Snowmobile dashboard mould
1. Thread cutting
Generally refers to the method of machining threads on a workpiece with a forming tool or an abrasive tool, mainly including turning, milling, tapping, threading, grinding, grinding and whirlwind cutting. When turning, milling and grinding threads, the transmission chain of the machine tool ensures that the turning tool, milling cutter or grinding wheel moves along the axis of the workpiece accurately and uniformly for each revolution of the workpiece. When tapping or threading, the tool (tap or die) rotates relative to the workpiece, and the first formed thread groove guides the tool (or workpiece) to move axially.
Turning threads on a lathe can use a forming turning tool or a thread comb (see thread processing tools). Turning threads with a forming turning tool is a common method for single-piece and small batch production of threaded workpieces due to the simple tool structure; turning threads with a thread comb tool has high production efficiency, but the tool structure is complex, which is only suitable for medium and mass production. Turning fine-tooth short-threaded workpieces. The pitch accuracy of the trapezoidal thread on the ordinary lathe can generally only reach 8-9 (JB2886-81, the same below); when the thread is processed on a specialized thread lathe, the productivity or accuracy can be significantly improved.
2. Thread milling
Milling is performed on a thread milling machine with a disk milling cutter or a comb milling cutter. Disc milling cutters are mainly used for milling trapezoidal external threads on screw, worm and other workpieces. Comb-shaped milling cutter is used for internal milling. Because it uses external common thread and taper thread, the length of the working part of multi-edge milling cutter is greater than the length of the thread to be processed, so the workpiece can be processed only by rotating 1.25~1.5 revolutions Finished, the productivity is high. The pitch accuracy of thread milling can generally reach 8~9, and the surface roughness is R5~0.63 microns. This method is suitable for mass production of general precision thread work or rough machining before grinding.
3. Thread grinding
Mainly used for machining precision threads of hardened workpieces on thread grinders.
Thread grinding is divided into single-line grinding wheel and multi-line grinding wheel grinding according to the different cross-sectional shapes of the grinding wheel. The pitch accuracy that can be achieved by single-line grinding wheel grinding is 5~6, and the surface roughness is R1.25~0.08 microns, and the grinding wheel dressing is more convenient.
This method is suitable for grinding precision lead screws, thread gauges, worms, small batches of threaded workpieces and relieving precision hobs. Multi-line grinding wheel grinding is divided into two types: longitudinal grinding method and plunge grinding method. The width of the grinding wheel of the longitudinal grinding method is smaller than the length of the thread to be ground, and the grinding wheel can be reversely ground to the final size by moving the grinding wheel one or several strokes in the longitudinal direction. The width of the grinding wheel of the plunge grinding method is greater than the length of the thread to be ground. The grinding wheel cuts into the surface of the workpiece radially, and the workpiece can be ground after about 1.25 revolutions. The productivity is higher, but the accuracy is slightly lower, and the dressing of the grinding wheel is more complicated. The plunge grinding method is suitable for relieving large batches of taps and grinding certain fastening threads.
4. Thread grinding
Use softer materials such as cast iron to make nut-type or screw-type thread grinds, and perform forward and reverse rotation grinding on the parts of the machined threads with pitch errors on the workpiece to improve the pitch accuracy. Hardened internal threads are usually ground to eliminate changes and improve accuracy.
5. Tapping and Threading
Tapping is to use a certain torque to screw the tap into the pre-drilled bottom hole of the workpiece to process the internal thread.
Threading is to use a die to cut an external thread on a bar material (or pipe material) workpiece. The processing accuracy of tapping or threading depends on the accuracy of the tap or die. Although there are many methods for processing internal and external threads, small diameter internal threads can only be processed by taps. Tapping and threading can be operated manually, and can also be used with lathes, drilling machines, tapping machines and threading machines.
6. Thread rolling
The processing method of using a forming rolling die to plastically deform a workpiece to obtain a thread. Thread rolling is generally performed on a thread rolling machine. Thread rolling machine or automatic lathe with automatic opening and closing thread rolling head, suitable for mass production of external threads of standard fasteners and other threaded couplings.
The outer diameter of the rolled thread is generally no more than 25 mm, the length is no more than 100 mm, and the thread accuracy can reach level 2 (GB197-63). The diameter of all blanks is roughly the same as the pitch diameter of the processed thread. Rolling generally cannot process internal threads, but for softer workpieces, non-slot extrusion taps can be used to cold extrude internal threads (the maximum diameter can reach about 30 mm). The working principle is similar to tapping. When cold-extruding internal threads, the required torque is about twice as large as that of tapping, and the machining accuracy and surface quality are slightly higher than that of tapping.
The advantages of thread rolling are:
1. The surface roughness is less than turning, milling and grinding;
2. The thread surface after rolling can improve the strength and hardness due to cold work hardening;
3. The material utilization rate is high; the productivity is doubled than the cutting process, and it is easy to realize automation;
4. The rolling die has a long life. However, the rolling thread requires that the hardness of the workpiece material does not exceed HRC40;
5. Higher requirements for the dimensional accuracy of the blank;
6. The precision and hardness requirements for rolling molds are also high, making it difficult to manufacture molds;
7. It is not suitable for rolling thread with asymmetric tooth profile.
According to different rolling molds, thread rolling can be divided into thread rolling and thread rolling.
Two thread rolling boards with threaded teeth are arranged relative to each other at a staggered 1/2 pitch, the static board is fixed, and the moving board makes a reciprocating linear motion parallel to the static board. When the workpiece is fed between the two plates, the movable plate advances and rubs the workpiece to plastically deform its surface into a thread.
There are 3 types of radial thread rolling, tangential thread rolling and rolling head thread rolling. Radial thread rolling: 2 (or 3) thread rolling wheels with thread profile are installed on mutually parallel shafts, the workpiece is placed on the support between the two wheels, and the two wheels rotate in the same direction at the same speed.
One of the rounds also makes a radial feed movement. The workpiece rotates under the drive of the rolling wheel, and the surface is squeezed radially to form a thread. For some lead screws with low precision requirements, similar methods can also be used to roll forming. Tangential thread rolling: also known as planetary thread rolling, the rolling tool consists of a rotating central thread rolling wheel and 3 fixed arc-shaped wire plates.
During thread rolling, the workpiece can be fed continuously, so the productivity is higher than thread rolling and radial thread rolling. Thread rolling head: It is carried out on an automatic lathe, and is generally used to process short threads on a workpiece. The rolling head has 3 to 4 thread rolling wheels evenly distributed on the outer circumference of the workpiece.
During thread rolling, the workpiece rotates and the rolling head feeds axially to roll the workpiece out of the thread.