The in-line thermoformer involves sheet being fed from either rollstock or an extruder to an oven, by use of a guide rail and pin system. Once heated, the sheet is conveyed into a forming area, and then trimmed. The in-line process is usually limited to sheets under 125 mils in thickness, because of handling problems with thicker material.


Most of the products thermoformed on in-line equipment range between 11 mil - 125 mils in thickness. Typical examples include: drink cups, trays, lids, baby wipe containers, and blister packaging. The vast majority of these products are thermoformed on multi-cavity molds at extremely high production rates.

In-line operations feature much shorter cycle times than other thermoforming processes. This efficiency is a result of forming thin gauged parts. It is also due, in large part, to the use of both vacuum and pressure being applied as the part cools. For example, a medical dose cup may run on a 250 cavity mold at 24 cycles/minute. Even allowing for some down time and modest efficiencies, daily dose cup yield from one in-line thermoformer would be approximately 7 million parts.

Because of the high thermoforming rates involved, most in-line Thermoformers are fed by rolled stock. If the in-line is tied to a sheet extruder, the combined line efficiency may suffer. For example, if the sheet extruder needs maintenance or goes down, the thermoformer is also inoperable until that problem is fixed. The sheet line and thermoformer are typically targeted or tied together only when one product will be run continuously, for many days at a time.

Female molds are usually used on an in-line machine, because spacing between cavities can be minimized. This reduces the amount of trim scrap and recycled material generated. Most parts are thermoformed with the plug assist technique to optimize wall thickness.