If you manufacture composite components, one of the most significant equipment decisions you will make is how to cure them. For decades the autoclave was the default for high-performance parts, but advances in out of autoclave (OOA) materials and oven design mean a composite curing oven is now the right answer for a growing share of applications.
This guide explains how the two approaches differ, where each one wins, and the questions to ask before you invest.
How Each Process Works
Both methods do the same fundamental job: they apply a controlled thermal cycle so the resin system cures correctly and the part develops its designed mechanical properties.
An autoclave is a pressurised vessel. Parts are vacuum bagged, loaded into the chamber, and cured under heat and positive pressure, typically several bar. The pressure consolidates the laminate, squeezing out entrapped air and volatiles to achieve very low void content.
A composite curing oven applies the same controlled heat, with consolidation provided by vacuum bagging alone. Modern composite ovens include vacuum ports and pumps, part thermocouple jacks, and programmable ramp and soak control, so the cure cycle is driven by the temperature of the part itself rather than just the chamber air.
Where the Autoclave Wins
Autoclaves remain the benchmark for the most demanding structural applications. The additional consolidation pressure delivers the lowest void content and the highest, most repeatable laminate quality, which is why primary aerospace structure has traditionally specified autoclave cure. If your customer’s specification explicitly requires autoclave processing, the decision is made for you.
Where the Curing Oven Wins
For everything else, the case for oven curing is strong and getting stronger.
- Capital cost. A composite curing oven typically costs a fraction of an equivalent autoclave. Pressure vessels are expensive to build, certify and install; ovens are not.
- Running cost. Pressurising a large vessel for every cycle consumes significant energy. Ovens heat only what needs heating, and modern insulation and airflow design keeps running costs down further.
- Working volume. Because there is no pressure vessel constraint, ovens can be built to almost any size, including large walk-in chambers for structural parts that would demand an enormous autoclave.
- Throughput and flexibility. Ovens heat up and cool down faster than autoclaves, and there is no pressurisation stage, so cycle times are shorter and scheduling is simpler.
- Materials have caught up. Modern OOA prepreg systems are specifically formulated to achieve low void content under vacuum-only consolidation, closing much of the quality gap for a wide range of components.
What to Look For in a Composite Curing Oven
If oven curing suits your parts, the specification of the oven determines the quality of the result. The essentials:
- Temperature uniformity. The working chamber must hold a tight tolerance across its volume, achieved through engineered airflow design. Ask any supplier for uniformity figures and how they are verified.
- Ramp and soak control. Resin manufacturers specify cure schedules with defined ramp rates and hold stages. The oven controller must execute these repeatably, ideally with stored programs for each part or resin system.
- Vacuum provision. Ports, jack panels, and appropriately sized pumps and manifolds for the number of bags you will run per cycle.
- Part thermocouples. Controlling the cycle from thermocouples on the part or tool, rather than the chamber air, ensures the laminate actually sees the specified thermal profile regardless of tooling mass.
- Data logging. Full cycle records for traceability, customer flow-down requirements and quality audits.
- Pyrometry and compliance. For aerospace work, ask about temperature uniformity surveys and system accuracy testing aligned with AMS2750, and how the oven supports Nadcap and AS9100 requirements.
Questions to Ask Before You Decide
- Does your customer specification mandate autoclave cure, or does it define the outcome (void content, mechanical properties) that an OOA route could meet?
- What is the largest part you expect to cure over the equipment’s lifetime, not just today?
- How many cure cycles will you run per week, and what does that mean for energy costs under each option?
- Do you need aerospace pyrometry compliance now, or might you in future? Specifying it at build stage is far cheaper than retrofitting.
Talk to a UK Manufacturer
Caltherm has designed and manufactured custom thermal processing equipment in the UK for over 40 years. Our composite curing ovens are built around your parts, your resin systems and your quality requirements, with options including vacuum systems for out of autoclave curing and instrumentation to support aerospace pyrometry.
If you are weighing up your curing options, contact our team for an honest conversation about which route suits your application. Call +(44) 01782 563865 or request a quote online.