1. Gate off difficult in the injection molding process, gate stuck in the gate sleeve, not easy to take off. When the mould is opened, the finished product appears crack damage. In addition, it is necessary for the operator to knock out the top of the copper rod from the nozzle, so that it can be loosened before demoulding, seriously affecting the output power. The main factor of this defect is poor brightness of the sprue taper hole and tool marks in the circumferential direction of the inner hole. Secondly, the material is too soft, the small end of the taper hole is deformed or damaged after using for a period of time, and the arc of the nozzle spherical surface is too small, which causes the riveting of the gate material here. The taper hole of gate sleeve is difficult to process, should choose standard parts as far as possible, if need to process by oneself, should also restrain oneself or buy special reamer. The taper hole shall be ground to above RA0.4. In addition, it is necessary to set the gate pull rod or gate ejection.

 2. Large-scale die moving fixed die offset large-scale die because of the different filling rate in each direction, as well as in the mold loading by the mold weight of the impact of dynamic, fixed die offset. In the above-mentioned cases, lateral offset force will be added to the guide pillar when injection, when the guide pillar is opened, the outer surface of the guide pillar is roughened and damaged, when the guide pillar is severe, the guide pillar is bent or blocked, or even unable to open the mold. In order to deal with the above questions, in the mold parting surface to add a high-strength positioning key on all four sides, the most concise and useful is the use of cylindrical key. The straightness of the guide pillar hole and the parting surface is the most important. When machining, the moving and the fixed die are aligned, and after the azimuth clamping, the boring machine is finished at one time. In addition, the guide pillar and guide sleeve of heat treatment hardness is necessary to reach the program request.

 3. In order to ensure that the forming surfaces of the core and the cavity do not touch each other under any circumstances, the guide pillar can not be used as a force-bearing or positioning part. In several cases, injection time, fixed mode will have an infinite lateral offset force. When the thickness of the plastic part is not uniform, the velocity of the material flow through the thick wall is high, and the pressure is high, and the side surface of the plastic part is not symmetrical, such as the opposite side surface of the die is not equal. 

4. During injection, the molten plastic in the mold cavity is subjected to an infinite back pressure, usually between 600 and 1000 KG/CM. Mold makers sometimes do not pay attention to this problem, usually change the original program standard, perhaps the dynamic template with low-strength steel plate instead, in the ejector pin mold, because of the two sides of the seat span is large, forming injection molding template bending. Therefore, it is necessary to choose excellent steel for the moving template, to meet the thickness, must not use a 3 and other low-strength steel plate, when necessary, should be in the moving template under the support column or support block, to reduce the thickness of the template, load-bearing forward adjustment. 

5. MANDRIL TWISTS AND TURNS, cracking may be a better quality of the Mandril, is the processing cost is too high, now usually used standard parts, quality to some poor. If the gap between the EJECTOR PIN and the hole is too big, the material will leak out. But if the gap is too small, the ejector pin will be stuck because of the increase of mould temperature. More risk is, sometimes the ejector rod is pushed out usually the interval will not move and break, the role of a once the exposed ejector rod can not reset and hit the die. In order to deal with this problem, the ejector rod from the beginning grinding, in the front end of the ejector rod save 10 ~ 15 mm cooperation section, some of the base grinding small 0.2 mm. After all ejectors are installed, it is necessary to strictly check the cooperation gap, usually in 0.05 ~ 0.08 mm, to ensure that all ejector arrangements can be flexible. 

6. Poor cooling or the cooling effect of the water leakage mould directly affects the quality and output power of the finished product, such as poor cooling, big shortening of the finished product, or uneven shortening and warping, etc. . On the other hand die whole or some overheating, so that the mold can not normal forming and stop production, severe so that the ejector pin and other activities of the thermal expansion card death and damage. Cooling System Scheme, processing to the shape of the commodity, not because the mold structure is messy or processing difficult to omit this system, especially the large and medium-sized mold must be fully considered cooling questions.

7. Kill. The sliding block is inclined and the reduction is not smooth. Because some moulds are bound by the area of the template, the length of the guide groove is too small, and the sliding block is exposed outside the guide groove after the core pulling operation is over, so the slide block is inclined in the post-core pulling period and the initial period of the die closing reduction period, extra is in the mold, the sliding block reset is not smooth, so that the damage to the sliding block, and even bending damage. According to experience, after the end of core-pulling action, the length left in the chute should not be less than 2/3 of the entire length of the guide groove. 

8. The fixed-pitch tension arrangement, such as the failure Hook and Hasp, is usually used in the fixed-pitch core pulling or in some secondary demoulding dies, because this kind of arrangement is set in pairs on both sides of the die, and its action requires the necessity of synchronism, that is, together with the clamp mold, open mold to one, with the orientation of decoupling. Once the synchronization is lost, the die plate which must constitute the drawing die must be tilted and damaged, the parts of these arrangements to have high stiffness and wear resistance, adjustment is very difficult, the arrangement life is short, try to prevent the use of other arrangements. In the case of small pull-out force, the tension spring can be used to push out the fixed die. In the case of large pull-out force, the core can slide when the moving die retreats, and the construction of the core-pulling action can be finished before parting the die, hydraulic cylinder core-pulling can be used in large-scale mould. Failure of inclined pin sliding block core-pulling arrangement. The disadvantages of this arrangement are that the processing is not in place and the material used is too small, the first two questions are: The tilt angle a is large, the advantage is to be able to take place in a short opening stroke of the larger core-pulling distance. However, when the drawing force F is a certain value, the flexuous force P = f/COSA is bigger in the process of core pulling, and the inclined pin is apt to deform and wear. At the same time, the upward thrust n = ftga of the inclined pin on the slider increases, which increases the positive pressure of the slider on the guide surface in the guide groove, and then increases the resistance of the slider when it slides. Easy to form sliding is not smooth, guide groove wear. According to experience, the angle a should not be greater than 25. 

9. Exhaust gas in injection mold is not free injection mold gas often occurs, which is caused by what? The air in the pouring system and the mold cavity; some materials are rich in moisture that has not been swept away by dryness and will be vaporized into water vapor at high temperatures; due to the high temperatures during injection molding, some unstable plastics differentiate into gases; some of the additives in the plastic material vaporize or react chemically with each other to form gases. Together with the causes of poor exhaust flow, also need to find out quickly. In the process of injection molding, the melt will replace the gas in the mold cavity, if the gas is not discharged in time, it will cause the difficulty of filling the melt, as a result, the injection dose is too small to fill the cavity; the air collar can form high pressure in the cavity, and enter the plastic interior under a certain degree of contraction, resulting in quality defects such as hollowness, porosity, arrangement and crazing; As the gas is highly compressed, the temperature in the cavity rises sharply, which causes the surrounding melt to differentiate, broil, and cause the plastic parts to appear somewhat carbonized and charred. It is mainly present the confluence of two melts, Gate Flange; the gas sweep is not smooth, so that the melt into the cavity speed is not the same, it is easy to form mobile marks and fusion marks, and make the mechanical function of plastic parts decline; Due to the obstruction of gas in the cavity, it will reduce the filling speed, affect the molding cycle, and reduce the tax power. The air bubbles in the cavity of the plastic part are usually distributed on the part opposite to the gate, while the air bubbles in the plastic material are distributed along the thickness of the plastic part The remaining water in the plastic material gasification of air bubbles, is not distributed in all the plastic parts.

 Source: Mold man magazine

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