12. Moulding and Casting¶
This week we had to:
- Review the safety data sheets for each of your molding and casting materials
- Make and compare test casts with each of them
- Compare printing vs milling molds
Casting methods¶
Before the crime for this week’s assignments, our fellow student Ashot Margaryan gave us a lecture where he told us about mold casting methods.
Injection molding¶
Injection molding is the most common production method in industrial manufacturing, and most of the plastic products we come into contact with every day are processed this way. From toys, auto parts, bottles to mobile phone cases. At a certain temperature, heated and molten resin raw material is injected into the mold cavity under high pressure and, after cooling and curing, forms a molded product.
Sand casting¶
Sand casting is an economical and most popular method of casting parts. Sand casting technology is used in the production of up to 80% of the world’s volumes of cast products. The production method involves pouring alloys and metals into pre-prepared molds made of compacted sand. In order for it to acquire the required viscosity and density, water and clay are added. Therefore, the technique is also called casting in sand-clay molds and casting into the ground.
Casting using gasified models¶
Casting using gasified models is one of the latest modern and promising technologies that can significantly reduce the cost of finished products of machine-building enterprises.
The main advantages of this method are the ability to obtain high-quality castings with a significant reduction in the labor intensity and cost of the process.
The essence of this casting method is as follows. The model of the part, previously made from foam plastic, is covered with sand. Liquid metal is poured into the mold, turning the polystyrene foam into a gas.
In this case, the metal replaces the foam model and takes the shape of the model.
Ashot also advised all of us on individual tasks, namely how to design the model so that in the future we could obtain the model using casting.
We decided to use this method as a group task, but as a foam model we used a model printed on a 3D printer from PLA plastic
Safety¶
Sand casting iron requires strict safety precautions due to the high temperatures and hazards associated with the molten metal. Here are the main safety precautions to consider:
1. Protective clothing and equipment
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Workwear: Workers must wear special protective clothing that protects against heat and sparks. This includes fireproof overalls, aprons, and mittens.
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Footwear: Safety shoes with heat-resistant soles and steel toes.
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Gloves: Heat-protective and fire-resistant gloves.
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Helmet and Goggles: A safety helmet with a face shield and heat-resistant goggles to protect your eyes from glare and sparks.
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Respirators: Used to protect the respiratory tract from dust and harmful gases.
2. Work area safety
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Cleanliness and order: The work area must be free of debris and foreign objects.
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Ventilation: Provide good ventilation to remove smoke and dust.
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Fencing: Casting areas should be fenced to prevent accidental entry by people.
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Alarm: Availability of alarm systems and danger warning signs.
3. Handling of molten metal
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Temperature control: Constant control of the temperature of the molten cast iron.
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Melting and Pouring: Use of specialized melting and pouring equipment which must be regularly inspected and maintained.
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Pouring ladles: Proper use of pouring ladles and checking them regularly for integrity.
4. Safety when working with sand molds
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Sand mixture: Use only high-quality sand mixture that meets safety requirements.
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Forming and Drying Molds: Proper drying of molds to prevent explosions upon contact with molten metal.
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Avoiding Moisture: Water and moisture in sand can cause steam explosions, so the sand must be dry.
5. Emergency measures and training
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Personnel Training: All employees must be trained in safety and emergency procedures.
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First aid measures: Availability of first aid kits and first aid equipment.
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Fire safety: Availability of fire extinguishers and fire extinguishing systems.
6. Other measures
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Regular inspections and audits: Periodic inspections of safety and working conditions.
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Reporting Violations: Having a system for anonymously reporting security violations.
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Compliance with these measures will minimize risks and ensure safe working conditions when casting cast iron in a sand mold.
“Moai” statue casting¶
As a group task for casting, we decided to use the Casting using gasified models method.
Usually, for this method, models are used from substances with a minimum density, for example polystyrene foam, but due to the circumstances, we decided to print the model on a 3D printer.
As a model, we chose the Moai statue from Easter Island.
At the beginning, we printed the sculpture on a 3D printer using PLA as filament. Since in the future we will pour hot metal onto it, we made the walls and infill minimal.
For iron casting, we visited the (Ashot)[(https://fabacademy.org/2020/labs/dilijan/students/ashot-margaryan/)] steel mill.
In general, the casting method Casting using gasified models is not practiced at this plant. But we decided to take this step.
Because after pressing the sand, due to the many wrinkles in the model, it would be impossible to remove the sand mold.
After pouring the cast iron, we removed the cast iron sand model:
As a result, we got the following result:
The result was good and all the surfaces cast well except the bottom, but that’s how it should be since that was our casting area.