Die-casting mold die casting mold FAQs

Die casting mold is one of the three elements of production, the structure is correct and reasonable casting mold for producing a prerequisite for the smooth, and in ensuring the quality of the casting (the plane passing rate) plays an important role. Because the characteristics of die casting process, the correct selection of process parameters is to obtain high-quality casting the deciding factor, mold is able to correctly select and adjust the process parameters of the premise, in essence, is the die-casting mold design and production of all sorts of possible factors expected a comprehensive reflection. Should the mold design is reasonable, in the actual production problems encountered in the small, casting the plane pass rate. On the contrary, mold design is unreasonable, for example, a casting mold design move given the same force package, and mostly in the fixed mold casting system, and on the punch after the injection of filling material can not be sent to the South producing die-casting machine, not the normal production , die casting has been glued to the set on. Although the model set to play a very light finish cavity, due to deeper cavity, there are still glued to the set mode on the phenomenon. Therefore, in the mold design, casting a comprehensive analysis of the structure must be familiar with the operation of the process of die casting machines, die-casting machines and to understand the possibility of adjustments to process parameters, lies in the filling characteristics of different situations and consider ways mold , drilled and fixed in the form of the eye before they can design a practical, to meet the production requirements of the mold. The beginning have said, the filling of liquid metal a very short time, the ratio of liquid metal pressure and flow rate is high, this die-casting mold is extremely poor working conditions, coupled with the heat shock chilling impact of alternating stress effect, are the life of the mold has a great influence. Usually refers to the life of the mold through careful design and manufacturing, under normal use conditions, with good maintenance occurs under natural damage, can not be repaired and scrapped before the die-casting modulus (including die-casting production waste number).http://www.prmindustry.com/Abstract...Articles section A. die failure of die failure are many factors, both external (eg high and low temperature casting mold is preheated, the amount of aqueous spray coating, die-casting machine tonnage match, die pressure is too high, within the gate too fast, open the cooling water is not synchronized with the die-casting production, casting materials, the type and level of composition Fe, casting size and shape, size, thickness, coating type, etc.). There are internal factors (eg mold material itself of metallurgical quality, blank forging process, mold design is reasonable, gating system design is reasonable, molds machine (EDM) process generated when the internal stress, the mold heat treatment process, including with the requirements of accuracy and finish, etc.). If there is early failure of the mold, you need to find out what internal or external, for future improvements. There are three main forms of failure die:
① thermal fatigue cracking damage to thermal fatigue cracking failure failure die casting production, mold repeatedly stimulated by the chilling effect of heat, forming the surface and its internal deformation, each involves the emergence of repeated cycles of thermal stress, resulting in damage to the organizational structure of two and loss of toughness, micro-cracks caused by the emergence and continued expansion, once the crack to expand, and squeeze into the molten liquid metal, coupled with repeated mechanical stress are accelerated expansion of the crack. To this end, on the one hand, when the initial die-casting mold must be fully warm. In addition, the production process in the casting mold must be kept at a certain temperature range, to avoid early cracking failure. At the same time, to ensure that pre-production tooling and manufacturing does not occur in the internal problem. Due to actual production, the majority of die failure is thermal fatigue cracking failure.
② broken power failure in the role of injection, the mold will be the weakest at the crack initiation, especially the mold forming surface of the dash marks or signs of power is not grinding light processing, or forming the corner are the most clear fine cracks appear first, when there is grain boundary phase or brittle coarse grains, that is prone to breakage. The brittle fracture when the crack soon, this fragmentation of the failure of the mold is very dangerous factor. To this end, on the one hand where the mold surface scratches, marks, etc. must be polished EDM light, even if it is part of the gating system must also be lighting. Also requires the use of mold materials, high strength, good ductility, toughness and fracture toughness are good
③ corrosion failure of the previous failure have said melt, commonly used in die-casting alloy zinc alloy, aluminum, magnesium alloy and copper alloy, aluminum die-casting has, Zn, Al, Mg is more active metals, they die material has better affinity, especially Al and easy bite mode. When the mold is high hardness, corrosion resistance is better, but if the surface forming a soft point, the disadvantage of corrosion resistance. However, in actual production, dissolution is only partial areas of mold, for example, the site of erosion within the gates directly (core, cavity) prone to corrosion phenomena, as well as softening the hardness of the stick at the prone aluminum mold.
Die-casting mold problems often encountered note points:
1, the gating system, overflow discharge system
Cases (1) for cold chamber horizontal die casting machine mold sprue requirements:
① pressure interior diameter size should be based on the required pressure than the pressure chamber filled with the degree to select the same time, the gate sets of diameter deviation should be higher than pressure deviation appropriate to enlarge the indoor track Jisi, which can avoid the pressure sleeve and gate indoor track different axes caused death punch card or wear a serious problem, and not too thin wall thickness of the gate sets. Gate sets the length of the injection should generally be less than the quoted range punch sent to extrusion coating from the pressure chamber.
② pressure within the chamber and the gate sets of holes in the heat treatment after grinding, then grind along the axis direction, the surface roughness ≤ Ra0.2μm.
③ shunt cavity with the formation of coatings, the indentation depth is equal to the depth of cross-runner, with a gate set bore diameter, along the ejection direction of the 5 ° slope. When using coated import type sprue, because shortening the effective length of the volume of pressure chamber can increase pressure chamber filled with degrees.
(2) requirements for mold runner
① cold horizontal mold runner should generally be located at the entrance to the upper pressure chamber diameter 2 / 3 or more parts, so as to avoid pressure chamber under gravity liquid metal into the runner early, early start to solidify.
② runner cross-sectional area inside the gate from the sprue should be gradually reduced until, for the cross-section appears to expand, the metal flow occurs when the negative pressure by the easy plane type of gas inhalation, increase the flow of molten metal wrapped in a vortex gas. The exit cross-section generally smaller than the entrance of 10-30%.
③ runner should have a certain length and depth. The purpose is to maintain a certain length from the steady flow and guidance role. If deep enough, the liquid metal cooling fast, depth too deep, too slow due to condensation, not only affects productivity but also increase the amount of back charge.
④ runner cross-sectional area should be larger than the cross-sectional area within the gate, to ensure that the liquid metal into the type of speed. The main runner of the cross-sectional area of ​​each branch runner should be larger than the cross-sectional area.
⑤ runner at the bottom of both sides of the fillet should be made to avoid early cracking, the second side can be made about 5 ° slope. Runner parts of the surface roughness ≤ Ra0.4μm.
3. Ingate
① liquid metal into the model should be immediately closed after the sub-surface, overflow tank and exhaust ducts should not be a positive impact on core. After the liquid metal flow into the type-cast as far as possible along the rib and into the heat sink from thick to thin-walled office at the filling and so on.
② Select the position within the gate, where possible, the minimum flow of liquid metal. Multi-unit within the gate, to prevent the entry of liquid metal-based convergence after a few shares, mutual impact, resulting in mixed vortex aeration and oxidation defects.
③ thin-walled inner gate thickness smaller pieces should be appropriate to ensure that the necessary filling speed, the gate should be set within easy removal without the casting body defect (meat).
4. Overflow tank
① overflow tank to facilitate removal from the casting, and try not to damage the body casting.
② open exhaust ducts on the overflow tank, the need to pay attention to the location of the overflow port, avoiding premature exhaust ducts blocked, so that the exhaust slot does not work.
③ overflow tank should not be opened on the same number of overflow or open a very wide thick overflow, so as to avoid the cold liquid in the liquid metal, slag, gas, paint, etc. from the overflow tank back cavity , resulting in casting defects.
2, rounded cast (including angle) is often marked on the map is not casting Note rounded R2, etc., we should not ignore the open system, the mold corner does not indicate the role of these, must not be made clear angle or too small fillet. Casting molten metal can filled with smooth rounded corners, so that the order of the gas discharge chamber, and reduce the stress concentration and prolong the life of mold. (Where casting is not easy to fill cracks or ring true because the emergence of a variety of defects). Patients with standard oil pan module supernatant corner more, relatively speaking, now Brothers to open the oil pan mode best, heavy oil pan is greater.
3, stripping slope in the ejection direction is prohibited due to undercut someone (often a test stick in the mold casting mold, with the incorrect approach, the cases of drilling, cutting, etc. to the local hard recessed).
4, the surface roughness of molded parts, casting serious lighting system shall be required to be lighting along the parting direction. As the molten metal pouring from the pressure chamber into the system and fill the cavity of the whole process only 0.01-0.2 seconds. In order to reduce resistance to the flow of liquid metal, less pressure loss as much as possible, need to flow through the surface of the smooth finish. Meanwhile, parts of the heating and pouring systems subject to more severe erosion conditions, the worse the finish there is the more easy to mold damage.
5, forming part of the hardness of the aluminum mold: HRC46 ° around the copper: HRC38 ° left and right processing, mold restoration margin should be left to do the maximum size to avoid welding.
Die-casting mold assembly of technical requirements:
1, the mold parting plane parallel with the template requirements.
2, guide post, guide sleeve and the vertical template requirements.
3, sub-type surface action, the fixed mold inserts scheduled to die Taoban plane and moving than 0.1-0.05mm.
4, push plates, reset rod flush with the parting surface, generally putting recessed 0.1mm or according to user requirements.
5, mold on the activities of all moving parts, reliable, no slack phenomenon pin without strings move.
6, the slider positioning and reliable, with the casting out of core distance, the slider after the block mold with parts 2 / 3 or more.
7, runner roughness smooth and seamless.
8, mold inserts when the local sub-surface clearance <0.05mm.
9, cooling water flow to the import and export mark.
10, forming the surface roughness of Rs = 0.04, no micro-injury

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          Peter   Huang