Synthetic yttrium aluminum garnet (YAG) is a promising material for electronics, optoelectronics, optics, fine mechanics, and instrument engineering. Activated YAG is widely used in laser technology for general industrial and defense purposes. Due to their unique structural, mechanical, optical and dielectric properties, various types of monocrystalline yttrium aluminum garnet have found the following applications:
- Optical YAG:
- the manufacture of optical components, such as prisms, lenses, windows, substrates for epitaxial deposition;
- workpiece circular, rectangular glasses to watch, followed by cut for exclusive watches.
- YAG: Nd3 + (Neodymium activator):
- manufacture of laser active elements used in laser systems for cutting and machining of various materials, product labeling;
- medical and cosmetology lasers;
- high-precision laser rangefinders.
- YAG: Er3 + (with erbium activator):
- manufacture of laser active elements used in modern lasers for medical and cosmetic purposes.
- YAG: Ce3 + (with tseriyvym activator):
Problem and Solution
For the production of YAG was designed and developed an automated system for the synthesis of crystals, the work of which took place in accordance with the technology. The technology of growing high-quality YAG crystals is very complicated and “capricious” and is being improved to the present day. One of the problems arising in the production of YAG is the complexity of the repetition of the process with each new chip, as external and internal factors change. Thus, the process of crystal synthesis lasts for 14 days, and its increase is no more than 1 grams / hour. At the same time, feedback for regulating technological parameters (power of induction heater, drawing speed, etc.) is conducted in terms of crystal growth rate for 1-5 minutes (to 100 mg for 5 min). Any minor vibrations significantly affect the behavior of the system. It was necessary to modify the problem areas of the technological process and bring them into the algorithm of the technological process, develop an automated process control system for the synthesis of YAG using new technology knowledge. The goal was to minimize the influence of external factors on the quality of the crystals and the high degree of repeatability of the quality of the crystal during each process.
Equipment for growing aluminum yttrium garnet consists of the following main components:
- Vacuum chamber.
- Generator induction heating.
- Drive rotating the crystal in a vacuum chamber.
- Drive movement of the crystal in a vacuum chamber.
- High-precision weighing jam-crystal.
- The cooling system of the heating chamber.
- Reception control uninterruptible power supply system.
- Machine Man, based on the touch panel interface.
The actuators of the movement and rotation of the rod with the crystal in the vacuum chamber, the generator, as well as the weight control are controlled from the control stand. The NI cFP 2220 industrial controller from National Instruments was used as the heart of the system. Data collection and interaction with actuator controllers is performed using the ICN-DAS 7000 series data acquisition modules. Communication between the cFP-2220 main controller and data acquisition modules is organized through the RS-485 interface. The rack also houses a touch panel with a human-machine interface connected to the controller via Ethernet. The software for the control system was developed in the NI LabVIEW programming environment. The program consists of two parts - the first (software core) is executed on the cFP-2220 controller, the second — the man-machine interface — is executed on the touch panel. The motion drive controller contains its own control program, which ensures its autonomous operation in the event of a possible system failure. When the system is started, the software kernel, built according to the state machine scheme, performs a survey of all system nodes to analyze their health. Then the system goes into tracking mode, carrying out the output of technological parameters (crystal weight, its length, diameter, voltage on the inductor) on the touch panel. The system expects the input of graphs of the voltage change at the inductor, the speed of movement and the speed of rotation. After the parameters are entered by the technologist, a transition is made to the automatic mode of crystal growth.