Vertical injection molding machine pressure setting parameters

Date：2014/6/3 14:07:27

Follow the progress of China's industries , the use of plastic products more widely , the requirements of its increasingly high -quality , home produced products is to apply more Jun Li . But how to provide customers with low-grade , fine , can meet a variety of compliance with even more conducive to the protection of the mold work facility , currently in plastic injection molding machines had not the primary problem, there is a world of injection molding machines and the choice of quality performance achieved hub that process parameters of injection molding machine settings. Especially in precision machining , plastic products when caught adjust the injection molding machine is more vital skills . To this end , I screw back pressure against the effects of the injection molding machine , injection pressure , holding pressure and clamping force demand factors and their settings avenue for a brief introduction.
A back pressure when the screw at the move, hardened plastic screw is pushed back through the process to reach the stop valve . Because melt endless being pushed forward in this area , there were pressures and probation on the screw and stop valve , push them in order to accommodate the additional melt , but also put the screw back connected hydraulic cylinders push , cylinder piston chamber pressure after oil will flow back to the tank through the pipe injection molding machine . If the rate of pressure oil tubes , the latter chamber hydraulic cylinder will produce a pressure , the greater the rate of return pressure oil , the greater the pressure in the fuel tank of the attack , the pressure is called backpressure. Backpressure of melt back pressure and screw / oil line back pressure. Large injection molding machines are usually called screw back pressure back pressure . Screw back pressure and melt back pressure has a direct relationship, structure ( metaphor screw diameter and the diameter of the cylinder piston ) with the injection molding machine related. Typically about 10 times the melt back pressure in the back pressure of the screw . Table 1 shows the melt value backpressure recommend some thermoplastics.
2 injection pressure injection pressure must be set sufficiently , it was later determined to injection mold filling speed and the environment . In the best injection pressure , injection cycle changed their mind should not go beyond 0.2 5 , it is best to control river in 0.1 9. If the injection cycle spans 0.1 . In addition to insufficient injection pressure decay l split out of a group of board material thermal shear proud bit immature material backpressure
Stop valve screw behind only flow between 2.1 also known as reflux valve , dip it in the injection stage before the melt front of the screw to prevent reflux back . In order to reach the constant stop valve open , the valve must only reset after the screw position similar progress , the optimum ratio should be inverted sew road off valve need only practical long distance 0.5 , the highest rate should be inverted index 20% of a 30% injection velocity.
2.2 One of the reasons the pressure oil temperature is caused by the mold temperature and pressure changes to add the oil , it can directly affect the normal work of the injection molding machine . Should make the car run oil production rebounded after regeneration deformities , injection confidential attention after hydraulic oil cooler temperatures. Ideal oil should bundle 30 a 5 ℃ [2;.
2.3 Gate injection rate is set in many cases depends on the size and location of the gate , in particular a gate diameter reaches 1.5 mm 0.5 . When the melt at high speed through the gate when the small , they produce a lot of shear stress in the melt , the greater the speed the higher the shear stress , which is a huge stress make a sharp rise in the temperature of the melt may cause degradation of plastics . If the gate diameter is slightly increased, the shear stress can be greatly reduced , etc. : defective parts injection molding machine pressure parameters set on it can be avoided. If the gate is increased in diameter from 0.8 mm to 0.9 mm, the expansion of the gate area increased 0.134m , representing an increase of 21.07% of the area . After the gate increases, the lack of material can be partially filled , the surface quality of the corresponding parts have begun to improve, obviously , increase the gate diameter will help to improve the state of the cavity is filled .
2.4 Vertical injection molding machine injection rate is the rate of molten material into the cavity line speed , the filling stage of the injection of the melt into the mold cavity must be controlled in order to adapt the speed of mold materials and product characteristics . For example, the injection rate should be set at the product , design and plastic properties of the wall thickness of the case as far as possible to allow faster , thin-walled parts will require very fast injection rates to ensure full product ; rather thick-walled parts you need to slow injection rate to prevent the formation of air pockets and flow marks . Injection can convert different injection rates at different screw position , in order to avoid the appearance of defects in parts , such as crazing , flash, scorch marks, weld lines , etc. , and controls the speed of the melt into the cavity , the speed can be affect the degree of molecular alignment and internal stress of the article , different injection rate control is called " multi-stage injection ." Multi-stage injection can not only improve the quality of the finished product , but also to shorten the injection cycle a clever % 10% , and the injection rate can be obtained using stroke control separately into the melt flow channel system and the optimal position of the cavity. The principle of multi-stage injection rate setting is in the best condition , changes in general is not the injection cycle . If there is a greater change in the injection cycle , possible causes are poor melt uniformity , lack of injection pressure , improper operation of the hydraulic control system , injection molding machine pressure oil unclean filtration system problem occurs, the multi-stage injection rate is not set correct and so on.
3 vertical injection molding machine holding pressure holding pressure is the pressure when the cavity has just been filled adopted . The injection volume and the residual effect is compensated by the supply of the cooling cavity and the required melt volume contraction , so that the cavity shape of the melt under pressure to cool the case . Thus, the product appearance requirements and dimensional tolerances in order to be guaranteed.
3.1 Numerical packing packing pressure range is usually 30 to 70 MPa, and sometimes up to 90 a 10 M Pa. Affect the actual use of the main factors holding pressure has processed plastic types , runner and gate design, mold operating temperature , melt processing temperature , thickness of the product , the shape and complexity of the products , as well as the need to provide packing stage the injection volume and percentage . In general, the value of the holding pressure should be 25% a 65% injection pressure may be up to a 10% to 95% of the production of thin-walled injection pressure parts . Proportional to the residual value of the holding pressure injection volume and injection cavity should be used. The remaining injection volume is larger, the larger the required holding pressure , the product produced larger piece weight change . Screw gasket ( article number of pieces needed to produce a given feed amount ) of the product piece weight value may reflect a change , the operator can use many of the injection screw values ​​to evaluate the stability of the level of the gasket production process . Dwell time is the position of the screw in the front is almost stationary time . Dwell time and part thickness , injection rate, gate design , plastic mold level and temperature. In addition, the injection pressure switch correctly set pressure point and turn segmented packing injection molding production time is also crucial to holding pressure. Premature pressure will have to turn to the use of excessive holding pressure melt promote cavities , so it is prone to lack of material ; dwell too late if the products will be compressed too large, the formation of many parts of the burr and stress over high , stripping is not stable enough , increase product piece weight , etc.; segmented packing can better improve packing product defects only caused by a single pressure.
3.2 Determination of the amount of the injection stage injection should first find out the best process parameters of injection molding machine products , and products produced pieces weighing heavy , assuming this piece weight Wo, then holding pressure and dwell time setting of injection molding machine set to zero , then the injection cavity and the injection stage of an amount only , so that the thus obtained product with a piece weight Gong injection volume only on the injection stage . Percentage of the amount of the injection stage injection = ( Rocky / Gong ) x lo%. When injected into the cavity of the people shall be the total injection volume of 95% a piece weight of 98% [3] . When the injection molding machine with a multi- cavity mold if required to ensure that each cavity filling is balanced . Z- Md d can be applied , such as injection molding analysis software for multi-cavity injection mold casting system runner and gate size to balance the flow optimized design .
4 clamping force Clamping force is to mold locking force injection molding machine provided it can offset the melt in the cavity mold opening force generated . Many people like to use the largest injection molding clamping force , but rarely consider the size and design of molds and injection volume form molds and products , in fact, the need for economic and technical , to ensure product quality , under the premise should be clamping force to the required minimum. Thus, the injection molding machine can significantly save energy on the one hand , on the other hand can reduce the degree of wear of injection molding machines and molds , injection molding machines and help extend the life of the mold , and the mold is also natural exhaust capacity can be increased , so that the mold easier to control a fill state . The program sets the optimum clamping force is : ¹ First, the clamping force injection molding machine to the highest , followed by the normal automatic or semi-automatic production . º three parts were weighed and averaged gross . The clamping force reduction st, until production stabilizes repeat º, to identify gross average. ¼ then clamping force reduction s t, and repeat º. Repeat ½ ¼, until a significant increase in the average gross weight . ¾ the obtained data lists , draw a workpiece clamping force GW curve. A BS production of injection molding machine with dumbbell tensile specimens parts PcsWgt a clamping force curve. Figure 1 shows , when the clamping force is reduced from 70t 4O t, GW parts begin to increase the value , and then reducing the clamping force more parts gross value increases significantly , and produce burrs , so the production best clamping force under steady conditions is 4O t. For security molds , mainly low-pressure mold test , which uses the clamping pressure hierarchical control , low-speed low-pressure injection molding machine , mold can completely only when affixing to achieve the desired boost lock shift mode before termination clamping force .
5 Conclusion
When vertical injection molding machine injection molding , vertical injection molding machine pressure related to personal life , safety equipment and molds and injection molding machine , but it is also a prerequisite to ensure product quality. Therefore, the use of injection molding machine technology to process each tuned to optimize the injection molding process , so that the injection molding machine, mold , plastic combined maximum effectiveness will be able to play the most crucial factor of production.
Stable level of injection molding machine production process can be to examine the phenomenon :
First , the injection cycle should be not more than 0.2 5 , preferably injection molding machine can be controlled within 0.1 5 ;
 Second, the use of injection molding machine screw litter changes reflect the value of the piece weight should be more stable.

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