The key requirements for tool magazines in non-standard CNC machining centers are high speed and high reliability. This paper discusses the design mechanism and structure of a direct-drive UFO-type tool magazine for machining centers, designs an absolute tool magazine program, optimizes the tool changing process, and conducts practical application in a 3-axis aluminum machining center. The results show that the program has high reliability and tool changing accuracy, meeting the machining requirements of non-standard equipment manufacturers.
With the increasing precision and complexity of product industrial design in China's manufacturing industry, coupled with the rapid development of the non-standard manufacturing equipment sector, the demand for non-standard high-speed machining centers is growing, and the requirements for performance such as speed and reliability are also becoming increasingly stringent. As the core of CNC machine tools, high-speed machining centers hold an irreplaceable position in high-precision manufacturing equipment due to their high speed, high efficiency, and high precision. Many domestic non-standard CNC machine tool manufacturers possess design and development capabilities that are at or near international levels.
However, many non-standard equipment manufacturers in China have put forward higher requirements for tool changing in high-quality high-speed machining centers under the premise of high-speed spindle and high-speed feed. my country has successfully developed the design of high-speed flying saucer-type tool changing program and system.
This paper describes the modification of a high-speed non-standard spindle using a Taiwan Teco AC servo drive and a Taian UFO tool magazine. The system was designed and the tool magazine program was developed.
1. Introduction to Non-standard Tool Magazine System
The PYA series high-speed machining center is a high-speed non-standard machining center machine tool independently developed and manufactured. It is mainly designed for non-standard machining of aluminum profiles. The spindle speed is 15,000 r/min, the spindle rated torque is 52 N·m, the rapid traverse speed of the X axis is 60 m/min, the rapid traverse speeds of the Y and Z axes are both 48 m/min, and the feed rates of the X, Y, and Z axes are all 36 m/s.
The structure of the UFO-type tool magazine is shown in Figure 1. It consists of a rotating body, tool holder units distributed on it, and a servo drive motor. The rotation of the tool magazine is driven by a cycloidal pinwheel reducer with an i=1:89 ratio. The tool magazine servo driver is a Teco JSDAP-30 AC servo driver, and the matching servo motor is a JSMA-PSC08A7 (power 0.75kW, torque 2.39N·m, speed 3000r/min, rated current 5A, output voltage 0~230V, encoder specification 17BIT absolute encoder). The tool magazine is a Taian UFO-type 16-position tool magazine. The UFO-type tool magazine uses hydraulic drive for direct tool grabbing, servo motor drive for position lookup, and an absolute encoder for tool position detection.
Figure 1 Schematic diagram of tool magazine structure
2. System Control Design
2.1 Servo Driver Parameter Settings
The tool magazine system is designed using Teco servo drives . The servo drives are configured for tool magazine control mode, and the servo motors are controlled with brakes. The brakes are powered by 24V DC. The servo drive parameter settings determine the system's operating mode. The specific parameter setting process is shown in Figure 2. The acceleration and deceleration settings require smooth start-up and braking without overshoot.
The maximum tool change rotation speed is set to 3000 r/min. Based on system requirements, the tool change speed of the PYA series machining center is set to 1500 r/min. The braking delay and action time are 66.67 μs, the number of tool magazines is 16, and the tool turret reduction ratio is set according to the tool positioning situation during on-site debugging. This system is set to 80.
Figure 2 Parameter Settings
2.2 Macro Programming Design for Tool Magazine System
To avoid confusion during tool magazine recall, and because the absolute UFO tool magazine uses mechanical retraction with an eccentric compression stroke of approximately 10mm, two retraction speeds are available. The low speed is used during compression retraction to prevent excessive mechanical impact from damaging the equipment. The tool change macro program is as follows:
2.3 System Programming Concepts
The prerequisite for writing a PMC program for a non-standard rapid tool magazine is that you must understand the working principle and operation process of the saucer-type tool magazine. This program is written according to the requirements of the non-standard rapid tool magazine of the PYA series machining center. Different non-standard high-speed machining centers have different tool magazines, but the working principle is basically similar. For the specific tool changing process of the PYA series high-speed machining center, please refer to Figure 3.
Figure 3. Tool changing process of the UFO-type quick tool magazine
2.4 PMC Program Design
Based on the tool changing requirements and process, and considering the needs of a rapid tool magazine, a PMC program was written. This program is suitable for the FUNAC0imateMD system. After field testing, the PMC program for the UFO absolute rapid tool magazine is as follows:
3. Summary
After the tool magazine program was developed, it has been applied to the PYA series CNC machining centers, achieving the goals of collaborative development and design. The tool change speed is comparable to that of similar high-speed machining centers from abroad. Its performance is reliable, the tool change process is smooth and without overshoot, and the motion is balanced without impact. The machining speed of this series of non-standard high-speed machining centers has been greatly improved, increasing the localization rate and independent development capability index, reducing production costs, and providing valuable reference for machining center tool magazine design. It is worthy of promotion.
