Mechanical Joints, Welding, and Manufacturing Processes
Types of Joints
Demountable: These joints allow you to separate or remove parts without damaging or breaking the union.
Fixed: These joints do not provide for the separation of parts.
Threads
A thread is any mechanical element that has a propeller-shaped channel constructed on a continuous cylinder.
Types of Threads
- According to the shape: Triangular, trapezoidal, square, round.
- According to the number of entries: 1 to 2.
- According to the direction of turn: Right or left.
Classes of Studs
Cylindrical pins, headless pins, long lag screws.
Fasteners
A fastener is a rectangular prism that is used to make the turn unite two mechanical parts. Some are conical in shape and fit over the top and bottom.
Tongue
These have a straight section and are adjusted to the sides.
Pins
A pin is a rounded and elongated part used for fastening two pieces together. Types include cylindrical, conical, and security.
Riveting
Rivets are cylindrical pieces fitted with a head and capable of being deformed by compression.
Welding
Welding is the stable union of two parts obtained by applying heat.
- Soldering: The filler material is typically tin, and the flux is a resin.
- Brazing: A gas torch is used. The filler material is usually brass, and the flux is typically borax.
- Oxyacetylene Welding: This uses an oxygen-acetylene torch. The filler material has the same composition as the base material. Equipment includes an acetylene generator, oxygen bottle, pipe, torch, and protective material.
- Arc Welding: This involves an electrode holder and welding electrodes.
Welding Technique
Bevel the edges and apply the filler material between the two pieces.
Electrical Safety
Use perfect electrical conductors, disconnect the switch if necessary, use personal protective equipment, and ensure the workplace is well-ventilated.
Oxyacetylene Safety
Ventilate the room, protect bottles from sun and heat, maintain a 10-meter distance, keep nozzles clean, monitor bottle pressure, ensure pipes are in good condition, keep flammable materials away, and have fire extinguishers readily available.
Manufacturing Technologies
These are the different ordered sets of transformation processes that a material undergoes throughout its development.
Mold
A container with a cavity into which material in a molten state is introduced. Upon solidifying, it takes the shape of the cavity. It has two parts: top and bottom. Other elements include a casting orifice, sprue, and feeder canals, allowing entry of the material.
Ladle
A deposit to offset the contraction of the piece.
Vents
Tubes that allow air to exit.
Core
Allows for a hole in the piece. Permanent molds can be reused.
Lost Mold
This is destroyed when the process is finished. Molding is done in one piece.
Molding Process
This is determined according to the nature of the mold and the method of disposal: gravity or pressure.
Gravity Molding
This is done by pouring the molten metal mass onto a mold, so it moves down by its own weight.
Sand Molding
This involves making the mold, configuring the lower mold, assembling the top of the mold, pouring the molten material, and procuring the piece.
Die Casting
This involves preheating, disposing of metal, solidification, and opening.
Benefits of Die Casting
Reuse of molds, rapid cooling, good finish, great metal achievement.
Disadvantages of Die Casting
Short mold life, difficulty shaping complex parts, high cost.
Lost Wax Molding
A drawback is that it is a very expensive process. It involves constructing the model pattern, constructing the casting, making the model in wax, preparing the sand mold, procuring the sand mold, and securing the molded part.
Pressure Molding
- Centrifugal Force: The mold rotates, and the dissolved iron fills the cavities due to centrifugal force. It is used in parts of revolution and thin parts.
- Injection: The metal is injected under pressure into the mold. It is used in parts with complicated shapes and sharp edges.
Deformation
Compression
- Manual Forging: Hot metal is suddenly beaten with a hammer to shape it manually.
- Mechanical Forging: Hot metal is beaten by mechanical hammers.
- Hot Stamping: Hot metal is placed between two molds and undergoes compression. Used for pure metals and alloys.
- Extrusion: Metal flows under pressure through nozzles whose parents have a section equal to the desired profile. Used for mild steel.
- Lamination: Metal is compressed between two rollers rotating in opposite directions. Used for all kinds of steel.
- Cold Stamping: Metal is subjected to compression on an array called a print through a press. Used for steel plates.
Pulling
- Stretching: Metal is subjected to traction and passes once through a fixed-diameter hole. Used for copper bars.
- Drawing: Metal is subjected to traction and passes successively through holes of increasingly smaller diameters. Used for mild and hard steel.