Filament Winding Process and Equipment

 

 

Brief description of winding molding process Composite materials have excellent characteristics such as high strength, high modulus, high stiffness, excellent vibration damping, fatigue resistance and corrosion resistance, and are widely used in the fields of national defense science and technology and civil engineering. The content of composite materials has become one of the important indicators for evaluating the performance of aerospace vehicles.

 

In the production technology of resin-based composite materials, fiber winding technology is the earliest developed and most widely used processing technology, and it is also one of the most important production technologies.

 

As a molding technology, fiber winding technology winds the yarn bundle on the mold according to certain rules through the relative movement between the wire nozzle and the mold to make a composite material component.

 

 

The fiber winding process is to wind the continuous fiber or cloth tape impregnated with resin glue on the core mold according to certain rules, and then solidify and demold it.

 

The fiber winding composite molding process is currently the most widely used molding process with the highest efficiency and the best molding effect. Its product performance is uniform and stable. It is also the earliest developed and widely used technology.

 

The fiber winding molding process refers to the process of immersing the fiber yarn in the resin glue under the action of fiber tension, and winding the fiber on the core mold by controlling the relative movement between the wire nozzle and the core mold: the molding technology of making composite parts according to certain arrangement rules. Figure 1.4 is a schematic diagram of the common fiber winding process.

 

 

The degree of resin crosslinking in the wet process is lower than that in the dry process, so it can be wound at room temperature.

 

According to the different physical and chemical states of the resin matrix during fiber winding, the fiber winding process is divided into three types: dry, wet and semi-dry.

 

Dry Winding Process

The dry winding process refers to heating the continuous fiber roving to impregnate the resin, removing the solvent at a certain temperature, and causing the resin glue to react to a certain extent to form a prepreg tape, which is then arranged on the mold according to certain rules and methods. The dry winding process has the advantages of environmental protection, convenience and high winding efficiency, but its cost is relatively high, the winding equipment is relatively expensive, the cost of prepreg is also several times that of ordinary fibers, and the temperature, winding rate and winding tension during molding have a great influence on the performance of the product, so the process difficulty is relatively large. The dry winding process is usually used in fields with high product performance requirements, such as the aerospace field.

 

Wet Winding Process

The wet winding process refers to a method in which continuous fiber filaments or fiber cloths are impregnated in resin through a glue storage tank, and are directly wound on the mold under the guidance of a wire nozzle, and then cured and molded. This method is widely used, has low requirements for winding equipment and materials, and is suitable for the production of most winding products.

 

Wet winding is affected by unstable factors such as tension, winding speed and resin impregnation degree during the molding process, so the quality of the wound product is not easy to guarantee. Compared with the dry winding molding process, the stability of the wet winding fiber on the mold is poor, so controlling the stability of the wet winding process is the prerequisite for ensuring the smooth winding.

 

Semi-Dry Winding Molding Process

The semi-dry winding molding process is a winding method between dry and wet methods. Like the dry winding molding process, the fiber needs to be pre-impregnated and then reacted to a certain extent. Each winding molding method has its applicable conditions. Among the three winding methods, the wet winding molding process is the most common application, and the dry winding molding process is only used in the field of high-performance, high-precision cutting-edge technology. The winding methods mainly include hoop winding, spiral winding and planar winding.

 

The Advantages of Fiber Winding Molding are as Follows:

 

High Precision.

Among various composite material molding processes, fiber winding has the highest fiber placement accuracy, especially after being equipped with a precision tension control system, the accuracy of the wound product has reached a high level.

 

High Productivity.

Due to the mechanization, automation and high-speed characteristics of fiber winding processing equipment, its productivity is greatly improved, which is convenient for mass production.

 

It can Form Huge Structures.

For example, winding high-pressure tanks (used for heating and curing winding components with higher strength requirements), and huge structures can be formed on site, thus saving transportation costs, which is unmatched by other molding methods.

 

High Strength.

The fiber content of fiber winding composite materials is high (up to 80%), so the fibers are in a tensioned state during the winding process, applying positive pressure to the core mold or the lower fiber, reducing the winding components, or even eliminating the need for placement. Heating and pressurizing in the autoclave to cure it, the strength is also higher.

 

Light Weight.

The weight of glass fiber pressure vessels is lighter than that of metal pressure vessels under the same volume.

 

Integral Molding.

It can be wrapped in the fiber together with other parts, reducing the assembly and connection processes often encountered by other methods, and improving the fatigue resistance of the structure.

 

Disadvantages of Winding Molding:

 

The adaptability of winding molding is small. Not all products with any structure can be wound, especially products with concave surfaces, because the fiber cannot be close to the surface of the core mold during the winding process, otherwise it will be suspended.

 

Fiber winding molding requires winding machines, core molds, curing furnaces, demolding machines and skilled technical workers, which requires a lot of investment and technology. Therefore, it can only reduce costs and obtain greater economic benefits in mass production.

 

Brief description of winding molding equipment The equipment used for fiber winding is a winding machine, which is usually composed of a control system, an impregnation system, a tension system and a winding machine. The components of the winding system are shown in Figure 1.5.

 

 

According to the freedom of movement of the nozzle, the winding machine can be divided into two-axis winding machine, four-axis winding machine, five-axis winding machine and six-axis winding machine. According to the motion control method, the winding machine can be divided into mechanical, program-controlled and computer-controlled.

 

The CNC Fiber Winding Machine Tool is Shown in Figure 1.6

 

 

The mechanical winding machine has a simple structure, low manufacturing cost, high reliability and specificity. Through the mechanical transmission relationship between the actuators, the fiber can be wound on the mold.

 

The mechanical winding machine is mainly aimed at fixed-shaped molds or specified fiber yarn trajectories. For components with special shapes or complex yarn arrangements, mechanical winding machines are no longer used. The program-controlled winding machine uses hydraulic control servo motors, and the use of dial switches as data input methods can change parameters relatively easily.

 

The program-controlled winding machine is divided into digital control winding machine and analog control winding machine. Digital control is a method of controlling intermittent digital quantities or performing operations on numbers according to information processing requirements. Analog control is a method of performing continuous analog control or no digital operations in information processing.

 

At present, most winding machines used in domestic production are digitally controlled. The characteristics of the computer-controlled winding machine are that the winding trajectory of the fiber is first calculated by computer, and then the coordinate trajectory of the moving axis is solved, and the winding of complex fiber trajectories is realized by computer-controlled multi-axis servo motor rotation.

 

Compared with mechanical winding machines and program-controlled winding machines, computer-controlled winding machines can wind composite products more accurately and diversely.

 

At present, my country’s fiber winding technology is in a mature development period. Fiber winding equipment has achieved computer digital control or microcomputer full servo control.

 

The manufacturing technology and winding process of two-axis, three-axis and four-axis fiber winding machines have matured, and various pressure vessels, electrical insulation products and sports products play an important role in winding molding. Multi-axis digitally controlled or microcomputer-controlled fiber winding machines developed by many domestic universities, research institutions and companies are used for the development and production of composite materials. It can not only provide high-precision winding machines for aerospace military and nuclear industries, but also provide general fiber winding machines for industry and complete production lines for civilian use.

 

For example, the large gantry CNC four-axis, five-axis, and six-axis linkage fiber winding machines developed by Harbin Institute of Technology:

 

The four-axis four- and eight-station CNC winding machines and five-axis and seven-axis fiber winding machines developed by Wuhan University of Technology;

 

The fully automatic internal curing high-pressure FRP pipe production line developed by Harbin University of Technology:

 

The gantry, horizontal multi-station, and multi-axis winding machines developed by Harbin Composite Materials Equipment Development Co., Ltd.;

 

The annular winding machines and spherical winding machines developed by Harbin FRP Research Institute and Xi’an Aerospace Composite Materials Research Institute:

 

The large-diameter, multi-functional, and high-precision CNC winding machines developed by Jiangnan Industrial Group Co., Ltd.;

 

The four-axis linkage winding machines based on microcomputer control and Siemens CNC systems produced by Lianyungang Weide Composite Materials Equipment Co., Ltd. and Xi’an Longde Technology Development Co., Ltd.;

 

The fixed-length reciprocating sand-filled pipe winding machines produced by Lianyungang Zhongtong Composite Materials Machinery Equipment Manufacturing Plant and Hengshui Fangchen FRP Equipment Technology Co., Ltd.;

 

The sand-filled FRP pipe continuous winding production line developed by Qingdao Langtong Electrical Equipment Co., Ltd., etc.

 

In recent years, my country’s winding technology has developed rapidly, but the overall automation, industrialization and innovation of winding equipment are still far behind those of developed countries.

 

Robots have the advantages of many degrees of freedom, high reliability and low cost. They can be used in winding molding to achieve accurate and flexible winding of composite products. Robot

 

Robotic winding technology includes winding trajectory design, analysis and post-processing, thus forming professional robot winding CAD/CAM software.

 

Foreign research on winding robots is relatively early and mature. France’s MFTech is the first company to study and commercialize robotic winding. The robotic winding equipment provided by the company makes full use of the flexibility of the robot. Composite winding molding can be carried out by grabbing the mold and driving the wire guide.

 

Canadian Compositum has developed a fully automatic winding system suitable for robots and CNC systems of various brands such as ABB and KUKA.

 

Dutch Taniq has developed the Scorpo robot, equipped with self-developed process design software, for fiber and rubber belt winding of fiber-reinforced rubber products.

 

The University of Leuven in Belgium uses the PUMA-762 robot in conjunction with a two-axis CNC winding machine to achieve winding and forming of various structural parts.

 

The University of Ottawa in Canada has conducted research on robot-based T-tube winding.

 

The Aachen University of Technology in Germany has established a composite flexible manufacturing unit and successfully produced parts such as machine tool spindles and aircraft fuselages.

 

The Delft University of Technology in the Netherlands has built a robot-assisted winding/stitching/welding workstation for composite product winding and other process research.

 

The Harbin University of Science and Technology and the Harbin Institute of Technology Robot Collective have jointly developed the first domestic robot winding workstation for winding of complex-shaped composite products such as elbows and tees.

 

My country is still in the initial stage in terms of robot winding trajectory design, analysis and post-processing, as well as robot winding CAD/CAM software research.