Automotive Prototype Manufacturing – Vacuum Casting for Large Complex Plastic Parts

For automotive R&D projects, choosing the right prototype process is not only about whether a part can be manufactured. Part size, geometry, required quantity, material, lead time, testing purpose, and total project cost all need to be considered.
For this U.S. automotive project, YS Precision manufactured a large plastic component measuring approximately 500 × 150 mm. The customer required around 15 parts for product testing and design verification before moving to the next development stage.
As shown in the project image, the component has a long, irregular profile with curved sections, openings, mounting features, recessed areas, and numerous small details along its length.
CNC machining was technically feasible, but machining every part individually would require considerable machine time and material removal. After evaluating the project requirements, we selected vacuum casting with a PC-like polyurethane material.
The silicone tooling and prototype parts were completed in approximately two weeks and prepared for shipment to the United States.
 

Project Requirements

Why Vacuum Casting Was More Cost-Effective Than Repeated CNC Machining

For prototype procurement, the lowest unit price does not always mean the lowest overall project cost.
This automotive component is approximately 500 mm long and has detailed features distributed across much of its body. If produced by CNC machining, each part would require a relatively large plastic blank, extensive stock removal, and multiple machining operations to complete the different features.
CNC machining can still make sense for the first one or two prototypes. However, when the customer needs a small batch of the same large component, repeating the complete CNC process for every piece can significantly increase manufacturing cost and machine time.
Vacuum casting offered a different approach.
After producing an accurate master pattern, we created silicone tooling that could reproduce the required parts in PC-like polyurethane. This reduced repeated machining operations and made better use of the customer's prototype budget.
For this project, the goal was not simply to find a cheaper process. It was to select a manufacturing method that matched the current development stage and required quantity.
 

A Large Automotive Part with Multiple Functional Features

Part geometry was another important factor in process selection.
Unlike a simple housing, this component combines a long, narrow body with changing profiles and many local structures. Openings, connection areas, raised and recessed features, and other details are positioned along the length of the part.
For vacuum casting, these characteristics affect mold layout, support, resin flow, venting, and demolding.
With a component around 500 mm long, maintaining the intended overall shape also requires attention during tooling and casting. The master pattern must accurately reproduce the important features because the same geometry will be transferred to the subsequent cast parts.
For the customer, this means the prototype batch can be used for more than appearance review. The parts can support fit checks, assembly trials, design verification, and functional evaluation, depending on the project requirements.
 

PC-Like Material for Automotive Prototype Parts

A PC-like polyurethane resin was selected for this automotive prototype project.
PC-like casting materials can provide a useful combination of rigidity, toughness, and surface quality for functional plastic prototypes. They are commonly considered for automotive housings, covers, trim-related components, brackets, and other development parts.
However, PC-like polyurethane is not identical to production-grade polycarbonate.
If the purpose of the prototype is to verify fit, assembly, geometry, or short-term functionality, PC-like vacuum casting can be an effective option.
If testing requires final material properties such as long-term heat resistance, UV performance, impact strength, or chemical resistance, we may recommend CNC machining in the specified engineering plastic or prototype injection molding instead.
This distinction helps avoid selecting a prototype material based only on cost while overlooking the actual validation requirement.
 

Balancing Prototype Cost, Lead Time and Project Risk

For purchasing teams, prototype sourcing often involves more than comparing quotations.
A lower-cost process has limited value if it cannot provide the parts within the development schedule or meet the intended testing requirements.
For this project, vacuum casting provided a practical balance between:

• manufacturing cost – avoiding repeated CNC machining of every large component;
• lead time – tooling and parts were completed in approximately two weeks;
• design flexibility – the customer did not need to commit to production tooling while the design was still under evaluation;
• batch consistency – parts were reproduced from the same master and silicone tooling;
• material performance – PC-like polyurethane was suitable for the intended prototype stage.

This is why we evaluate the complete project rather than recommending the same manufacturing process for every low-volume order.
 

CNC Machining, Vacuum Casting or Prototype Injection Molding?

The appropriate process changes as an automotive program develops.
CNC machining can be a good choice for early prototypes, low quantities, tight machined features, or projects requiring the actual engineering material.
Vacuum casting is often suitable for small batches of complex plastic parts when repeated CNC machining becomes inefficient and polyurethane prototype materials meet the test requirements.
Prototype injection molding may become more appropriate when the design is stable, quantities increase, or production-grade thermoplastics are required.
For purchasing and engineering teams, selecting the right process at each stage can help control both development cost and tooling risk.
 

From Prototype Tooling to Delivery in Approximately Two Weeks

The silicone tooling and prototype production for this project were completed in approximately two weeks.
After casting, the parts were finished and inspected before being packed for export to the United States.
Our team coordinates the project from drawing review and process selection through manufacturing, inspection, finishing, and international shipment, giving overseas customers a single point of contact throughout the order.
 

Automotive Prototype Manufacturing at YS Precision

YS Precision provides automotive prototype manufacturing and low-volume manufacturing services based on customer 3D CAD files, 2D drawings, material specifications, tolerances, and testing requirements.
Depending on the project, we can support:

• CNC automotive prototype machining;
• 5-axis CNC machining;
• vacuum casting and urethane casting;
• functional plastic prototypes;
• prototype injection molding;
• sheet metal prototyping;
• surface finishing and inspection;
• low-volume production.

Whether you need an initial prototype, a small validation batch, or parts for the next stage of development, our engineering team can evaluate the geometry, quantity, material, tolerances, lead time, and intended application before recommending a suitable manufacturing route.
 

Request a Quote for Your Automotive Prototype Project

For a faster quotation and manufacturing review, please send:
3D CAD files + 2D drawings + quantity + material requirements + surface finish + critical tolerances + intended testing requirements.
We will review the project and recommend an appropriate process based on your technical requirements, development stage, cost, and delivery expectations.
Send your automotive prototype project to YS Precision for review and quotation.