Screw Milling Machine CNC Transformation

Injection molding machines and extruders are used as special machines for producing plastic products. They are widely used worldwide. As an important component of the extruder and the injection machine, the processing quality of the screw directly affects the performance of the extruder and the injection machine.
The traditional manual operation of the screw to process the poor consistency, low efficiency, processing quality can not be guaranteed. The use of numerical control technology to process screw has become an inevitable trend. At present, CNC milling machines specially designed for machining screws are expensive and difficult to be accepted by users. However, economical CNC screw milling machines transformed from lathes using economical numerical control systems and stepper motors have lower functions but are less reliable. Poor sex, more problems during use.
Nanjing Sikai Electronic Enterprise Co., Ltd. installed a SKY numerical control system on a lathe at the request of a user in Guangdong, and successfully reconstructed a CNC screw milling machine specialized for machining screws. It has the advantages of low cost, strong functions, high ergonomics, high precision of the processed screw, good uniformity, etc., and it can easily process various special requirements such as variable diameter and variable pitch (including sectional variable pitch and continuous variable pitch). Screw.
The system has a Chinese interface, full-screen program editing functions, and programming procedures are very convenient. The amount of program memory is large, and 10,000 machining programs can be stored reliably. The drive of the machine tool adopts digital AC servo motor and the power has sufficient margin, so the stability and reliability of the machine tool are very good, and the problem of screw machining is effectively solved.
The SKY CNC screw milling machine was successfully transformed on an ordinary lathe. Its basic structure is shown in Figure 1.

1. Spindle (A) Digital AC servo motor 2. X axis digital AC servo motor 3. Z axis digital AC servo motor 4. Workpiece 5. Milling spindle 6. Top

The machine tool is equipped with milling heads on the carriages of ordinary lathes and equipped with digital AC servo motors to control the rotation of the spindles and the X- and Z-direction movements of the carriages to realize three-axis linkage. Through the three-axis linkage control, various shapes of screw are machined.
Remove the lathe tool holder and install the milling head. The milling head and the spindle are driven by the digital AC servo motor directly through the timing pulley and the timing belt. The X and Z directions are directly connected to the ball screw through the coupling directly from the digital AC servo motor to control X and Z movement. In this way, the entire machinery is not changed much, the mechanical structure is simpler, the operation is more flexible, and the transmission error is reduced.

The SKY CNC system was used to modify the screw-type milling machine, and an encoder mounted on the motor was used as a detection element. The driving device was a digital AC servo motor, thereby forming a follow-up system with an input of θj and an output of θ0. Due to the higher resolution of the encoder, the feedback uses digital pulses, and the servo part uses double-pulse input control to ensure its anti-jamming capability.
The SKY series CNC system has both closed-loop and semi-closed loops, depending on user requirements.
The SKY CNC system is based on a universal PC platform. For a special screw machining program, a general parameterized automatic programming module can be programmed in C language. In order to facilitate the use, SKY CNC screw milling machine built-in parameter programming module, the principle shown in Figure 2. According to the various parameters of the screw, parameter equations can be established

According to the accuracy requirement of the screw, the corresponding increment dt can be obtained, and the corresponding space point position X, Z, A can be obtained and output according to the numerical control code.
Through the numerical control transformation of screw milling, remarkable results have been achieved, and the accuracy and consistency have been greatly improved, resulting in greater social and economic benefits. At present, there are many ordinary screw milling machines in the country, so the prospects for numerical control transformation are very broad.