Application of efficient tools for gear manufacturing technology development

In the gear manufacturing process of each company's tooth is roughly the same. The majority of automobile gear hobbing, shaving gear and heat gear honing process, a small number of enterprises, and some car companies grinding process after hobbing and heat, and the gear transmission industry in general with a hot grinding process.
Hobbing system tooth processing accounts for more than 70% share of high-speed hobbing significant. In order to achieve high-speed hobbing, gear hobbing machine must increase the rigidity, hob head drive power, improve the CNC, servo function, temperature compensation, but also to promote the application of high performance, efficient tool.
Hob materials applied in the current production-based high-speed steel, but also the use of carbide inserts block hob or the overall PM carbide hob. High-speed steel hob use of a coating, such as M35, M42, A4 tool materials, the application of TiN coating and its matrix toughness, heat-resistant, wear-resistant coating, to prevent chipping, cutting speed can be increased to 120 ~ 150m/min. Using powder metallurgy sintering forming method of manufacturing solid carbide hob, also has a good effect. This tool after the coating, the cutting speed can be increased more than 250m/min, the axial feed can be achieved ~~ 6mm / r. And as long as the equipment allows to achieve dry cutting. The dry cutting can reduce the original cutting coolant mist pollution of the environment, and the excellent performance of carbide coated tool making it significantly longer service life and reduce processing costs.
Hobbing hob and the workpiece is equivalent to a pair of meshing with each other Worm, in accordance with the continuous develop into a way, the straight-line tooth of the hob blade envelope cut out the workpiece involute line tooth. Hobbing process for subsequent processing, such as shaving before heat treatment or heat treatment after grinding teeth to allow the appropriate allowance, tooth root and partly in hobbing processing into requirements. Hob speed is higher, the head a few more, the shorter the cutting time. Order to improve efficiency, in addition to improve the speed of the hob and the feed rate, should be as long hob. Increase the number of head can increase the cutting speed, reducing the number of cutting edge cutting, hob cut, reduce wear and improve tool life. The hob commonly 2 to 4, 5 to 7.
Increasing the diameter of the hob and the number of groove to increase the chip thickness, can also increase productivity. Hob diameter is limited by the machine tool structure but because of the limited scope for increasing increase the strength of the groove number, in many cases will affect the cutter, so there will be two rows of three rows of alveolar into one dual- Cutters or Cutters. This hob is both can be used to rough cut, fine cut can also be used. Cutter strength can increase the cutting parameters, improved chip formation conditions, but also adapt to the requirements of heavy cutting along the entire blade reasonable distribution of the cutting area. Compared with the ordinary hob, efficiency is improved by 4-6 times, Guchang called heavy cutting hob.
Along the workpiece axial feed at the same time in the whole process of hobbing, the hob also along hob axial displacement, ie, for channeling knife campaign to make all the cutter in the hob on to participate in cutting, balanced cutter wear to improve the tool life. If the workpiece tooth surface roughness deterioration spot burr increased or unusual sound, it is timely sharpening.
Carbide hob hardened gear processing method has many years of application in the enterprise, but in most cases, only used to replace the coarse grinding. This is due to the rotary cutting hardened the Qie Ruqie hob bomb to cause the workpiece tooth mutations, In addition, the moment of extrusion high temperature makes the workpiece tooth surface annealed to generate a soft point, affecting the contact strength of the workpiece, so the use of its The metal removal rate than teeth grinding features, instead of rough grinding with good results. Also useful carbide forming scraping cutter spiral bevel gear finishing and successful examples, but forming tool is very expensive, and limited life expectancy, the application is not extensive.
Often applied within the tooth, double or gear shaper process. Compared with hobbing, both of which developed into a principle, but the tool the Qie Ruqie the impact of gear shaper cutter spindle moving up and down by the inertia force, unless the process conditions do not permit the use hobbing, otherwise is not applied gear shaping process. For this reason, dry cutting shaper processing method has been little progress.
Large modern hobbing machine, gear milling head according to the configuration of the user's requirements, the disc cutter insert milling and dividing by tooth internal gear tooth allowance resection, follow-up and then the teeth grinding cut method to obtain the final tooth. Compared with the use of gear shaping process, the efficiency is increased by several times. Of course, limited by the milling head of the internal tooth, workpiece inner diameter should be large enough.
In addition, using to the method of milling milling and plug straight teeth, fine cutting edge of the cutter can be made into the workpiece as the involute shape, processed reserved to the grinding teeth of the margin may be smaller; Helical milling within , knife block according to the helix angle pulled at an angle, but the the discoid cutter can not as hobbing continuous into the exhibition, thus cutting out the tooth is to approximate the involute margin to be left to grinding teeth slightly larger. The high-powered tooth milling head with a preloaded mechanical transmission chain, motor or hydraulic motor drive to provide the basic conditions for efficient processing. Optimization of cutting parameters coated cutter or carbide veneer cutter, to improve the metal removal rate and tool life assurance, and dry cutting.
For example, processing P1600/2000 efficient hobbing machine with an internal gear milling head 107 teeth, the modulus of 9 helix angle of 8 degrees, 210 mm face width, 42CrMoS4 material internal gear, using air-cooled dry cutting, the total milling time 135 minutes (one-time cutting), the same amount of resection, with inserted teeth in the general machine tools, processing, at least, two or three days.
To reduce gear noise increasingly high demand for traditional rolling to shaved hot Heng process can not meet this requirement due to capacity constraints,. Such as the use of a hot mill process, because of high manufacturing costs so that corporate decision makers indecisive. Mass-produced vehicle transmission gear, a strong internal tooth honing wheel honing process to resolve this contradiction, Gear Finishing provides a feasible method.
Traditional honing process honing margin does not exceed 10 microns, just after shaving by heat treatment of the tooth surface finishing processing, increase the number of surface quality, and therefore can not improve the toothed gear to. Strength within the gear honing is not the same heat treatment after finishing a larger allowance (20 to 50 microns), meet the technical requirements; and the tooth surface to form a mesh texture, unlike the grinding teeth cyclical strip texture, it can reduce tooth contact frequency, thereby reducing the noise. The honing tool can be used a resin-bonded sand, silicon carbide or CBN honing wheel can be used.
Processing outside the teeth, in order to save costs, often dressing resin bonded honing wheel, diamond dressing wheel dressing in the trimming. Strong honing process is mainly used in mass production of automotive gears, the workpiece mode of 0.3 to 6 mm, diameter 250 mm, the teeth 20 to 50 mm wide, the final gear precision can reach six or more, the processing cost of about half of the grinding teeth.