Steps of plaster mould casting

By: Steve Manik

In mould casting, melted aluminium is poured into a cavity in the required shape of product. When the hot aluminium comes into contact with mould its temperature goes down very fast. This causes the quick solidification of product being produced. Mould makers face the challenge of making sure that all the parts of mould cavity are properly filled, whatever the local temperature of aluminium might be or the hole might be narrow from which melted metal is to be filled.

Fluent goods give chance to mould designers to keep track of melted aluminium as it is poured into the mould. This gives them time to identify probable defects due to trapped air, extreme cooling of metal and possible defects of mould due to combined action of high temperature and high pressure. Mould designers are also able to detect folding free surface that can entrap air bubbles, break free surfaces which may cause excess oxidation of the metal and the progressive solidification of the aluminium.

What is plaster mould casting?
Plaster mould casting, it is also known as Rubber Plaster Moulding (RPM) is a system of making aluminium or zinc castings by pouring liquid metal into plaster (Gypsum) moulds.

Step – 1: Model or master pattern:
a) Made from client’s drawing or CAD file.
b) Stereolithography, traditional hand made or machined.
c) Model is engineered to include:
a. Metal shrinkage
b. Mould taper (if needed)
c. Machine stock (if needed)
d) You may “clone” or adapt client supplied model if requested.

Step – 2: Foundry Pattern equipment:
a) Negative moulds are made from model
b) Core plugs are made from moulds
c) A positive resin cope and drag design is now made from negative moulds.
d) Core boxes are made from core plugs
e) Gating, runner system and flasks are joined as needed.
f) Duplicate sets of tooling might be made from the master negative.

Step – 3: Plaster mould:
a) A liquid plaster slurry is poured around the cope and drag pattern and into the core boxes.
b) The plaster mould is next removed from the cope and drag pattern.
c) The plaster mould and cores are then baked to remove moisture.

Step – 4: Pour Casting:
a) Melted metal is made by degassing, and a spectrographic sample is taken to check the chemical analysis.
b) The melted metal is then poured into the assembled plaster mould.
c) The plaster is removed by mechanical knockout and high pressure waterjet.
d) After cooling of the casting, the gates and risers are then removed.

Step – 5: Secondary operations:
a) The raw castings are inspected and serialized.
b) Castings may then need (as per client specifications):
a. Heat treatment
b. X-Ray
c. Penetrant inspection
c) After finish inspection, casting is ready for:
a. Machining
b. Chemical film, chromate conversion, paint or special finishes
c. Assembly
d. Form-in-place gasketing.

Plaster craft is a hobby, which gives you chance to make a few pennies worth of material into beautiful wall hangings and sculptures.

Plaster crafting is quite safe if you observe safety rules while mixing plaster. Once it is hardened three is little or no hazard from handling plaster things. Plaster is usually Plaster Of Paris. It is called by various names depending on its producer-viz.-Plaster Of Paris, casting plaster or just plaster.


I am freelance writer, I have written on many fields that are under the sun. Accuracy, clarity and impact are the hallmarks of my work. If I have to define myself in a few words, I would say I am a copywriter, I have good command over research, expertise to explore extensively and ability to prove that. I can write on any subject, from food to travel, paradise to Hades, flowers to nuclear bombs & more. More articles at www.article-ghost-writer.com and www.bhunit.co.in