We will see the methods now to obtain plastic objects of diverse forms.
The heating of monomer is common to all the processes so that, due to the plasticity, the wished form is obtained
1 Molded by injection
In this case, the polymer is introduced by a hopper that falls until the small spindle (worm drive). The small spindle pushes the polymer that according to advances is warmed up by some electrical resistance.
Once in its destiny, the melted polymer is introduced in a mold that a fixed plate has and one mobile.
The polymer is introduced between both plates, it is left awhile so that the movable plate cools off and when opening itself, the plastic piece leaves with the form of the mold.
We will see a video on this method
2 Molded by extrusion
In this method, the fused polymer is pushed by the small spindle until the fuze. When leaving taking the form that the fuze grants to him. When coming out a refrigeramiento system exists (cold air forced circulation) so that the plastic has the wished form and does not fall to the extracted being of the fuze.
3 the compression molding
The polymer in the form of grains is introduced, in a mold that contains a system to contribute heat and to maintain always warms up it. The mold and contramolde are united to warm up the material and to obtain the wished piece
4 Molded by blowing
Used in the industry to make hollow pieces as bottles and certain containers. We will see a video where this process acquires knowledge
5 Molded to the emptiness
In this system part of a polymer lamina (red) that is placed on the mold, subject by some clips. To the extracted being the air that there is within the mold, the plastic descends taking the form from the mold, When opening itself the clip, obtains the object
There is a great variety of glues in the market with very specific applications. Some adhesives, as the white tails for wood, are specific of uniting wood and they are not useful for other types of materials, whereas others, as epoxy, are but versatile and can unite different materials.
The Adhesives can be rigid or flexible. Some unite of almost instantaneous form while others need but time. It is always important to see the instructions of use for a good union
As it regulates general, the surfaces to unite must be free of fat or dust. The fat of the skin even can harm to the union.
|Types of Glues|
|The white tails (PVA) are sticky with thick aspect and white, used for wood with a time of maximum fixation of 24 hours, although the fast ones usually have a degree of union to the little minutes.||Epoxi. Substances are bicomponent that, by chemical reaction of their two components, acquire a great past hardness few minutes. There is a great variety of them and serve to unite different materials as plastics, ceramics, metals.|| Adhesives of cyanoacrylate. They emphasize by:
To emphasize that the gases that give off can damage to the eye
Other systems of union are:
The screwed one
Using a screw, a nut and washers, one is used when it is foreseeable to disassemble the object.
We can distinguish several types:
- By heat. Employee for thermoplastic, the temperature rise founds the faces to unite and applying a compression force to determine the pieces.
- By ultrasounds. Waves of ultrasounds in the surfaces of the pieces are emitted, which causes the vibration of plastic molecules, causing a temperature rise and facilitating the union.
- By laser. For small pieces, a beam is emitted laser that brings about the temperature rise of the zone to unite. The high addressability of the beam is very precise dice laser.
The mechanization of plastics
By means of certain machines we can give certain form to the plastic objects. Of the machines tools that you know certainly are the drill or the mountain range to pierce, but we are going to see other two of special importance in the industry, that is the winches and the milling machines.
In the turning, the piece jaws and tour subject to some on the longitudinal axis of the same, rotating to the piece. It is important to fit it well so that the turn is clean (it does not vibrate).
While it turns, the blade comes near to the piece and eliminates peripheral material, giving rise to cylindrical or conical forms.
In this case it happens the opposite. The piece does not move and is the sharp element (it mills) the one in charge to eliminate the leftover material of the piece.
A little evento reflect