Special fixture for the hottest grinding of the ta

  • Detail

The machining accuracy of the spindle taper hole has a direct impact on the radial runout accuracy of the axis of the spindle taper hole of the lathe. During the trial production of new products and small batch production, because the process equipment is not matched, the fixture for fine grinding the taper hole of the main shaft is supported on the front and rear support journal positions of the main shaft with two center frames, and the taper hole is ground after alignment. Due to the poor rigidity of the center frame, inconsistent clamping errors, and time-consuming alignment, the grinding accuracy of the spindle taper hole is low. After repeated grinding for several times, the accuracy can only reach the radial runout of 0.008 ~ 0.01mm at the 300mm far end, and the contact surface of the taper hole is 70%. The stress-strain shape on the operating surface is also different, which is difficult, low production efficiency, and not suitable for mass production. Therefore, a special fixture for grinding the taper hole of the spindle is designed as shown in the figure

1 fixture structure

the fixture for grinding inner conical holes is mainly composed of base 12, front support 10, rear support 7 and connecting sleeve 6. The front bracket 10 and the rear bracket 7 are respectively fixed on the base 12. In order to enable the workpiece to be loaded and unloaded safely and smoothly, the front and rear support holes adopt split support structures. In order to improve the contact stiffness and service life of the support hole, protect the workpiece support surface from being scratched, and facilitate the lubrication of the support surface, the front and rear support holes adopt inlaid copper tiles, namely sliding bearings 8 and 9. The two sliding bearings are each composed of three copper tiles. The front support bearing bush 9 is made into a conical hole, which is matched with the 1:12 cone of the workpiece. The joint surface of the front and rear support holes and the base is aligned through assembly scraping, grinding, and ensuring that the coaxiality of the front and rear support holes and the parallelism to the guide rail of the grinder bed are within the range of 0.005mm, and are at the same height with the grinder head frame, the spindle center, and the grinding wheel shaft center. In order to prevent the accuracy loss caused by the wear of the front and rear support hole surfaces and affect the machining accuracy of the workpiece taper hole, the fixture accuracy needs to be inspected at a fast curing speed (every 3 months or 300 sets) on a regular basis

the floating connection part at the rear end is composed of flat top tip 3 (modified with standard taper cemented carbide tip), steel ball 14, shift rod 4, copper screw 5, connecting sleeve 6, tension spring 13, etc

1. Grinder head frame 2 Head frame flange 3 Flat tip 4 Paddle 5 Copper screw 6 Connecting sleeve 7 Rear support 8 Copper tile 9 Taper hole copper tile 10 Front support 11 Workpiece (spindle) 12 Base 13 Tension spring 14 Steel ball

figure grinding spindle taper hole fixture

2 working principle

the axial positioning of the workpiece is tensioned backward (symmetrically tensioned) by the tension spring 13 through the connecting sleeve 6 clamped on the workpiece and on the rear end, forcing the steel ball 14 to press against the carbide flat tip 3 (the flat tip 3 is installed in the spindle taper hole, and the spindle is fixed without rotation), thus limiting the axial movement of the workpiece and ensuring the positioning accuracy of the workpiece. The flange plate 2 rotates, and the workpiece is driven and rotated by the shift rod 4 and the connecting sleeve 6 to realize the grinding movement

when unloading the workpiece, just loosen three copper screws 5 and the lock nuts on the front and rear supports, and then open the front and rear split supports to unload the workpiece

3 summary

the machining accuracy of the workpiece of this structure can stably meet the requirements of the radial runout accuracy of the conical hole to the supporting Journal (0.005M at 300mm to speed up the construction of the RO Ro Wharf in the new harbor area m), and the surface roughness is Ra0.4 M. the contact surface is more than 80% when tested with the standard taper sample gauge. It meets the technical requirements of the spindle, has a large reserve of accuracy of the softening coefficient of compressive strength, is easy to operate, and improves the productivity

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