Week 12:MOLDING AND CASTING
Assignment:
- Design a 3D mould, machine it, and cast parts from it.
This week we are having the task to 3d model and mill that using Roland MDX 20 Milling Machine.After that negative of the mold is created using that we have to create the cast.
Introduction to MOLDING AND CASTING
Molding - molding is an intresting process for manufacturing plastic parts. Molding is a manufacturing process in which we are creating our own shapes using materials such as wood and wax ,followled by casting with plastics, metals and even with rubber. molding is usually preferred process for manufacturing plastic parts. casting involves pouring liquid metal into a mold, which contains a hollow cavity of the desired shape, and then allowing it to cool and solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process. Casting is most often used for making complex shapes that would be difficult or uneconomical to make by other methods
3-D modelling LOVE symbol
while designing we have to keep in mind that Casting is a manufacturing process in which a liquid material is poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. In order to hold the liquid I have designed a rectangular cavity on which the 3d model of love is placed. Mold design is one of the most important steps in the process because the shape and attributes of the mold will directly affect the final product. I designed the love symbol in rhinoceros.The idea is to make a positive mold in wax, then using that make the negative mold and to finally cast(metal and plastic).
my Love design files are available here
Milling my mold in Roland MDX 20 Milling Machine
Rough cut is done first with 1/8 flat end mill
finally finish cut is done with 1/8 ball nose end mill
finally milling is completed
Casting
I used Mold max 60 for preparing the mold with 100:3 mixing ratio.24 hours we have to wait after precuring
Mold Max60 is a Shore 60A tin catalyzed silicone rubber formulated for applications requiring high heat resistance (up to 560°F/294°C). It features a low mixed viscosity and cured rubber exhibits very low linear shrinkage. Parts A and B are mixed 100A and 3B by weight. Pot life is 40 minutes and cure time is 24 hours. Applications include making foundry patterns, flat pattern reproductions and casting low-melt metal alloys such as tin and pewter.
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The mold obtained is having some breaks in between,so I used Liquid silicone rubber (LSR1) for preparing the mold.two parts are there which has to be mixed with 100:10 mixing ratio.This process als require 24 hours.
In the same manner I went of making the new mold and it was sucess
LSR’s specific properties are a result of its unique chemical structure. Its backbone is formed by a
series of siloxane bonds which, compared to carbon bonds, are stronger and more stable. This provides liquid silicone rubber products with:
- Superior temperature range performance. Liquid silicone products won’t elongate at high temperatures. They also remain flexible at temperatures as low as -40˚C. High thermal stability makes LSR parts suitable for heavy-duty applications.
- Chemical stability. Liquid silicone rubber parts are chemically inert, hypoallergenic and resistant to bacteria growth. They also feature high biocompatibility, which makes them suitable for healthcare applications. However, they can degrade when exposed to certain organic compounds, or to highly acidic or basic environments.
- Electrical resistance. On its own, LSR offers high resistance to corona discharge, making it a good choice for use as an insulator in high-voltage applications. However, it is also possible to add conductive materials without compromising the other properties of an LSR component, so that it can be used to make keyboard contact points and other electrical parts.
- Liquid silicone rubber molded parts are odorless and tasteless. Unique colors and visual effects can be achieved through the use of pigments and master-batches. Parts are also ozone and UV safe. Other notable features of liquid silicone rubber parts include:
- Resistance to steam and humidity
- Flame retardancy
- Low creep and compression set
- Weatherability
- Vibration absorption
- Corrosion resistance
- Resistance to mold, mildew, and bacteria growth
- UL component recognition
Metal Casting
An alloy is a mixture of metals, or a mixture of metal and another element. White metal alloys are those which are light-coloured and generally have a lead or tin base. These alloys are also known as Babbitt metal, or bearing metal, a term which is generally preferred over ‘white metals’. Babbitt metal can be one of several alloys used as a bearing surface in a plain bearing. Babbitt metal is being melted in heating furnace and finally poured in to the mold.
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finally the metal casting is done and my Love symbol is created .It was little bit a long process .
Plastic Casting
finally glossy epoxy resin was used to cast ,with an added red colored coloring pigment .
I got a better cast of the love symbol after this procedure.
