y-axis lead screw (1.6), the C-axis guide rail (1.8) is fixed on the upper surface of the workbench base (1.7), the C-axis sliding block (1.9) is installed at the bottom of the rotary table (1.10), the C-axis sliding block (1.9) is in sliding fit with the C-axis guide rail (1.8) and is directly driven by the C-axis motor (1.11), the bed body double-side column (1.12) is installed on the bed body base (1.1), the top front side of the bed body double-side column (1.12) is provided with two X-axis guide rails (1.13), four X-axis sliding blocks (1.14) are installed on the back surface of the X-axis slide (1.17), the X-axis sliding blocks (1.14) are in sliding fit with the X-axis guide rails (1.13), the power is transmitted by the X-axis motor (1.15) and the X-axis lead screw (1.16), two Z-axis guide rails (1.18) are installed on the front surface of the X-axis slide (1.17), four Z-axis sliding blocks (1.19) are installed on the back surface of the Z-axis slide (1.22), the Z-axis sliding blocks (1.19) are in sliding fit with the Z-axis guide rails (1.18), the power is transmitted by the Z-axis motor (1.20) and the Z-axis lead screw (1.21), the pendulum box (1.23) is fixed at the lower end of the Z-axis slide (1.22), the milling head box (1.24) is connected to the right side of the pendulum box (1.23), the pendulum box (1.23) and the milling head box (1.24) are provided with the liquid nitrogen internal spraying type single pendulum milling head, the tool magazine (1.27) and the tool changing robot (1.28) are installed on the right side of the machine tool, the chip pocket (1.29) is installed below the bed body base (1.1), and the bed body base (1.1) is horizontally placed on the ground by the four bed body feet (1.30). Liquid nitrogen heat insulation transmission control system assembly: self-pressurized liquid nitrogen tank (2.1) is placed in the left rear of the machine tool, the liquid outlet valve (2.2) on the self-pressurized liquid nitrogen tank (2.1) is connected with the input vacuum hose (2.4) through nut one (2.3), and the input vacuum hose (2.4) is connected with the stainless steel hard pipe (2.6) through nut two (2.5); the stainless steel hard pipe (2.6) is sequentially connected with the pressure reducing valve (2.7), the flow meter (2.8), the safety valve (2.9), the regulating valve (2.10), the temperature sensor (2.11) and the pressure sensor (2.12) through the threaded and flange connection form, and the stainless steel hard pipe (2.6) is heat insulated by the polyurethane foam wrapping method; the stainless steel hard pipe (2.6) is connected with the vacuum hard pipe (2.15) through nut three (2.14), and the vacuum hard pipe (2.15) is connected with the middle section vacuum hose (2.17) through nut four (2.16), and the middle section vacuum hose (2.17) is connected with the output vacuum hose (2.19) through nut five (2.18); the stainless steel hard pipe (2.6), the vacuum hard pipe (2.15) and the middle section vacuum hose (2.17) are fixed on the machine tool protection panel (2.23) by using a plurality of fastening clamps (2.13); in addition, the valve actuator (2.20) of the regulating valve (2.10) is reinforced on the machine tool protection panel (2.23) through the bracket (2.21), and the data acquisition and transmission module (2.22) is bonded on the machine tool protection panel (2.23); The pendulum head part assembly in the liquid nitrogen inside spraying type single pendulum milling head: the pendulum head box (1.23) is fixed at the lower end of the Z-axis ram (1.22) by bolt connection, the pendulum head bearing (3.6) is installed in the pendulum head box (1.23), and the bearing gland (3.5) is used to press the outer ring of the pendulum head bearing (3.6); the pendulum motor stator (3.3) is installed on the inner surface of the pendulum motor shell (3.2); the pendulum shaft core (3.7) is installed into the pendulum head box (1.23) along the inner ring of the pendulum head bearing (3.6), and a gap is left between the pendulum shaft core (3.7) and the pendulum head box (1.23), the pendulum motor rotor (3.4) is installed on the outer surface of the pendulum shaft core (3.7); the pendulum motor shell (3.2) with the pendulum motor stator (3.3) is installed into the inner cavity of the pendulum head box (1.23) and fixed by bolts; the pendulum vacuum spindle (3.8) is installed in the pendulum shaft core (3.7) by interference fit, the pendulum rotating seal joint movable ring (3.10) is screwed into the left end of the pendulum shaft core (3.7) by thread; the free end of the output vacuum hose (2.19) passes through the Z-axis ram center hole (3.12) and the L-shaped hole (3.13) of the pendulum mounting cover (3.1) in turn, the free end of the output vacuum hose (2.19) is inserted into the inner hole of the pendulum rotating seal joint static ring (3.9) by transition, the pendulum rotating seal joint static ring (3.9) is screwed into the outlet of the L-shaped hole (3.13) by thread; the pendulum mounting cover (3.1) is fixed on the outside of the pendulum motor shell (3.2) by bolts, at this time the pendulum rotating seal joint movable ring (3.10) and the pendulum rotating seal joint static ring (3.9) are in precise contact with the end face, which plays a rotating dynamic sealing role; the pendulum head box (1.23) is covered by the pendulum head box side cover (1.26) by bolts; The milling head part assembly in the liquid nitrogen inside spraying type single pendulum milling head: the milling head box (1.24) is fixed to the right side of the pendulum head box (1.23) by bolts, the fixed joint (3.11) is screwed into the right end of the pendulum head shaft core (3.7) by threads until it abuts against the pendulum vacuum core (3.8); the broach disc spring (4.9) is installed on the vacuum interlayer broach rod (4.8), the vacuum interlayer broach rod (4.8) is installed in the main shaft core (4.10); the main shaft rotary sealing joint dynamic ring (4.6) is screwed into the tail end of the vacuum interlayer broach rod (4.8) by threads, the broach cylinder (4.7) is integrally installed at the tail end of the main shaft shell (4.21); the main shaft rotary sealing joint static ring (4.4) is screwed into the terminal (4.3) by threads, the terminal (4.3) is installed on the broach cylinder (4.7), the connecting pipe (4.2) is screwed into the outside of the terminal (4.3) until it abuts against the main shaft rotary sealing joint static ring (4.4); the broach claw (4.11) is interference fitted into the inner cavity of the main shaft core (4.10) at the head end, the broach wedge (4.12) is connected with the vacuum interlayer broach rod (4.8) by threads; a through air suction hole (4.20) is machined on the main shaft shell (4.21) and the main shaft shell head cover (4.22) and is sealingly connected with the air suction pipe (4.19); the assembled milling head part is installed in the milling head box (1.24) and is fixed by bolts, so that the air suction pipe (4.19) extends out of the milling head box (1.24); an exhaust pipe (4.23) is inserted into the exhaust port (4.5) on the broach cylinder (4.7) through the milling head box (1.24); a pendulum inside vacuum hose (4.1) is selected, one end of which is threadedly connected with the fixed joint (3.11) and the other end is threadedly connected with the connecting pipe (4.2), the milling head box top cover (1.25) is used to seal the open end of the milling head box (1.24) and is bolted.

2. The compact single swing head five axis machining center with liquid nitrogen internal spray cooling machining capability of claim 1, wherein, When the liquid nitrogen internal spray cooling processing is carried out, first, the heat insulation sleeve (4.17) is screwed into the tool holder (4.13), then the internal cooling tool (4.15) is inserted into the spring collet (4.14), and the spring collet (4.14) is screwed into the tool holder (4.13), and then the locking nut (4.16) is locked; next, the tool holder (4.13) is inserted into the taper hole of the spindle core (4.10), at this time the heat insulation sleeve (4.17) is in interference fit with the ring-shaped sealing ring (4.18) in the broach wedge (4.12); finally, through the broach command, the broach cylinder (4.7) loads the hydraulic pressure to pull the vacuum interlayer broach rod (4.8), the broach wedge (4.12) moves, then the broach claw (4.11) is opened and the tool holder (4.13) is pulled tight, at this time the main shaft rotary sealing joint static ring (4.4) and the main shaft rotary sealing joint dynamic ring (4.6) are in contact with the end face, realizing the rotary dynamic sealing of the liquid nitrogen flow; at the discontinuity between the vacuum interlayer broach rod (4.8) and the heat insulation sleeve (4.17), the ring-shaped sealing ring (4.18) realizes the static sealing of the liquid nitrogen flow; when changing the tool, the main shaft rotary sealing joint static ring (4.4) and the main shaft rotary sealing joint dynamic ring (4.6) are separated at the end face, at this time the liquid nitrogen is discharged through the exhaust pipe (4.23) through the exhaust port (4.5).

3. The compact single swing head five axis machining center capable of liquid nitrogen internal spray type cooling machining according to claim 2, characterized in that, When processing, the liquid nitrogen passes through the inner cavity channel of the input vacuum hose (2.4), the stainless steel hard pipe (2.6), the vacuum hard pipe (2.15), the middle section vacuum hose (2.17), the output vacuum hose (2.19), the swing head rotary sealing joint static ring (3.9), the swing head rotary sealing joint dynamic ring (3.10), the swing head vacuum mandrel (3.8), the fixed joint (3.11), the swing head internal vacuum hose (4.1), the connecting pipe (4.2), the main shaft rotary sealing joint static ring (4.4), the main shaft rotary sealing joint dynamic ring (4.6), the vacuum interlayer broach rod (4.8), the broach wedge (4.12), the heat insulation sleeve (4.17) and the internal cooling tool (4.15) in sequence.

4. The compact single swing head five axis machining center with liquid nitrogen internal spray cooling machining capability of claim 2, wherein, When processing metal parts, the internal cooling tool (4.15) used has a cutting edge cooling jet port (5.2) along the tool internal cooling channel (5.1), and the liquid nitrogen can directly cool the cutting edge (5.4); when processing polyether ether ketone and other high molecular material parts, the internal cooling tool (4.15) used has a jet port (5.3) at the root of the cutting edge (5.4), close to the tool bar of the internal cooling tool (4.15), so the liquid nitrogen can only indirectly cool the cutting edge (5.4); the nitrogen gas diffused in the cutting adjacent area can be sucked away by the suction pipe (4.19).

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