A tub is a deep draw, not a big cup

An ice cream tub looks simple until you check the draw ratio. A 500 ml tub with a 95 mm diameter and a 75 mm depth is pulling material far beyond what a drinking cup demands, and the base is where it shows: too thin and the tub buckles under the freezer stack. Shantou Longsheng Industry Co., Ltd. forms these tubs on its multi-station thermoforming lines, and the parameters that matter are consistent across PP, HIPS and paper-board laminates.

Draw ratio and pre-stretch

The practical ceiling for single-step forming in PP sits around a draw ratio of 1.2 to 1.4 depending on the plug and the sheet grade. Beyond that, plug-assisted pre-stretch becomes mandatory. The plug stretches the sheet downward before vacuum or pressure completes the shape, which lets material from the sidewall flow to the base instead of thinning it locally. Plug material and temperature are as important as the machine: a warm plug with a low-friction surface distributes thickness evenly.

Holding the base thickness

Customers typically specify a base thickness within 15 percent of nominal. Achieving that requires:

• Sheet temperature held within a narrow window, checked at several points across the width
• Controlled plug depth and speed
• Uniform cooling, because a base that cools unevenly warps after demolding
• Consistent sheet gauge from the extruder, which is why we often supply the extrusion line together with the former

Domed lids and the seal

Domed lids are shallow draws but need a flat, accurate seal flange. The rim has to sit on the tub wall with a defined interference so the lid snaps and stays. We cut tub and lid tools as a pair and verify the fit on assembled samples.

Material notes

PP gives toughness and freezer performance; HIPS gives a bright, glossy surface at lower cost; paper-board laminates suit premium and sustainability-led brands but demand lower forming temperature and careful moisture control in the sheet.

About Shantou Longsheng

Founded 1998 in Shantou, Guangdong Province, China. 30,000 m², "Longsheng" trademark, 25 granted patents (1 invention, 24 utility models), high-tech enterprise. Sheet extruders, multi-station thermoformers, vacuum forming machines, cup making machines and precision molds.

https://www.stlongsheng.com