With the development of new plastic materials and processes, plastic products have been more and more widely used for their characteristics of light weight, good strength and low cost. The helical gears as a leader in transmission tools, their transmission has gradually meshing, high degree of coincidence, high load-bearing capacity, stable transmission, etc. so the gears are widely used in transmission. Therefore in modern transmission, such as printing equipment, photographic equipment, toy cars, etc. more and more plastic helical gears are used as transmission components.
The most difficult thing for most people with helical gears is how to realize the automatic demoulding of products while ensuring the accuracy of products. Here Asia Billion Innovational Technology company as a professional helical plastic gear injection mold manufacturer, we want to help everyone understand how we achieve this products.
For the helical gear ejection method, there are generally two methods: one is direct ejection without any special ejection design, this design method is only suitable for the case where the angle of the helical gear is not large and the thickness of the gear is not large. However from a theoretical point of view, this ejection design will inevitably damage plastic products during the ejection process, especially the helical teeth, so in actual design, the designer should fully consider whether the degree of damage to the product will affect the product in the later stage. The other way of ejection is to design a special spiral ejection with some bearings, the product is ejected along the spiral direction of the helical gear which is under the help of the rotation bearing.
The specific design idea is: use two-way thrust ball bearings to fix the mold cavity to the two-way thrust ball bearings, design a spiral groove at the lower end of the core side, and design two cylindrical pins outside the push sleeve. In this way, during the ejection process, the push sleeve moves forward, and the core mold insert moves through the spiral groove under the action of the pin, and the product maintains linear moving due to the key on the push rod, so that it can release the helical gear demouding.
Several issues to be noted in this design:
(1) In the selection process of the push sleeve, the size of the push sleeve should be enlarged as much as possible, so as to ensure that the push sleeve has sufficient wall thickness to install the pin. The choice of push rod diameter should be consistent with the size of the inner hole of the product.
(2) When designing the spiral groove, the spiral direction must conform to the oblique angle direction of the helical gear, and the stroke should be greater than the wall thickness of the product.
Design of gate and runner for helical plastic gear injection mold:
In the design of the gate form, a point gate method is adopted, a runner is made on the back of the fixed formwork, and a puller rod is designed behind the gate. In this way, the scrap can be removed from the conical gate during the mold opening process and separated from the product.
Mold structure and working process
The working process of the mold: after the injection is completed, the pressure is kept and cooled, and it is driven by the injection molding machine. The fixed template and the fixed mold pad are separated, and the waste materials in the gate and runner are separated from the gate and runner under the action of the pulling rod, and the mold is continued to open. When the stopper reaches the working position, the fixed mold pad and fixed mold The seat plate is separated, so that the waste material is separated from the pulling rod, and the mold is opened. When the limit stop ring touches the fixed plate, the fixed plate stops moving, and the lock is separated by the injection molding machine, and the moving plate is separated from the fixed plate. After reaching the mold opening distance, the injection molding machine stops moving, and the ejector device of the injection molding machine pushes the fixed plate of the ejector rod forward. In this way, under the action of the pins on the push sleeve, the movable mold inserts make a spiral movement, and the product comes out of the movable mold cavity. After the demoulding work is completed, under the action of the reset spring, the jacking plate is reset, and the next injection process is started.
Asia Billion Injection tooling plant view:
China formulates national standards for plastic injection molded gears
The plastic gear industry ushered in the first national standard. In 2019, the National Standardization Management Committee officially released the national standard for the accuracy of plastic gears "GB/T38192-2019 The definition and allowable value of the deviation of the tooth surface on the same side and the radial comprehensive deviation of the precision of injection molded plastic cylindrical gears." This standard fills the gap and reaches the international advanced level, which is what China's plastic gear industry has been looking forward to for decades.
Gear as the most widely used mechanical transmission device has a long history of development. Since the successful development of fiber nylon in 1935, the polymer synthetic material industry has developed rapidly, and a new type of material has been applied to gears to form plastic gears. Compared with metal gears, plastic gears have the advantages of light weight, low inertia, low noise, and self-lubrication. Its products are processed by open mold, which has high production efficiency and low cost. Especially in the past two decades, with the successful development and modification of high-strength, high-abrasion resistance and other high-performance engineering plastics, plastic gears have developed toward higher loads, and the application of plastic gears has been further expanded and more There is an application trend of "placing steel with plastic". It can be said that the rapid development of plastic gears is a worldwide trend in the field of gears.
However, today, with the increasing development and application of plastic gears, my country has no plastic gear standards, especially the lack of the most basic plastic gear accuracy standards, which seriously restricts the development of my country's plastic gear industry. At present, there is still a certain gap between the manufacturing level of plastic gears and developed countries, resulting in a passive situation in which my country still needs to import a large number of high-end plastic gears from abroad. If you want to break through this dilemma, you need to start research from many aspects such as gear product design, plastic material research and development, gear injection mold design and manufacturing, new injection molding equipment and new injection molding process research, and gear inspection and experiment. The establishment of a standardized system is inseparable. However, due to the large difference between plastic gears and metal gears in terms of design requirements, manufacturing methods, application places, etc., the formulation of plastic gears' own precision standards has considerable complexity, which has become an urgent problem to be solved in the Chinese gear industry.
With the introduction of the precision plastic gears, gear companies are deeply excited. The accuracy standard of injection-molded plastic gears provides a standard basis for product measurement and grade determination, which is conducive to ensuring the quality and reliability of products, thereby guiding the orderly competition and healthy development of products, and promoting continuous innovation and industrial technological progress. It can not only regulate the production behavior of enterprises, establish a benign market order, promote industrial technological progress, but also broaden procurement channels for enterprises, reduce external dependence, improve working time, and greatly reduce procurement and maintenance costs.
Plastic injection molded gear has its particularity, with the characteristics of small modulus, tooth shape formed by mold at once, and reinforced structure. Therefore, the accuracy of the injection molding gear and its measurement method cannot be completely equivalent to adopting the ISO1328 and ISO/TR10064 series standards. Although the accuracy standard of my country's injection gears is not equivalent to the ISO standard, it is consistent with ISO in terms of macro aspects, and is in line with international standards as much as possible.
The helical plastic gear injection mold making is much more complex than the normal injection mold and spur plastic gear injection mold. there are only fewer companies in China have the capacity for the helical gear plastic injection mold making and inspection capacity, Asia Billion are proud of to be one of them with better service , competitive price and excellent engineering support. Please let us know freely if we can help you too.