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Aluminum Die Casting Defects Case Study

Automotive engine oil pan

1, defects that appear

The product is an essential part of the car engine, the working environment is harsh, and it is required not to leak oil. We mainly encounter the sensor hole air holes in the production of this product that can not meet the requirements, large plane local air holes into pepper powder, it is difficult to lift.

2, the reasons for the generation

1) Oil sump is a deep cavity part, aluminum liquid from the water mouth to the water tail, the process is long, easy to produce cold material. And the sensing air hole is an isolated part, which is not conducive to the discharge of cold material.

2) The principle of product die-casting release agent is manual spraying, the amount of spraying changes every time, and there are more unstable factors, causing the product to be easily deformed.

3) Bad exhaust.

3, Solution

1) Open a slag collection bag in the sensor part to facilitate the discharge of cold material in this part.

2) Use ABB robots to ensure stable and fast spraying.

3) Open an exhaust block on the mold to get the best exhaust effect.

Thermostat housing

1, Defects that occur

The product needs not to show water under high temperatures and pressure, so the sealing groove of the product is required to be very strict. Product sealing slot requirements do not allow air holes, such as in production, the end of the product often appear pepper-like air holes, will cause the product scrap; and the proportion of air leakage caused by more.

2, the reasons for the generation

1) complex structure of the product, more tabs in the middle, the aluminum liquid is not smooth in the flow, at the end of the product is easy to produce rolled gas.

2) The wall thickness of the product varies too much, the smallest place is only 4 mm, but the thickest place can reach 30 mm, and it is easy to produce shrinkage and shrinkage holes in the wall thickness.

3) There is an 85 mm long sliding block on the product, which is easy to pull on and crack the product, causing air leakage.

3, Improvement measures

1) Add a vacuum exhaust device to the mold to reduce the amount of gas in the mold cavity.

2) Open a partial extrusion pin at the product wall thickness to reduce the product shrinkage and shrinkage hole.

3) Make program changes to the machine, set core extraction spraying, and spray lubrication to the oblique extraction core to reduce the phenomenon of strain and cracking.

Aluminum alloy base

1, defects

The problem of casting inlet buckling, buckling crack, and deformation after cooling occurs during the trial production of the product.

2, Causes of occurrence

1) Casting heat sink with the thin and narrow wall, in order to cast water tail heat sink forming good and take high speed and high-pressure molding, resulting in a large impact on the inlet port buckling die buckling crack.

2) The casting is too long, uneven wall thickness, different crystallization strength of each part, and the shrinkage in cooling have different differences causing distortion and deformation.

3, improvement measures

1) Do surface cloaking treatment at the inlet of the mold to improve the buckling mold.

2) Take vacuum die-casting, not to reduce the inner gate speed and improve the internal quality when reducing the injection speed and pressure, so as to reduce the impact on the inlet port during the injection and improve the buckling mold.

3) Adopt cooling without water spout to reduce the deformation by pulling the casting during cooling.

4) Pre-align the product in the condition of semi-cooling of the casting, when the internal stress of the product is not completely released.

Gear chamber

1, Defective problem

Air leakage was found during product air inspection.

2, Cause Analysis

The casting structure is complex, and in order to achieve a good appearance and required strength, the filling speed is up to about 60m/s and the specific pressure is more than 820kg/cm2. Therefore, a great impact on the part shown, so that the product surface burns, sticky aluminum; at the same time, due to the large difference in wall thickness of the part, the cooling rate is not the same and will lead to shrinkage, shrinkage crack, and these defects will lead to air leakage in the product in the gas inspection.

3, solution

1) Adopt point cooling method for die cooling in the corresponding part, which increases the local cooling effect; adopt local extrusion pin process to solve the problem of shrinkage.

2) Do surface cloaking treatment at the inlet of the mold to improve the buckling die and solve the burn.

The gas station connection body

1, defect problem

Casting both sides of the core extraction cavity buckling injury and lamination, the fixed mold forming surface of the two fixed columns has water lines or cold separation.

2, cause analysis

1) Due to the thin and long cores on both sides, the casting is wrapped by aluminum liquid, the temperature rises quickly, causing the cores to adhere to the inner cavity of the casting, and strains when taking off the mold.

2) After closing the mold, the core and the mold with a gap, resulting in feeding, forming a flying edge, after opening the mold, the core extraction, the flying edge can not be normal off, was caught in the mold, after closing the mold, the flying edge with the core inserted, the next filling, aluminum liquid in the flying edge on both sides of the molding, forming a sandwich.

3) The two fixed pillars on the molding surface of the fixed mold extend into the mold 35 mm, and are slender, with cooling water inside the mold, the top of the pillar is closer to the cooling water channel, after opening the mold, the pillar position cools down faster, and when spraying, the mold release agent is easy to remain because of the small space in the cavity of the pillar.

3, Solution

1) Install additional cooling points inside the extractor core on both sides of the mold to take away the heat from the end properly.

2) Polish the surface of the extractor core to stick to aluminum and cloak it to prevent the flying edge from sticking. Enable deceleration, deceleration position 525 mm to prevent flying edge.

3) Open 1/3 of the cooling water at the two pillars after normal, reduce the mold temperature appropriately, and blow out the residual mold release agent in the inner cavity after spraying in the fixed mold.

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