If you have ever worked out a cost estimation for plastic parts, you were likely surprised at the high cost of injection molds. When molding plastic parts, the injection mold is the most expensive part of the project and can dramatically increase costs for small part runs. So why are these molds so expensive?
During the injection molding process, plastic pellets are heated to their melting point then injected into a cavity (the mold). As the plastic cools, it hardens into the shape of the cavity to form the part. These molds are subjected to thousands of pounds of pressure every cycle, so they must be made from materials that can withstand repeated use without deforming, typically steel. But no matter how durable the material, injection molds don’t have an infinite lifetime. How many parts a mold can produce before failing depends on the plastic being molded.
Injection molded parts not only have high tooling costs, but they require large lead times as well to create the mold. And once formed, it is very difficult (sometimes impossible) to make changes to these molds. Major design changes halt production as a new tool has to be made.
Conversely, CNC machining has no tooling costs and a very short lead time. Designs are uploaded to the machines and parts can start being produced right away. It is also easy to make design changes with a simple adjustment to the programming.
Cost estimation for plastic parts also goes up the more intricate a design becomes. A complex injection mold is far more costly and also increases the risk of part failure. Certain geometries and shapes can’t be achieved through injection molding. Instead, multiple parts must be made and then fabricated together, increasing costs and lead times. Injection molded parts also require fabrication in order to achieve tight tolerances.
CNC machining, particularly CNC milling, can easily produce parts with complex geometries as well as superior surface finishes. At Reading Plastic, we excel at tight tolerance machining. Our experienced technicians can produce parts that hold tolerances of +/- .001 with surface finishes as smooth as 15Ra.
The last variable in cost estimation of plastic parts is the material being molded or machined. For example, PEEK (polyetheretherketone) is one of the best high-performance plastics on the market, featuring exceptional strength and high temperature resistance. But because of these properties, PEEK requires special heating equipment and is extremely tough on injection molds. A molding tool can only produce a few hundred PEEK parts before having to be replaced.
However, in its solid state, PEEK is readily machinable by CNC milling machines. PEEK plastic machining is the preferred option in most high precision applications, especially when the components need to deliver excellent mechanical and wear properties
CNC machined plastic parts reduce waste and lead times, getting your parts to you faster and cheaper than injection molding. If you have a project in mind, call us today at 610-926-3245 or email site2@readingplastic.com to request a free quote. Our team can produce your parts quickly and precisely, no matter how complex.
