Types of Molding PDF

The possibilities with rubber, plastic and silicone molding unfold like an infinite universe, so it can be overwhelming to navigate the industry and all of its offerings as you search for exactly the right “thing.” It might be anything from a rubber o-ring or weather stripping to a tiny computer par...

The possibilities with rubber, plastic and silicone molding unfold like an infinite universe, so it can be overwhelming to navigate the industry and all of its offerings as you search for exactly the right “thing.” It might be anything from a rubber o-ring or weather stripping to a tiny computer part or element used in aerospace, but it is usually needed to accomplish a business goal or to complete some sort of mission or project. Wherever you look, you will find confirmation that plastic, rubber and silicone molding can be crafted to fit just about any need or application. Some type of molding can literally be found everywhere, in objects ranging from household items and appliances to industrial parts and manufacturing lines. Rubber, plastic and silicone molding is in our cars, homes and everyday products. WHAT EXACTLY IS MOLDING? Molding usually consists of some kind of rubber, plastic or silicone compound subjected to a process that allows it to take a number of different forms. Molding is often associated with the goal to create a seal or barrier that gives a bit, such as to expand or contract and then regain its original shape. Molding elastomers typically starts with some kind of uncured rubber, utilizing heat in most vulcanization processes. Silicone’s most basic raw-material element is quartz sand. Its abundance and easily altered chemical structure can be modified and processed in a number of ways, including in unison with various thermoplastics and metals. TYPES OF MOLDING 1. Blow Molding About the same as glass-blowing in that a heated tube or other implement is inserted into the material and air is blown through to enlarge the rubber/plastic/silicone to fit the mold. Once cooled, the object is removed. This technique is generally used to produce a high volume of hollow, one-piece objects Advantage: Creates a hollowed shape needed for some projects. https://youtu.be/NE4c1gwzPb4 2. Compression Molding Involves using high pressure to squeeze a pre-formed piece of rubber into a mold between two or more plates, depending on the part or product configuration. The pre-formed piece of rubber must weigh more than the finished part so that when pressure is applied, all the air is expelled from the mold. The excess is cut away, while the shaped product progresses to be cured using heat and more pressure, a process called vulcanization. Typically, compression molding fits the budget when the needed quantity is low and the part cross-section is large. https://youtu.be/FvzhutJ1H80 2. Compression Molding Advantages: Existing compression tooling makes for lower costs Technique does not require a high quantity Ideal for medium- and large-sized parts or components Able to handle any type of rubber, no matter how challenging or unwieldy 3. Extrusion Molding usually used for making something long and hollow, such as a pipe, straw or some kind of tube. Unlike other methods where material is injected into a specific cavity detail, extrusion places the material directly through a die to determine the form it takes. The resulting long tube is then cooled and can be cut for diverse usages, including drinking straws and feeder-line applications for a bar, restaurant or agriculture. Advantage: Creates a unique tube shape for a number of different applications. https://youtu.be/_h8MUwHw-_E 4. Injection Molding (Hot Runner) uses a screw nozzle that is continuously fed by a barrel using a pump. For thermoplastics, a hot runner system is utilized where material travels to pack the mold full via a gate/runner/sprue system, which is terminology for the material’s entry point and distribution. The newly formed parts are cooled in the mold and solidify before an ejector system releases them from the cavity detail. https://youtu.be/o1M6u0nwUCg 4. Injection Molding (Hot Runner) Advantages: Eliminates pre-forms completely Cuts out any human-operator handling of the component Unit costs are generally low Short production process 5. Cold Runner Injection Molding Uses a closed, thermoset mold, but the rubber is liquid silicone and it comes in two parts, one of which has a platinum catalyst. Both are considered high-viscosity liquids, and they somewhat resemble cold molasses. A mixing-metering pump combines them and delivers the liquid into the injection device to be shot into the mold chamber. Within the heated mold the platinum catalyst compels a rapid- cure process that saves money and time compared to traditional processes. 5. Cold Runner Injection Molding Advantages: Ideal for high-volume production Can be colored to suit Has a short cure time 6. Rotational Molding Called rotomolding and rotates the mold as it is coated from the inside to form the desired product. It is a relatively slow process compared to other molding types and is usually suited for the creation of a large, hollow object such as a tank for liquid or gas. The centrifugal force of the rotational motion ensures evenly coated walls and little waste. Advantages: Economical for certain applications Viable for manufacturing https://youtu.be/lAQYfJAuw5M 7. Transfer Molding incorporates a container above the mold where the rubber sits and gets pushed into the mold using a piston-powered (sometimes called a plunger) gate/runner/sprue system. The piece is then cured using heat and pressure. Transfer molding, like injection molding, will usually cost less per unit than compression molding since the rubber does not enter the mold cavity until after it closes and quantities are more exact. Advantages: Requires fewer pre-forms since one fills many cavities Enables tighter control on dimensional tolerances since excess material does not push or hold the mold open, which is preferred for micro-component production Color can be added Lead time is short due to ease of process and preparation Liquid Silicone Rubber (LSR) Liquid Silicone Rubber fits a multitude of applications for different industries. It not only has existed since the 1970s, but it is also unique in its innate properties. Many sources familiar with the different types of molding agree that injection molding is the most efficient, effective and versatile. It is the cutting edge of rubber/silicone/plastic molding and continues to improve as research and development advance new and better polymers and formulas. Liquid Silicone Rubber (LSR) Advantages: Odorless, tasteless Hypoallergenic, inorganic backbone Hygienic — resistant to mold and bacteria growth Hydrophobic — repels water High biocompatibility Fatigue and tear resistant Low compression set High elongation High thermal stability Ozone and UV resistant Performs at extreme temperature ranges Custom colors available for many visually pleasing possibilities Electrically insulative and conductive grades available UL component recognition Range of hardness levels available Excellent for outdoor applications What Kinds of Companies Utilize Rubber, Silicone and/or Plastic Molding? Aerospace Engineering Agriculture Entertainment Architecture Food service Grocers Automotive Manufacturing Consumer goods Medical Construction Military Dental Plumbing Electrical Printing Electronics Publishing Energy/power generation Retail Toys/games