Cylindrical spiral groove is the combination of several spiral lines on the cylinder. When milling a cylindrical spiral groove on a milling machine, the relative motion of the milling cutter and the workpiece must conform to the spiral forming motion law. Cylindrical spiral grooves are common in some parts. Then, how to process the cylindrical spiral groove? Now let's talk about the milling method of cylindrical spiral groove.
1、 Technological characteristics of cylindrical spiral groove milling
1. Milling cylindrical spiral groove, milling cutter and workpiece conform to the law of spiral forming motion. That is, in addition to the rotary motion of the milling cutter, the workpiece must also rotate at a uniform speed while the workbench drives the workpiece for longitudinal feed, and ensure that when the workbench moves a distance equal to the lead of the helix, the workpiece rotates at a uniform speed for one cycle. During the longitudinal feeding, the spindle of the dividing head is driven by the table lead screw through the exchange of gears to realize the rotation of the workpiece. When milling multi line spiral grooves, it is also necessary to Realize indexing adjustment according to the number of lines.
2. Due to the different uses of workpieces with spiral grooves, the cross-sectional shapes of spiral grooves are also diverse. For example, the section of the tooth groove of the cylindrical spiral groove cutter is triangular or curved, the normal section of the spiral groove of the constant speed cylindrical cam is rectangular, and the axial section of the Archimedes worm is trapezoidal, etc. The profile of milling cutter for machining spiral groove should be consistent with the normal section shape of spiral groove. Therefore, the correct selection of milling cutter is the key to ensure the section shape of spiral groove.
3. When milling a cylindrical spiral groove, because the spiral angles on the surface of cylinders with different diameters are not equal (large diameter, large spiral angle; small diameter, small spiral angle), there is interference in the processing, which causes the side of the spiral groove to be overcut and the groove shape distortion. The overcut phenomenon is more serious when using disc milling cutter than when using end milling cutter. Therefore, the spiral groove with rectangular normal section can only be milled with end milling cutter. When the disk-shaped milling cutter is used to process spiral grooves with other cross-section shapes, the diameter of the milling cutter should be as small as possible to reduce the overcut of interference.
4. When using a disk-shaped milling cutter to mill a cylindrical spiral groove on a horizontal milling machine, in order to make the normal section shape of the processed spiral groove as close to the profile of the milling cutter as possible, the workbench of the milling machine must be turned by an angle in the horizontal plane, so that the rotation plane of the disk-shaped milling cutter is consistent with the tangent direction of the spiral.
2、 Milling of cylindrical spiral groove
1. Exchange gear calculation
When milling the cylindrical spiral groove, the workpiece is clamped on the dividing head, and the relative motion law of the milling cutter and the workpiece is realized by connecting the table screw and the dividing head with the exchange gear. Usually, the side shaft change gear method is adopted.
2. Selection of milling cutter
Correct selection of milling cutter is the key to ensure the section shape of cylindrical spiral groove. The profile of milling cutter should be consistent with the normal section shape of spiral groove. The commonly used milling cutters are end milling cutter, angle milling cutter, forming milling cutter, etc.
3. Interference phenomenon in milling rectangular groove
When milling the spiral groove on the milling machine, when the workpiece rotates for one cycle, the distance that the milling cutter moves in the axial direction relative to the workpiece is equal to the lead. On a spiral groove, the lead of both the notch and the spiral at the bottom of the groove is equal, that is, the lead of all parts on a spiral groove is equal.