Powder Metallurgy and Plastic Forming Processes

A process used to increase density and dimensional accuracy in powder metallurgy (P/M) parts. It involves pressing the sintered part using dies to achieve a more precise shape and surface finish.

A type of cold restriking operation in which a mandrel or tool is used to press through holes, slots, or hollow features in the part, ensuring dimensional accuracy.

A special case of cold restriking involving closed-die forging, where a P/M part is pressed between dies under high pressure to create a more precise shape and higher density with no excess material.

A pre-sintering process where the P/M compact is heated to a lower temperature before the final sintering step. This increases the strength of the compact so that it can be machined more easily.

The percentage of solid material in a P/M part, compared to the density of the fully dense material. It's indicative of the part's strength and density.

Operations performed after sintering to achieve desired features and properties in P/M parts. These can include cold restriking, heat treatments, electroplating, or other surface finishing techniques.

The process of heating a P/M part to a high temperature to bond the powder particles together and create a solid material. The temperature and time of sintering influence the part's density and properties.

A process where molten metal fills the pores of a sintered compact, sealing the surface for further operations like electroplating.

A process where the pores of a sintered compact are filled with a lubricating oil, creating self-lubricating components.

Bearings that do not require external lubrication, as the oil contained within their pores expands during operation, creating a lubricating film.

The percentage of empty spaces in a material, crucial for impregnation processes.

A common material for producing self-lubricating bearings, often with added components like graphite and stearic acid.

A component added to self-lubricating bearings to improve their lubricating properties, reducing friction.

A volatile additive used to create interconnected channels and pores in self-lubricating bearings, aiding in oil impregnation.

A process where the porous structure of a compact is filled with lubricating oil after sintering, typically using vacuum and capillary action.

Impregnation can also be used to apply wax for lubrication or moisture resistance, resin for strength, bonding, or corrosion resistance, or plastic to improve the surface for plating.

A type of extruder where the material is already melted before entering the machine, and the screw primarily pushes the material through the die.

An extruder where the material is fed as granules or particles, and the screw both heats and compresses the material until it melts before pushing it through the die.

A process where a heated plastic sheet is stretched and formed over a die, similar to how a cloth drapes over a body.

A process where a heated plastic sheet is formed by vacuum pressure pulling it against a mold.

A process where a heated plastic sheet is shaped by applying pressure and heat to mold it into a desired form.

A type of powder metallurgy (P/M) process where a liquid phase is formed during sintering, allowing for better bonding between powder particles. This is often used in dental amalgams, where mercury reacts with silver-copper alloy to form a solid structure.

A process of compacting powder under pressure, often used in powder metallurgy (P/M) to produce solid shapes. It's like pressing a sandcastle - the more pressure, the denser the structure.

A type of powder metallurgy (P/M) process where the powder is compacted in a die to create a specific shape. It's like pressing a cookie cutter into dough, forming a desired shape.

The ability of a metal to withstand pulling forces without breaking. It's like the strength of a rope - a higher tensile strength means it's less likely to break under tension.

A design consideration for parts made using powder metallurgy (P/M) that ensures the part can be easily removed from the die after pressing. Think of removing a cookie from a cutter - if it's too complex, it might get stuck.

A design consideration in powder metallurgy (P/M) where the ratio of unpressed to pressed length needs to be kept below 2, if possible. It's like stacking a book tower - the taller the tower, the harder it is to press it down evenly.

A design consideration in powder metallurgy (P/M) where walls should be straight and uniform in thickness. It's like building a brick wall - straight and even bricks create a stronger structure.

Plastics that can be repeatedly melted and reshaped without significant degradation. They are often used for disposable items, packaging, and some durable applications.

Plastics that undergo irreversible chemical changes when heated, forming a rigid, hard, and infusible material. They are often used for durable goods, electrical components, and structural applications.

The ability of plastics to resist the effects of solvents, chemicals, and oxidizing agents.

The property of plastics that allows them to withstand the penetration of gases or vapors.

The property of plastics that allows them to resist the penetration of water.

Plastics used in engineering applications due to their high strength, durability, and resistance to various conditions.

The use of lighter materials in vehicle construction, reducing overall weight and improving fuel efficiency.

The use of plastics in areas of an automobile that are not subjected to significant loads or stresses.

The use of plastics in parts that must bear loads and stresses, such as bumpers, tanks, and body panels.

The main reason why plastics are increasingly used in many industries.

A process where metal powder is compacted and heated to a high temperature, causing the particles to bond and form a solid part.

A P/M process where a high-energy electric discharge spark is used to compact and sinter metal powder into a dense part in a very short time.

A P/M process that uses gravity to fill a mold with powder and then sinters it to create a porous, low-density part.

A P/M process that uses induction heating for rapid and even heating of the part, making it suitable for parts that require short soaking times at high temperatures.

A P/M process where the part is pressed in a sealed container under high pressure and temperature, allowing for a more dense and uniform structure and improved properties.

An extrusion process where the plastic material is already melted before entering the machine, and the screw primarily pushes the material through the die.

An extrusion process where the plastic material is fed as granules or particles, and the screw both heats and compresses the material until it melts before pushing it through the die.

A process that utilizes the rotation of a screw to compress and heat plastic material, transforming it into a molten state that can be extruded through a die.

A special thread form on the screw of an extrusion machine that is designed to accommodate the specific type of plastic being extruded.

The part of an extrusion machine where the plastic material is fed in.

The part of an extrusion machine where the molten plastic is forced through to create its final shape.

The cylindrical chamber of an extrusion machine where the screw rotates and the plastic material is heated and compressed.

The pressure built up in the extrusion process as the plastic material is forced through the die.

A molding process where material is heated and pushed from a separate chamber (transfer pot) through an orifice into a mold cavity. This method provides even heating and allows detailed mold designs.

A plastic molding method where material is heated and forced into a mold cavity under pressure. It is typically used for mass production of parts.

A method of producing plastic parts where liquid plastic is poured into a mold and allowed to solidify. It's a cost-effective option that doesn't require specialized equipment.

A method used for producing plastic parts with intricate designs. The process involves heating the material in a separate chamber and then transferring it into the mold under pressure.

Compared to other manufacturing processes, sintered parts generally have lower mechanical strength due to internal pores acting as stress concentrators. These pores are like tiny cracks that weaken the material.

The density of a sintered part significantly influences its strength. Increasing density leads to higher tensile strength, hardness, and often improved elongation.

P/M parts made from pure metals generally have better strength properties compared to those made from alloys. This is because alloying elements can disrupt the metal's internal structure.

Techniques like hot isostatic pressing (HIP) and spark sintering aim to improve the density and strength of sintered parts, bringing their properties closer to those of wrought products.

Powder metallurgy (P/M) is widely used in automotive and appliance applications, especially for small parts (<0.5 kg) where it offers cost-effective near-net-shape production.

P/M is crucial in aerospace applications where near-net-shape components are required. Examples include turbine disks, fuselage parts, and rocket nozzles made from superalloys, titanium, or tungsten.

P/M techniques have advantages in superalloy production, minimizing alloy segregation, carbide clustering, and cost issues.

P/M is also employed in biomedical applications, such as surgical implants, thanks to its versatility in creating intricate shapes with controlled porosity.

P/M involves various stages, including powder preparation, compacting, sintering, and secondary operations. Each step contributes to the final properties of the part.

A process in vacuum forming where hot air is blown between the plastic sheet and mold before the vacuum is applied. This acts as a cushion and delays cooling, reducing thinning and assisting in creating detailed shapes.

The uneven thickness of a plastic part caused by differential cooling rates during vacuum forming. Regions that contact the mold first cool faster, leading to thinning.

A common problem in vacuum forming where it is difficult to form accurate right-angle corners due to the plastic sheet's tendency to pull away from the mold.

The use of aluminum as the material for molds in vacuum forming. This is cost-effective and provides adequate stability for the process.