Design of an aluminum alloy shell die-casting mold

By analyzing structure and formability of shell parts, we focused on detailed analysis and research on main aspects of mold design; we analyzed and designed parting surface position of mold, structure of pouring and overflow system, and ejection mechanism, a structure of multi-point gates on thick wall on the side was adopted; a specific structural design was made for core and cavity of mold, using an ordinary two-plate structure with cavity in fixed mold and core in movable mold; moreover, core and cavity are made into movable inserts for easy repair and replacement. Mold structure is simple and practical, fully meeting design requirements of mold.
Aluminum alloy materials have lightweight characteristics. With continuous development of casting and forming process technology, die-casting process and mold design of aluminum alloy materials have developed rapidly. Design of die-casting molds is an important part of die-casting forming and has an important impact on cost, efficiency and accuracy of finished products of the entire processing process. Therefore, many scholars at home and abroad have conducted research and analysis on die-casting molds. Through experimental comparative analysis, Ma Dongwei found that main factors affecting size of aluminum alloy styles are residual stress and changes in solid phase crystallization; Shi Baoliang conducted relevant analysis on typical parts of structural parts used in automotive industry, focusing on performance characteristics of aluminum alloy castings under high pressure; Jin K C designed thin plate die-casting mold using two geometries, proposed a new overflow system based on numerical simulation, conducted an actual vacuum die-casting test of part of channel without backflow, and manufactured a high-quality sample using proposed optimized mold design; Péter Szalva compared high-cycle fatigue behavior of high-pressure die-casting and vacuum-assisted die-casting, described how casting defects affect fatigue failure, found that vacuum-assisted die casting significantly reduces pore size and volume, reduces occurrence of oxidized flakes, and thus increases number of failure cycles. Research of above scholars is all about microstructure of product parts after die-casting and structural performance analysis of aluminum alloy castings. Structural design and simplification of die-casting mold have not been mentioned yet. Therefore, direction of this research is to design an aluminum alloy shell die-casting mold. This design can effectively avoid defects such as cold insulation, slag inclusions, bubbles, looseness, and unformed heat sinks caused by die-casting process.

1. Die casting structure and process analysis

Figure 1 shows shell parts, which are made of aluminum alloy die-casting. Casting structure is relatively complex and wall thickness is different. Wall thickness of end face of shell is 5 mm, wall thickness of surrounding sides is 3 mm, and wall thickness of five bosses on one side is 15 mm. There are 25 heat sinks on the back, which are relatively dense. Width of narrow end is 1 mm, slope of one side is 1.5°, and depth is 9 mm. Wall thickness is 5 mm with four ribs and 1.5 mm with six ribs.

Figure 1 Shell parts diagram
After a comprehensive analysis of structural characteristics of casting, flow direction and characteristics of aluminum alloy liquid in mold should be considered when designing mold, material flow direction and relationship with direction of heat sink should be reasonably selected; due to uneven wall thickness of castings, casting defects such as slag inclusions and looseness are prone to occur during die casting. Therefore, location of inner gate should be selected reasonably so that casting can be fully formed during die casting. Considering structure of shell and actual production conditions, this die-casting mold design adopts a one-mold-one-cavity structure.

2. Mold structure design

2.1 Selection and design of parting surface

According to structural characteristics of casting and design requirements of parting surface, large end surface of shell is selected as parting surface of movable mold and static mold. In order to facilitate demoulding of casting, finished product should be left on the side of movable mold. Draft angle of inner surface of shell is 2.5° on one side and depth is 48 mm. Tightening force of forming part can keep shell on core side, so core is selected to be on movable mold and cavity is on fixed mold. Structural form is shown in Figure 2.

Figure 2 Parting surface settings

2.2 Design of pouring system and overflow system

According to design principles of die-casting mold pouring system, metal flow direction should be parallel to direction of heat sink to avoid defects such as cold insulation, slag inclusions, bubbles, looseness, and unformed heat sinks. In addition, position of inner gate should be set at thick wall, so that molten metal can fill thick wall first to avoid casting defects such as slag inclusions and looseness in thick wall. Therefore, in order to quickly fill mold cavity with molten metal, six ingates are provided on one side of shell boss. Runner adopts a stepped arc transition design to ensure sufficient filling speed. Sprue is equipped with a diverter cone, and diverter cone is designed with an arc transition structure, which can speed up filling speed of molten metal during die casting. Overflow tank should be set at the end of material flow direction. As shown in Figure 3, 13 overflow grooves and exhaust channels are provided on three sides of casting forming cavity.

Figure 3 Layout of pouring system and overflow system

2.3 Launch institutional design

This mold uses a push rod to push out casting. In mold design, position selection of push rod is crucial. Generally speaking, push rod position should be set at position where casting has the greatest tightening force on core and at thick wall of casting to prevent casting from being damaged when pushed out. After comprehensive consideration, all push rods adopt Φ8 mm round push rods. There are 6 push rods on the top surface of inner surface of casting and 12 push rods on the end surface of casting. In addition, 9 push rods are installed at sprue and runner, 13 push rods are installed at all overflow troughs. This design can fully meet launch requirements.

2.4 Cooling system design

Improving die-casting production efficiency, as well as quality and density of die-casting parts and reducing thermal stress, largely depend on adjustment of mold temperature. Considering that die casting is a thick-walled casting and is produced in small and medium batches, during continuous operation, in order to maintain high quality and high productivity of casting, a water cooling device needs to be installed in mold to allow heat to be quickly discharged with circulating flow of cooling water. Mold adopts a relatively simple cooling system, and cooling water channel is set in cavity with higher mold temperature (i.e., fixed mold insert). Six Φ10 mm cooling water channels are set up along length of cavity. There are six water nozzles on each side of fixed mold and fixed mold insert is threaded (sealed). Water inlet pipe and water outlet pipe are set on side opposite operator, water nozzles on both sides are connected with soft water hoses (tightened with a tightening reed) to form a complete water cooling circulation system, as shown in Figure 4.

1. Fixed mold plate 2. Fixed mold insert 3. Movable mold insert 1 4. Movable mold insert 2 5. Gate sleeve 6. Diverter cone 7. Movable mold plate 8, Push plate fixed plate 9. Push plate 10. Moving Mold base plate 11. Push rod 12. Reset rod 13. Guide sleeve 14. Guide column 15. Pad 16. Push plate guide 17. Push plate guide 18. Faucet 19. Limiting nail 20. Hexagon socket bolt
Figure 4 Mold assembly drawing

2.5 Mold structure and final assembly design

Figure 4 shows final assembly structure diagram of this mold. This mold adopts an ordinary two-plate structure. Considering complexity of casting structure and cost factors of mold production, cavity and core parts of mold adopt movable inserts, which are embedded in movable and fixed mold plates respectively. Moving and fixed mold inserts, moving and fixed mold plates adopt H7/K6 transition fit, are connected and fixed with bolts. This design facilitates processing of mold forming part, as well as repair, replacement and size adjustment of forming part. Mold closing of moving and fixed molds adopts combination of four guide pillars and guide bushes to ensure stable and accurate mold closing. In order to ensure that push rod can slide smoothly, push rod is fixed in push plate and push plate fixed plate. A structure of four push plate guide posts and guide bushes is used to support weight of push plate and push plate fixed plate to ensure that push rod operates smoothly and will not deform. Four Φ20 mm reset rods are installed in moving mold plate and fixed in push plate. After push-out action is completed, when mold is closed, reset rod in movable mold drives all push rods to complete reset.

3. Production verification

A domestic research institute currently has a 300 t cold chamber die-casting machine. Mold used is mold designed and developed this time. It adopts an ordinary two-plate structure with cavity in fixed mold and core in movable mold. Trial production of this aluminum alloy shell was completed by preparing aluminum alloy liquid and optimizing relevant parameters of die-casting process. Product produced after removing slag bag and sawing off gate is shown in Figure 5. This trial production effectively avoided defects such as cold insulation, slag inclusions, bubbles, looseness, unformed heat sinks caused by die-casting process, and achieved expected results.

Figure 5 Trial product sample

4 Conclusion

(1) Designing main forming part structure as an insert and processing it separately can not only control dimensional accuracy of casting, but also enable rapid repair, replacement and adjustment of wearing parts.
(2) Through structural analysis of casting, we chose to set up multiple internal gates at thick wall on the side of casting, and designed lateral runner into a stepped arc transition form, which not only ensures complete formation of heat sink, but also satisfies rapid filling of casting. requirements.
(3) By analyzing casting forming process, choosing to set up multiple overflow grooves at the end of metal flow direction can avoid casting defects such as cold shut, slag inclusions, bubbles, looseness, and unformed heat sinks during die casting.
(4) Structure of this mold is that core is in movable mold and cavity is in fixed mold. Main forming part adopts an inlaid structure, and mold adopts an ordinary two-plate structure. After mold testing, it was verified that mold operates smoothly and reliably, appearance quality and dimensional accuracy of die-casting parts fully meet product drawing requirements without any casting defects.

Die-casting mold design to adapt to variations in casing structure

For two similar casing die-casting parts, two mold structures and two reasonable push-out mechanisms were designed. For thin-walled high-tightening casing castings, use of a two-level ejection mechanism successfully solved problem that castings are easily broken by push rod when cavity is in movable mold; use of auxiliary gates overcome problem of insufficient filling of side gates. Secondary push-out mechanism used has a simple and practical structure and reliable operation.

Graphical results

Figures 1 and 2 are parts diagrams of forward and reverse (YL102) aluminum alloy casing of single flange axial flow fan respectively. It can be seen that it is a composite structure composed of an inner edge end cover and an outer edge flanged cylindrical part. Inner and outer edges are connected by three φ5mm circular cross-section ribs. Difference between two casings is that outer flange and inner end cover of forward casing are at both ends of casing, while outer flange and inner end cover of reverse casing are on same side. It is characterized by low overall strength, thin and long outer edge cylinder wall, strong wrapping force on core. When designing die-casting molds, if traditional full push rod push-out mechanism is used, opposite result will occur.

Figure 1 Front casing parts diagram

Figure 2 Reverse casing parts diagram
According to traditional structure, cavity is set in fixed mold and core is set in movable mold. Aluminum liquid poured into cold pressing chamber is pressed into sprue of sprue sleeve at high speed by injection punch, is injected vertically upward through lateral runner and inner gate of fixed mold insert 15 into mold cavity under guidance of diverter cone, pressurized and cooled before opening mold; ejection cylinder of die-casting machine pushes push plate 3, then pushes all push rods to eject casing casting. Figure 4 is movable mold insert. Since ejection positions of eight φ4mm outer edge push rods 11 are cleverly placed on φ108mm diameter close to φ102mm inner hole, half of φ4mm push rod end faces coincide with outer edge cylinder wall of casing casting, so that casing casting will not undergo any deformation or breakage when subjected to strong ejection force, thus forward casing can be formed and ejected smoothly.

Figure 3 General assembly diagram of forward casing die-casting mold

1. Bottom plate 2. Fastening screw of movable mold 3. Push plate 4. Push rod fixed plate 5. Push plate guide sleeve 6. Push plate guide post 7. Reset rod 8, 21. Rib push rod 9. Moving mold plate 10. Outside Rim cylinder core 11. Outer edge push rod 12. Fixed mold plate 13. Fixed mold guide bush 14. Moving mold guide post 15. Fixed mold insert 16. Installation hole core 17. Fixed mold core 18. Inner edge push rod 19.Bearing chamber hole core 20. Inner core 22. Sprue sleeve 23. Sprue push rod 24. Moving mold insert 25. Diverter cone 26. Moving mold cover 27. Pad 28. Cylindrical head hexagon socket screws

Figure 4 Moving mold insert
Wall thickness of reverse casing is only 1mm, while thickness of mounting flange is 4mm. Strength of intersection at the back is very different, and there is severe stress concentration. When push rod is ejected, it is easily broken (see Figure 5). This is because structure of reverse casing determines that outer edge cylindrical cavity can only be placed in movable mold, and outer ejection point can only be placed at base of flange lug on the edge (φ4.5mm mounting hole side), result of which is that lugs of cylinder wall will break during ejection. Swing-bar type two-level push-out mechanism is used to push casing casting in cavity out of cavity after getting rid of large tight force between cylinder wall and core.

Figure 5 Fracture location diagram

Figure 6 General assembly diagram of reverse casing die-casting mold (re-rolled structure)
1. Sprue sleeve 2. Outer edge cylinder core 3. Inner core 4. Bearing chamber hole core 5. Inner edge push rod 6. Rib push rod 7. Installation hole core 8. Fixed mold core 9. Moving mold Insert 10. Fixed mold guide bush 11. Fixed template 12. Moving mold guide post 13. Moving mold guide bush 14. Reset rod 15. Push plate 16. Push plate push rod 17. Moving template 18. Fastening screw 19 .Moving mold cover 20. Flange outer edge push rod 21. Push plate guide column 22. Front push rod fixed plate 23. Front push plate 24. Rear push rod fixed plate 25. Front push plate guide bush 26. Rear push plate Guide bush 27. Back push plate 28. Base plate 29, 34, 35. Cylindrical head hexagon socket screws 30. Roller 31. Swing bar 32. Rotating shaft 33. Connecting rod 36. Rib push rod 37. Sprue push rod

In conclusion

When considering ejection options, stiffness and strength of die casting should be more comprehensively evaluated. Some die-casting parts seem simple, but they cannot be pushed out at one time; two-stage push-out mechanism is relatively complex, so two-stage push-out mechanism is generally not used. When designing mold, full-pusher push-out mechanism should still be the first choice.

Development of rapid design system for magnesium alloy die-casting molds based on big data analysis

Magnesium alloy die-casting molds can form castings with high filling temperatures, complex internal cavities, long service life, easy high-temperature bonding between formed parts, and fast cooling rates. If traditional design methods are used, design workload will be large and mold design cycle will be long. At present, CAD/CAM/CAE/CAPP technology is core and key development direction of modern mold design. Using a dedicated CAD integrated system to quickly design magnesium alloy die-casting molds can not only shorten design cycle, but also improve rationality and processing accuracy of mold structure. This topic applies artificial intelligence to traditional magnesium alloy die-casting mold design, adopts development concept of big data + special magnesium alloy die-casting mold CAD system, uses VC++6.0 and Windows series windowed operating system integrated development environment to develop a magnesium alloy die-casting mold CAD integrated system based on big data analysis. System adopts Chinese interface, drop-down menu design, simple operation, and more accurate, fast and convenient die-casting mold design, which has good reference significance.
Taking magnesium alloy laptop back cover die-casting mold as an example, this paper introduces general process of rapidly designing magnesium alloy die-casting molds using a die-casting mold CAD integrated system based on big data analysis. This system can not only quickly and reasonably design side core pulling and complex cavity structure of die-casting mold, but also query relevant data of die-casting mold design. Practice has proven that this system can quickly complete design of cavity die-casting molds, and has reference value for rapid design of complex magnesium alloy die-casting molds.

Graphical results

AZ91D magnesium alloy laptop back cover replaces original engineering plastic. It has characteristics of low density (1.82g/cm3), high specific strength, good mechanical properties, good electromagnetic shielding, good electrical and thermal conductivity, good cutting performance, and good die-casting performance. It is one of ideal materials for back cover of laptop computers. However, it has disadvantages of large volume shrinkage (0.8%), difficulty in demoulding when opening mold, easy formation of concentrated shrinkage cavities and cracks. Geometric shape of magnesium alloy laptop back cover is shown in Figure 1. Its overall dimensions are 350mm*250mm*11mm, and average wall thickness is 0.6mm. There are holes and grooves for assembly around casting, especially if there are rectangular holes for assembly on the side, lateral core pulling mechanism needs to be considered. In order to simplify mold structure, demoulding mechanism adopts an inclined ejection method. According to design requirements, high-precision dimensions of fitting parts are selected as IT11, and the overall dimensions are selected as IT12. Minimum value of parallelism tolerance and coaxiality tolerance of die castings is 0.1mm.

Figure 1 3D view of laptop back cover

Figure 2 Specific design process of rapid die-casting mold

(a). Movable mold

(b) Fixed mold
Figure 3 Die-casting mold working parts
With guidance of rapid mold design system and visualization system, you only need to set shrinkage rate of magnesium alloy material (0.8%) to automatically generate die-casting mold working parts, including movable and fixed molds of die-casting mold, inclined slider and gating system. The entire process is automatically generated by software to avoid human errors and make mold cavity size more accurate. Mold core and cavity automatically generated by system are shown in Figure 3. In this link, big data analysis can be used. Because volume shrinkage of magnesium alloy die-casting parts is large, when castings are demoulded, castings will be difficult to demould due to large shrinkage. Forcible demoulding will cause large cracks and other defects. After construction of working parts of die-casting mold is completed, the overall mold cavity and gating system can be rounded through system software to minimize adhesion stress and avoid casting defects.

(a) CAD integrated system

(b) Standard mold base calling interface
Figure 4 Magnesium alloy die-casting mold CAD integrated system and standard mold base calling interface


Figure 5 Magnesium alloy die-casting mold CAD integrated system standard parts calling interface

Figure 6 Three-dimensional assembly diagram of die-casting mold

Figure 7 Two-dimensional assembly diagram of die-casting mold
1. Fixed mold base plate 2, 3, 11, 18, 19, 20, 24. Hexagon socket screws 4. Gate sleeve 5. Positioning screw 6. Fixed mold fixing plate 7. Guide pillar 8. Guide bush 9. Fixed mold Cavity 10. Moving mold core 12. Moving mold fixed plate 13. Support plate 14. Push rod 15. Push plate hexagon socket screw 16. Push rod fixed plate 17. Moving mold base plate 21. Return spring 22. Inclined top 23. Inclined Top fixed block 25.Reset lever

In conclusion

After the overall design of die-casting mold is completed and confirmed by mold motion interference inspection, the overall structure of die-casting mold is reviewed and verified based on big data analysis, details of die-casting mold are optimized and corrected, possible problems that may arise in later die-casting mold trial are predicted. Eliminate other design factors that cause defects in die-casting parts due to die-casting equipment and die-casting processes. When conditions permit, motion simulation and filling process simulation can be performed. After analyzing simulation results, the overall structure of die-casting mold can be optimized. After confirmation, digital manufacturing can be carried out to ensure one-time success in later die-casting mold trial. A single part can also directly generate a two-dimensional engineering drawing, which facilitates processing of a single part using traditional processing methods. The entire working process of magnesium alloy die-casting mold can be seen from two-dimensional assembly diagram. It can be seen that the overall side core-pulling mechanism of mold adopts an inclined top mechanism. Mold structure is simple, which reduces number of relatively moving parts in mold cavity and avoids damage to die-casting mold due to high cavity temperature and sintering of relatively moving parts in cavity.

Analysis and understanding of die-casting mold design and die-casting process

Die-casting mold is an important process equipment in die-casting production. Molten metal cools and solidifies in die-casting mold, eventually forming a die-casting part. Shape, size, quality of die-casting parts, and smoothness of die-casting production are closely related to die-casting mold. Therefore, it is crucial to design die-casting mold correctly and reasonably.

1. Basic structure of die-casting mold

Commonly used die-casting molds are composed of two half-moulds, called fixed mold and movable mold. There are also more complex die-cast molds with more than two mold halves. Components of die-casting mold are shown in Figure 1.

Analysis and understanding of die-casting mold design and die-casting process

Functions of components of die-casting mold are as follows:

(1) Sprue is connected to pressure chamber or to lateral runner, including sprue sleeve and diverter cone.

(2) Gating system: Channel through which alloy liquid enters mold cavity, including inner runner, lateral runner and sprue.

(3) Cavity is formed on insert to form geometry of die casting.

(4) Core pulling mechanism completes extraction and insertion actions of movable core, including slides, sliders, cylinders, slashes, etc.

(5) Overflow system discharges gas and stores cold metal residues, etc.

(6) Temperature control system controls temperature of die-casting mold, including cooling water pipes and heating oil pipes.

(7) Ejection mechanism ejects die-casting parts from mold cavity, including ejector pins, etc.

(8) Movable mold frame connects and fixes movable mold components, including sleeve plates, support plates, etc.

2. Design of die-casting mold

When designing a die-casting mold, you should pay attention to following points:

(1) Use advanced and simple structures as much as possible to ensure stable and reliable operation, daily maintenance and repairs.

(2) Modifiability of gating system should be considered, and necessary modifications can be made during debugging process.

(3) Reasonably select various tolerances, scales and machining allowances to ensure reliable module fit and required die-casting accuracy.

(4) Select appropriate mold materials and reliable heat treatment processes to ensure service life of die-casting mold.

(5) It should have sufficient stiffness and strength to withstand clamping pressure and expansion force, and should not cause deformation during die-casting production process.

(6) Use standardized die-casting mold parts as much as possible to improve economy and interchangeability.

When designing mold, it is also necessary to calculate total projected area and injection pressure during die-casting production based on projected area of casting to select a die-casting machine of appropriate tonnage. Formula is as follows:

F expansion force = 100 P injection specific pressure * S projected area

F clamping force = F expansion force/K coefficient

In formula, K coefficient is generally selected as 0.85.

After die-casting machine is selected, size, center position, reset rod hole position and other dimensions of parts connected to die-casting machine are designed based on size of die-casting machine’s dynamic and static traveling plates and injection eccentric position.

With development of my country’s automobile manufacturing industry, more and more automobile parts are made of aluminum alloy, such as automobile engine cylinder blocks, cylinder heads, oil pans and various connecting brackets. As die-casting technology becomes increasingly mature, various automobile manufacturers have higher and higher requirements for internal quality of die-casting parts, especially German Volkswagen, which has the most stringent requirements. Each type of engine die-casting product has a corresponding set of technical requirements. Product porosity requirement is a necessary requirement for each type of component.

Some parts are very complex in structure, and some corresponding structures need to be made on mold to achieve mass die-casting production. For example, there are threaded holes at various angles on parts. To ensure quality of processed products, cores must be made at corresponding positions of mold, as shown in Figure 2.

In Figure 2, A is a positioning hole, and B is three M8 threaded holes, which are at an angle of 10° to positioning holes. The two threaded holes on the right are through holes; C is a two-bolt through hole, at an angle of 5° to positioning hole; D hole is a threaded hole at 34° to positioning hole, and length is 38mm.

Core pulling mechanism can be divided into two types according to driving mode: mechanical type and hydraulic type. Mechanical core pulling mainly uses oblique pins, bent pins, gears, racks, etc. to achieve core pulling and reset during mold opening and closing process. Working principle of hydraulic core pulling mechanism is relatively simple. It directly uses hydraulic cylinder to perform core pulling and resetting actions. Hydraulic core pulling mechanism can select size of hydraulic cylinder according to size of core pulling force and length of core pulling distance. When designing product in Figure 2, first consider the three holes C and D that need to be cast. You can use a hydraulic core-pulling mechanism to use an angled slide to form holes in production. Figure 3 is a schematic diagram of slide mechanism of D hole. In this way, hydraulic cylinder can be designed outside mold. Advantage of this design is that mold can be made thinner and easier to maintain during continuous production.

During continuous production process, core-pulling hole of mold will be deformed due to repeated insertion and sliding. In the middle and late stages of mold life, phenomenon of core-pulling and grinding will often occur. In order to solve this problem, an insert can be added to core hole. If core hole is deformed, insert can be replaced (see Figure 4). This method can also be applied to ejector pin of mold. As long as an insert can be added, this structure can be made.

Due to requirements of some parts drawings, special-shaped ejector pins of specified sizes need to be placed in some areas on casting. The four ejector forming parts within circle (see Figure 5) are in the form of steps with a diameter of 8mm. Since dynamic mold cavity of casting is relatively deep, holding force generated is very large, and force required when ejector pin is ejected from casting is large. Ejector pin is easily broken during die-casting production process. Since diameter of ejector pin in casting forming part is determined by product drawing, ejector pin with stepped thickness can be designed according to characteristics of product to ensure life of ejector pin.

Since there are oil cylinders with angles C and D on mold, there is no room for the three M8 threaded holes shown in B to use oil cylinders to make pre-cast holes. The two M8 threaded through holes are 18mm deep. To ensure internal quality, pre-cast holes must be made. We have adopted method of making docking special-shaped cores to solve this problem. Docking form is shown in Figure 6.

Cores are not butted normally and are staggered by a certain distance. Part where two cores are butted has a normal draft angle (generally designed between 1° and 1.5°). Draft angle of outer sides of the two cores is normal draft angle plus angle with positioning hole.

Since internal quality of some complex products cannot be guaranteed through die-casting process parameters in thick and large areas, it is necessary to consider adding a local extrusion mechanism when designing mold. Principle of this mechanism is insert core in the shortest time after injection is completed, so that this area is compacted and air holes are reduced. Core-pulling forming part of extrusion mechanism has no die draft, so it is only suitable for short-range structures.

3. Die-casting process system design

After large frame of mold is designed, design of pouring system begins. In the past, this part was done based on practical experience based on two-dimensional or three-dimensional drawings. Position and direction of ingate is adjusted according to internal quality of product during production process. In the past decade or so, with continuous development of numerical simulation technology for casting filling and solidification process and market demand of foundry industry, commercial software for casting process simulation has continued to appear. Many OEMs also require to see die-casting simulation process before designing mold. Therefore, many mold manufacturers use two simulation software, MAGMAsoft or ANYCASTING. At the beginning of design, designed 3D is imported into this program to set die-casting process. After setting parameters, simulation software performs certain calculations to obtain a simulation animation that is close to actual production effect, as shown in Figures 7 to 10.

Die-casting process requires simulation to achieve following effects:

(1) Alloy liquid should arrive at ingate more or less at the same time.

(2) Alloy liquid should be filled smoothly during filling process.

(3) There should be no air entrainment or turbulence effects during filling process.

(4) Before filling is completed, alloy liquid cannot seal slag bag passage.

(5) Cold metal generated from filling process cannot be stored in casting and should all be driven into slag bag.

According to filling simulation and particle tracking simulation, as well as requirements of die-casting process, position and size of mold’s runner and slag collection bag must be optimized accordingly; according to solidification simulation and wall thickness of casting, locations of cooling water and heating oil pipes in mold, as well as point cooling points can be determined; according to mold erosion simulation, it can be determined which parts of mold need to be sprayed. Through simulation analysis, process of manual optimization of gates and slag collection bags is solved during design, which saves mold modification process caused by deviations based on experience during mold manufacturing.

In order to further improve quality of castings, some companies use vacuum technology to reduce scrap rate and create higher value. Japan’s vacuum technology is very mature, and our country has also learned from some of their experience. Vacuuming technology requires that area of mold exhaust channel is 1:100 of punch area. Start vacuum pump 0.4 seconds before start of fast injection. When designing mold, you can determine number of vacuum exhaust wave plates or vacuum valves based on complexity of product and size of mold. Figure 11 is vacuum structure on mold.

If vacuum technology is well applied, scrap rate of castings must be reduced to at least 20% of original scrap rate. However, due to high price of vacuum equipment, some die-casting factories only use it on product molds with high scrap rates.

Analysis and countermeasures on typical early failure cases of aluminum alloy high-pressure die-casting molds

Failure of die-casting mold shortens life of mold, which not only increases cost of product, but also seriously affects production, becoming a key issue that urgently needs to be solved in production. Article analyzes and discusses typical early mold failure cases during use of aluminum alloy high-pressure die-casting molds. A case analysis was conducted on common failure mechanisms of molds, namely: cracking, thermal fatigue cracks, erosion, cavitation, and deformation, and technical solutions were pointed out.

Surface of mold is “cavitated” – mold design issues

“Cavitation” phenomenon: “Pockmarks” are formed on the surface of die-casting products.

Cavitation erosion is caused by expansion of cross-sectional area of runner path, which causes pressure of aluminum alloy liquid to drop during flow of runner, forming a negative pressure cavity inside liquid aluminum alloy. During die-casting process and pressurization stage, negative pressure “bubbles” explode on the surface of mold, damaging mold material and causing formation of “pits”. Formation of defects can take 200-300 modes.

Reason for formation of “cavitation”: expansion of cross-sectional area of runner

In picture above, cross-sectional area of side main runner A = 825mm²; it bifurcates into two branch runners, B and E. Cross-sectional area of B+E runner is 1317mm²; in this way, pressure of liquid aluminum alloy drops during flow of runner, and a negative pressure cavity is formed inside it. Branch runner of E further branches into C+F; cross-sectional area of E is: 750mm²; cross-sectional area of C+F is: 1032mm²; pressure of liquid aluminum alloy further drops, creating a negative pressure cavity inside.

“Cavitation Erosion”: Microscopic Analysis and Solutions

Picture on the left is a scanning electron microscope photo, which shows holes on the surface of mold material that were exploded by negative pressure bubbles caused by cavitation. Picture on the right shows that surface treatment process of mold material, that is, nitriding treatment and surface coating treatment, cannot prevent formation of cavitation pits. Usually, hardness of mold material is 470HV, while hardness of coating is 2200HV; increasing surface hardness cannot solve problem of cavitation erosion. The only solution is: modify runner design and design mold according to design principles.

Mold design principles

Basic principles of new mold design: 1. Starting from material, cross-sectional area of main runner is in a compressed state on the path to inner gate. 2. R of turn is more than twice width of cross section. 3. Gate shape: fan gate, tapered tangent gate, chisel gate. 4. Follow gate size definition. 5. Any ejector pin should be parallel to surface of mold and must not protrude or be recessed.

Mold corrosion-influence of injection speed and mold design

“Erosion” phenomenon: Mold has less flesh and part of it is “worn” away. Product is fleshy, shape of product changes, and ejection problems occur.

Picture on the left is movable mold side of product, and circled part is corrosion part. Picture on the right shows fixed mold side of product, and corrosion is also occurring on the back of picture on the left. After mold produced more than 300 molds, corrosion and cavitation occurred near inner gate.

Cause of “corrosion” defects: inner gate speed is too fast. Sprue design is unreasonable, and solidified aluminum alloy in gate blocks part of inner gate.

In this case, corrosion of inner gate is due to expansion of cross-sectional area of liquid aluminum alloy during flow of gate. Partial aluminum alloy liquid, dispersed. Since inner gate is relatively thin, part of aluminum alloy liquid that reaches inner gate first solidifies and blocks part of gate. In this way, effective area of inner gate is reduced. As a result, when subsequent liquid aluminum alloy flows through inner gate, effective area is drastically reduced. In this way, local speed exceeds set gate speed, resulting in corrosion. Improvement plan: Strictly follow sprue design principles to avoid local blockage of gate leading to corrosion. Liquid aluminum alloy can dissolve approximately 3.2% iron. Amount of corrosion is proportional to 2.7th power of inner gate speed. Local gate speed is too high, causing inner gate to be corroded on hundreds of products.

• Early Thermal Fatigue – Effect of Temperature Difference

Thermal fatigue phenomenon of mold: micro-cracks form on the surface of mold, and after expansion, pieces will fall off. Casting cannot be ejected.

In a large die-casting mold (3,500 tons), after producing 3,200 products, a large number of thermal fatigue cracks formed on the mold surface near inner gate, causing product to “stick to mold.”

Note: If there is a problem with toughness of mold material, there should be cracks at R corner of boss.

Causes of mold thermal fatigue: Temperature difference on mold surface affects thermal fatigue resistance of material.

Mold material hardness measurement shows that hardness of mold material on runner is 40-42HRC. At non-runner area, hardness is 46HRC. It shows that temperature of liquid aluminum alloy is on high side. At the point where it flows through sprue, temperature is around 630 degrees. It exceeds tempering temperature of mold by 600 degrees. It further shows that temperature of die-cast aluminum alloy is abnormal (too high).

• Problem of early mold failure: mold cracking—temperature field considerations in mold design

Temperature field design of mold includes: distance between cooling water channel and mold surface, water flow rate, water hole diameter of water channel, shift production, and spray amount of water-based release agent, spray angle, spray distance, degree of atomization, heat taken away by water-based release agent, etc.

Case picture above shows mold of a 3,000-ton die-casting equipment. Cooling water is 23mm away from mold surface. In infrared imager test, mold surface temperature changes from 275℃/169℃/120℃. There are several reasons for cracks: 1. Internal cooling water channel is 23mm away from surface. 2. Mold crack is at R corner of step, and thickness changes greatly. 110mm to 280mm. Heat treatment residual stress concentration. 3. Groove of triangular insert is processed by electric discharge machining. It is recommended to process it before heat treatment, so that stress distribution will be along mold shape, and cooling water channel needs to be calculated.

Calculation of cooling water channels

Taking aluminum alloy A383 as an example, its specific heat is: 2.90 J/cm³/℃, and its heat capacity is: 1094 J/cm³.

If we consider that 1 cubic centimeter of aluminum alloy is cooled from a liquid state at 593℃ to a solid state ejected from casting at 450℃, heat dissipated is:

Aluminum alloy heat dissipation per cubic centimeter = specific heat + 2.90X (liquidus temperature – product ordering temperature)

＝1094＋2.90X（593－450）

＝1500（J/cm³）

If we consider 50 cubic centimeters of aluminum alloy, heat dissipated from solidification to ejection is:

＝50cm³X1500J/cm³

=75(KJ)

If we consider a 50 cubic centimeter aluminum alloy, shift output is 200 pieces/h; then, shift output needs to be determined in mold temperature field design step. At this time, thermal power emitted by aluminum alloy is 75KJX200 pieces/h=15000 (KJ/h).

If moving and fixed molds each take away 50% of heat, then heat power emitted by mold in moving mold is: 7500 KJ/h.

By using chart, you can check specific data such as distance of cooling water from mold surface, diameter of cooling water channel used, flow rate of cooling water, etc. By looking up table, we can see that if distance between cooling water channel and mold surface is 47mm, heat power taken away is: 80KJ/cm²/h; if protruding R is 80mm, then after correction on curve, it is found that distance between mold cooling water channel and mold surface is: 35mm.

If cooling water flow rate is 6L/min and a 6mm diameter water channel is used, heat taken away is 400KJ/h. Required length of cooling water channel is: 7500/400=18cm. If cooling water flow rate remains unchanged and a 10mm diameter cooling water channel is used, then length of water channel is: 13cm.

Calculation sheet for cooling channels in Excel

Take cylinder mold as an example:

Casting product weight: 22 KG

Die casting cycle time: 90 s

Die casting alloy: aluminum alloy

Casting surface area: 5000 cm²

Calculated total cooling water channel length is: 1230 cm;

Distance between cooling water and surface: 29.9 mm-33.2 mm

Heat taken away by cooling water channel per centimeter length: 415 KJ/h

Cooling water flow (6mm hole diameter): 5.8 L/min

Cooling water flow (10mm hole diameter): 2.3 L/min

Above is the total cooling water channel length. During temperature field design process, casting needs to be decomposed. Calculate distance between cooling water channel of a certain decomposition part and mold surface, water flow rate, aperture of water channel based on wall thickness and contacting mold surface area.

Even if mold materials and heat treatment have good process and quality control, there will still be problems with mold. Reason is that temperature field of many molds has not been calculated. How close is cooling water to surface? This is especially true for molds that are slightly cold.

Picture shows that cylinder mold has cracks on the side of mold insert on the side of crankshaft sleeve, causing mold insert to leak. Among them, leakage part and liquid level of liquid aluminum alloy pre-filled (about 15%) are basically at same level. It shows that water inside cold water pipe boils, causing volume of water to expand, mold becomes cracked and leaks. Cooling water channel is 11.8mm away from surface. Suggestion: Distance between cold water channel and mold surface should be more than 15mm to avoid mold cracking.

Deformation of mold—Consideration of dimensional expansion

Calculation of material expansion: expansion = material thermal expansion coefficient x temperature difference x 450. For large molds, it is especially important to consider that mold is used at high temperatures rather than room temperature. If temperature difference between surface and back is 95℃, bulge of mold surface is 0.5mm, and sum of two sides is 1mm. Taking these variables into account can avoid local mold cracking, die casting flash, and mold deformation problems.

Definition of R angle size, release agent spraying is part of temperature field

Size of R angle of product has always been one of factors affecting life of mold. For most products, R angle should be controlled above 1.5mm.

As shown in the figure, R angle of communication die-cast base station housing product is 90 degrees. After producing 1,000 products, mold cracked. When R angle of mold material decreases from 1.5mm to 0.5mm, impact toughness of mold material decreases from 22J to 16J. And if R drops to 0.25mm, toughness of mold material drops to 8J. Since die-casting molds are produced at high temperatures, it is recommended that R angle of mold cavity be controlled above 2.5mm. Note: There should be no additional knife marks on R corner.

Spraying of water-based release agents will affect life of mold. After producing 60,000 pieces of products, mold shown in the picture developed severe thermal fatigue cracks in wall thickness of casting. There are no thermal fatigue cracks in thin wall areas. It is necessary to consider local spray amount of water-based release agent, spray angle, and calculate heat taken away by release agent. 1cm³ of water-based release agent can take away 2600J of heat. If heat of 1cm³ aluminum alloy from liquid to solidification is taken away by spraying of release agent, then required spraying amount of release agent is 0.7cm³. Specifically, it is also necessary to calculate amount of release agent sprayed based on the shape of product.

In conclusion

1. Formation of “pits” on mold surface caused by surface cavitation of mold is a mold design problem. As long as die-casting mold runner design principles are strictly followed, the entire cross-sectional area of main runner from material to inner gate is in a shrinking state, and problem of cavitation erosion can be easily solved.

2. Problem of local corrosion of inner gate of mold is that principles of die-casting mold design are not followed when designing mold gate. During injection process, part of aluminum alloy liquid flows in runner, first reaches inner gate, solidifies and blocks part of gate, so that subsequent aluminum alloy liquid reaches inner gate. During injection flow process, local injection rate is too high, which leads to corrosion of mold gate. Solution to overcome this type of corrosion is to strictly adhere to design guidelines of die-casting mold to avoid pressure drop of liquid aluminum alloy during flow of runner, causing blocking of some pouring openings.

3. The early thermal fatigue of mold is mostly related to temperature difference on the surface of mold material. Article discusses material stresses and strains caused by temperature differences. Conclusion of case analysis is that aluminum alloy liquid temperature is too high, causing a large number of early thermal fatigue cracks on the mold surface after production of 3,200 products. Reason is that liquid temperature of aluminum alloy is abnormally higher than tempering temperature of mold material and reaches 630℃, which causes hardness of part in contact between mold and liquid aluminum alloy to decrease and cause early thermal fatigue cracks.

4. There are many reasons for mold cracking. This article discusses mold cracking phenomenon caused by mold temperature location. For specific temperature field calculations, you need to calculate design of cooling water channel according to excel table cited in article. Minimum distance between cooling water channel and mold surface is 20mm, and point cooling distance is 15mm, so that mold will not crack.

5. Deformation of mold is due to fact that mold is produced at high temperatures, so mold material itself will expand, resulting in both linear dimensional changes and surface convex shape changes. Considering these variables can solve flash problem and deformation problem.

6. Size of R angle is crucial. Mold may begin to crack at R angle after 1,000 mold cycles. Recommended R value is R greater than 2.5mm. Release agent spraying is part of mold temperature field. Specific spraying amount needs to be calculated to measure and control spraying amount. Only in this way can goal of extending service life of mold be achieved.

Experience sharing on die-casting mold design for new energy vehicle motor housing

Replacement of fuel power by electric motors has become an inevitable trend. As a core component of new energy vehicles, design and production of motor housings has become the key.

Today we will take a look at difficulties and key issues in design of motor housing die-casting mold, as well as corresponding solutions.

01 Current status of China’s motor housing die-casting industry

Casting of motor shells is in its infancy in China, everyone is constantly exploring and making progress.

Die casting has gradually become a fast-growing metal precision casting method due to its advantages of high efficiency, less/no cutting, short production process, simple and concentrated process, high product precision, and smooth surface. Especially aluminum alloy die-casting process has become one of indispensable processes in automotive industry.

In recent years, due to continuous development of domestic automobile industry, demand for large-scale precision die-casting molds is increasing. Although design and production of large-scale precision die-casting molds in China have made great progress, there is still a certain gap with foreign advanced countries.

Because quality of such products will directly affect performance of automobile motor, subsequent processing and manufacturing costs are high.

Therefore, higher requirements are placed on yield, production efficiency, manufacturing cost and reliability of such molds.

For die-casting, quality of castings ultimately depends on whether die-casting mold structure design, gating system design, and overflow system design are reasonable.

Below we will focus on design of mold for a new energy vehicle motor housing casting.

02 Product structure and material

Figure above shows three-dimensional model of casting of new energy vehicle motor housing. Casting has a complex structure, its performance requires good strength and hardness, high surface finish, and good corrosion resistance.

Dimensions of casting are 420*265*235mm, and weight of machined product is about 9200 grams. Maximum and minimum wall thicknesses are 15mm and 4mm respectively, average wall thickness is 5.5mm, and thickness distribution is relatively uniform.

Position of rotor installed inside product needs to be machined, and air holes are not allowed after machining. At the same time, product is tested for leaks. Large cavity of product passes 0.2MPa gas at room temperature, inflation time is 20s, pressure holding time is 30s, detection time is 20s, and leakage is less than 30cc/min.

According to customer requirements, product material is aluminum alloy ADC12. ADCl2 aluminum alloy is widely used in the field of processing and manufacturing of auto parts. Its chemical composition is shown in the table below.

Si	Cu	Mn	Mg	Fe	Zn	Ni	Sn	Pb	Ti	Al
9.6-12	1.5-3.5	≤0.5	≤0.3	≤1.3	≤1.0	≤0.3	≤0.2	≤0.2	≤0.3	Margin

Motor housing is an integrated water-cooled motor housing, casting process and mold structure are more complicated than old split water-cooled motor housing.

Cooling channel of old-fashioned motor is formed by cooperation of two parts, inner shell and outer shell, which greatly reduces difficulty of manufacturing and processing parts.

New type of motor housing itself has an inner cavity and an outer cavity of a cooling water channel, and a cooling liquid is passed through water channel to cool motor rotor.

This has very high requirements on internal quality of casing, and no leakage defects are allowed.

Moreover, machined surface of inner hole of motor shell is large, probability of defects such as slag holes and shrinkage cavities on machined surface is high, stator is installed as a heat-shrink interference fit in later stage, which increases difficulty of product manufacturing and production, greatly increases difficulty of designing and manufacturing die-casting molds.

03 Mold scheme design

Initial plan determined

Die casting machine tonnage selection

According to casting information: projected area of the whole mold is 1560c㎡, quality requirements of casting, we choose casting ratio of 100MPa, safety factor of die-casting machine is generally 1.2, and tonnage F of die-casting machine is calculated according to expansion force of casting:

Since motor housing has strict restrictions on leakage of castings, external dimensions and molding height of castings are large, in order to have sufficient clamping force, internal quality of castings can be guaranteed during injection and filling.

According to theoretical calculation and equipment configuration of existing die-casting machine in die-casting factory, casting is selected to be produced on DCC2000T die-casting machine.

Considering that spray cannot be sprayed during die-casting process, there will be strains, which will easily lead to leakage, so technical requirements for surface coating are added to insert to solve strain problem;

At the same time, cylindrical insert is properly divided to facilitate replacement of mold parts in the future.

Selection of punch and calculation of pressure chamber fullness

The larger proportion of this space, the more air there is, and this air has a great influence on porosity of casting when filling mold.

When pressure chamber is overfilled, alloy liquid dissipates more heat in pressure chamber, and a large number of chill layers is also extremely unfavorable for filling.

Therefore, for castings with high airtightness requirements such as motor housings, when selecting diameter of punch, it is advisable to control fullness of pressure chamber within range of 50-70% when designing general pressure chamber, and choose a larger pressure chamber fullness as much as possible;

For this example, we selected punch diameter of Φ130mm, and calculated pressure chamber fullness is 60.5%, which meets reasonable requirements of pressure chamber fullness.

Gating system design

According to characteristics of shape of motor shell casting and design requirements of mold structure, drawing on design experience of runners of similar die castings, mold adopts a four-slider structure, mold inlet is arranged from cover surface of power output gearbox,  mold inlet is arranged from cover surface of power output gearbox, and pouring method of olecranon-type inner gate with vertical end faces of two runners is adopted, which is beneficial to flow of molten metal.  

Gating system of two runners shortens filling stroke, optimizes thermal balance of the overall temperature of mold, ensures that inner and outer substrates of cooling channel on motor housing are effectively filled;

Internal and external quality of product, mold stability, and mold life have been greatly improved. At the same time, production efficiency can be improved and manufacturing cost can be reduced.

Spill system design

Due to high leakage requirements of castings, overflow grooves and centralized exhaust blocks are arranged at the end of cavity filling to ensure good slag collection and exhaust of mold, which provides a guarantee for production of high-quality parts with high efficiency and high yield.

Mold Heating and Cooling System Design

In order to ensure thermal balance of mould, avoid sticking and straining of mould, and improve productivity of die casting and internal quality of casting, mould adopts measures of setting up heating oil passages on dynamic and static inserts, sleeve plates and sliders, and controlling mold temperature by mold temperature controller.

During die-casting process, when mold temperature drops, mold can be heated, when mold temperature increases, heat is taken away to cool mold, and mold temperature is controlled within a certain range.

Determining Right Die Casting Process

After pouring and drainage system design is completed, basic data of each part can be obtained from three-dimensional data:

Handle weight: 3490 grams

Net weight of the blank is: 9240 grams

Slag bag weight: 1730 grams

Use P-Q2 diagram tool to make a matching diagram between mold and DCC2000-ton die-casting machine (see above diagram), and select appropriate process parameters as shown in the table below.

Project	Unit	Parameter
Select model	Ton	DCC2000T
Ingate area	Mm2	1000
Punch diameter	mm	Φ130
Melting cup length	mm	800
Chamber fullness	Ton	60.5
Ingate speed	M/s	38
Filling time	ms	115

Mold flow analysis and scheme optimization

According to pre-selected process parameters, mold flow analysis software was used to simulate filling and cooling process of mold (as shown in figure below):

By viewing mold flow analysis video, we can observe simulated solidification process and temperature distribution of molten metal in mold, find out where isolated liquid phase region appears and where alloy liquid feeding amount is insufficient, find that there are some flow defects in filling process, which provides a basis for improving design of gating system and provides a reference for optimization scheme.

During mold flow analysis of simulation results, it was found that position where cold shut and pores appear on casting is the place where molten metal arrives first. Under high-speed filling, it is easy to form backflow entrainment, cold dirty molten metal to converge, and fusion of molten metal is not ideal.

From this, it can be judged that air holes and cold shuts are easily formed here. Combining above results, it can be judged that cold shuts and air holes defects appear in this part. On the one hand, casting structure is complex and forming is difficult, main reason is that effect of slag collection and exhaust is not enough.

Judging from simulation analysis results, current design of pouring system has certain quality risks, especially on the surface of inner cavity of motor shell. Air holes inside casting are easily exposed during subsequent machining process, and casting has risk of leak testing;

It is necessary to discharge void in mold as much as possible, so that mold cavity is in a vacuum state, which is conducive to formation of cavity and reduces occurrence of casting defects; we decided to take following measures to improve:

Solution①

Gate is moved inward to inner arm, allowing gate to fill mold thickly along arm, so that gate can be directly filled into deep cavity of motor casing, so as to improve smooth filling flow of alloy liquid;

Solution②

Adjust position of slag bag, position of slag bag is based on mold flow filling, and slag bag inlet is opened at the end of filling, which is better for exhaust and slag discharge;

Solution③

By setting a large-flow exhaust stop valve at the end of mold exhaust channel, die-casting process can achieve a large-flow exhaust throughout process, ensuring extremely low gas residue at each position of mold cavity of shell, thereby reducing filling resistance and probability of air entrainment in inner cavity.

According to comprehensive consideration of casting weight of product, filling rate of melting cup, the overall leakage coefficient of mold, difficulty coefficient of product, and referring to selection data, choose to use two sets of VM120 mechanical vacuum valve layout and mold skyside at the same time. And a die-casting vacuum system is added outside mold, with a vacuum tank volume of 1000L; to ensure continuous supply of a stable vacuum source.

Mold flow analysis after optimization scheme

Re-run mold flow analysis after improving sprue (see figure below):

Judging from optimized mold flow results, defect parts have been greatly improved compared with those before improvement. In improved mold flow analysis, alloy liquid flows smoothly in many coiled gas and coiled parts before improvement, and several defect-prone parts have been greatly improved. During solidification process, final solidified area coincides with location of hot joint, and shrinkage cavities appear in larger area of hot joint, but volume of shrinkage cavity is small and within a controllable range.

04 Mold trial verification

Finally, above-mentioned optimized design scheme was used to complete mold making, and optimized process scheme was adopted. According to determined optimal process parameters, DCC2000 die-casting machine was selected for die-casting production of motor shell. Final die-casting parts are shown in figure below:

Surface of casting is smooth, without obvious defects, and surface quality is good. Trial processing and air tightness testing of casting have been carried out, original design requirements have been met. Trial processed products are as follows:

05 Summarize

For motor housings with complex structures, pouring system from both sides is conducive to filling of molten metal;

Mold flow analysis can accurately predict various defects that may occur in castings, thereby optimizing casting process, improving quality of castings, and shortening trial production cycle;

Feeding method of olecranon-type inner gate can better control flow direction of molten metal;

Pre-establishing a reasonable die-casting process is conducive to smooth progress of mold flow and actual mold testing.

After above-mentioned series of mold design parameter optimization, mold making and mold testing, after mold testing verification, mold structure runs smoothly, action is reliable, production process rhythm meets design settings, produced castings have undergone dimensional inspection and machining production verification, which fully meet design requirements.

Deliver qualified molds to customers according to scheduled construction period. Through design optimization of new energy vehicle motor housing die-casting molds (see figure below for a simplified diagram of mold structure), we have accumulated valuable reference experience for design of similar products and die-casting molds for new energy motor housings in the future.