Key Points of Grinding Technology for Thread of Grinding Wheel Sheet

Key Points of Grinding Technology for Thread of Grinding Wheel Sheet

(1) Controlling the ambient temperature of the screw grinder. The standard constant temperature precision is 20 +1 C, and the reference temperature can be adjusted to 2-3, but the temperature fluctuation can not exceed 1 C in a day. In order to facilitate fine grinding and debugging, the measuring temperature of the workpiece should be in accordance with the ambient temperature during processing.

(2) The screw grinder shall be installed on an independent foundation with anti-vibration ditches and away from railways, highways and all vibration-generating machinery. The power supply used in thread grinder should have voltage stabilization device and protection device of sudden power failure.

(3) Before grinding threads, the machine tool needs to run empty for a period of time, so that the grinding wheel spindle, the machine tool master screw pair, and the workpiece are in a state of thermal balance, so as to avoid the influence of thermal deformation on grinding accuracy.

(4) The diameter and thickness of the flake wheel used in single-line grinding are in the range of 400-500 mm and 10 mm respectively. To install and balance the grinding wheel carefully, the fit clearance between the grinding wheel hole and flange should be appropriate and evenly distributed. After several balances, the screw should be tightened symmetrically and the end face of the grinding wheel should be pressed. Oil-resistant rubber or cardboard should be used as the backing. After balancing, the grinding wheel should not be removed again, and should be used until the wear limit of the grinding wheel.

(5) The radial circular runout of the spindle tip after installation is less than 2 micron, the 60 degree conical surface should be taken positive tolerance, and the center hole of the workpiece should be in contact with the tip, and the contact area should be 70%-80%. The pressure between the tailstock top and the workpiece should be appropriate and adjusted at any time during grinding to eliminate the additional pressure caused by the thermal deformation of the workpiece on the tailstock top.

(6) In thread grinding, the workpiece's outer circle is the auxiliary base surface, and the radial cutting force and workpiece stress are eliminated by means of the center frame to reduce the bending during grinding. The center frame should adopt a closed structure with three-point force. The number of the center frame is n=l/10d (l is the length of the workpiece, D is the diameter of the workpiece).

(7) When grinding threads, the relative motion of grinding wheel and workpiece is required to form a spiral surface with definite tip. The traditional pure mechanical screw grinder achieves the required pitch by choosing and calculating the pitch exchange gear or replacing the nut screw. Attention should be paid to the accuracy and meshing clearance of the switching gears. Low accuracy, too large or too small meshing clearance will cause the transmission chain error to increase.

(8) According to the size and direction of workpiece spiral elevation, the inclination and direction of grinding wheel spindle components should be adjusted accurately. The inclination and direction of grinding wheel dresser must also be consistent with that of grinding wheel spindle components. When the inclination angle is greater than 5 degrees, the base of driving grinding wheel motor must be adjusted accordingly. The accuracy of the above adjustment affects the degree of interference between grinding wheel and workpiece helical surface, which is especially important for the thread with large helical lift angle.

(9) The transverse feed of precision thread is generally 0.005-0.015 mm.  In order to reduce pitch error caused by thermal deformation, grinding from tailstock to headstock should be adopted. In order to make the grinding allowance uniform, dynamic tool alignment should be carried out in the middle part of the reeling pattern.

(10) Some threaded grinders (such as GL-2 and GL-4 in Germany) can grind the long lead screw which exceeds the center distance through the spindle hole with "super-long lead screw connector". At this time, before clamping the workpiece with three-jaw self-centering chuck, it is necessary to carefully adjust the spiral surface.

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