How to Prototype Overmoulded Parts Without Tooling

Overmoulding isn’t new, and if you’re a product designer, chances are you already know how it works in high-volume production. But what’s less known is that overmoulding is possible during the prototyping and low-volume stages too.

Using a mix of 3D Printing and Vacuum Casting, we help product designers create multi-material parts without the need for expensive tooling. Whether you’re prototyping, building short batches for testing, or bridging to production, we offer flexible overmoulding solutions for low-volume runs.

How It Works

To replicate overmoulding at low volumes, we use a combination of 3D Printing and Vacuum Casting to simulate overmoulding. Here’s how:

• 3D Printed substrate with Vacuum-cast overmould
  Start with a rigid 3D Printed part and overmould it with a soft elastomer using Vacuum Casting. This is great for ergonomic grips, seals, or edge protection.
• Vacuum cast to Vacuum cast
  We can overmould one vacuum-cast part with another, using compatible polyurethane resins to replicate the two-material effect. This allows for more realistic material combinations than 3D Printing alone.
• 3D Print to 3D Print bonding
  While not technically overmoulding, we can adhere 3D Printed parts to each other using surface treatments or adhesives. This is useful for simulating overmoulded components or quick visual mock-ups when you need a faster turnaround.

Each method gives you more freedom during prototyping and early-stage production, with no need to invest in steel tooling.

When to Use Prototype Overmoulding

This approach is ideal when:

• You want to test form, fit, and feel before committing to production tooling.
• You’re building appearance models with realistic materials and textures.
• You need short-run functional parts with multiple materials.
• You’re validating usability or ergonomics with real users.
• You’re bridging the gap between prototypes and production

What Materials Can Be Used?

We offer a wide range of Vacuum Casting materials that mimic production-grade plastics and elastomers. You can combine rigid and soft materials in the same part, with options for clear, tinted, or colour-matched finishes.

Examples include:

• Rigid polyurethane simulating ABS or PC.
• Soft elastomers that mimic TPE, TPU, or silicone.
• Flexible resins with Shore A hardness ranging from 30 to 90.

These materials are ideal for grips, buttons, seals, or protective layers.

Real-World Examples

Short Run/Low Volume Manufacturing
To avoid the cost and complexity of two-shot injection moulding, one of our clients used vacuum casting to overmould soft TPU onto SLS nylon parts, creating functional conveyor rollers for testing and low-volume use.

Consumer Food Storage Prototyping
One of our customers used vacuum casting to prototype a food storage container with overmoulded features for lid sealing and grip around the body. With team members based in multiple locations, they needed a small batch for internal approvals before moving to tooling. Vacuum casting gave them a realistic, functional sample to review and test, helping them move forward with confidence.

Low Volume Medical Device Development
By using vacuum cast overmoulding, a client was able to quickly produce multiple prototypes in different urethane hardnesses. This allowed them to validate functionality during user testing as part of their prototyping program.

Why Choose Low-Volume Overmoulding?

The main benefit is speed and flexibility. You can test real materials and make changes quickly, without being locked into tooling. It’s also a great way to get stakeholder buy-in, show investors a near-final version of the product, or run early-stage user trials with realistic samples.

Whether you’re refining a prototype or building a short production run, overmoulding with 3D Printing and Vacuum Casting is a practical, cost-effective way to create complex parts with more than one material.

Talk to Us About What’s Possible

If you’re developing a product that combines soft and rigid materials, and you’re not quite ready for full-scale production, we can help. Our team can guide you through material choices and the right manufacturing approach to suit your stage of development.

Not sure if your part is a fit for this process? Just ask. We’re happy to take a look and offer honest feedback.

3D Printing, Injection Moulding, Knowledge Hub, Vacuum Casting