The factors of
injection molding are as follows:
1, pressure
The operating pressure provided by the pressure system (oil pump) or motor of the injection molding machine is mainly applied to the injection device, the glue-molding device, the mold-opening device, the ejection device, the shooting device, the core-pulling device, and the like, in the injection molding machine. After the control panel inputs the relevant parameters, the processor converts it into a signal of each program action, thereby controlling the pressure required for the execution of each action program.
The pressure setting principle is: to overcome the corresponding strength of the action resistance, but in order to match the speed of the action, the parameter value needs to be adjusted accordingly.
2, speed
The above-mentioned pressure is used to complete the required moving speed of each action program (the flow rate of the system hydraulic oil), and the basic level of the speed is divided: slow flow 0.1-10, slow speed 11-30, medium speed 31-60, high speed 61-99.
The control of the injection speed is applied to different product structures and materials to set the size value. It is not distinguishable here (engineering/general plastic, crystallization/amorphous plastic, high temperature/low temperature plastic, soft rubber/hard plastic) Confusing the audiovisual, making a relatively easy to understand explanation, the injection speed is a difficult process to control in the injection molding process, unlike other process elements have standard data for reference (subsequent detailed introduction).
1) The numerical setting of the injection speed mainly follows the following points:
According to the fluidity of the material; soft plastics such as PP, LDPE, TPE, TPR, TPU, PVC, etc. have good fluidity, and the cavity resistance is small when filling, and generally can be filled with a lower injection speed. Cavity. Commonly used medium viscosity plastics such as ABS, HIPS, GPPS, POM, PMMA, PC+ABS, Q glue, K glue, HDPE, etc. have slightly poor fluidity, and the glossiness of the product is not high or the product is moderately thick. In the case of wall thickness or bone thickness of 1.5MM or more, the injection speed can be filled with medium speed, and the filling speed should be appropriately increased according to the product structure or appearance requirements.
For example, PC, PA+GF, PBT+GF, LCP and other engineering plastics have poor fluidity. Generally, high-speed injection is required during filling, especially for GF (glass fiber) materials. If the injection speed is too slow, the surface of the product will be caused. The floating fiber (the surface is silvery) is severe.
2) Control of the melt speed;
This parameter is one of the most easily overlooked processes in daily work, because most colleagues believe that the process has little effect on the molding, and the parameters can be adjusted casually. However, in the injection molding, the melting parameters are the same. As the glue speed is as important, the melt speed can directly affect the melt mixing effect, molding cycle and other important links.
3) Control of the opening mode speed;
Mainly set different parameters for different mold structures. For example, the two-plate flat mold can adjust the high-speed mold clamping before starting the mold-locking low pressure and adjust to the rapid mold opening after the product is separated from the mold cavity to effectively improve the production efficiency. However, when the mold of the row position adjusts the speed of the open mold, it is necessary to switch the fast and slow speed of the mold according to the height and structure of the row position. Due to the complex structure of the special mold structure and core-pulling mold, it is explained in the following chapters.
4) control of ejector speed;
Mainly depending on the demoulding status of the product, in principle, it should be as fast as possible to ensure that the product does not appear white and top height, or deformation. Otherwise, it is necessary to adjust the parameters according to the actual situation. Of course; in general, the top is adjusted for the first time. The true speed is better at medium and low speeds (15%-35%), which can effectively extend the service life of the thimble and thimble cylinders.
3, location
Switching point between fast, slow, high and low pressure of each action
1) control of the location of the injection;
In the debugging of injection molding parameters, the position of the injection glue should be adjusted according to the weight and structure of the product. It is often said that the product needs to be adjusted according to the single weight of the product. For example, the weight of a product is about 50G. It is produced by 90T injection molding machine. The theoretical injection amount of this model is 120G, the melt glue stroke is 130MM, and the weight per MM melt is about 120G, the melt glue stroke is 130MM=0.92G, which is the glue of the product. The distance is 50×0.92=46MM. If the end position of the melt glue is set at 60MM, the product quality is basically OK when the glue is applied to 14MM.
2) Control of the position of the melt glue;
Generally speaking, in order to meet the required amount of glue for the molded product to set the distance of the melt, most of the colleagues ignore the three-stage switching position of the melt, and only pay attention to the end position of the melt, of course; the molded article of general difficulty is in the position of adjusting the melt. It is not necessary to switch between fast and slow or high back and low back pressure, so as to achieve the required product quality, but it is better to switch the melt speed and back pressure adjustment position in the production of color masterbatch and heat sensitive plastic. Control the quality of the products.
3) Position control of the unlocking die;
Mainly set the switching point with the need to unlock the mold speed
1 Under normal circumstances, the switching point of the mold opening speed is that the molded product is slow before the mold cavity (about 5-15MM), and the rear turn is fast, which can effectively shorten the time required for mold opening, and finally turn to slow speed (ie, open mold buffer) The position is generally started from the end of the required mold opening position of 20-40MM. (The termination position depends on the product structure and whether the robot is used), which can effectively extend the service life of the injection molding machine and the stability of the mold opening action.
The structural factors of some special molds, such as three-plate molds or core-pulling molds, must be determined according to the actual conditions. For example, the three-plate molds must be moved to the nozzle plate when the mold is opened on the middle plate. After the flow channel is separated from the product, the male and female molds are separated again. Therefore, it is necessary to add 1-2 switching points at the position of the mold opening. The medium speed-slow speed-high speed-slow speed and the large tonnage machine can be as needed. Add a few more switching points, in short, the quality of the molded product is not affected during the mold opening process and the motion process is stable.
2 The setting of the clamping position depends mainly on the structure of the mold, such as: the planar mold structure (that is, the parting surfaces of the front and rear molds are all flat, no slider/core, no insertion structure), and the clamping speed is switched. The "fast-medium speed-low pressure-high pressure" can be directly used in the four-stage position. The principle of switching the position is: the rapid stroke of the mold clamping is about 70% of the mold opening stroke. (The quick termination position of the three-plate mold is regarded as The size of the mold depends on the size of the mold, the main role is to shorten the mold clamping cycle. After the medium speed, it acts on the deceleration buffer of the high speed mode-locking. (It will switch to the low voltage protection function after the medium speed is over)
The termination position of the mode-locking medium speed is very important, which determines the starting position of the low-voltage protection of the mode-locking. Some of the old-funded colleagues are very vague about the low-voltage of the mode-locking. It is thought that it can be locked by the random setting, but it is not. If the clamping mode is not properly set, the protection function will be completely lost, which is fatal to the fully automatic production of the mold. How to correctly set the low voltage protection function will be described in detail in the following sections.
4) Control of the position of the thimble;
Theoretically, the ejection length of the thimble is twice the height of the mold cavity (ie, the core) of the mold, but in actual operation, it is not necessary to completely set the position according to this method, and the main purpose is to facilitate the removal of the product. However, in the initial adjustment of the thimble position, it is necessary to gradually lengthen, first out of the mold thimble stroke 50%, and then depending on the product in the production process.
4, temperature
Necessary conditions for plastic melting and mold heating
1) Control of the temperature of the material pipe;
In general, plastics with different properties have relatively standard molding temperatures, such as: ABS = (distinguish between high impact material 230-260, low impact material 190-230), SAN = 180-220, HIPS = 180- 220, POM=170-200, PC=240-300, ABS/PC=230-260, PMMA=200-230, PVC=(different high density 160-200, low density 140-180), PP=180-230 , PE = (distinguish between high density 240-300, low density 180-230);
TPE=(distinguish between high density 170-200, low density 140-180), TPR=(distinguish between high density 170-200, low density 140-180), TPU=(distinguish between high density 160-200, low density 120-160) PA=230-270, PA+fiber=250-300, PBT=200-240, PBT+fiber=240-280, and the addition molding flame retardant (ie fireproof material) has a molding temperature lower than that of ordinary materials by 20-30 degrees. The specific use temperature depends on the production conditions, because the molding temperature directly affects the fluidity, viscosity, mold temperature, color, shrinkage, and product deformation of the plastic.
2) control of mold temperature;
The mold temperature is mainly determined by different plastic fluidity. It is simple to understand that it is a key process to overcome the poor fluidity. For example, PC material and PA+ fiber have poor fluidity, and the flow resistance during filling is large, so it needs to be faster. The speed of the shot is used to fill.
In addition, when producing PC transparent material, it is necessary to improve the surface temperature, rainbow printing and internal bubbles, etc., and the higher mold temperature is required. If the mold temperature is low, the surface silver silk will appear when the fiber is added. Floating fiber).
In general, the following data can be used to adjust the mold temperature:
ABS=30-50 (products with high surface quality requirements or controlled deformation can be increased to 60-110 degrees) PC=50-80 (high surface quality or thin-walled products can be increased to 85-140 degrees) HIPS= 30-50 (transparent PS and products with high surface quality requirements can be increased to 60-80 degrees)
PMMA=60-80 (thin products with high surface quality and surface quality can be increased to 80-120 degrees) PP=10-50, PE=10-50 (high-density or thin-walled products can properly increase mold temperature) Rubber (TPE, TPR, TPU)=10-50,
PA, PBT=30-60 (high surface quality and glass fiber material can be increased to 70-100)
5, time
The time each action is performed
1) control of filling time;
Including injection time and pressure holding time
1 shot time:
The general requirements of the product in the case of qualified quality is as short as possible, because the injection time directly affects the internal stress and production cycle of the product, in principle, the thinner the glue position of the product, the shorter the injection time, and vice versa The shrinkage problem needs to be extended as appropriate.
In addition, the use of multi-stage and fast and slow speed switching products requires a longer shot time, and the setting of the shot time needs to be set according to the volume of the product (the longer the product requires the longer the shot time), the production needs to be considered here. The plastic nature, such as: general plastic ABS in the product wall thickness of 2.0MM, the injection speed is moderate, the tube temperature is moderate, the flow direction is about 65 mm / sec (different mold structure or process flow is different).
2 holding time:
In principle, the holding time mainly controls the surface shrinkage of the product and the size of the product structure. However, the control method that fully grasps the holding time can also use the pressure maintaining to adjust the deformation degree of the product (so the adjustment process is a precision tuning process, which will be followed by The chapter details the way it is adjusted).
Here we mainly explain the use of pressure to control the shrinkage of the product. Generally, the pressure reduction is used to control the shrinkage of the product according to the shrinkage position of the product. Not all shrinkage can be solved by holding pressure, such as shrinkage position. At the end of the melt filling, the use of holding pressure to control the shrinkage will result in excessive positional stress near the nozzle position, causing whitening, sticking, or warpage of the product.
2) thimble extension
Time; mainly controls the residence time when the thimble is ejected, which is convenient for the robot to pick up the product.
3) core pulling time;
Control the operating time of the core-molding device of the injection molding machine (mainly used to control the stroke of the action with time). If the core of the core-pulling stroke is controlled by the inductive switch, the core-pulling time may not be set.
