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英文原文
Cylinder block machining process design
Engine parts in the engine block is a more complex structure of spare parts box, its high precision, processing, complex process, and the processing quality will affect the overall performance engine, so it has become the engine manufacturer's focus parts one.
1. Technical Characteristics of the engine cylinder block
Engine block is the basic engine parts and skeleton, while the engine when the general assembly of the base components. Cylinder's role is supporting and ensuring the piston, connecting rod, crankshaft and other moving parts work, the exact location; to ensure the engine ventilation, cooling and lubrication; to provide a variety of auxiliary systems, components and engine installation.
1.1 Technical Characteristics
Cylinder cast for a whole structure, and its upper part 4 cylinder mounting hole; cylinder standard cylinder is divided into upper and lower divisions into two parts; cylinder to the rear of the front-side arrangement of the previous three coaxial mounting hole of the camshaft and the idler axle hole.
Cylinder process features are: the structure of complex shape; processing plane, more than holes; uneven wall thickness and stiffness is low; processing of high precision typical of box-type processing part. The main processing of the surface of cylinder block top surface, the main bearing side, cylinder bore, the main and camshaft bearing bore holes and so on, they will directly affect the machining accuracy of the engine assembly precision and performance, mainly rely on precision equipment, industrial fixtures reliability and processing technology to ensure the reasonableness.
2. Engine block process design principles and the basis for
Technology program is the preparation of the master process is to process planning and key process equipment design guidance documents. The correct process of program design, facilitate the systematic application of new scientific and technological achievements and advanced production experience, to ensure product quality, improve working conditions, and improve process technology and process management level.
2.1 Process design principles
Design Technology program should be to ensure product quality at the same time, give full consideration to the production cycle, cost and environmental protection; based on the enterprises ability to actively adopt advanced process technology and equipment, and constantly enhance their level of technology. Engine block machining process design should follow the following basic principles:
(1) The selection of processing equipment, processing equipment, the principle of selection adopted the principle of combining rigid-flexible, processing each horizontal machining center is located mainly small operations with vertical machining center, the key process a crank hole, cylinder hole, balancer shaft hole High-speed processing of high-precision horizontal machining center, an upper and lower non-critical processes before and after the four-dimensional high-efficiency rough milling and have a certain adjustment range of special machine processing;
(2) focus on a key process in principle process the body cylinder bore, crankshaft hole, Balance Shaft hole surface finishing and the combination of precision milling cylinder head, using a process focused on a setup program to complete all processing elements in order to ensure product accuracy The key quality processes to meet the cylinder capacity and the relevant technical requirements;
(3) All fixtures are used hydraulic clamp, clamping components, hydraulic pumps and hydraulic control components used in Germany or the United States producing high quality and reliable components;
(4) The whole line used in all wet processing, using standalone BTA, high-precision machining processes critical horizontal machining center with constant cooling and to install high-precision high-voltage double-circuit band-pass fine filtration system, all with high-pressure processing center in the cold.
According to the technological characteristics of automobile engine cylinder block and the production mandate, the engine block machining automatic production line is composed of horizontal machining center CWK500 and CWK500D machining centers, special milling / boring machine, vertical machining centers matec-30L and other appliances.
(1) top and bottom, and tile covered only the combination of aperture rough milling machine dedicated to this machine to double-sided horizontal milling machine, using moving table driven parts, machine tools imported Siemens S7-200PLC system control, machine control cabinet set up an independent, cutting automate the process is completed and two kinds of automatic and adjust the state;
(2) high-speed horizontal machining center machining center can be realized CWK500 the maximum flow of wet processing, but because of equipment, automatic BTA treatment system through the built-in tray under the wide-type chip conveyor and the completion of the machining center can be dry processing; machine tool spindle speed 6000r/min, rapid feeding speed 38m/min;
(3) The combination of front and rear face rough milling machine tool using hydraulic transmission; control system imported Siemens S7-200PLC system control, machine tools have a certain flexibility;
(4) The special machine TXK1500 this machine vertical machining center by the modification of shape, with vertical machining center features and performance, this machine has high strength, high wear-resistant, high stability, high accuracy, high-profile etc.;
(5) high-speed vertical machining center matec-30L of the machining center spindle high speed 9000r/min. Control system uses Siemens SINUMERIK840D control system;
(6) high-speed horizontal machining center spindle CWK500D highest speed 15000r/min.
2.2 Process design basis
Affect the engine block part of the process design factors are manifold. Specifically, can be understood from the following aspects.
(1) product object, product drawings and technical documents related to the complexity of the engine block under the precision requirements of the process to take corresponding measures. Production targets for the four-cylinder automobile engine cylinder block;
(2) the production program, the production of the nature and type of production of the engine block the production program of 400 million;
(3) The annual effective system of work equipment, working for 320 days, with an average equipment loading rate of 80%, two shifts, 16 hours / day.
3. Engine block machining process design the main content
Engine block complex structure, high precision, large size, is thin-walled parts, there are a number of high precision plane and holes. Engine block machining process characteristics: mainly flat and the hole processing, processing of flat generally use planing, milling methods such as processing, processing of hole used mainly boring, processing and multi-purpose drilling holes. As the cylinder complex structure, so how to ensure that the mutual position of the surface processing precision is an important issue.
3.1 The selection of blank
Engine block on the materials used are generally gray cast iron HT150, HT200, HT250, there is also cast aluminum or steel plate, this engine block using high-strength alloy cast iron. Cylinder in the processing prior to aging treatment in order to eliminate stress and improve the rough casting mechanical properties.
Improve the rough accuracy, reduction of machining allowance, is to improve the automated production line system productivity and processing quality of the important measures. As the foreign box-type parts of rough quality and high precision, and its production-line system has been implemented directly on the blank line, not only eliminating the need for blank check device also saves the rough quality problems due to waste of machining time, increase overall efficiency. Therefore, the refinement of rough is to improve the productivity of the most promising way out. For the engine block production line, can be rough in parts on-line pre-milling six face, removing most of the margin, to facilitate direct on-line parts.
3.2 machining process selection and processing of the benchmark
Choose the right processing technology base is directly related to the processing quality can ensure the parts. Generally speaking, process benchmarking can be divided into coarse and fine reference base.
(1) The baseline for the on-line thick rough, which is particularly important the choice of benchmark crude, if crude benchmark choice unreasonable, will the uneven distribution of machining allowance, processing and surface offsets, resulting in waste. In the cylinder production line, we have adopted for the coarse side of the base;
(2) refined the base of this box for the engine block parts, the general use of “side two sales” for a full range of uniform benchmarks. For the longer automated production line system, due to pin holes in the course of the wear and tear caused by inaccurate positioning, therefore, will be divided into 2-3 segment pin holes used. In the cylinder pin hole of the process, we have adopted to the side, bottom and the spindle hole positioning, in the processing center on the process.
3.3 Machining Processing Stages and processes of the arrangements
Often a part of many apparent need for processing, of course, the surface machining accuracy are different. Processing of high precision surface, often after repeated processing; As for the processing of the surface of low precision, only need to go through one or two on the list. Thus, when the development process in order to seize the “processing high precision surface,”this conflict, the reasonable arrangement processes and rational division stage of processing. Arrange the order of the principle of process is: after the first coarse refined, the first surface after the hole, the first benchmark other. In the engine block machining, the same should follow this principle.
(1) roughing stage engine block machining process, the arrangements for roughing process, to fully carry out rough rough, trim most of the margin in order to ensure production efficiency;
(2) semi-finishing phase of the engine block machining, in order to ensure the accuracy of some important surface processing, and arrange some semi-finishing operations, will be required accuracy and surface roughness of the surface of the middle of some processing to complete, while demanding the surface of semi-finished, to prepare for future finishing;
(3) The finishing stage of requiring high accuracy and surface roughness of the surface processing;
(4) secondary processing, such as small surface screw holes, you can finish of the major surface after the one hand, when the workpiece deformation process little impact at the same time also reduced the rejection rate; In addition, if the main surface of a waste, these small the surface will not have to be processed, thus avoiding a waste of man-hours. However, if the processing is very easy for a small surface bumps the main surface, it should be placed on a small surface finish prior to the main surface finishing;
(5) should make proper arrangements for secondary processes such as product inspection process, in part roughing stage, the key process before and after processing, spare parts all the processing has been completed, should be appropriate arrangements.
Stage of processing division, has the following advantages: First, it can take measures to eliminate the rough workpiece after the stress, to ensure accuracy; second, finishing on the back, and will not damage during transport the surface of the workpiece has been processed; again, first roughing the surface defects can be detected early and promptly deal with rough, do not waste working hours. But most small parts, do not sub very thin.
3.4 cylinder surface of the main processing and secondary processes
Cylinder surface and support the main processing operations are:
(1) plane processing At present, the milling of engine blocks is the primary means of planar processing, domestic milling feed rate is generally 300-400mm/min, and foreign 2000-4000mm/min milling feed rate compared to far cry, to be on increasing, therefore, improve the milling feed rate, reduce overhead time is to improve the productivity of the major means of finishing a number of plane engine block when the milling feed rate to reach 2399 mm / min, greatly improved efficiency;
Top surface of the cylinder milling is a key process in the process, the flatness requirements for 0.02/145mm, the surface roughness of Ra1.6um. Processing in the cylinder, the use of side and spindle bearing bore positioning, top, bottom and middle vagay only aperture while processing used in the processing line outside of the knife device can better meet the engine block machining accuracy ;
(2) General holes machining holes in general are still using the traditional processing of drilling, expansion, boring, reaming, tapping and other craft approach. Issues in the design process of specific programs, use of coated cutting tools, cutting tools and other advanced tools within the cooling, and using a large flow of cooling systems, greatly improving the cutting speed, improved productivity;
(3) deep hole processing of the traditional processing method is used to grade twist drill feed, low efficiency of their production, processing and quality is poor. The deep hole in the engine block processing, the use of gun drilling process;
(4) The three-axis machining holes for the cylinder-axis machining holes holes of high precision, long working hours of the restrictive process. Thus, work arrangements, processing methods, tools and so on should be special attention. All cover pre-processing, that is, semi-circular hole and the cylinder block main bearing cap of the shortage of processing, its main purpose is to remove blank margin, release stress, to prepare for the post-order processing; in crankshaft machining processing center hole, using double-sided Boring, boring the first holes in the crankshaft hole at one end to 1 / 2 length, and then turn 180 degrees workbench, from the other end and then bore another 1 / 2 length.
(5) The cylinder bore machining cylinder hole cylinder machining processing is a key process in the one, under normal circumstances, the machining process as a rough boring, semi-fine boring, precision boring and honing. Cylinder bore wall for the early detection of casting defects, eliminate stress, should be thick cylinder boring holes in advance; due to the structural characteristics of the different cylinder bore, must be in honing process to improve the cylinder bore surface quality. In the high-volume production, the cylinder bore honing generally use the multi-axis grinding machine or honing Automatic Line. Here we use honing automatic lines, from the coarse-heng. Fine-heng and testing equipment, composed of three;
(6) Cleaning Cleaning is divided into wet cleaning and dry cleaning. Machining cylinder automatic production line using a large flow of wet cleaning;
(7) Detect points outside the line detection and line detection of two kinds. Quality inspection in the engine block, according to the actual situation with lines outside the detection, the main use of coordinate measuring machine integrated measurements of the cylinder, each 200 samples 1-5 pieces, each class random one.
3.5 cylinder processing the choice of cutting parameters
Engine block choice of cutting parameters including cutting speed, feed rate and feed rate option. As the processing equipment is used in high precision and rigidity of machine tools and high-speed machining centers in order to ensure the efficiency of cutting may be the appropriate choice of cutting a larger amount. The main processing engine block surface plane and bearing bore, cylinder bore holes such as the processing, while the plane and bearing bore, cylinder bore of the processing method is mainly milling and boring, so the discussion here, the choice of cutting parameters are mainly milling and Boring choice of cutting parameters.
(1) milling the choice of the amount of usage the choice of milling milling effect is directly related to good or bad. Generally speaking, the choice of dosage milling principles: Face milling cutter should be as much as possible when you first take a larger milling depth and width of milling, and then select the larger milling rate of as much as possible. Milling in a specific amount of choice when many factors involved, but in general, rough milling large margin when the workpiece, processing requirements low, the main consideration of the durability of cutter; Fine Milling margin is small, high precision machining, improvement in the quality processing of primary consideration;
In the engine block of the milling process, the use of machine tools as having a high stiffness, high-speed machine tools, big power, rigidity is good, so has chosen the relatively large amount of cutting.
(2) boring dosage amount of choice options under the rough finishing process varies. Rough, the selection of a larger depth of cut, finish, the selection of a smaller depth of cut. Depth of cut determined later, as cutting a large amount of use. In the cutting depth and feed rate after the selection can be a reasonable tool to ensure durability under the conditions of use calculations or look-up table method to determine the cutting speed. In general, the rough, choose a lower cutting speed, finishing, the selection of a higher cutting speed.
In the engine block boring process, the selection of machine tools as having a high stiffness, high-speed machine tools, big power, good rigidity; tool for foreign advanced tools, high quality, rigidity is good, so has chosen the relatively large amount of cutting.
4. Summary
Through the engine block of the structure and process characteristics of the analysis, discusses the engine block machining process design principles and basis of the choice of cutting parameters, and U-turn at high speed milling and boring, for example, design, analysis of the engine cylinder body of high-speed milling and turnover boring process, and in the processing need to pay attention to.