Thermoform Trim Tooling Explained

Why it is different from flat die cutting

A flat die cuts a two dimensional outline out of a sheet. A trim tool cuts a part that has already been formed, so the cutting edge has to follow a contour and meet the part at the right angle all the way round.

That makes the tool a machined assembly rather than rule set into board, and it makes fit far less forgiving. A trim tool that is slightly out does not cut slightly badly; it damages parts.

Where it is used

Formed packaging, food trays, and medical device trays are the common cases. Anywhere a sheet is heated, formed over a mould, and then has to be separated cleanly from the web.

Medical work in particular drives the tolerance, because the tray has to hold a device in a fixed position and seal reliably.

What to tell the tool maker

The part geometry, the material and gauge, the machine it runs in, and the cycle rate. As with flat tooling, a physical sample beats a drawing when the two might disagree.

Common questions

What is trim-in-place tooling?

Trim-in-place tooling cuts formed parts free of the web within the same machine cycle as forming, rather than as a separate downstream operation.

How is a thermoform trim tool different from a steel rule die?

A steel rule die cuts a flat outline from a sheet using rule set into board. A trim tool is machined to follow an already formed three dimensional part, so it is an assembly rather than a rule die, and the tolerance is tighter.

What industries use thermoform trim tooling?

Mainly formed packaging, food trays, and medical device trays, where a heated sheet is formed over a mould and then has to be separated cleanly from the web.