Conformation by Merger: Types, Procedures, and Techniques
Conformation by Merger
Types of Conformation by Merger
Conformation by merger involves heating a material to its melting point, transforming it into a liquid, and then pouring it into a mold. After cooling and solidifying, the material is extracted from the mold. The following factors are considered during the emptying process:
- The mold must withstand high temperatures without deforming.
- The mold should allow for homogenous solidification to prevent deformation of the final product.
- Molds must have openings for air outlet when the molten material is loaded.
A cast consists of two parts:
- Bottom: The principal part and opening.
- Top: Serves as a cover and forms the contour.
Molds can be of two types:
- Permanent: Intended for repeated use and producing identical parts.
- Lost: Destroyed after the completion of the process.
Types of Procedures
Conformation procedures are classified into two groups:
- Gravity Types: The material is poured into the cast, allowing it to flow down under its own weight. Lost Wax casting is used for parts that are difficult to extract. It involves creating a wax model that is then covered with plaster.
- Pressure Types: Molten material is injected into the mold under pressure. Accurate permanent molds are used and subjected to pressure to prevent them from opening due to the injection pressure. Injection molding is the most common pressure type. The molds used are called matrices. This procedure is used for complex parts made of plastic and light alloys.
Other Conformation Techniques
Extrusion
The material is heated until it reaches a pasty state. Then, a plunger applies pressure, forcing the material through a hole that shapes it into the desired form.
Sintering or Powder Metallurgy
This technique involves obtaining objects from one or more metals. The materials are converted into powder, compressed, and subjected to high temperatures in a mold within an oven.
Deflection
This method involves subjecting the material to forces that exceed its elastic limit, causing it to become malleable. The deformation can be done cold or hot. The forces applied can be compression or traction. This technique is used with metals and plastics.
Lamination
This involves passing a continuous mass between two overlapping rollers that rotate in opposite directions. It can be done cold or hot.
Forging
This method involves subjecting the heated material to significant forces and pressures. Typically forgeable materials include aluminum, copper, and iron. The material is heated to a temperature below its melting point and then struck with a hammer or pressed.
Drawing
This technique involves passing a wire through a series of holes with decreasing diameters, called dies, until the desired diameter is achieved. It is a cold deformation process.
Joining Techniques
Types of Joints
Joints can be:
- Removable: The joint can be disassembled and reassembled as needed.
- Permanent or Fixed: Disassembly is impossible without breaking the joint.
Rivets and Bolts
A rivet or bolt is a small cylindrical rod with a head at one end used to join sheets or pieces. Permanent deformation is applied to the other end through pressure or a stroke, creating another head.
Welding
This is a process of joining parts by applying heat to the joint area until the material melts. Autogenous welding is a type of welding that does not require filler material. Within welding with filler material, we distinguish:
- Heterogeneous Welding: A filler material with a different composition than the base material is used.
- Homogenous Welding: The filler material has an identical or very similar composition to the base material.
Soft Welding is heterogeneous. It uses an alloy of tin and lead, commercially available in bars or wires, which melts at around 230°C. A deoxidizing resin can be applied to ensure a strong joint. It is used for welding lead in water supplies, printed circuit boards, cables, and thin sheets of tin foil.
Strong Welding involves joining two pieces with a metal that has a high melting point, even higher than the material being joined. It is heterogeneous.
Oxyacetylene Welding: This involves joining two parts using the heat produced by the combustion of acetylene with oxygen. Heat is applied to the connection points to achieve fusion. A filler metal, similar to the base material, is usually added in the form of rods. When no filler material is needed, it is called autogenous welding. (Acetylene and oxygen bottles, hoses, cutting torch, and protective equipment are required.)
Electric Arc Welding: This method uses the heat generated by an electric arc that jumps between the workpiece, connected to one pole of a power source, and a metal bar called an electrode. The electrode gradually melts, forming a bead and filling the gap between the two parts being joined. A transformer is required for this type of welding. It is homogenous.
Keys
These are wedge-shaped prismatic steel parts that are inserted between two joined parts to transmit forces between them.
Filing
This operation shapes a metal part by removing excess material in the form of filings. A file is a hardened steel bar with a ridged surface. Files can have different shapes. Two phases are distinguished:
- Roughing: Carried out with a single file, removing a large amount of material.
- Finishing: This finishing operation is carried out with fine files, removing small amounts of material.
Milling
This involves machining prismatic bodies with a rotating cutter, allowing for various tasks. The milling machine, also called a universal tool, uses a cutting tool to shape workpieces. The cutting action is achieved by the rotating teeth of the cutter, which are arranged in a circle.
Oxyfuel Cutting
This technique allows for cutting low-alloy steel. It is based on the property of steel to burn quickly in pure oxygen when it reaches its ignition temperature, which is lower than its melting point. The equipment is similar to that used for oxyacetylene welding.
Electroerosion
This method uses an electric spark to remove metal material. The workpiece and an electrode, acting as a tool, are submerged in a dielectric liquid. A high voltage is applied between them, creating an intense electric field that raises the temperature until the dielectric evaporates. When the dielectric disappears, an electric discharge occurs, further increasing the temperature.
Computerized Numerical Control (CNC)
CNC is a system for controlling automatic machines that provides work orders through a computer program. These orders can include dimensional data and technological instructions.
Measurement Errors
Systematic or Determinate Errors
These errors have a defined value and determine the accuracy of a measurement. There are three types of systematic errors:
- Instrumental: Due to wear, corrosion, or defects in the measuring instruments. They can be detected and corrected through proper calibration using standard references.
- Personal: Due to the observer’s characteristics. They can vary and may be more pronounced in individuals with vision problems. They can be minimized with care.
- Methodological: These are more difficult to detect and correct. They are related to the suitability of the measurement process being used.
Random or Indeterminate Errors
These are small errors produced by variations in experimental conditions. They are reflected in the dispersion of data. They can be minimized by repeating the measurement several times and calculating the average.
Absolute Error
The difference between the approximate value and the exact or average value.
Relative Error
The ratio between the absolute error and the exact or average value, usually expressed as a percentage.