Thread cold rolling forming method
The traditional method of threading is mainly to use a forming tool or a grinding tool to machine a thread on a workpiece. There are mainly turning, milling, tapping, wire grinding, grinding and cyclone cutting.
When turning, milling and grinding threads, the machine's drive chain ensures that the turning tool, milling cutter or grinding wheel can accurately and evenly move a lead along the workpiece axis. During tapping, the tool (taper or die) rotates relative to the workpiece and guides the tool (or workpiece) for axial movement by the previously formed threaded groove.
I. working principle:
The workpiece is plastically deformed by a forming rolling die to obtain a threading process, and the thread rolling is generally performed on a thread rolling machine or on an automatic lathe to which an automatic opening and closing thread rolling head is attached. Suitable for mass production of standard external fasteners and other threaded couplings. The outer diameter of the rolling thread is generally not more than 25 mm, the length is not more than 100 mm, the thread precision is up to 2 (GB197-63), and the diameter of the blank used is approximately equal to the median diameter of the thread to be machined. Generally, the internal thread cannot be processed by rolling, but the workpiece with softer material can be cold-squeezed with a grooveless extrusion tap (maximum diameter of up to 30 mm), and the working principle is similar to tapping. The torque required for cold extrusion of the internal thread is about 1 times larger than the tapping, and the machining accuracy and surface quality are slightly higher than the tapping.
II. Advantages of thread rolling:
1) Surface roughness is less than turning, milling and grinding;
2) The surface of the thread after rolling can be strengthened by cold work to improve strength and hardness;
3) high material utilization rate;
4) Productivity is multiplied more than cutting and is easy to automate;
5) Rolling die has a long life.
III. Threaded silk
Roll: two band-shaped thread rolling flat shifted 1/2 pitch relative arrangement, the static plate fixed and movable plate parallel to the static plate for reciprocating linear motion. When the workpiece is fed between two plates, the movable plate forward of the workpiece rubbing pressure, so that the surface formed by the plastic deformation of the thread (FIG. 6 [Roll]).
IV. Thread rolling
There are three types of thread rolling: radial rolling, tangential rolling and rolling head rolling.
1, Radial rolling:
Two (or three) threaded roll wheels are mounted on mutually parallel axes. The workpiece is placed on the support between the two wheels, and the two wheels rotate in the same direction at the same direction (Fig. 7 [radial rolling]);
One of the rounds is also used for radial feed movement. The workpiece is rotated by the rolling wheel and the surface is radially extruded to form a thread. For some screws with less precise precision, a similar method can be used for roll forming.
2, Tangential rolling:
Also known as planetary rolling, the rolling tool consists of a rotating central rolling wheel and three fixed curved wire plates (Fig. 8 [tangential rolling]). When the wire is rolled, the workpiece can be continuously fed, so the productivity is higher than that of the wire and the radial wire.
3, Rolling head rolling:
It is carried out on an automatic lathe and is generally used to machine short threads on workpieces. There are 3 to 4 rolling rollers distributed around the outer circumference of the workpiece in the rolling head (Fig. 9 [Rolling Head Rolling]). When the wire is rolled, the workpiece is rotated, and the rolling head is axially fed to roll the workpiece out of the thread.
When turning, milling and grinding threads, the machine's drive chain ensures that the turning tool, milling cutter or grinding wheel can accurately and evenly move a lead along the workpiece axis. During tapping, the tool (taper or die) rotates relative to the workpiece and guides the tool (or workpiece) for axial movement by the previously formed threaded groove.
I. working principle:
The workpiece is plastically deformed by a forming rolling die to obtain a threading process, and the thread rolling is generally performed on a thread rolling machine or on an automatic lathe to which an automatic opening and closing thread rolling head is attached. Suitable for mass production of standard external fasteners and other threaded couplings. The outer diameter of the rolling thread is generally not more than 25 mm, the length is not more than 100 mm, the thread precision is up to 2 (GB197-63), and the diameter of the blank used is approximately equal to the median diameter of the thread to be machined. Generally, the internal thread cannot be processed by rolling, but the workpiece with softer material can be cold-squeezed with a grooveless extrusion tap (maximum diameter of up to 30 mm), and the working principle is similar to tapping. The torque required for cold extrusion of the internal thread is about 1 times larger than the tapping, and the machining accuracy and surface quality are slightly higher than the tapping.
II. Advantages of thread rolling:
1) Surface roughness is less than turning, milling and grinding;
2) The surface of the thread after rolling can be strengthened by cold work to improve strength and hardness;
3) high material utilization rate;
4) Productivity is multiplied more than cutting and is easy to automate;
5) Rolling die has a long life.
III. Threaded silk
Roll: two band-shaped thread rolling flat shifted 1/2 pitch relative arrangement, the static plate fixed and movable plate parallel to the static plate for reciprocating linear motion. When the workpiece is fed between two plates, the movable plate forward of the workpiece rubbing pressure, so that the surface formed by the plastic deformation of the thread (FIG. 6 [Roll]).
IV. Thread rolling
There are three types of thread rolling: radial rolling, tangential rolling and rolling head rolling.
Two (or three) threaded roll wheels are mounted on mutually parallel axes. The workpiece is placed on the support between the two wheels, and the two wheels rotate in the same direction at the same direction (Fig. 7 [radial rolling]);
One of the rounds is also used for radial feed movement. The workpiece is rotated by the rolling wheel and the surface is radially extruded to form a thread. For some screws with less precise precision, a similar method can be used for roll forming.
2, Tangential rolling:
Also known as planetary rolling, the rolling tool consists of a rotating central rolling wheel and three fixed curved wire plates (Fig. 8 [tangential rolling]). When the wire is rolled, the workpiece can be continuously fed, so the productivity is higher than that of the wire and the radial wire.
It is carried out on an automatic lathe and is generally used to machine short threads on workpieces. There are 3 to 4 rolling rollers distributed around the outer circumference of the workpiece in the rolling head (Fig. 9 [Rolling Head Rolling]). When the wire is rolled, the workpiece is rotated, and the rolling head is axially fed to roll the workpiece out of the thread.
