CNC Plastic Trimming

Plastic Trimming Is A Critical Step After Heat Forming Plastic

We know that trimming the part after heat forming plastic is just as critical as the molding itself.  Thus, depending upon tolerances, the method of trimming will vary.

  • LOW TOLERANCES: ATI trims parts “by hand”, which oftentimes can be done in the molding cycle, thus creating considerably less cost than fully robotic CNC trimming.
  • TIGHT TOLERANCES: For those parts with very tight tolerances to meet, ATI then employs our fully robotic 5 axis routers.
CNC Plastic Trimming Associated Thermoforming Inc.

Secondary Machining Frequently Needed

In the trimming process, we remove the excess sheet (flashing), which is a result of the thermoforming process. Additionally, we may also have need to do some secondary machining. The molded part has only one molded surface, which creates an uncontrolled surface on the opposite side. Thus, we employ the secondary machining to address important dimensions on that uncontrolled surface. Examples of the need for secondary machining are:

  • Spot facing for accurate stand-off or block locations, thus allowing parts to be fabricated in the most cost efficient manner
  • Addressing specific wall thickness to tolerance
  • Creation of precision openings
  • Creating venting or louvres


We have seven 5-axis routers, most equipped with tool-changers. These machines give us the capacity to trim parts as large as 6’ X 12’.   In addition, we have 3 vertical machining centers and a CNC lathe.  Importantly, we have invested significant monies to ensure that all the routers have programming flexibility.   Hence, we achieve additional, critical flexibility for scheduling by utilizing:

  • A standard Fagor controller
  • TCP-Tool Center Point programming
  • Repeatable fixture locating system-zero reference point in all fixtures
  • Detailed set-up sheets

We create our CNC programming in-house, utilizing the latest version of MasterCam. Get a quote today for your project.