The five major hazards of excessive temperature rise of the 注塑機 are: thermal deformation of the machine, reduced oil viscosity, deformation of rubber seals, accelerated oil oxidation and deterioration, and reduced air component pressure.
One of the hazards: thermal deformation of the machine
The moving parts with different coefficients of thermal expansion in the hydraulic components are stuck due to their smaller fit gaps, causing malfunctions, affecting the transmission accuracy of the hydraulic system, and deteriorating the working quality of the parts.
Harm two: reduce the viscosity of the oil
Excessive temperature rise of the injection molding machine will cause the viscosity of the oil to decrease, increase the leakage, and the volumetric efficiency of the pump and the efficiency of the entire system will be significantly reduced. As the viscosity of the oil decreases, the oil film of the sliding valve and other moving parts becomes thinner and cut, and the frictional resistance increases, resulting in increased wear.
Hazard 3: Deformation of rubber seals
Excessive temperature rise of the injection molding machine will deform the rubber seals, accelerate the aging failure, reduce the sealing performance and service life, and cause leakage.
Hazard 4: Accelerate the oxidation and deterioration of oil
Excessive temperature rise of the injection molding machine will accelerate the oxidation and deterioration of the oil, precipitate bituminous substances, and reduce the service life of the hydraulic oil. The precipitates block the damping orifice and the slit valve port, causing the pressure valve to become stuck and unable to move, and the metal pipe is stretched and bent, or even ruptured.
Hazard 5: Leading to poor work quality of components
Excessive temperature rise of the injection molding machine will cause the quality of the parts to deteriorate. The dissolved air in the oil will escape, resulting in air pockets, which will reduce the working performance of the hydraulic system. The ideal working temperature of the hydraulic system should be between 45 degrees and 50 degrees. The reason is that the hydraulic system is designed according to a selected pressure oil viscosity.But the viscosity will change with the oil temperature, which will affect the work in the system. Components, such as oil cylinders, hydraulic valves, 等。, reduce control accuracy and response sensitivity, especially for precision injection machines. 同時, if the temperature is too high, it will accelerate the aging of the seal and cause it to harden and crack.If the temperature is too low, the processing energy will be consumed and the operating speed will be reduced. 因此, it is necessary to pay close attention to the working temperature of hydraulic oil. There are many reasons for the high oil temperature, but most of them are due to the failure of the oil circuit or the failure of the cooling system.
(1) According to different load requirements, frequently check and adjust the pressure of the overflow valve to make it just right.
(2) Choose hydraulic oil reasonably, especially the oil viscosity. When conditions permit, try to use a lower viscosity to reduce viscosity friction loss.
(3) Improve the lubrication conditions of moving parts to reduce friction loss, which is conducive to reducing work load and heating.
(4) Improve the assembly quality and accuracy of hydraulic components and hydraulic systems, strictly control the clearance of matching parts and improve lubrication conditions. The use of sealing materials with a small friction coefficient and improved sealing structure to reduce the starting force of the hydraulic cylinder as much as possible to reduce the heat generated by the mechanical friction loss.
(5) Add cooling devices when necessary. 一般而言, most of the customers who have been engaged in the injection molding industry for many years have the ability to judge by themselves and choose the appropriate injection molding machine to produce. 然而, 在某些情況下, 客戶可能需要製造商嘅幫助，以決定使用哪台注塑機, 甚至客戶可能只有產品樣品或想法, 然後詢問製造商是否可以生產該機器或比較哪種型號. 合適.
另外, 一些特殊產品可能需要特殊設備，如壓力蓄能器, 閉環路, 注射壓縮, 等。, 更高效地生產. 可見，如何確定合適的注塑機生產是一個極其重要的問題. The following information is provided for readers’ reference.
The important factors that usually affect the selection of an 注塑機 include molds, 產品, 塑料, 成型要求, 等. 因此, the following information must be collected or available before making a selection:
Mold size (width, height, thickness), weight, special design, 等。;
The type and quantity of plastics used (single raw material or multiple plastics);
The appearance size (length, width, height, thickness), weight, 等. of the injection molded product; 成型要求, such as quality conditions, production speed, 等.
After obtaining the above information, you can follow the steps below to select a suitable 注塑機:
1. Select the right model: The model and series are determined by the product and plastic.
Since there are many types of injection molding machines, it is necessary to correctly determine which injection molding machine or series the product should be produced from at the beginning, such as general thermoplastics or bakelite raw materials or PET raw materials. Color, two-color, multi-color, interlayer or mixed color, 等. 另外, some products require conditions such as high stability (closed loop), high precision, ultra-high shooting speed, high shot pressure, or rapid production (multi-loop), and suitable series must also be selected for production.
It can be put down: Determine whether the “Large Column Inner Distance”, “Mold Thickness”, “Mold Minimum Size” 和 “Die Plate Size” of the machine are appropriate according to the mold size to confirm whether the mold can be put down.
The width and height of the mold must be smaller than or at least one side smaller than the inner distance of the large column;
The width and height of the mold should be within the size range of the mold plate;
The thickness of the mold must be between the mold thickness of the injection molding machine;
The width and height of the mold must meet the minimum mold size recommended by the injection molding machine, and it will not work if it is too small;
3. Obtain: The mold and the finished product determine whether the “mold opening stroke” 和 “mold stroke” are sufficient to take out the finished product.
The mold opening stroke must be at least more than twice the height of the finished product in the direction of opening and closing the mold, 並且必須包括噴出嘅長度;
The stroke of the supporting mold must be enough to eject the finished product;
4. 上鎖: 噸位 “夾緊力” 由產品和塑料決定.
当原材料喺高壓下注入模具腔時, 生成模具支撐力. 因此, the clamping unit of the injection molding machine must provide enough “夾緊力” to prevent the mold from being opened. The calculation of the clamping force requirement is as follows:
Calculate the projected area of the finished product in the direction of the switch mold from the appearance size of the finished product;
Die support force = projected area of the finished product in the direction of the switch mold (cm2) × number of mold cavities × pressure in the mold (kg/cm2);
The pressure in the mold varies with the raw materials, generally 350～400kg/cm2 for raw materials;
The clamping force of the machine must be greater than the clamping force, and for the sake of safety, the clamping force of the machine is usually 1.17 times greater than the clamping force;
At this point, the specifications of the clamping unit have been preliminarily determined, and the tonnage of the model has been roughly determined, and then the following steps must be carried out to confirm which injection unit has a screw diameter that meets the requirements.
5. Full injection: Determine the required “injection volume” from the weight of the finished product and the number of mold cavities and select the appropriate “screw diameter”.
To calculate the weight of the finished product, the number of mold cavities (one mold and several cavities) shall be considered;
For the sake of stability, the injection volume needs to be more than 1.35 times the weight of the finished product, 噉係, the weight of the finished product needs to be within 75% of the injection volume;
6. Good injection: The conditions such as “screw compression ratio” 和 “注射壓力” are determined by the plastic. Some engineering plastics require higher injection pressure and appropriate screw compression ratio design to have better molding effects. 因此, in order to make the finished product shot better, the needs of injection pressure and compression ratio should also be considered when selecting the screw. .
一般而言, a screw with a smaller diameter can provide a higher injection pressure.
7. Shoot fast: and confirm the “shooting speed”.
Some products require high injection rate and rapid injection to form stable molding, such as ultra-thin products. 喺呢種情況下, it may be necessary to confirm whether the injection rate and rate of injection of the machine are sufficient, and whether it needs to be equipped with pressure accumulators, closed-loop control and other devices. 一般而言, under the same conditions, the screw that can provide a higher injection pressure usually has a lower shot speed, 恰恰相反, the screw that can provide a lower shot pressure usually has a higher shot speed. 因此, when selecting the screw diameter, the injection volume, injection pressure and injection rate (注射速度) need to be cross-considered and selected.
另外, a multi-loop design can also be used to shorten the molding time with synchronized compound actions.
