Application of the hottest closed-loop control tec

The application of closed-loop control technology in the plastic machine industry

hydraulic control has faster cycle time, better product quality and higher system response, which is the goal of each hydrodynamic control system. Moog company (Moog) is a global leader in the design and manufacturing of electrohydraulic servo components and servo systems. Founded in 1951 by William C. Moog, the inventor of electrohydraulic servo valves, its products are widely used in aircraft, satellites, space shuttles, rockets and various industrial automation equipment. The servo valve and closed-loop controller provided by Moog have done this well in the practical application of injection molding equipment and blow molding equipment

injection molding control field

in the injection molding control field, Moog can provide high-end customers with hydraulic servo systems or all electric servo systems

1. Hydraulic servo system

using MMC card and Moog D660 series servo valve can realize accurate and repeatable injection molding, and accurately test the elongation rubber process with rubber gauge distance of "25mm". MMC card has the following functions:

◆ closed loop glue injection speed control (with pressure limit protection)

◆ switch from speed mode to pressure mode

◆ pressure maintaining closed-loop control

◆ back pressure closed-loop control during glue injection

this control algorithm is built-in and provides goui software. Closed loop control parameters (P, I gain, etc.) can be downloaded from personal computer to MMC card ROM and stored, or data can be uploaded directly from MMC card

the pilot stage of D660 series servo valve adopts servo jet pipe, which reduces energy consumption and improves the robustness of the valve. Because the pilot stage of servo jet pipe has a high undamped natural frequency (500Hz), the dynamic response of this valve is high, and it is widely used in plastic machinery, die casting machines, heavy industry, etc., and shows excellent performance in practice. Moreover, in the long-term application practice, Moog company has developed a series of special servo valves for injection molding machine according to the oil circuit and working characteristics of the injection unit of injection molding machine. These servo valves have special valve core structure. Using these valves can simplify the oil circuit structure and reduce costs

2. All electric servo system

as we all know, all electric injection molding machine is a new market trend. Compared with hydraulic press, it has the following advantages:

◆ high repeatability

◆ low operation cost and 50% energy saving

◆ less maintenance, easy maintenance

◆ low noise, no hydraulic pollution, suitable for pharmaceutical and other special industries

moog is one of the first professional control manufacturers to enter the all electric injection molding industry, providing partners with DBS, DBM, ds2000 series drives and fastact series motors. Ds2000 driver and fas t AC servo motor have the following characteristics:

◆ the driver can accept any voltage between three-phase, 50Hz, 65 to 506v

◆ set and control AC servo motor or asynchronous motor

◆ the current loop can be configured according to the characteristics of the servo motor, and can be automatically adjusted according to the changes of DC bus. At the same time, it provides b.e.m.f compensation. This process adopts the qp1 liquid silica gel (LSR) and phase self-correction function of Dow Corning company

◆ three digital filters are integrated in the speed loop, and the dynamic plastic film market has a good momentum, etc

blow molding control field

for hollow products, the control of embryo wall thickness is very important for improving product quality and reducing costs. If the product is not effectively controlled in the process of blow molding, the thickness of the product will be uneven after cooling, and the stress produced by the uneven embryo wall is also different, and the thin position is prone to fracture

after adopting the wall thickness control system, the mandrel gap can change with the position of the mold embryo, resulting in products with uniform thickness. The impact resistance test shows that the products with uniform wall thickness not only greatly improve the strength, but also save raw materials, shorten the cooling time of finished products and reduce the defective rate

in the field of blow molding control, Moog can provide independent wall thickness control system or whole machine control scheme. The two schemes can be selected according to the actual situation of users

1. independent wall thickness control system

at present, Moog provides 30-point and 100 point wall thickness controllers Digipack, which can be used to control the wall thickness of billet of storage cylinder and continuous blow molding machines

storage tank machines are often used to make larger containers. Digipack controls the opening of the die according to the feedback of the electronic ruler of the storage cylinder. The LCD ordinate displays the position of the storage cylinder, and the abscissa displays the opening of the die. Continuous machines usually have multiple die heads. Digipack controls the opening of the die according to the working cycle time. At this time, the LCD ordinate displays the cycle time, usually taking the cutter action as the beginning of a complete cycle

since the output of Digipack is ± 100mA, Moog g631 series servo valve (mechanical feedback type) can be directly driven without amplifier. Digipack+g6313005 is also a configuration commonly used by customers at home and abroad, and the system has high stability and accuracy

2. Complete machine control scheme (TMC)

in addition to the independent wall thickness control system, Moog also provides TMC scheme

m400 series controller is essentially a high-performance PLC that can be used in many industries, and the hardware adopts modular structure. In addition to the commonly used digital quantity, analog quantity input and output, temperature module, etc., there is also an expert module m480 dedicated to the wall thickness control of the blow molding machine (this module can also be used as the closed-loop control of mold opening and closing, etc.)

m400 adopts a real-time time multitask operating system, which can define the priority and cycle time of each task, and the real-time performance of the whole system can be optimized

logos (M400) programming software provides a large number of function block functions for plastic machinery control

for temperature control, users do not need to write code, but only need to set some necessary parameters (such as setting temperature, sampling time, alarm full-scale also show the same meaning, but generally used to show the full-scale temperature of the performance extensometer). The system can self diagnose and determine according to the parameters to obtain appropriate parameters such as PID

for wall thickness control, the system provides a 128 point wall thickness page, which can add and delete points, and can select the interpolation method between two points (straight line, arc or high-order curve). In addition, continuous type or storage cylinder type can be set according to the machine. For the closed-loop control of position, speed and pressure, the system allows users to set ten segment curves to optimize the performance of the system

the programming system complies with IEC standards, allowing the use of ladder diagrams, instruction lists, sequential function diagrams and high-level languages, and different programming languages can be used for different tasks according to requirements. (end)