Screw rolling, the rotary forming process for producing lead screws by rolling method, for producing threaded rods, also called thread rolling. During rolling, the round bar blank gradually undergoes plastic deformation under the action of a rotating roll to form a threaded long rod-screw.
The screw rolling process is divided into hot rolling and cold rolling. Selecting quality machine tools to look at ALLES CNC, screw rolling has the advantages of high productivity, metal saving, good mechanical properties of rolling parts and simple operation compared with traditional turning methods; especially for cold-rolled screws, due to strength and hardness Increased, the service life is greatly extended. The surface roughness of the rolled screw is worse than that of the turning screw.
There are two main types of rolling methods: the cross rolling method and the cross rolling method.
When the lead screw is rolled by the cross rolling method, the axis of the roll is parallel to the axis of the workpiece, and the roll has a spiral hole type. If the helix angle of the roll is the same as the helix angle of the workpiece, and the spiral direction is opposite to the spiral direction of the workpiece, the workpiece has no axial movement. The workpiece rolled by this method has high precision, but the length of the workpiece is limited by the length of the roll. If the helix angle of the roll is not equal to the helix angle of the workpiece (generally not more than 25%), the working axial direction can be moved to roll the long lead screw, but the precision is poor. The former is called the spiral hole type cross rolling method, and the latter is called the axial feed cross rolling method.
When the lead screw is rolled by the cross-rolling method, the axis of the roll is inclined at a certain angle with the axis of the rolling piece, and the rolls rotate in the same direction. There are two types of holes on the roll: an annular hole type and a spiral hole type. The roll angle of the annular hole type is equal to the helix angle of the workpiece, and the workpiece moves axially. This method is called an annular hole type cross rolling method. A lead screw having the same pitch and different diameter can be rolled on a set of rolls, and the screw having different rotations and different numbers of heads can be rolled. This type of roll can be repeatedly ground and is economical, but the workpiece accuracy is low.
The helix angle of the spiral hole type is different from the helix angle of the workpiece, and the difference between the two is the angle between the roll axis and the workpiece axis. The workpiece moves axially. This method is a spiral hole type cross-rolling method, which can produce a screw with a large pitch, and has high precision, but the roll processing and the roll adjustment are difficult.
Rolls can be divided into spiral rolls and ring rolls according to their different tooth grooves; they can be divided into single-sided rolls, double-side rolls and cylindrical rolls according to their different shapes; they can be divided into open rolls and closed rolls according to the rolling principle. . The root of the closed roll is involved in the extrusion of the metal. The outer diameter of the workpiece to be rolled is accurate, the top of the tooth is flat, and the precision lead screw is mostly used. The rolls are mainly composed of a forming section and a finishing section. The forming section bites the blank and imparts radial compression to form the thread. The shape of the section of the finishing section is strictly consistent with the shape of the product.
According to the rolling method, the screw mill is divided into two types: horizontal rolling mill and cross rolling mill; according to the rolling mill structure, there are three-roller type and two-roller type; according to the transmission method, there are roller active type and rolling piece active type; Special mills and mills for various purposes. In addition to rolling the screw, the multi-purpose mill can also roll other threaded parts, splines, gears and oil grooves and can be knurled.