How to establish stable sequential solidification and suppress shrinkage porosity in LPDC cooling water circuit design?

How to establish stable sequential solidification and suppress shrinkage porosity in LPDC cooling water circuit design?
The cooling water circuit is the core of actively controlling the solidification gradient. Low pressure casting relies on sequential solidification to allow the thick walled hot spot to solidify last, relying on continuous shrinkage through the sprue; The layout of the waterway is incorrect, the supplementary channel is sealed in advance, and the shrinkage defect persists without solution.
1、 Quantitative parameters of waterway aperture and distance cavity
The commonly used aperture for cooling water circuits is between 8 and 12mm; The distance between the outer wall of the waterway and the surface of the mold cavity is 12-18mm; molds with a distance less than 10mm are prone to thermal fatigue cracking; The cooling efficiency is insufficient when the diameter is greater than 22mm, and there is heat storage in the thermal section.
Waterway spacing: The center to center distance between two adjacent waterways is 25-35mm; the hot section is densified and the spacing is reduced to 20-25mm; the thin-walled area can be relaxed to 35-45mm to avoid excessive cooling and cold insulation.
Control the water temperature difference between the inlet and outlet of the waterway to 5-10 ℃; Excessive temperature difference indicates insufficient flow and uneven cooling; The inlet water temperature of the temperature control unit is usually 40-60 ℃, and it is not better to be colder.
The hot spot position adopts a surrounding waterway and a spiral waterway to enhance heat dissipation; Thin walled filling with fewer water channels at the end to prevent rapid cooling and isolation at the front edge.
Xinfeng Machinery conducts filling and solidification simulation, matching the water path to ensure a positive solidification gradient from thin wall to thick wall, and then to the gate.
2、 Key points for waterway layout, sealing, and leak prevention
The waterway should be as direct as possible to reduce sharp bends at right angles, which can cause large eddies and easy accumulation of scale, leading to long-term blockage and cooling failure; Turning priority R ≥ 1.5D arc.
High temperature resistant quick couplings or threaded seals are selected for waterway joints, and the sealing ring has a temperature resistance of ≥ 180 ℃; Ordinary rubber rings quickly age and leak water, which can cause local quenching of the mold cavity and random outbreaks of defects.
The slider and insert have independent internal waterways, with separate flow control. The slider's thermal balance and main mold are adjusted separately;
Waterway pressure test: After processing, press 0.8-1.0MPa and hold for 30 minutes until there is no leakage before assembly.
3、 Differences in cooling systems for overseas customers
Southeast Asian mold waterways are simple, mainly direct waterways, with few independent temperature controls, relying on mold release agent spraying to fine tune temperature, resulting in large fluctuations in yield.
North American Tier 1 mold water circuit partition independent temperature control, each circuit flow and temperature are monitored, solidification gradient is written into process files, and abnormal alarms are triggered.
European customers commonly use closed-loop temperature control units with PID automatic water temperature adjustment, stable thermal balance, reduced manual intervention, and guaranteed OEE.
The thick walled large components in the Middle East have a large heat saving volume, and the waterway is thickened and encrypted to increase water flow and offset heat storage in high temperature environments day and night.
4、 Solidification defects caused by waterway failure
Insufficient hot spot water supply → hot spot solidifies first, gate seals in advance → interrupted shrinkage repair, internal shrinkage porosity becomes loose;
The waterway is too close to the mold cavity → the surface of the mold cavity is cooled, resulting in surface cold insulation and microcracks;
Blockage of waterways and accumulation of scale → gradual decay of cooling, slow decline in yield, and delayed appearance of defects;
Waterway seepage → local rapid cooling, uneven casting structure, unstable machining deformation.
5、 Long tail traffic layout ideas
Cooling water circuit, sequential solidification, and shrinkage porosity belong to the category of solidification simulation and process optimization search, targeting simulation engineers and process engineers.
keywords LPDC mold cooling channel layout、low pressure casting shrinkage porosity control by cooling；
Question class: Water channel distance from cavity surface LPDC;
Comparison category: zone cooling vs single loop cooling for casting die.
Suitable for solidification simulation and mold temperature control scheme pages.
6、 Common misconceptions in the industry
Misconception 1: The colder the cooling water, the better. Low temperature strong cooling disrupts the order of solidification, and the sprue solidifies in advance, which actually exacerbates shrinkage.
Misconception 2: The more waterways there are, the better the cooling. Excessive cooling in thin-walled areas, rapid cooling at the filling front, and high incidence of cold insulation.
Misconception 3: If the waterway is pressurized once without leakage, it will be permanently safe. Scale and aging sealing rings will gradually leak and block.
FAQ
Q: What is the recommended distance for the cooling water circuit to leave the mold cavity?
A：12–18mm。
Q: Conventional waterway aperture?
A：φ8–φ12mm。
Q: Reasonable temperature difference between inlet and outlet water?
A: 5-10 ℃.
Q: How to handle the hot water circuit?
A: Encrypt, surround waterways, and enhance heat dissipation.
Q: What are the standards for water pressure testing?
A: Maintain pressure at 0.8-1.0MPa for 30 minutes without any leakage.
Q: Sequential solidification of core objectives?
A: Thin walls solidify first, hot joints solidify later, and the sprue solidifies and shrinks last.
Q: What are the characteristics of cooling control in North America?
A: Partition independent temperature control, real-time monitoring of temperature and flow rate.
Q: What are the drawbacks of right angled bends in waterways?
A: Vortex fouling can easily block the cooling circuit.