Molds and Copying Pieces

Molds and Copying Pieces

Summary: During these seven classes, we have been working on a mold with the objective of copy a piece which we can reproduce several times in different materials such as a silicone rubber, polymorph and some others, which were given to us by the teacher. However, the first step was made the mold and select the piece. The piece was a key ring with a complex details. For creating the mold, we use a Lego pieces for made an edge where we put a bed of clay. After that, we put the key ring there, cleaned and flattened the surface with the objective of fill the top part of our mold with a plaster #3 which was our first option to make the mold. Next to it, we put away the clay and fill the other face of the mold with more plaster #3. Finally it doesn’t work out as well as we wanted because the mold brooked up while we was separating both faces of our mold , then we decide to use another material called epoxy resin, which work better and did not brook up. Thus we made our mold and get our final replica, which was made in silicone rubber.

________________

THEORICAL FRAMEWORK

Kinds of molds

Temporary and permanent molds: Recipients of the desired shape are known as molds, they are made of different materials such as sand, plaster, clay, metal, etc. The molds can be used once or several times. In the first case they are known as temporary molds because those molds can be used just once and which can be used several times, are known as permanent molds.

Disposable and removable Models: The molds are made by means of methods which can be wood, plastic, wax, plaster, sand, polyurethane, metal, etc. If the models are destroyed in preparing the piece, says these are available or disposable and if the models serve several foundries they are called removable.

Epoxy resin: Poly epoxy resin or epoxy is a thermoset polymer that hardens when mixed with a catalyst or curing agent. Epoxy resins are commonly formed of two components which are mixed before use; when mixed react causing the solidification of the resin, the curing is conducted at room temperature, for curing or drying the cross making high weight molecular bonds are formed.

Applications

Depending on the molecular weight epoxy resins have many applications, from adhesives to coatings for cans and drums among others.

________________

Features

* Minimal shrinkage during the curing process , since the process usually involves no byproducts stripping .

* Adhesion: Because of its rich chemical structure polar hydroxyl groups and ethers , epoxy resins are excellent adhesives, without long exposure times or high pressures .

* Excellent mechanical properties: Superior to any other coating. Its low contraction rate decreases the possibility of tensions.

* High electrical insulating power.

* High chemical resistance has come influenced by the curing agent.

* resist moisture

* resist the attack of corrosive fluids

* Withstands high temperatures

Presentation

The presentation for marketing epoxy resins come in a wide range from low viscosity liquids to solids and high melting point powders.

Precautions Employment

It is essential, during handling, consider hygiene measures appropriate work:

* Local ventilated

* wear gloves and safety glasses

Storage

The lifetime of the two parts separately is 12 months protected from humidity and a temperature of 15 - 25 ° C, in the original packaging unopened.

Catalyst

A catalyst is a substance class, during catalysis, altering development of a reaction. Catalysts that increase the rate of reaction are called positive catalyst whereas those causing decreased speed catalysts are scored as negative.

________________

Applications

A substance that becomes faster or slower the speed of a chemical reaction without participating in it.

Features

Specialized catalysts are chemical compounds, many organic to increase, decrease or eficientica one aeration.

Catalysis is the process by which increases or decreases the rate of a chemical reaction. The catalysts can act in two ways, the first forming an intermediate and the second absorption.

For example, reducing the reaction rate are called "negative catalysts" or inhibitors. In turn, the substances which increase the activity of catalysts are termed positive catalysts or promoters, and that are referred to deactivate catalyst poisons.

The "production" of the most important industrial chemicals involves catalysis. For example, reduction of the ethyne to ethene, palladium catalyst (Pd) is "poisoned" partially lead acetate (II) (Pb (CH3COO) 2). Without catalyst deactivation, the ethene produced is subsequently reduced to ethane.

...