1. Demolding
1) Mechanical demoulding
Used for hammering, hydraulic press or jack to separate the electroforming part from the mandrel.
2) Heating or cooling demoulding
Using the difference in thermal expansion coefficient between the electroformed metal and the mandrel, heat or cool, so that the gap between the electroformed part and the mandrel will be released due to thermal expansion and contraction. Oven, blowtorch, hot oil, etc. can be used for heating, and dry ice, alcohol, etc. can be used for cooling.
3) Melting and demoulding
Mandrels made of low melting point materials, or permanent mandrels coated with low melting point materials, and mandrels made of thermoplastics, can be melted (or softened) by heating to separate the electroforming part from the mandrel.
4) Chemical dissolution and demoulding
The disposable aluminum alloy mandrel can be dissolved in 30% (volume) hydrochloric acid or 30-50% sodium hydroxide solution for demoulding.
Two, reinforcement
Use the electroforming method to make die-casting molds and injection molds for rubber and plastic products, as well as the processing of aluminum and aluminum alloys, zinc and zinc alloys. If the pressure is not high, the thickness of the electroformed nickel mold shell is 4-5mm. However, if the pressure is high, the formwork needs to be reinforced, and the method is as follows.
1. Casting low melting point alloy
The formula of low melting point alloy usually cast is: lead 75%, antimony 15%, tin 10%. In order to prevent the mold shell from changing during casting
shape, the electroforming part can be electroplated with a layer of tin first, and then placed in the center of the molding sand (steel tank), while paying attention to ventilation and cooling, while injecting low melting point alloy. The electroforming temperature is kept below 200°C.
2. Metal thermal spraying
Spray aluminum-silicon (containing 6% silicon) alloy or copper material with flame or electric arc. When spraying, first spray a layer of primer (Ni package A1 material) about 130μm (relevant instrument: dry Film Thickness Gauge), and then spray other metals. When spraying, you should also pay attention to the cooling problem of the mandrel, which is easy to deform due to heat.
3. Copper plating
4. Epoxy resin casting
It should be noted that: ①Slight shrinkage during epoxy resin curing; ②The strength of epoxy resin is much weaker than that of metal, so the bearing load should be carefully calculated.
5. Spark erosion of steel
The electroformed part is first plated with a layer of copper as an electrode, and a strip-shaped cavity is formed on the steel block by electric spark erosion. The scars and tumors on the electroformed part are removed, and the electroformed mold shell is embedded in the strip-shaped cavity obtained by etching Cavity in the steel block, thus making the mold.
