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TPE Injection Molding Guide: Process, Design, and Manufacturing Best Practices

Created on 01.26
TPE injection molding is now a key way to make things that need to be flexible, strong, and comfortable to hold. Thermoplastic elastomers (TPEs) are used in everything from soft-touch gadgets to seals in factories and parts in cars. They're a good middle ground between hard plastics and regular rubber.
Unlike rubber that's been heat-treated, TPEs can be molded using normal injection molding machines. This means faster production, the ability to recycle, and cheaper costs. This guide will tell you how TPE injection molding works, how it's different from materials like HDPE, and what companies and customers should know to get reliable, good-looking products.
Close-up of plastic polymer granules.

TPE Material Properties and Comparison With Other Plastics

TPEs have properties like rubber but can be processed like plastic. This makes them great for things that need to feel soft, be flexible, resist impacts and vibrations, stand up to chemicals and oils (depending on the type), and be molded onto hard plastics like PP, ABS, and PC.

HDPE vs TPE Injection Molding Properties

Property
HDPE
TPE
Flexibility
Low (rigid)
High (rubber-like)
Surface Feel
Hard
Soft / grip-friendly
Typical Use
Containers, pipes
Handles, seals, grips
Elastic Recovery
Poor
Excellent
Overmolding
Limited
Excellent
HDPE injection molding works great for strong, stiff parts. TPE injection molding is the way to go for parts that need to bend, stretch, or feel nice to touch.

Common TPE Types and Their Best Uses

  • TPV (Thermoplastic Vulcanizate): Stands up well to heat, oil, and chemicals.
  • TPU (Thermoplastic Polyurethane): Super tough against scrapes and wear.
  • SBC-based TPE: Really soft feel, great for things people use every day.
  • TPO: Light and resists impact, often found inside cars.
For a deeper breakdown of TPE grades, properties, and application matching, you can reference the Protolabs TPE injection molding materials guide.

The TPE Injection Molding Process: A Step-by-Step Overview

As we mentioned in the beginning, you can mold it using standard machines. Still, you need to watch what you're doing to keep the material in good shape.
  1. Drying (Optional but Recommended): Lots of TPEs don't grab moisture, but some (like TPU) do. Drying the stuff for a couple of hours stops marks and holes from showing up.
  2. Melting: The TPE goes into a hopper, and a screw melts it using heaters and friction.
  3. Injecting: The melted TPE gets shot into a mold at high pressure. TPE can be picky, so you have to get the speed right—too fast and it burns, too slow and the mold doesn't fill all the way.
  4. Packing and Cooling: Once the mold is full, you keep the pressure on to make up for shrinkage. TPE shrinks more than hard plastics, so you need to nail the cooling time to stop warping.
  5. Ejecting: The part pops out. Because TPE is bendy, the system that pushes it out needs to be designed so it doesn't rip or mess it up.
1600T TPE injection molding machine

Critical Mold Design Elements for Soft Materials

Designing a mold for TPE is different than for a hard plastic. Since the material is soft, it can stick to the mold or get messed up when it's pushed out.

Key Design Recommendations:

  • Wall Thickness: Keep it even. Around 1.5 mm to 3.0 mm usually works. If the thickness changes too much, you get sink marks because the thicker parts cool more slowly.
  • Draft Angles: Even though TPE is flexible, it can still stick. An angle of 1° to 2° is a must. If the part has a soft, grippy surface, you might need even more angle.
  • Gating: Tunnel or fan gates are best. They leave less of a mark, which is important for soft surfaces.
  • Venting: TPE traps gas easily. Make sure there are vents at the ends of where the material flows. Vents for TPE should be shallower than for hard plastics to stop material from leaking out.
  • Ejection: Don't use small, pointy pins that could poke through the material. Use bigger pins or plates to spread the force out.

TPE Injection Molding Machines and Recommended Parameters

Parameter
Recommended Range (General)
Notes
Melt Temperature
170°C – 230°C
Grade dependent; SBCs run cooler than TPUs.
Mold Temperature
10°C – 40°C
Lower temperatures improve cycle time and "snap" release.
Injection Pressure
500 – 1,500 psi
High enough to fill but low enough to avoid flash.
Screw Speed
50 – 100 RPM
Moderate speeds prevent excessive shear heating.
Shrinkage Rate
0.5% – 2.5%
Very high; must be accounted for in mold sizing.
Pro Tip: According to industry-standard processing data provided by Fast Heat UK, high-performance TPE grades often require higher melt temperatures (up to 240°C) and specific injection pressures between 500 and 1,000 Bar to achieve optimal flow in complex molds. We recommend starting with a low injection speed and gradually increasing it to find the balance between surface quality and air entrapment.

The Advantages of TPE in Modern Manufacturing

Lots of industries are starting to use TPE, and it's not just because it feels nice. It's also got some real pluses when it comes to getting things made.
  • Overmolding: TPE can be molded right onto something hard, like a handle made of nylon, so you don't need glue or screws. This makes for a product that lasts and looks good.
  • Easy to Color: TPE isn't like rubber. It's see-through or light, so you can dye it just about any color you want or even make it totally clear.
  • Good for the Earth: TPE can be recycled completely. You can grind up the extra bits from molding and use them again. This cuts down on waste and helps the environment.
  • Stands Up to Chemicals: Some kinds of TPE can handle things like alcohol, acids, and being sterilized for medical use. That's why they're so necessary in hospitals and restaurants.

Conclusion

TPE injection molding is super flexible for making new stuff. But to do it right, you need to know your materials, have a good mold design, and keep the process under control.
If you're making things that need to feel soft, parts that are molded together, or bendy products for industry, then it's best to work with a TPE injection molding manufacturer that knows what they're doing. You'll get better results, spend less money, and get your product out faster.
Contact us now for customized TPE injection molding solutions. We can help you find the right manufacturing plan for your next production plan.

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