Trimming Rotomolded Parts


Trimming is a finishing operation that removes excess plastic so that rotomolded parts fit correctly and work properly. Traditionally, rotational molders cut plastic parts by hand; however, manual trimming can result in inconsistent cuts and higher scrap rates. Hand trimming also adds labor costs and exposes workers to safety hazards from routers and saws. 

Automated trimming improves safety, consistency, and efficiency while reducing labor costs and scrap rates. Yet rotomolders now have a choice of trimming methods. CNC routing that uses five-axis equipment provides fast, accurate cutting. Robotic routing for rotomolded parts adds a sixth axis and important benefits. Both trimming methods have advantages, so what’s the right choice for your application?  

CNC Routing

CNC routing uses computer numerical control (CNC) to follow programmed instructions without a manual operator. Computer-aided manufacturing (CAM) software turns a computer-aided design (CAD) files into G-code and generates a tool path. There’s support  for complex shapes that would be difficult to produce by hand, and production runs are cost-efficient even with one-off parts like large plastic tanks.

With five-axis CNC routing, computer-numerically controlled tools remove unwanted or excess material from rotomolded parts and products. By moving the CNC tool tangentially to the part’s surface, this multi-axis machine supports smooth surface finishes and complex designs. Five-axis CNC routing also produces compound radii on plastic surfaces.

Robotic Routing

Six-axis robots for plastics trimming have a large working environment and are equipped with rotary joints that provide greater freedom of movement. Robotic routing cuts thick sheets cleanly, is suitable for a wide range of rotomolding materials, and can handle three-dimensional (3D) parts. Robotic routers can also process more parts per hour than CNC equipment.

With six-axis robotic routing, an industrial robot is equipped with a rotating router bit that’s attached with a collet. The tool rotates at a high speed along a defined path. Depending on the application, the robot can be programmed to cut through the plastic part completely, or to trim excess material. Rapid tool changes on the fly are another benefit of robotic routing. 

Ask Gregstrom About Plastics Trimming

Gregstrom Corporation of Woburn, Massachusetts (USA) is an experienced rotational molder with a wide range of value-added services. We offer both five-axis CNC machining and six-axis robotic routing and can help you to choose the best trimming method for our application.  To discuss your application or to learn more about our rotational molding services, contact us.