LPDC release agent selection, spraying process, hidden sources of aluminum adhesion, pores, and flow patterns

LPDC release agent selection, spraying process, hidden sources of aluminum adhesion, pores, and flow patterns
Release agents not only affect demolding, but also affect cavity heat exchange, surface quality, and gas evolution; Many factories only recognize one type of release agent, standardize spraying parameters, and mix appearance parts, thick walled parts, and hot section parts, resulting in repeated defects.
1、 Classification and Applicable Scenarios of Release Agents
Graphite based release agent: good lubrication, low release resistance, suitable for thick walled and high packing force castings; Disadvantages: Easy to accumulate carbon, use with caution for X-ray and pressure parts, high risk of carbon inclusion.
Ceramic based release agent: high temperature resistance, stable coating, low gas production, suitable for new energy shells, automotive X-ray parts, and exterior parts; Low thermal conductivity can alter the heat transfer efficiency of the mold cavity.
Water based long-term release agent: thin coating, low gas production, suitable for continuous and stable mass production; The spraying amount is strictly controlled, and excessive spraying can easily form pores and streaks.
Dilution ratio: The conventional ratio of ceramic release agent to water is 1:8-1:15; Graphite release agent 1:10-1:20; High concentration, thick coating, high gas production; The concentration is too low, and the coating is damaged and stuck with aluminum.
Xinfeng Machinery provides separate SOP for mold release agent grades, ratios, spraying pressures, and spraying times based on casting types.
2、 Quantitative standard for spray parameters
Spray pressure: 0.25-0.4MPa; Poor atomization, uneven coating thickness, local adhesion of aluminum without coating, and gas production due to excessive coating thickness.
Spray distance: The spray gun is 180-250mm away from the cavity surface; if the distance is too close, local coating accumulation may occur; The distance is too far, the atomization is scattered, and the effective coating is insufficient.
Spray timing: After opening the mold, blow the aluminum dust in the mold cavity first, then spray. After spraying, blow and dry for 5-15s. The coating is equipped with a hydration mold, and water vaporization directly produces pores.
Spray lightly at the hot spot to avoid excessive coating and heat accumulation; Thicken the coating appropriately at the risk of strain.
3、 Differences in mold release agent control for overseas customers
Southeast Asia extensively uses low-cost graphite release agents, which accept carbon inclusions and rely on infiltration to remedy pores.
North American automotive parts require ceramic release agents, graphite release agents are prohibited from being used for X-ray inspection parts, and release agent materials are included in the PPAP material list.
European customers prioritize low gas long-term water-based ceramic release agents, with closed-loop control of spray volume to reduce volatile products and stabilize yield.
The temperature in the Middle East workshop is high, and the moisture of the release agent evaporates quickly. It is necessary to increase the dilution ratio appropriately to prevent the coating from drying, cracking, peeling, and sticking to aluminum.
4、 Abnormal defect chain of release agent
High concentration of release agent, excessive spraying → thick coating, excessive gas production → subcutaneous pores, surface streaks;
Insufficient drying of the coating, with hydration mold → water vaporization → batch porosity;
Wrong selection of release agent, graphite agent used for X-ray parts → carbon inclusion, X-ray scrap;
Uneven spraying and partial lack of coating → High temperature aluminum liquid directly adheres to the mold cavity → Aluminum adhesion strain.
5、 Long tail traffic layout ideas
Low pressure casting release agent, ceramic release agent, graphite release agent, spray coating process, aimed at process and quality engineers.
keywords LPDC release agent selection、ceramic vs graphite release agent low pressure casting；
Problem class: Solution ratio for ceramic release agent aluminum casting;
Comparative category: water-based release agent high temperature die casting.
Suitable for special pages on surface quality and defect improvement.
6、 Common misconceptions in the industry
Misconception 1: The more release agent sprayed, the better, the thicker the coating, the more gas produced, and the higher the incidence of porosity defects.
Misconception 2: Graphite release agent has strong universality and cannot be used for X-ray parts, which poses a risk of carbon inclusions.
Misconception 3: Directly closing the mold after spraying without blowing and drying, residual moisture is an important source of pores.
FAQ
Q: What is the standard water ratio for ceramic release agents?
A：1:8–1:15。
Q: Recommended spraying pressure?
A：0.25–0.4MPa。
Q: What are the main shortcomings of graphite release agents?
A: Easy to produce carbon inclusions, not suitable for X-ray components.
Q: Why do we need to blow dry after spraying?
A: Remove moisture to prevent water vapor from causing pores.
Q: Which type of release agent is preferred for exterior parts?
A: Low gas ceramic based release agent.
Q: Spray distance?
A：180–250mm。
Q: Hot spot spraying strategy?
A: Lightly spray to reduce coating buildup.
Q: What are the requirements for North American mold release agents?
A: Graphite release agent is prohibited for X-ray parts, and the material needs to be registered.