Generally speaking, the processing methods of worm grinding wheel can be divided into two categories:
1. Forming method processing:
Gear milling cutter, forming gear grinding machine, the profile of the milling cutter and the forming grinding wheel is the profile size of the tooth groove of the worm grinding wheel tooth.
2. Generating method processing:
Gear hobbing, gear shaping, gear grinding (including worm grinding wheel gear grinding machine, the grinding wheel profile is rack type.) Generating grinding and forming grinding use single-piece grinding wheels, both of which grind one tooth at a time. The grinding wheel of the generating grinding is larger than that of the forming grinding. The generating grinding uses the involute forming principle; the forming grinding is to repair the grinding wheel into the shape of the gear involute. The diameter of the grinding wheel used by the worm grinding is similar to that of the generating grinding, but thicker. The worm grinding uses the principle of meshing of the rack and the gear. You can analyze the efficiency and accuracy of other aspects by yourself.
Cylindrical worm transmission
The tooth surface of ordinary cylindrical worm (except ZK worm) is generally machined on a lathe with a straight blade turning tool. Depending on the installation position of the turning tool, the tooth profile curve of the machined worm tooth surface in different sections is also different. According to different tooth profile curves, ordinary cylindrical worms can be divided into four types: Archimedean worm (ZA worm), involute worm (ZI worm), normal straight profile worm (ZN worm) and cone envelope cylindrical worm (ZK worm). GB10085-88 recommends the use of ZI worm and ZK worm.
Archimedean worm (ZA worm)
For this worm, the tooth profile is an Archimedean spiral on the plane perpendicular to the worm axis (i.e., the end face), and the tooth profile on the plane containing the axis (i.e., the axial tooth profile) is a straight line, and its tooth profile angle α0=20°. It can be turned on a lathe with a single tool (when the lead angle γ≤3°) or double tools (when γ>3°) with a straight blade. When installing the tool, the top surface of the cutting edge must pass through the axis of the worm. This worm is difficult to grind and inconvenient to process when the lead angle is large.
Normal straight profile worm (ZN worm)
The end face tooth profile of this worm is an extended involute, and the normal (N-N) tooth profile is a straight line. ZN worm is also turned on a lathe with a single or double tool with a straight blade. This worm is also difficult to grind.
Involute worm (ZI worm)
The end face tooth profile of this worm is an involute, so it is equivalent to an involute cylindrical bevel gear with a small number of teeth (the number of teeth is equal to the number of worm heads) and a large helix angle. ZI worm can be turned on a lathe with two straight blade turning tools. The top surface of the blade should be tangent to the base cylinder, one of the tools is higher than the axis of the worm, and the other tool is lower than the axis of the worm. The tooth angle of the tool should be equal to the helix angle of the base cylinder of the worm. This worm can be ground on a special machine tool.
Conical envelope cylindrical worm (ZK worm)
This is a nonlinear helical surface worm. It cannot be processed on a lathe, but can only be milled on a milling machine and ground on a grinder. During processing, in addition to the spiral motion of the workpiece, the tool also rotates around its own axis. At this time, the envelope surface of the rotary surface of the milling cutter (or grinding wheel) is the helical tooth surface of the worm, and the tooth profiles on the I-I and N-N sections are both curves. This worm is easy to grind, has high precision, and is increasingly widely used.
As for the tooth profile of the worm grinding wheel paired with the above-mentioned worms, it is completely different from the tooth profile of the worm. The worm grinding wheel is generally processed by a hob or a fly cutter on a gear hobbing machine. In order to ensure that the worm and the worm grinding wheel can mesh correctly, the tooth profile of the hob cutting the worm wheel should be consistent with the tooth profile of the worm; the center distance during deep cutting should also be the same as the center distance of the worm drive.
