hob is cutter along the cylinder or cone for the spiral arrangement of gear cutting tool for according to the generating method of machining cylindrical gear, worm gear and other cylindrical toothed workpieces (see gear cutting, gear). according to the different purposes, the hob is divided into gear hob, worm gear hob, non involute gear hob and gear set, etc..
the hobbing machining, cutting speed and depth of cut should be decreased with the increase of the tensile strength of the workpiece material, therefore the selection of suitable coating can improve the cutting speed (in some cases can improve feed rate). pvd coating can provide protection for nearly all hob. standard of the tin coating for the lubricant of low speed rolling effective cutting; ticn coating can increase the hardness and wear resistance of the hob, suitable for abrasive machining of workpiece material; tialn coating is developed for dry cutting, has excellent toughness and heat resistance. a new type of alcrn coating developed recently for dry cutting has excellent wear resistance, heat resistance and oxidation resistance.
the fierce competition in the global market requirements gear manufacturers continuous breakthroughs in improving production efficiency and reduce production cost limit. this means that must be used by high-quality materials manufacturing and advanced hob of high performance protective coatings for high speed hobbing. due to higher prices of advanced cutting tools, so some production workshop to use, hob. this is because they do not have a comprehensive analysis of all aspects of the production process to determine the correct cost calculation method, from the calculation of the total cost to each processing cost calculation.
in order to achieve a higher efficiency of gear cutting, the design of the hob is tending to develop high efficiency and long. the whole tool steel material is made with a handle, which is smaller in diameter and usually longer than that of a hole with a hole. they are installed in the gear hobbing machine, the positioning handle neck ends, rather than with a hole that is installed in the hob spindle.
integral belt handle hob is usually used for the processing of worm gear, and the diameter of the gear is required to be relatively close to the diameter of the worm gear. the optimized design of the belt handle hob is the most suitable for large batch, high efficiency processing. and the large diameter, large pitch gear (such as truck transmission box or mining machinery gear) is usually used with a hole hob processing.
the influence factors of the cutting time can be shortened, including increasing the feed rate, cutting speed and increasing the number of the hob head. hob designers in order to optimize the hob performance, try to use a small diameter hob, because in a given surface speed (sfm), the smaller the diameter of the hob, the higher the cutting speed. as with handle hob diameter is small and the non porous, and similar diameter perforated hob compared with greater length. therefore, it can be more can be mobile cutting zone, and the hob every knife can more cutting workpiece. a hob with a sharp cutting edge moves into the cutting zone along its axis.
the rolling process can be used, and the cooling liquid can not be used. however, many users are more willing to use dry rolling, because it can eliminate environmental pollution, and save the cost associated with the treatment of coolant. in order to protect the cutting edge under the condition of high speed dry cutting, the dry type rolling requires a high quality coating with high temperature stability and low thermal conductivity.
because of the whole structure, the cutter is installed on the gear roller machine and the parts are less, so the assembly stiffness is better than that of the hole cutter. the cutter can be installed in the top of the state between the grinding, installation and measurement accuracy of detection. compared with the belt hole cutter shank cutter to remove the accumulated between the hole and the mandrel radial jumping error, as well as by isolation and mounting nut is caused by the swing error.
high wear resistance and high level of room temperature hardness and cutting temperature of high level of hardness and cutting high level of hardness and cutting. although the high quality steel and coating materials cost higher than the lower performance, but can produce a higher cutting speed of the small diameter with a handle hob, which can shorten the processing cycle time and reduce the cost of each processing. under the appropriate processing conditions, the efficiency of each processing cost is usually greater than the increase in the cost of each tool, which can reduce the total processing cost of each piece of work piece.
in hobbing machining, the tool suitable coating is very important, it can improve productivity and reduce the cost of processing, in some cases of machining, the tool life increased by a factor of, can save tools cost and reduce the number of tool change, reduce downtime.
the preparation of cutting edge has an important influence on the coating properties. sharp cutting edges can produce smaller cutting force and lower cutting heat, but the coating is thin, increasing the cutting edge chipping of danger, it is only suitable for small feed rate and cutting; after cutting edge passivation coating thicker, with more stability of anti collapse edge, but also larger cutting force; after cutting edge chamfering and passivation treatment has the stability of anti collapse edge and therefore very suitable for hard and brittle tool materials and high feed rate cutting.