Key Factors in Choosing Plastics for CNC Machining
When selecting the right plastic material for Swiss precision machining, there are countless factors that can be taken into consideration. When it comes down to it though, there are a handful of these factors that really influence the viability of a material at the machining stage for any given application. Three of these include durability, machinability, and cost. Based on these key factors, here are our top 5 choices for plastics for precision CNC machining.
Top 5 Plastics for Swiss Precision Machining
Polyether Ether Ketone (PEEK)
Polyether ether ketone, often shortened to PEEK, is a high grade engineering thermoplastic used for demanding applications. Unlike most other thermoplastics, PEEK is fairly thermostable in its solid state which makes it a unique choice for use cases where high temperatures or pressures are to be expected. Due to its unique properties, PEEK generally comes at a higher price point than other thermoplastics- but it is one of just a few that can be used in high stress applications including aerospace parts and even medical implants. In its unfilled state, PEEK is both food safe according to FDA standards and safe for medical device use both outside and inside of the body. In the case of precision CNC machined parts, PEEK can be used as reinforcing rods for the spine and other parts of the human body. There are a few different variants of PEEK material, including:
- 30% glass filled PEEK
- 30% carbon filled PEEK
- bearing grade PEEK (carbon fiber, PTFE, Ketron, etc)
Although these filled PEEK variants can help enhance physical properties like tensile strength and rigidity, only unfilled PEEK is graded for food safe use and medical device manufacturing use.
For more information on medical grade materials, check out our signature BC Medical Grade line.
Polyoxymethylene (POM)
Polyoxymethylene, also known as POM or Delrin, is another engineering thermoplastic that is well suited to precision CNC machining as a result of its excellent dimensional stability. While it can be injection molded, it is also often extruded into bar stock material to be machined for automotive components and industrial parts. POM presents some challenges in machining in that it is not as rigid as most metals. This softer nature means that POM workpieces must be secured carefully in order to reduce the risk of damage from any clamps, spindles, and so forth. They also warrant the use of supports across their length to keep them from sagging or otherwise warping. On the bright side, this makes POM an excellent candidate for centerless grinding, which uses no clamps at all to grind the material down to the desired size and shape along its entire length. Once the material has been ground to a proper size, it can be machined with relative ease using sharp cutting tools and a lubricating fluid.
Nylon Polyamides
Although often used interchangeably, polyamides and nylons are not necessarily one and the same. Rather, nylons are a subset of polyamides; meaning that all nylons are polyamides, but not all polyamides are nylons. While there are a couple of other types of plastics that fall under the polyamide umbrella, nylons are the most suitable for Swiss precision machining. Similarly to POM, nylon displays excellent dimensional stability. Machining this material does present some challenges to maintaining that stability, but this can easily be accounted for with design features like billets and ribs for additional support. As a material for Swiss precision machining, nylon polyamides are most suitable for components like gears, bushings, and bearings thanks to its high wear resistance.
Polytetrafluoroethylene (PTFE)
Polytetrafluoroethylene, more commonly known as PTFE or its trade name, Teflon, has many applications that extend beyond nonstick coatings in cookware. In industrial part manufacturing, PTFE is actually known as a material with excellent chemical resistance, making it a preferred choice for parts like seals, valves, and insulators in automotive and industrial applications. PTFE can be quite tricky to machine for a variety of reasons, including its tendency to warp under extreme pressures like those applied in CNC machining. In addition, high temperatures generated during the machining process can cause PTFE to melt or even degrade prematurely. The risk of deformation can be minimized with the use of extremely sharp carbide tools and a lubricating fluid to help keep the workpiece cool during machining.
Polyvinyl Chloride (PVC)
Like polyamides, polyvinyl chloride (PVC) is more of an umbrella category that describes a multitude of plastic variants with similar features and compositions. A few of these variations include:
- Unplasticized PVC (UPVC)
- Chlorinated PVC (PVC-C)
- Modified PVC (PVC-M)
- Oriented PVC (PVC-O)
In precision CNC machining applications, you will always find rigid PVCs like those listed above being used for their resistance to flexion. While most commonly used for pipes and fittings, there are countless other applications for CNC machined PVC parts including gears, valves, caps, trim pieces, and more. PVC bar stock can serve as a highly cost effective and versatile material for manufacturers across all industries, wherever precision is needed.
Benefits of Using High-Quality Engineering Plastics
With certain materials, like PEEK and POM, high quality material may be the only option. However when it comes to materials like nylon and PVC, the range of material quality to choose from becomes much more vast.
Lower quality materials with a lower initial price tag may be more tempting to select at the beginning- but as we’ve discussed before, low quality almost always comes with hidden costs in the form of short part life, poor durability, or dimensional instability that could have been avoided with the use of higher quality materials to begin with. For that reason, we always select only the highest quality materials for our precision grinding services to ensure that your final plastic parts perform as desired.
From metals to plastics, we’re precise in everything we do.
Speak with our team to explore our precision material supply today.