Those who have worked in die casting industry for many years know that producing a qualified die casting is not as simple as "injecting molten metal into a mold." Behind it lies wisdom of countless engineers and craftsmen, involving hundreds of adjustments and optimizations. Every cycle of mold preheating, parameter debugging, casting formation, ejection is interconnected and logically rigorous. There can be no shortcuts. Without respect for technology, defects such as porosity, insufficient material, sticking to mold, and shrinkage cavities can occur. These can range from affecting product performance to causing the entire batch to be scrapped, resulting in huge losses.
After 20 years of experience, I've combined my observations and knowledge with industry standards to break down core process of high-pressure die casting into a crystal-clear breakdown. I'm sharing this comprehensive guide to provide quick and easy access for newcomers or internal training programs. If you follow these methods to improve your skills, I believe you're just one step away from achieving a closed-loop system – practical verification!
Next, we'll jump straight to hands-on practice, explaining each step from initial preparation to final molding. Just follow steps directly; don't let your imagination run wild.
First, a mold temperature above 220℃ is fundamental.

 

Making mold temperature is paramount. After setting up mold, we need to "warm it up." One method is to use a mold temperature controller for heating. Turn on controller and set it to 300-320℃ to heat mold. Temperature should stabilize at around 220℃ (this can be fine-tuned for different products, but should maintain a fluctuation of ±10℃). Another method is to use a heat gun to evenly heat mold surface. Production begins once a certain temperature is reached. This method results in significant temperature fluctuations and is not recommended unless quality requirements are not high.
Why is using a mold temperature controller recommended? Unstable and highly fluctuating mold temperatures are detrimental to product molding. If mold temperature is too low, molten aluminum will cool rapidly upon entry, causing premature solidification, leading to cold shuts and insufficient filling. If mold temperature is too high, product will stick to mold, and solidification time will be prolonged, resulting in longer mold dwell times, longer production cycles, and lower production efficiency.
To ensure stable production and consistent quality, it is essential to ensure uniform and stable temperatures throughout mold before starting production. This prevents uneven stress, deformation, and cracking caused by localized temperature differences.
Secondly, application of release agent determines stability of mold.

 

Application of release agent is also crucial. Improper spraying can affect product molding, mold pulling, sticking, and deformation. To achieve perfect results, core steps are:
Targeted Spraying of Release Agent: This seems simple, but without experience, it's difficult to master. Too much or too little release agent will leave residue, leading to bubbles, pinholes, cracks, and cold shuts on product surface. Too little will not provide lubrication, causing product to stick to mold and be easily damaged during ejection, potentially resulting in poor flowability and formation of cold material.
Drying Cavity After Spraying: Mold cavity must be thoroughly dried after spraying. Residual moisture from release agent will turn into gas at high temperatures, becoming trapped in molten aluminum and creating pores, affecting product's density.
Secondly, perfect mold closing is crucial.

 

Mold closing is a vital and critical step in die casting, acting as a "sealing point": moving and fixed molds close precisely, forming a completely sealed cavity to prepare for molten metal filling. This is also indispensable for ensuring product dimensional accuracy.
We require a tight, gap-free mold closure. Otherwise, during high-pressure filling, molten aluminum will overflow from gaps, forming flash and burrs. This not only wastes material but also affects product dimensional accuracy and may even cause pressure loss, resulting in poor product density.
To determine if mold closure is good, besides ensuring mold is properly aligned during assembly, we must precisely match closing force to product's projected area. This avoids leakage due to excessive looseness or damage to mold due to excessive tightness. Parallelism of die-casting machine's template must also meet requirements.
Fourth, "quantitative molten metal feeding" determines molding quality.

 

Robotic arm precisely grasps a fixed quantity of molten aluminum and slowly pours it into die-casting machine's pressure chamber (material pipe). Core of this step is "precise quantity control."
Too much: Excess aluminum liquid increases sprue wear and may cause excessive pressure during injection, damaging mold.
Too little: Insufficient aluminum liquid will not fill mold cavity, directly causing material shortages and product scrap.
- Practical tips: Pour aluminum liquid smoothly to avoid splashing and air entrapment, which will affect subsequent molding.
Fifth, Injection: "High-speed, high-pressure + vacuum" double protection

 

This is the most crucial step in die casting! Injection piston of die casting machine propels aluminum liquid at high speed and high pressure, quickly filling mold cavity along gating system. Simultaneously, vacuum valve system activates, evacuating air from mold cavity.
- Speed and pressure: High speed ensures aluminum liquid fills mold cavity before solidification (especially for thin-walled parts), while high pressure allows aluminum liquid to fully adhere to mold, improving product's detail molding rate.
- Vacuum function: Vacuuming completely removes air from mold cavity, preventing air entrapment and porosity in aluminum liquid. This is a key process for high-airtightness products (such as automotive cylinder blocks and hydraulic valve bodies).
Sixth, Holding Pressure: "Solidification under Pressure" for a Denseer Product
After molten aluminum fills mold cavity, injection piston does not immediately retract but continues to maintain a certain pressure, allowing molten metal to crystallize and solidify under pressure.
- Core Purpose: To prevent shrinkage cavities and porosity caused by volume contraction during solidification, thus improving internal density and mechanical strength of product.
- Time Standard: Holding pressure time needs to be adjusted according to product thickness. For thin-walled parts, it is generally 3-5 seconds, while for thick-walled parts, it can be extended to 8-10 seconds to ensure complete solidification.
Finally, Mold Opening and Ejection: "Smooth Removal" for a Finishing Touch
After casting has completely solidified, moving mold and fixed mold separate, and ejection mechanism smoothly ejects casting from cavity. Finally, casting is removed by a robot or manually, completing the entire die-casting process.
- Precautions: Ejection force should be even to avoid excessive force that could deform or damage casting; after removal, residual impurities in mold cavity must be cleaned promptly to prepare for next mold production.
Die casting is no small matter; every step is crucial.
Seven processes of high-pressure die casting may seem simple, but they are actually interconnected—inadequate mold preheating, excessive release agent application, insufficient holding pressure time… neglecting any detail can lead to product scrap.
Mastering these seven standard processes will be invaluable, whether for beginners to quickly get started or for experienced workers to standardize operations and improve yield rates. Share this with your colleagues in the workshop, and together we can use these standard processes to control every step of process, making production more efficient and products of higher quality!