Hard/Soft Two-Shot Molding: Material Temperature Rules

Two-color vertical machines mold two different plastics into one part on the same machine — most commonly a hard substrate overmolded with a soft material using a rotating table.

Material guidelines

• The two materials must have a clear difference in melting temperature: 60 °C is recommended, and at least 30 °C.
• The first shot should be the material with the higher melting point — typically PC or PC/ABS. The second shot is typically TPU or TPE.
• Typical thicknesses: PC substrate 0.6–0.7 mm, soft layer 0.4 mm or more.

Improving adhesion

• Make the contact area as large as possible and add grooves to increase bonding.
• Alternatively, use a core-pull on the first shot so that part of the second-shot material flows into the first-shot part.
• Keep the mold surface for the first shot as rough as possible.