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Prospects for Precision Measurement Technology
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Helium of cubic boron (CBN) is the second diamond, the artificial synthesis of a new superhard cutting tool materials, their hardness only to diamond, cutting and grinding in the marketing process has been widely used. Helium of cubic boron (CBN) The application in machining
1. PCBN inserts with hardened steel finish turning
Fine by PCBN tool hardened steel cars, the workpiece hardness higher than 45HRC, the best results. The cutting speed is generally 80 ~ 120m/min, the higher the hardness of the workpiece, cutting speed should take low value, such as car 70HRC hardness of workpiece, the cutting speed should choose 60 ~ 80m/min. Depth of cut fine car in 0.1 ~ 0.3mm, feed rate at 0.05 ~ 0.025mm / r, fine surface roughness after the car was Ra0.3 ~ 0.6μm, dimensional accuracy up to 0.013mm. If a good standard rigid CNC lathe, PCBN tool rigidity and cutting edge sharp, the fine surface roughness after the car up to Ra0.3μm, dimensional accuracy of up to 0.01mm, with a CNC grinding machine can achieve the level.
If the machine tool rigidity, the choice of the cutting speed is low, selection of fine vehicles PCBN composite blade can be intermittent surface.
0.3mm fine car allowance is generally about as much as possible before quenching to improve the dimensional accuracy and reduce the thermal deformation, in order to ensure uniform fine car cutting margin, extending the life of PCBN cutting tools.
Fine cars generally do not have the cutting fluid, because at higher cutting speeds, a lot of cutting heat from the chips away, few will stay on the surface affect the surface quality and precision.
Finish turning the blade should use high strength and toughness of 80 ° diamond blade, tip radius of between 0.8 ~ 1.2mm in order to protect the tool edge, the use of fine oil stone before the required chamfer.
Fine car is a hardened piece of new technology, process to be done before the test can be used with the workpiece material, hardness and size of the same bar, finishing on the same machine, or rough test, the key is to test the tool and cutting parameter selection and process systems have sufficient rigidity. At present, the process has been adopted, such as FAW Group carburizing with PCBN cutting tools (58 ~ 63HRC) of 20CrMnTi transmission gears shift fork slot, using the process parameters for the υc = 150m/min, f = 0.1mm / r, αp = 0.2 ~ 0.3mm, realized the car instead of grinding.
2. Machining of hard cast iron and gray cast iron
(1) machining of hard cast iron
Turning hardened steel using PCBN tools, require higher quenching hardness 45 ~ 55HRC, machining of hard cast iron, as long as the hardness level of medium hardness (45HRC), will achieve good machining results. Such as automobile engine cylinder head exhaust valve seat, the seat is the use of copper, molybdenum high-chromium alloy cast iron materials, its hardness is usually approximately 44HRC, its seat on the hole with countersink (hinge), two processes car , mostly in the private automatic online processing, and the gun tube bore a hinge to. Cutting parameters used for the: υc = 71.6m/min, υf = 26.5mm/min, αp = 1.0mm, using BC broaching oil, processed from the use of PCBN cutting tools, with the previous process used a variety of carbide blades compared to the average durability of 1200 tool parts, machined surface roughness Ra0.4μm, seat plane swing difference ≤ 0.05mm. Dongfeng Motor Company engine plant since 1988, after the use of PCBN cutting tools, the effect has remained stable, the introduction of equipment can solve the problem of domestic tool.
(2) high-speed milling of gray cast iron
High-speed milling of gray cast iron, generally rough, of course you can use the K class carbide, finishing helium silica ceramic blade available. Such as in a side containing eight cutter blade mounted on the switch to only the two symmetrical PCBN inserts, and cutting speed increased by 4 times, the result is the same metal removal rate, while the cutting force fell 3 / 4, tool life and processing quality than the former.
Of pearlitic cast iron and chilled cast iron, PCBN tools also should adopt the high-speed processing, compared with other tool materials can increase the cutting speed, longer tool life and reduce the surface roughness.
3. High-speed casting hole boring
Rod used in pairs in high-speed boring boring PCBN inserts with single-chip boring compared to the balance is good, thereby increasing the rigidity of the boring bar, in a given feed, the use of PCBN can be double-blade boring achieve high metal removal rate and surface quality.
At present, the engine manufacturer has been more on the cylinder bore cylinder block (or cylinder) finishing PCBN cutting tools have been used. Such as Shanghai Volkswagen and FAW Group's engine plant, tanks are used for fine boring holes PCBN inserts and automatic compensation (υc = 500m/min, f = 0.2mm / r, αp = 0.1mm). So out of the cylinder bore machining high precision, dimensionally stable, and high efficiency, long tool life.
For boring holes, although ceramic or coated blade can be used, but the blade should be with a negative rake angle, which will increase the resistance to cutting and chip removal, easy to make slender boring bar vibration. If the use of PCBN cutting tools for high-speed boring, the hole surface quality, high production efficiency.
4. Reaming holes in hardened steel or hard casting
Processing of such parts of the hole should be plated with CBN reamers. This reamer is in their hardness of 45 to 42HRC steel or 9CrSi steel as substrate, with before and after the orientation and cutting some of its manufacturing base to high precision, the design must be reasonable. As they guide the first part of the reamer diameter is less than cutting edge part of the diameter of 0.04mm, the length of the cutting zone is greater than the workpiece hole depth, the length orientation after cutting the length is greater than its diameter should be less than the diameter of the cutting blades 0.02 mm. Reaming in order to flush cuttings and cutting fluid can lubricate the machined surface, the reamer to open the substrate with two deep spiral groove.
Machining hardened steel parts, such as a factory hole φ12.06 ± 0.05mm, hardness is 45HRC, bottom size φ12 ± 0.01mm, cylindrical hole required for the 0.005mm, the surface roughness is Ra0.2μm. By a group of five electroplating CBN reamers after processing, to achieve better economic results. Some of the engine manufacturer or CBN electroplated with diamond reamer to the cylinder block main bearing holes Heng hinge, instead of honing the original, so that processing efficiency is improved by several times, and quality.
5. For machining difficult to machine materials
Use with positive rake angle of the PCBN tool, choose the appropriate cutting parameters, namely υc = 100m/min, f = 0.05 ~ 0.2mm, αp = 0.1 ~ 0.2mm, solution or emulsion with extreme pressure coolant oil, machine Austria s body of stainless steel (45HRC), high temperature alloy steel, high manganese steel, high strength steel and high nickel alloy steel and other materials, can obtain higher machining efficiency and surface quality.
CBN grinding wheel Application in Grinding
CBN cutting tools used to produce materials in addition to, its largest application areas is made of CBN abrasive, grinding and honing for high-speed and efficient processing, and can greatly improve grinding efficiency, accuracy and improve the quality of their grinding a level.
1. Grinding car parts - camshaft and crankshaft
Automobile engines with multiple cam cam, cam quenched coarse and fine grinding of the cam is the key to the quality process. Are generally used by imitating shaped grinding, workpiece speed increase is limited, the workpiece grinding burn is easy to produce cracks, by imitating shaped by grinding, the cam contour surface of the curve to the impact by the wheel diameter, it is difficult to ensure that the correct cam contour curve. Production practice proves that when large diameter wheel, grind the cam lean, when the grinding wheel diameter hours, grind the cam fat, and only when close to or equal to the diameter of the grinding wheel by wheel diameter cam mode (usually φ570mm), its copying error close to zero, that is, the cam grind the surface of the cam contour curve is close by mode. In actual production, which are generally used in grinding wheel diameter from the D600 (or 610) used in D500, and the ideal wheel diameter (570) a difference of many, so the total production of most of the camshaft cam curve exceeded. To solve this problem, we rely on the use of imitation cam grinding wheel CBN grinding, CBN grinding wheel diameter can be made of the D575, CBN abrasive layer thickness is 4 ~ 5mm, the minimum diameter of the grinding wheel is the D565, grinding diameter Although the scope is only 10mm, but the grinding part number is the equivalent of dozens of pieces of ordinary wheels, not only guarantees the right cam profile, but it does not produce the phenomenon of grinding burn.
Liton industrial automation company, such as CBN grinding wheel with the camshaft, and the cost reduced by 50%, the cam surface of the fatigue strength increased by 30%; Dongfeng Motor Corporation diesel engine plant in Xiangfan vitrified CBN grinding wheel with coarse chilled cast iron camshaft , the cam grinding allowance t = 4 ~ 5mm, υ sand = 60m / s, rotating speed n = 100r/min, υf = 0.1mm / s, high-speed grinding fluid, CBN grinding wheel base is equivalent to 20 life corundum grinding wheel.
2.CBN wheel grinding of holes, including
Internal grinding efficiency has been low, the main reason is the grinding speed, grinding wheel material and the rigid rod problem. The production process used in the dressing wheel, replacement wheel of time work accounted for nearly one-piece 1 / 3 to 1 / 5. If the inner circle or groove grinding with electroplated CBN grinding wheel and the wheel speed, increasing the mill diameter, the workpiece can be an appropriate increase in speed and feed rate, not only to ensure that hole (arc) diameter, width size and shape bit precision, surface roughness and to avoid burns, but also improve the processing efficiency can be doubled, reducing processing costs.
Such as domestic processing factory with an annual output 600,000 sets of textile machinery bearings, grinding φ15.5 +0.04 arc adjacent holes and slots in the past with a chromium corundum (GG) wheel, two processes were required in two M224 internal grinding machine processing, the slot (arc) diameter difference and coaxial with the hole size is difficult to guarantee, and low efficiency, the use of CBN grinding wheel, the bold stroke of the mill to improve the feed rate, saving the trimmed and replacement of wheel of time, solve the original problem. Later changed to hole, ditch while grinding, that is, two wheels mounted in the rod mill, the grinding efficiency by 1 times, saving a grinder. The processing of the surface roughness for the grinding process parameters used Ra0.63μm: υ sand = 36m / s, υ2 = 19m/min, f rough cut = 1μm / r, f fine cut = 0.5μm / r, optical grinding time t = bs, a 10% concentration of the emulsion values.
3. Using CBN grinding wheel gear
Gear grinding in the past is the use of a single tooth and multiple tooth grinding, tooth grinding Although one can obtain higher precision, but low efficiency, high cost, multi-tooth grinding, although the production efficiency, but its processing worse quality than a single tooth grinding. The use of a CBN grinding wheel, grinding, whether single or multi-tooth Tooth grinding, electroplated CBN grinding wheel or grinding vitrified grinding wheel, the effect is highly significant:
(1) CBN grinding wheel profile can be made high precision, due to high durability, less frequent dressing, without regular adjustment tools, access to stable teeth gallery, lead and pitch accuracy.
(2) enable high-speed and high feed rate of grinding teeth grinding surface roughness is low and does not burn, the grinding efficiency can be increased under the conditions of access to higher gears (6 ~ 7).
(3) CBN wheel life long, grinding performance, saving the grinding wheel dressing change, adjustment and parts testing machine, and many auxiliary time.
4. Application of CBN abrasive machining difficult to machine difficult materials and surface
Of hardened steel or chilled cast iron bore honing, CBN honing stone can be used for high strength, high hardness and high heat-sensitive alloy steel, stainless steel, heat-resistant steel and alloys, the appropriate use of high hardness, high strength of the CBN wheel, the extremely high pressure liquid or emulsion grinding fluid to cool down. Face of long or complex rail surface, the cam shaft grinding machine by model should be adopted Dengjun CBN grinding wheel.
CBN materials to promote the key process in the machining of
CBN materials, whether made or produced abrasive tool, used in high speed cutting or grinding, can receive to improve product quality, improve processing efficiency, shorten the processing cycle and reduce processing costs and other significant effects. Thus, in processing, to promote CBN tool (grinding) is to improve the manufacturing technology with strong measures. However, if the general to promote the use, there are many problems.
In order to better promote the use of the production of CBN tool (grinding) with, should do the following work:
1. To play a CBN tool (grinding) with Research Institute (as) the leading role
At present, many of CBN materials manufacturers, production is also a lot, but not much high-quality, CBN cutter (grinding) with the stability of the user less. The reason is mainly mechanical processing sector CBN expensive knife (grinding) a lack of choice and use of knowledge acquired in a few effective CBN tools in their conditions of economic contraction, not easily invest in technology trials. To solve this problem, only the CBN tool (grinding) with Research Institute (the) initiative to further the production of machinery manufacturing unit, select the production efficiency and quality of the weak links, and already has or can easily create the CBN point processing conditions, in consultation with users signed a contract to jointly develop applications CBN. Research unit from the tool provided free of charge testing the CBN cutter (grinding) with, the user is responsible for providing the necessary conditions of production test pilot. This played a multi-active, choose from the CBN to the tool manufacturing quality, will to the best, the fastest speed of the user from preparation to the use of test conditions, see the results of the target value to the contract, do not take test fee will be solved production problems, it is easy to promote. The tool center () can also be recovered gradually after the profits of the supply, as long as the two sides have maintained mutual benefit, collaborative relationships will be stronger. Our factory is the use of this approach with a number of Research Institute (University) has developed a lot of new technology.
2. To achieve the joint development of three-point line, the CBN - tool manufacturing - the user or CBN and Tools Manufacturing - Machine Tools - CBN users to develop applications
Many in machining processing difficulties, although the CBN tools can be used to solve, but for the present conditions, not separate domestic Which can be done, because not all CBN tools have strange and universal processing capacity. We have used the CBN inserts fine boring boron cylinder, the effect is not better than the new ceramic blades. The reason is that many, such as CBN quality, content, brand specifications and whether the combination of agents for boron cast iron. The CBN abrasive grinding effect of the factors that influence even more, in addition to their quality of raw materials, proportion and abrasive manufacturing technology, there are also conditions of use and technology. Such as the grinding speed (using the high speed grinding speed), grinding rigid, vibration-free, automatic fine feed and finishing compensation mechanism, the appropriate grinding parameters and coolant, etc., which are complementary to each other important factors, by the parties work together to improve their quality of its products, mutual promotion, to make CBN tools and equipment used successfully in production.
3. Active CBN tool (grinding) with manufacturing and research using technology
Users want to use a pragmatic CBN tools, this, request tool manufacturing units, in addition to CBN tools and to improve manufacturing technology, product quality should also establish clear standards and methods of identification, the distribution of certain performance parameters, such as the CBN tool content and brands, CBN abrasive hardness and precision, concentration, based on the production and use of this test, to maximize the user experience in the production of different cutting parameters and machining coolant obtained results were analyzed, so that CBN tool to get qualitative improvement. CBN tools, the scope of the technical conditions of use and application support (such as equipment and coolant, etc.), the user can correct selection and use of CBN tools.
4. You need to improve product quality awareness, the courage to improve the manufacturing technology
21st century is the era of high technology, products must have a high-performance, high-quality no market, business vitality. Therefore, as soon as possible to improve the level of manufacturing technology, and promote the use of CBN tools to improve manufacturing technology is a powerful measure, which requires not only the competent authorities of the strong funding and support, organized, planned to gradually extend the technical support and CBN tools use, but also requires the user to the courage to accept the new materials, new technology, change the old concepts and management methods of production, that knife (grinding) with all indicators of consumption is very low cost, product cost can only account for 1 / 100 or so, rather than to improve production efficiency and ensure product quality prevail, it would limit high quality and efficiency of the blade (grinding) applications and advanced equipment with capacity to play. Practice has proved that, CBN cutter (grinding) with the effectiveness of the process not only improve product quality, but also improve economic efficiency.
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