Casting Processes CCHS Plastics Technology

Table of Contents What is Casting? Liquid Resins Hot-melt Plastics Plastisols & Organisols Dissolved Plastics Simple Castings Dip Castings Rotational Castings AdvantagesDisadvantages Table of Contents

What is casting?  Casting is a process that involves introducing a liquefied plastics material into a mold and allowing it to solidify.  Contrary to using a significant force, casting relies on atmospheric pressure to fill the mold cavity.  Casting processes use four different types of materials: Table of Contents

Casting Materials 1.Liquid Resins Liquid resins are monomers that include nylon, acrylic, polyester, and phenolic.Liquid resins are monomers that include nylon, acrylic, polyester, and phenolic. Liquid resins harden through a chemical reaction.Liquid resins harden through a chemical reaction. Used in simple casting processes.Used in simple casting processes. Table of Contents

Casting Materials cont… 2.Hot-melt Plastics Hot-melt plastics are melted and rotationally formed and cooled.Hot-melt plastics are melted and rotationally formed and cooled. Used in rotational casting processes.Used in rotational casting processes. Table of Contents

Casting Materials cont… 3. Plastisols and Organisols Plastics particles suspended in a plasticizing solvent.Plastics particles suspended in a plasticizing solvent. Hardened by evaporating the solvent, or drawing the solvent into the particles.Hardened by evaporating the solvent, or drawing the solvent into the particles. Used in clip casting processes.Used in clip casting processes. Table of Contents

Casting Materials cont… 4.Dissolved Plastics Plastics pieces are dissolved in a volatile solvent and hardened by evaporating the solvent.Plastics pieces are dissolved in a volatile solvent and hardened by evaporating the solvent. Table of Contents

Types of Casting  Simple Casting – liquid resins or molten plastics are poured into molds and allows to polymerize, or cool  Embediments – Objects are completely encased in a transparent plastics casting material  Usually polyester, epoxy, acrylic, silicone, or polyurethane. Table of Contents Clear Casting Directions

Types of Casting cont…  Dip Casting - Dip Casting and coating is a thermofusion process in which a hot metal mold or objects is dipped into a room temperature liquid plastisol.  Coin Purses, Plastic Gloves, Spark Plug Covers Table of Contents Dip Casting Directions

Types of Casting cont…  Rotational Casting – relies on a rotating mold to evenly distribute plastics material against its walls.  The mold rotates on 2 planes to ensure complete and even coating.  Used to create hollow, completely closed objects. Table of Contents Rotation Molder Directions

Advantages of Casting  Low costs  Simple  Versatile  Products are under little or no internal stress Table of Contents

Disadvantages of Casting  Low output rate to high cycle time  Only fair dimensional accuracy  Moisture and air bubbles occur  Solvents and additives can be hazardous Table of Contents