The core points of high-quality die-casting mold design

1. It is necessary for an excellent die-casting mold design plan to achieve the following goals

1. The die-casting mold can meet the high-quality requirements of the product.

2. Die-casting molds can complete the high yield requirements in a useful moment.

3. The die-casting mold can fulfill the requirements of further extending the service life under normal production conditions.


2. To accomplish the above goals, the following conditions must be met

1. Reasonable setting of feeding direction. The meter parameters can guarantee the technological requirements of die-casting production.

2. The size and method of feeding can accurately grasp the sequence, direction, and subsequent meeting points and filling points.

3. The position of slag discharge and gas placement is accurate, smooth and efficient, and it can adjust the filling order.

If the pouring system planning can have a good grasp of the filling flow direction and state speed. The position of the slag bag and the gas tank are set at the confluence or the final filling area, and the secretion is smooth (the slag bag can also delay the confluence and prevent the vortex). It can minimize the resistance during filling and reduce energy consumption. The chance of one-time molding is very high. There is no need to increase pressure and speed to obtain qualified products, and the yield is high. Similarly, it is also very advantageous for the life extension of die-casting molds and die-casting machines. Therefore, the core skills of die-casting die-casting molds are the design skills of the pouring system.


3. To have the above conditions, design engineers need to meet the following requirements

1. Familiar with the determination of die casting process and its parameters.

2. The filling effect of various ways of runner is clear.

3. Grasp the skill of the flow channel to the feeding sequence.

4. Grasp the skill of overflow tank (slag bag) to fill the direction and order of confluence.

5. After analyzing the characteristics of the product structure, determine the best filling scheme.

The feeding method determines the filling status (including direction, dispersion or gathering, etc.), while the runner method is the decision factor of the feeding sequence. You only need to be familiar with the basic method of feeding and runner, and understand The possible effects, combined with the analysis of the component structure, wall thickness change characteristics, the determination of the fundamental process parameters, and the wonderful settings of the slag ladle and exhaust, can plan a high-quality pouring system.

High-level die-casting mold designers can not only greatly satisfy customers’ requirements for product production, die-casting mold life, and cost control. In addition, production companies themselves will reduce costs and improve efficiency due to their high success rate.

Points of attention to the problems of die-casting molds often encountered in the production of die-casting:

1. Pouring system and overflow system

(1) Requirements for the direct runner of the die-casting mold on the cold-chamber horizontal die-casting machine:

① The diameter of the pressure chamber should be selected according to the required specific pressure and the degree of pressure chamber filling. Together, the inner diameter error of the sprue sleeve should be appropriately enlarged by a few more than the error of the pressure chamber diameter, and then it can be prevented from being caused by the pressure of the sprue sleeve and the pressure chamber. The internal diameter is different from the axis, which causes the problem of stuck or severe wear of the punch, and the wall thickness of the sprue sleeve should not be too thin. The length of the sprue sleeve should generally be less than the ejection lead of the injection punch, so that the paint can escape from the pressure chamber.

② The inner hole of the pressure chamber and the sprue sleeve should be finely ground after heat treatment, and then ground along the axis, and the surface roughness is less than or equal to Ra0.2μm

③ The diverter and the cavity forming the paint have a recessed depth equal to the depth of the runner, and its diameter matches the inner diameter of the sprue sleeve, with a 5° slope in the demolding direction. When using the coated sprue, it can increase the filling degree of the pressure chamber because of the shortening of the volume of the useful length of the pressure chamber.


(2) Requirements for runners of die-casting molds

① The entrance of the runner of cold horizontal die-casting mold should generally be located at the position above 2/3 of the inner diameter of the upper part of the pressure chamber to prevent the molten metal in the pressure chamber from entering the runner prematurely under the effect of gravity and starting to condense ahead of time.

② The cross-sectional area of ​​the runner should gradually decrease from the sprue to the inner gate. In order to show the cross-sectional expansion, the molten metal will present a negative pressure when it flows through, and it is easy to inhale the gas on the parting surface and add the molten metal to flow. The vortex envelops in the air. Generally, the cross section at the exit is 10-30% smaller than that at the entrance.

③ The runner should have a certain length and depth. The intention of insisting on a certain length is to stabilize the flow and guide the effect. If the depth is not enough, the molten metal will cool down quickly, and if the depth is too deep, the condensation will be too slow, which will affect the production rate and add the amount of recharge material.

④ The cross-sectional area of ​​the runner should be greater than the cross-sectional area of ​​the inner gate to ensure the speed of the molten metal. The cross-sectional area of ​​the main runner should be greater than the cross-sectional area of ​​each branch runner.

⑤ The two sides of the bottom of the runner should be rounded to prevent early cracks, and the two sides can have a slope of about 5°. The surface roughness of the runner part is less than or equal to Ra0.4μm


(3) Inner gate

① The parting surface should not be closed immediately after molten metal enters the mold, and the overflow groove and exhaust groove should not impact the core from the front. After the molten metal is poured into the mold, the flow direction should follow the cast ribs and fins as much as possible, and fill the thick wall to the thin wall.

② When selecting the position of the inner gate, make the molten metal flow as short as possible. When selecting multiple inner gates, it is necessary to prevent the several molten metal from gathering and impacting each other after entering the mold, and then the disadvantages such as vortex entrapment and oxidation doping will occur.

③ The thick parts of the inner gate of the thin-walled parts should be appropriately smaller to ensure the necessary filling speed. The setting of the inner gate should be easy to cut and not make the casting body incomplete (meat-eating).


(4) Overflow trough

① The overflow groove should be easy to remove from the casting, and try not to damage the casting body.

② When opening an exhaust groove on the overflow groove, pay attention to the position of the overflow port to prevent premature blockage of the exhaust groove and make the exhaust groove ineffective.

③ It is not necessary to open several overflow ports on the same overflow tank or open a very wide and thick overflow port to prevent the cold liquid, slag, gas, paint, etc. in the molten metal from returning to the cavity from the overflow tank , Forming the shortcomings of castings.

2. Casting fillet (including corners)

Casting drawings often indicate requirements such as unfilled corners R2, etc. We must not ignore the effect of these unmarked rounded corners when opening the die-casting mold, and must not make clear corners or too small rounded corners. The casting fillet can make the molten metal fill smoothly, make the gas in the cavity discharge sequentially, can reduce the stress concentration, and extend the life of the die-casting mold. (The casting is not easy to show cracks in this place or show various shortcomings due to poor filling). For example, there are many clear corners on the standard oil pan mold. Relatively speaking, the brother oil pan mold is the best now, and there are more heavy engine oil pans.

3. Demoulding angle

Artificial undercutting is forbidden in the demolding direction (often the casting sticks to the mold during mold trial, and when it is handled incorrectly, such as drilling, hard chiseling, etc. to make the part recessed)

4. Surface roughness

Molding parts and pouring system should be polished carefully as required, and polished along the demoulding direction. Since the molten metal enters the pouring system from the pressure chamber and fills the cavity, the entire process is only 0.01-0.2 seconds. In order to reduce the resistance to the flow of molten metal and minimize the pressure loss as much as possible, it is necessary to flow through the surface with high smoothness. At the same time, the heating and erosion conditions of the casting system are worse, and the worse the finish, the more easily the die casting mold will be damaged.

5. The hardness of the forming part of the die-casting mold

Aluminum alloy: around HRC46°

Copper: about HRC38°

During processing, the die-casting mold should be left as far as possible for correction, and the upper limit of the size should be set to prevent welding.


Die-casting die-casting mold assembly skills requirements:

1. Requirement of parallelism between parting surface of die-casting mold and template plane.

2. Requirement of straightness of guide post, guide sleeve and template.

3. On the parting surface, the plane of the movable and fixed mold inserts and the movable and fixed mold cover are 0.1-0.05mm higher

4. The push plate and reset rod are flush with the parting surface. Generally, the push rod is recessed by 0.1mm or according to user requirements.

5. All movable parts on the die-casting mold move reliably, and there is no sluggishness in the pin and no string movement.

6. The positioning of the slider is firm, the core is kept at a distance from the casting when the core is drawn out, and the cooperation part of the slider and the block is more than 2/3 after the mold is closed.

7. The runner roughness is lubricated and seamless.

8. Part of the gaps in the parting surface of the insert when closing the mold

9. The cooling water channel is dredged, and the import and export signs are marked.

10. Forming surface roughness Rs=0.04, no slight damage.

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