The Reality of Thermoforming

A common misconception about vacuum forming is that the part comes out of the machine completely finished. In reality, the part is formed out of a larger, continuous sheet of plastic. Once removed from the mold, it is essentially a shape trapped in a flat perimeter of excess plastic.

Enter 5-Axis CNC Trimming

To extract the final product, the excess material must be trimmed away. While hand-trimming is possible for prototypes, production runs require a 5-Axis CNC Router.

• What is 5-Axis?: Unlike a traditional 3-axis router that only moves X, Y, and Z (up/down/left/right), a 5-axis head can tilt and rotate. This allows the cutting bit to approach the 3D plastic part from any angle, cutting horizontally along the sides of a tall enclosure.
• Absolute Consistency: The CNC is programmed using the original CAD model. It follows the exact same path every single time, ensuring that part #1 and part #10,000 have identical trim lines and mounting hole placements.

Designing for the Trim

When engineering a vacuum formed part, we must design a specific "trim fixture"—a jig that holds the formed part securely using secondary vacuums while the CNC bit rapidly cuts around it. If the part vibrates during cutting, it ruins the edge finish. Proper fixture design is a hallmark of an experienced thermoforming partner.