This technical decision belongs to thermoform trim cutting dies service scope. An outer contour cannot be derived by tracing a top-view photograph of a formed part. The free component can flex, and flange width or corners may not be uniform. Measurement must describe how the part will seat.
Separate the finished edge from the process flange
Define the edge that must remain on the product and the excess area used during forming. The trim line separates them. Copying the existing sample edge without a finished dimension can repeat variation from the previous process.
Use a reference network rather than one centre
Measure opposing edges, corner radii and functional holes or recesses at several points. Define the seating surface. Compare the free part with a fixture-like seated condition.
Check variation between samples
Overlay multiple thermoformed samples when available and observe perimeter differences. Do not mistake local deformation in one part for intentional tool geometry. Set acceptable flange using the real process spread.
Keep dimensions and orientation in the drawing
Add part orientation, top face, locating points and required remaining flange to the DXF or AI contour. The cutting path should be one clean closed vector with duplicate lines removed.
Application note
Send the physical sample, finished outer dimensions and flange that must remain so the trim line can be built from all three.
- Use the current material and dimensions.
- Compare a clean sample with the defective sample.
- Record the decision with photographs and drawings.
