Mass production high demand grinder parts
In view of the current problems existing in the machining process of the aero-engine aluminum-magnesium casing of the author’s unit, the machining process route and cutting parameters are reconstructed and optimized by using the milling-turning composite technology, the machining strategy of the key parts of the casing is improved, and the composite special tool is used for high efficiency. Processing methods, innovative parts clamping methods, increase the processing efficiency of aluminum-magnesium casings by 3 to 5 times; through the application of new technologies such as automatic measurement, automatic compensation, automatic alignment and tool life monitoring, the key and important dimensional accuracy is ensured at the same time. Effectively monitor the processing status during the processing process and improve the process stability; carry out preliminary technical research and technical reserves for the construction of subsequent automated and efficient composite processing production units, and it is expected to explore a new way for the processing of new-generation aero-engine aluminum-magnesium casings . Mass production high demand grinder parts
01 Preamble
The aluminum-magnesium casing is an important part of the aero-engine, and it mainly undertakes the engine power output mechanism, the lubricating oil lubrication system and the external engine parts [1]. Due to the particularity of the structure, its processing technology is complex and the processing flow is long; the processing method is relatively traditional, the cutting method needs to be improved, and the cutting efficiency is not high; the quality of traditional tools is unstable, the error of repeated clamping is large, and there are many manual tapping contents, which is easy to use. produce quality problems. These factors lead to the long processing cycle, low cutting efficiency and poor quality stability of the current aluminum-magnesium casing.
The manufacturing precision of the new generation of aero-engines is getting higher and higher, and the required manufacturing technology is also constantly being upgraded. It has automatic alignment, automatic tool setting, automatic measurement, automatic compensation function, tool management and monitoring functions. The tools in the tool magazine can be shared, and the processing programs can be called separately. Automatic production scheduling can be realized when replacing parts or processes, and continuous and uninterrupted processing can be achieved to meet the high-efficiency composite processing requirements of typical aluminum-magnesium casings. Mass production high demand grinder parts
2.1 Reconstruction of the high-efficiency composite machining process of the casing
At present, the processing route of aluminum-magnesium casing is divided into rough machining, semi-finishing and finishing [2]; according to the processing equipment, it can be divided into CNC lathe processing, CNC vertical machining center processing, CNC four-axis machine tool processing, and CNC five-axis machine tool processing. , clamp repair and other procedures, which are characterized by many processing procedures, many equipment used and long production cycle. Figures 1 and 2 show the original processing flow of the typical parts aluminum-magnesium casing 1 and aluminum-magnesium casing 2.
How to reconstruct the technological process, reduce the processing procedure and shorten the production cycle is the primary task of this research. After research and analysis, the required conditions are as follows: ① There should be more advanced equipment. ②It is necessary to analyze whether the centralized production method of the test process can meet the quality requirements. ③It is necessary to innovate the clamping technology of the existing workpiece. Mass production high demand grinder parts
(1) Selection of processing equipment The research selected is a high-precision milling-turning compound five-axis machining center equipment, which can realize turning, five-axis milling compound machining, using high-speed and high-precision SHK100 tool holder, machine tool spindle, The bed and cutting fluid are equipped with a constant temperature cooling device, which can perform temperature detection and compensation in real time. The maximum spindle speed is 12000r/min, the positioning accuracy is 0.006mm, the repeat positioning accuracy is 0.003mm, the tool magazine capacity is 200, and 8 worktables can be automatically exchanged. , connecting with MES can realize order-based production process control, single-process flow or multi-process, multi-variety mixed-flow production, belonging to a single flexible composite manufacturing unit.
(2) Analysis of the advantages and disadvantages of the centralized production method of the process The advantages of the centralized process: ① It is conducive to the use of efficient special equipment and CNC machine tools, improving production efficiency, reducing the number of processes, shortening the process route, and simplifying production planning and production organization. ②The number of machine tools, operators and floor space can be reduced. ③It can reduce the number of workpiece clamping, which can not only ensure the mutual position accuracy of each machined surface, but also reduce the number of fixtures and shorten the auxiliary time for clamping the workpiece. Mass production high demand grinder parts
Disadvantages of process concentration: large investment in special equipment and process equipment, more troublesome adjustment and maintenance, long production preparation, debugging and processing cycle, if special equipment is used, it is not conducive to production conversion.
With the development of modern numerical control technology, especially the application of composite machining centers, the arrangement of process routes tends to be more concentrated in processes. When a single piece is produced in small batches and multiple varieties, it is more suitable to adopt a composite processing and flexible production method with concentrated processes.
(3) Innovation of the box clamping method In the original process route, CNC vertical lathe processing and five-axis machine tool processing must be carried out independently, using different fixtures respectively. The fixture will interfere with the existing processing content, and the fixture needs to be innovatively designed. The main methods are as follows.
1) Change the original two-hole positioning on one side to three-hole positioning on one side. The three-hole positioning on one side limits the 6 degrees of freedom of the workpiece. The advantage is that the positioning accuracy is high and stable and reliable. The problem to be noted is that the three-hole positioning on one side belongs to over-positioning, and the manufacturing accuracy of the fixture and the machining accuracy of the positioning holes of the parts are very high, such as After optimization, the first process of processing the aluminum-magnesium casing 1 of the typical part—the 3×φ6mm positioning hole processed by the milling-turning compound machine tool and the third process—the location of the 3×φ7.9mm positioning hole processed by the milling-turning compound machine tool The degrees are controlled within 0.015mm, and the flatness and parallelism of the end faces at both ends can reach 0.01mm, which can fully meet the positioning and clamping method. The personnel manually finds that the center of the part coincides with the center of the B-axis of the machine tool, which can be directly guaranteed by the positioning of the fixture. Mass production high demand grinder parts
2) Change the original upper end face compression and side boss compression to only rely on the surface to use the process bolt holes to reversely pull and fix the clamping parts. As shown in Figure 3, the bolts are pulled back and fixed, and they are pressed on the rigid part of the bottom end blank, which eliminates the compression deformation error of the parts and solves the problem of interference between the clamp pressing plate and the bolt during the processing.
Through the machining test, the machining process route was reconstructed, and the milling-turning compound five-axis machining unit was used to divide the machining process into two rough machining on the front and back of the part, and then two finishing processes on the front and back. It effectively simplifies the processing process; at the same time, using the new functions of the existing equipment and the innovation of processing technology, the original manual thread tapping, fitter scraping and other contents are converted into numerical control processing. Finally, the processing flow of the reconstructed aluminum-magnesium receiver 1 and aluminum-magnesium receiver 2 is shown in Figure 4.
2.2 New quality control technology in efficient composite machining of casing
In the original CNC machining process of the casing, the process quality control method of the parts is that each batch of parts and the first part of each process must pass the three-coordinate inspection and pass the first part and the second inspection before they can be processed, and wait for measurement. The time is generally more than 2h, causing the production of parts to be interrupted and the equipment to stop waiting. Now through the in-machine online measurement and compensation processing technology, the key and important dimensions in the process are detected and controlled, and the first piece measurement requirement of each process can be canceled. After all milling and turning composite processes are completed, the workpiece is full-scale. The three-coordinate measurement detection can effectively reduce the measurement waiting time between processes. Mass production high demand grinder parts
(1) The application of on-machine measurement technology for casing processing is as follows.
1) Optimize real-time online measurement technology to ensure key and important dimensional accuracy. The existing milling-turning compound five-axis machining center equipment has its own on-machine measurement function, which can realize dimensional control and compensation in process processing, and shorten the search for workpieces in CNC machining. In time, the clamping processing efficiency and product qualification rate have been improved, providing strong support for digital, automated and intelligent processing.
The main point is that the key and important dimensions of the parts should be carried out after all rough machining and semi-finishing are completed. Due to the concentration of processes and the long processing time, the key and important dimensions should be finished after the stress of the parts is effectively released. , will get good geometric dimensional accuracy. During its execution, it should be noted that: first, the parts need to be automatically washed clean; the probe must be re-calibrated before measurement, and then the dimensions of the parts and workpiece zero alignment must be carried out; the final finishing cutting parameters of the parts should be the same as those of the test cutting Keep the same; at the same time, when judging the measurement results, set the tolerance range that allows the change of the error value. If the tolerance range is exceeded, the system will automatically alarm, so as to ensure the reliability of the measurement system. Mass production high demand grinder parts
2) Align the workpiece origin in real time to avoid the thermal deformation error of the machine tool. Affected by its own structure, working temperature and ambient temperature, the machine tool can generally produce a thermal deformation error of 0.03-0.06mm within 8h from morning to night, which mainly affects the position accuracy of Y-axis and Z-axis. cause parts to be out of tolerance.
The specific improvement method is: set a reference plane on the fixture of each machining process of the part, before using the online measurement system, first calibrate the probe itself in real time, and then carry out the reference measurement alignment and compensation, so as to judge and adjust the machine tool. Thermal deformation error and measurement system error. When the machine tool is stopped for more than 2 hours, the preheating program should be run for 15 minutes before the parts are processed to ensure that the machine tool spindle and the bed are in a state of thermal equilibrium and thermal stability.
(2) Tool life and state management The details are as follows.
The tool life control is mainly realized through the tool life management function of the machine tool system. Each tool can be set to the cutting control time and the alarm prompt time. During processing, the system will automatically record the cutting time of the tool. When the cutting time reaches the lower limit alarm value, the system will The tool replacement prompt alarm will appear. If it is not replaced in time, the tool will be disabled and the processing will be stopped. Mass production high demand grinder parts
1) Automatic tool setting and damage monitoring. The tool magazine of the equipment has its own in-machine and out-of-machine infrared tool setting systems, and standard tools can be used for automatic calibration and calibration. Before the tool is used, perform automatic tool setting in the machine as required. After cutting, return to the tool magazine for external damage detection. When the tool diameter and length data exceed the set value, the device will issue an alarm to indicate that there is a problem with the tool. If a small-sized tool breaks during processing, it will send an alarm after being detected by the external tool setting device when it is put back into the tool magazine to ensure that the processing process is under control. The tool monitoring process is shown in Figure 5.
2) Adaptive cutting power monitoring. The power monitoring system can use the power monitor to record and learn the maximum absorption value reached by each tool during machining. Insert the power monitor command PWM (50) after the spindle rotates and before the cutting block (G1, G2 or G3). , 2), the cutting power can be monitored for abnormal conditions during processing. The meaning of its PWM(50, 2) is the maximum power threshold corresponding to 50% of the spindle absorption value, and the intervention delay is 0.2s. Mass production high demand grinder parts
2.3 Optimization and improvement plan of cutting efficiency in high-efficiency machining of casing
(1) Turning of the eccentric groove on the end face by milling. There is an eccentric ring groove of φ449.4mm on the 1 end face of the aluminum-magnesium casing. The slewing center of the 25.4mm eccentric size is not coincident, and the eccentric hole of 25.4mm needs to be re-aligned before CNC lathe processing, which is a single CNC turning process. When using the milling-turning compound equipment, milling can be used instead of CNC turning, and the coordinate system can be offset by 25.4mm using the five-axis oriented machining command. Since the parts do not rotate during slot milling, the table does not generate centrifugal force. Using the high-speed rotation of the small milling cutter, the processing efficiency is doubled compared to CNC turning, and there is no need to re-clamp and align the fixtures and parts.
(2) The original rough turning is replaced by milling and turning. As shown in A-A in Figure 6, the machining allowance at the small end φC of the part blank is large. Generally, turning is used to remove the allowance. However, due to the large size of the part, when the part rotates, The centrifugal force generated is large, resulting in low cutting efficiency and long processing time. By using a high-speed and efficient milling-turning hybrid method of milling cutters instead of rough turning, and then using turning tools to finish turning to final size, the cutting time of parts can be reduced by 1 hour, and the time is shortened by 75.6%.
(3) Selection and improvement of cutting tools In the high-efficiency CNC machining of aviation casings, the selection of tools directly affects the processing quality and efficiency of parts. When choosing a tool, the cutting performance, reliability and machining accuracy of the tool are mainly considered [3].
1) The application of the three-blade drill in the processing of threaded bottom holes and bolt holes. The three-edged solid alloy drill is a medium-sized carbide drill. The three-edged drill can be used to replace the original center drill, drill bit and boring tool in the processing of threaded bottom holes and bolt holes. It can be processed to size at one time, and the processing efficiency is 3 to 5 times higher than that of twist drills. , and the aperture size is stable, and the position and verticality are good. Its main features: ①The drill core is thicker and stronger than the two-blade twist drill, thus compensating for the weak point of poor toughness of cemented carbide. ②The front end of the tool nose is formed into a special shape, which can be automatically centered during cutting without machining the center hole. ③With many cutting edges and good centering, the feed per revolution increases by 2 to 3 times, and high-speed cutting can be performed, thereby greatly shortening the processing time. ④High machining accuracy, dimensional accuracy up to H7, and position accuracy can be doubled. ⑤ The tool life is long, and the processing of alloy steel, cast iron and aluminum alloy can be increased by 1 to 2 times respectively. ⑥ There are many cutting edges, and the drill is well centered, which is suitable for processing holes with a hole depth of 3 to 4 times the diameter. Mass production high demand grinder parts
2) Application of special milling cutters and composite cutters for aluminum-magnesium alloys. The special milling cutter for aluminum-magnesium alloy is adopted to realize high-speed, high-efficiency and high-quality machining of the casing. The milling cutter is generally made of 0.6μm ultra-fine high-speed steel material. After heat treatment and quenching, the hardness is 58HRC. It has high wear resistance and strength. It is a high-hardness and high-speed cutting milling cutter. The tool generally adopts three-blade, 35° helix angle, double-blade + arc ligament design, and large-capacity chip removal groove, which makes the chip removal smoother, the cutting edge is lasting and sharp, the cutting force is small, and the size is well controlled.
The center drill, drill bit, submerged drill, boring tool, rounding, chamfering and other tools originally used in the processing of stepped holes in the same position and multiple dimensions are combined into a composite tool, and multiple sets of dimensions are machined in place at one time, for example, 60°, 90° °, 120° three chamfering cutters replace the original special fixed-size chamfering cutters, and use buried holes and high-speed milling to process chamfering dimensions and remove burrs, effectively reducing the number of tools, tool change time and fitter workload.
(4) Optimize and improve the numerical control tapping technology to replace the manual tapping operation of the fitter. In this research process, all threads are completed by numerical control tapping, which effectively replaces the manual tapping operation of the fitter and improves the thread processing. Precision and productivity. Since there are few remedial measures for the out-of-tolerance thread of CNC tapping, it is easy to cause the entire casing to be scrapped. The main reasons for analyzing the out-of-tolerance of the thread include the breakage of the tap and the out-of-tolerance of the thread breakage, the excessive synchronization error between the spindle speed and the feed, which causes the out-of-tolerance of the thread size, the tap runout is too large, and the tap position and the bottom hole position during tapping are not coaxial. It is easy to cause thread out of tolerance, etc., especially when processing AJ threads with a pitch diameter tolerance zone of only 0.03 ~ 0.05mm, it is more difficult. Its solution is as follows.
1) Optimize the tapping program. The CNC system of the equipment used is Siemens 840D sl, among which CYCLE84 tapping command has a number of detail function options, which has better protection to prevent tap breakage and thread size out of tolerance. Mass production high demand grinder parts