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Description of gear hobbing process


 

Date:[2014/3/18]
 

1 the hobbing principle
Hobbing is in accordance with the principle of generating method to process gear. Hob to process gear is equivalent to a pair of cross axis helical gear meshing. In the meshing gear pair, a number of teeth, rarely only one or a few, spiral angle is large, it evolved into a worm shaped gear, in order to form a cutting edge, the gear is perpendicular to the direction of the helix open groove, grinding, flank, forming cutting edge and front, rear corner, then becomes a hob. The relative movement of hob and gear blank by engaging transmission, cut out the tooth in the tooth blank, formed the involute gear tooth surface, as shown in Figure 1a. During hobbing cutter spiral line, distribution in each tooth have been cut out of a thin layer of metal teeth, each tooth on the hob rotating cutter tooth cut out by several turn, involute tooth profile is composed of a cutting edge of a series of envelope and instantaneous position, as shown in Figure 1b. Therefore, hobbing overtime tooth surface forming method is generating, forming movement is complex composed of rotary motion hob rotating motion and of the workpiece (B11+B12), the composite movement called the generating motion. When the gear and the gear rotates continuously in the workpiece, the entire circumference are cut out all the cogging. In this process, the form of the tooth surface and the gear indexing is performed at the same time, thus generating motion is the movement.
Fig. 1 the hobbing principle
To sum up, in order to get the involute tooth profile and tooth number of gear, gear hobbing, gear hob and the workpiece must maintain the relative motion between the strict, i.e. when the hob turned 1 rpm, workpiece accordingly turned K/Z (K for the hob head, Z for the workpiece tooth number).
The transmission principle of the 2 processing of spur gear
Processing on hobbing machine straight tooth cylindrical gears must have two movement: the formation of involute tooth profile of generating motion and the formation of straight tooth (wire) movement.
Transmission principle diagram Figure 2 for hobbing spur gear.
Transmission principle diagram 2 hobbing spur gear
(1) the transmission chain rotation B11 and workpiece rotation B12 generating motion transmission chain links of the hob spindle (4 - 5 - UX - 6 - 7 - stage) for generating motion transmission chain. By the transmission chain to ensure strict movement between the workpiece and tool, the UX transposition mechanism to adapt to the changes in the number of teeth and the number of the cutter head. This is an inner transmission chain, it not only requires the transmission ratio is correct, but requires both hob and the workpiece rotation direction must comply with a pair of crossed axes helical gear meshing direction of relative movement. When hob rotating direction, the direction of rotation of the workpiece is determined by the hob helical direction.
(2) the main transmission chain the main transmission chain is the chain link power source and the hob spindle. As shown in Figure 2, the main transmission chain: Motor - 1 - 2 - UV - 3 - 4 - hob. This is a transmission chain, transposition mechanism of the transmission chain of UV for forming speed adjustment of involute tooth profile, should be based on the conditions of hob speed to adjust its transmission ratio.

The transmission principle of the 3 machining helical cylindrical gear
Helical cylindrical gear with straight tooth cylindrical gear, tooth profile is involute, but the direction of tooth is not linear, but the spiral line. Therefore, machining cylindrical helical gear also need two forming movement: one is the formation of involute tooth profile generating motion; another is the formation of tooth long spiral motion. The former and the machining of straight toothed spur gear, the latter requirement when moving along the axial direction cutter, workpiece to generate additional rotation based on generating motion of B12, to form a spiral tooth line trajectory.
Transmission principle diagram 3 hobbing helical cylindrical gear
Figure 3B is a schematic diagram of drive hobbing helical cylindrical gear, the generating transmission principle of motion transmission chain, vertical feed movement transmission chain, the main transmission chain and spur gear of the same, just add an additional motion transmission chain between the tool and workpiece holder (hob: mobile A21) - 12 13 - uy - 14 - 15 - synthetic mechanism - 6 - 7 - UX - 8 - 9 - stage (workpiece rotational B22), in order to ensure the spiral tooth line, the transmission chain is also known as differential motion transmission chain, wherein the transposition mechanism to adapt to changes in L and uy direction of spiral helix wire the. Figure 3A can illustrate this question: spiral line of workpiece is dextral, when hob along the axial feed f (unit mm), hob from a to B, then the workpiece for generating motion of B12 beyond, plus rotation BB ', in order to form a spiral tooth lines. Similarly, when the hob to point C, CC ′ work should be additional rotation. In turn, when the hob to point P (a workpiece spiral L), workpiece rotational PP ', just added a turn. The direction of rotation additional motion B22 and workpiece generating motion B12 rotation direction is the same, the direction of feed screw direction and hob depends on the workpiece. As shown in figure B12 and B22 to the same calculation of additional movement, with the 1 turn, the reduction of 1. In hobbing helical cylindrical gear, to make sure the two rotational motion of B12 and B22 at the same time to work without interference, need in the driving system configuration motion synthesis mechanism, then the two motion synthesis, then transfer to a workpiece. The actual rotating workpiece is by generating motion of B12 and the formation of spiral additional movement of B22 synthesis.
Characteristic of hobbing process 4
(1) the hobbing machining precision of generating method, there is no theoretical error of the tooth profile of form milling teeth, so teeth with high accuracy, can be processed 8~7 level precision gear.
(2) high productivity hobbing belongs to the continuous cutting, no additional loss of time, productivity than the general milling, slotting high.
(3) a hob cutter hob processing module and pressure angle and the same number of teeth cylinder gear.
In gear hobbing machining, the most widely used, it can be processed straight tooth, helical gears, worm gear, the spline shaft can be processed. But in general can not be processing gear, gear sector and at double gear is very close. Hobbing is suitable for single piece and small batch production and mass production.
5.Y3150E type gear hobbing machine
The Y3150E gear hobbing machine is a medium-sized general hobbing machine, mainly used for the processing of spur and helical gears, also can use the radial cut into the method of machining worm gear. Max diameter of the workpiece can be processed for the 500mm, maximum modulus 8mm, figure 4 is the shape of the machine tool diagram. Column 2 is fixed on the body 1 knife, slide plate 3 can move along the guide column. Cutter body 5 mounted on the turret slide plate 3 can rotate around the horizontal axis, with their. Hob is arranged on the cutter rod 4, rotate. The workpiece is mounted on a work table 9 spindle 7, rotate with the work table. Column 8 and table 9 packed together in a saddle 10, can be moved along the horizontal guide rail of machine tool. For radial position adjustment of the workpiece or the radial feed movement.
Keywords: gear hobbing gear processing Shenzhen gear double gear complex gear precision gear hobbing Yu Jiaxin Shenzhen Shenzhen Yu Jia Xin Hardware Products Co., Ltd.