Study On Design Automation Technique Of Roadheader Cutting Head

Roadheader is a specialized equipment which used to excavate tunnel, generally, it possesses the function of excavate, chip removal, automovement, shoring, and guiding, etc. It could be used to excavate underground tunnel, tunnel through mountain, water diversion tunnel, underground utility tunnel, underground passage, coal road, etc. According to the characteristic of cutting objective, roadheader could be divided into two classes, soil roadheader and rock roadheader, rock roadheader could be divided into TBM (Turnel Boring Machine) and selective roadheader further. Selective roadheader could move its boom up and down or left and right freely, it belongs to singlepoint cutting machine. Selective roadheader could concenter its power so it could cut harder rock, its working section could be any shape, it could excavate selectively according to the condition of its objective, it possesses better mobility, and its cost is lower. Selective roadheader includes longitudingal shaft roadheader and crossshaft roadheader. Crossshaft roadheader possesses two symmetrical cutting head, the axis of cutting head is perpendicular to boom, the transverse cutting force is less, steady cutting movement is easy to acquire, gears are arranged densely so the cutting effect is better, and the loading characteristic is good. Crossshaft roadheader is mainly used to excavate coal road or mine road, generally, protodyakonov scale of hardness of its cutting objective is less then f8. Normally, ore is brittle substance, its compression strength is the biggest, its shear strength takes the second place, and its tensile strength is the smallest. There is some randomness in the distribution and structure of ore, but pressure-release effect and collapse effect are common. Ore underground is squeezed in three directions, while being cut, squeezing force of cutting side is removed, ore is only pushed by the force on the other directions, tensile deformation appears nearby, cutting strength decreases, or even ore is pushed out, the phenomenon is called pressure-release effect. Because of the brittleness, not only ore on top face of gear will break away, but also ore besides the gear, so the groove is always wider then the gear, the phenomenon is called collapse effect. Generally, compact core cutting theory is used to describe the interaction process between gear and ore: elastic deformation of ore body, producing of microcrack, producing of compact core, development and break out of compact core are the four steps of the process. The producing and development of compact core not only will consume much energy and will induce intense vibration in cutting force, but also will produce much ore dust. According to compact core cutting theory and ore characteristics, cutting head should produce big enough tensile strength to crash ore to reduce cutting force and specific density consumption, and cutting action should happen in pressure-release region. The application of vibration cutting theory is a break through, experiments show that cutting force and specific density consumption are obviously reduced. Cutting head is core operating mechanism of Selective roadheader, its capability will directly influence the performance of complete machine. The performance index to evaluate cutting head includes productivity, specific density consumption, cutting hardness, fluctuation coefficient of cutting force, service life of gear, dust rate, etc. Cut head is the most Complex component of Selective roadheader and gear the part which directly act on ore. A good deal of parameters should be considered in cutting head design, shape parameters, dimension parameters, swing speed, autorotation rate etc should be consider integrally, gear shape parameters, dimension parameters, material, formation of gear holder, format of distribution, space angle parameters etc should be consider partially. In addition, spatial movement parameters of gear, cutting parameters, force conditions of gear and cutting head should also be considered. Not only all the parameters are complex, but also they are interrelated and interrestricted, so the design of cutting head is the difficult part and key point in the design of the whole machine. According to crossshaft roadheader, there are three types of cutting modes, longitudingal feed cutting mode, vertical swing cutting mode, and horizontal swing cutting mode which is the main cutting mode. Accordingly, in the cuttingprocess, there are three types of movements of cutting head which includes longitudingal feed movement, vertical swing movement, horizontal swing movement, and autorotate of cutting head. Movement of gear is resultant movement of one type of movement and autorotate of cutting head. In different cutting mode, the movement of gear is different, in longitudingal feed cutting mode gear perform plane cycloid movement, in vertical swing cutting mode gear perform arc cycloid movement, and in horizontal swing cutting mode gear perform arc spiral movement. The outline formed by gear points while cutting head autorotating is called enveloping surface, according to crossshaft roadheader, enveloping surface is generally make up of two paraboloids and one spherical cap. The most important structural dimension of enveloping surface is peak diameter, which should be determined by pressure-release effect, cutting speed, cutting force, and productivity, etc. Gear is the part which directly act on ore, it must be rigid enough so that it can cut off ore, it must be antiabrasive to extend service life, and it must possess high temperature stability. At present, selective roadheader mainly adopt pickaxe shape gear as its cutting part. Pickaxe shape gear is made up of cutter holder and alloy cutter, alloy cutter should possess enough degree of hardness and be abrasive resistance, cutter holder should possess enough rigidity and be long enough. The position relationship between gear and cutting head body can be described by spatial distribution parameter and spatial angle parameter. Spatial distribution parameter illustrates how gear point distributes on enveloping surface of cutting head, to meet the need of chip removal, gear point is distributed along even lead angle parabolic spiral, and being decided by spiral parameter, distribution angle, and cutting line distance. After gear point position being decided, spatial angle parameter still needed to place gear and toothholder on cutting head body. Here, two equivalent series of parameters, cutting function angle parameter by which we can easily describe the angle between gear and ore and assembly technique angle parameter by which we can easily describe installation process of gear, are being adopted and conversion...