Simply shrinking a micro mold design to a small size isn’t effective. Micro molding requires tolerances and design features that even world-class molders don’t believe can be done. Micro molding resins and thermoplastics and the standard route, but micro molding materials are only the beginning of this high precision puzzle.
Selecting The Best Micro Molding Materials
There is no perfect material, each is unique and accomplishes a specific purpose. We work with a wide variety of micro molding materials and have done extensive research on melt flow and behavior and we have determined an excellent process for the most demanding micro mold projects.
There are several questions that will be helpful as you select the best micro molding material for your project. Here are some questions we typically start with:
- What environmental conditions will the part need to operate under?
- Does it need to withstand solder reflow temperatures or other high-heat situations?
- Does it touch the human body or other bio-materials?
- Are there lubricity or hydroscopic properties to include or exclude?
Selecting the perfect micro molding resins and thermoplastics is very much an art form. Knowing how a given resin will perform with the desired micro-features takes experience. We’ve seen a lot over our 30+ years, and are glad to assist where we can.
Examples of micro molding resins and thermoplastics
Polyethylene, first accidentally developed in 1898 by Hans von Pechmann, is considered the most “widely used” of the plastic resins available. It is estimated that 80 million metric tons of material are used annually. It’s most common use is for packaging, specifically plastic bags.
Polypropylene was first developed in the mid-1950s by scientists Paul Hogan and Robert L. Banks (the same two from Phillips Petroleum that discovered the HDPE). They were working with ethylene and propylene separately for a project and “accidentally” combined the two materials forming both crystalline polypropylene and linear polyethylene.
Nylon, or polyamide, is a highly engineered thermoplastic synthesized from ethylenediamine. The material was first introduced in 1938 by DuPont as a fiber and then as an injection moldable grade in 1941.
Polycarbonate was first sold commercially in 1958 when both Bayer and GE scientists from across the globe independently “discovered” similar processes for producing the material earlier that decade. GE’s material, Lexan, and Bayer’s Makrolon are still very common brands of PC today.
Delrin (Acetal / Polyoxymethylene / POM)
Polyoxymethylene, or Acetal, or its more common trade name, Delrin, was first developed in the 1920s but because it was not considered thermally stable it wasn’t initially commercialized. It wasn’t until 1952 when DuPont scientist stabilized the process, a patent was filed in 1956, and commercial production began in 1960.
Polysulfone, known for its “toughness and stability at high temps,” was first introduced to the market in 1965 by Union Carbide. It is considered the “highest service temperature of all melt-processable thermoplastics.” It’s also used as a high-end replacement to Polycarbonate for specialty applications.
Polybutylene terephthalate (PBT)
Polybutylene Terephthalate was first marketed in 1970 by the company now known as Ticona. PBT is a semi-crystalline resin with “excellent” mechanical and electrical properties. It is also considered highly resistant to chemicals. The material tends to shrink very little during forming and is mechanically very strong.
Acrylic (Polymethylmethacrylate / PMMA)
Acrylic, developed in the 1930’s as a coating, commercialized in 1937 as a moldable resin. Although it comes in many other variations it is probably best known by the name of Plexiglas and has played an important role in safety and glass replacements. Its extremely high durability and transparency make it a perfect candidate for long life applications.
PEEK (Polyether ether ketone)
British chemical company, Imperial Chemical Industries (ICI), first patented the PEEK formulation in 1978 under the trade name Vitrex. The PEEK polymerization is considered an “organic polymer thermoplastic” and is resistant to thermal breakdown and is mechanically and chemically very stable.
Ultem (Polyetherimide / PEI)
Polyetherimide, otherwise known by its trade name Ultem, was introduced by General Electric (now SABIC) in 1982. PEI is considered to be a relative to PEEK. It’s typically cheaper than PEEK, it’s also clear (or amber) but is less resistant to heat and strength when compared to its cousin. It can withstand continuous use temperatures of 340°F (170°C).
LCP (Liquid Crystal Polymer)
LCP, or Liquid Crystal Polymer, as a moldable resin is fairly new even though the components and research that ultimately lead to the resin we know today happened as early as 1888. It wasn’t till 1980, almost 100 years later, that the injection moldable version was available to the market.
Other Micro Molding Materials
There are 1000’s of micro molding resins and thermoplastics and we have processed many of them. If there is a specific material that you’d like to know about for use in micro mold applications please let us know. You can also download our micro mold material selection and our thin wall study.
References available in downloadable PDF.