Hot-Press Molding vs Autoclave: Which Is Right for Your Carbon Fiber Part?
Prepreg carbon fiber needs heat and pressure to cure. The two most common ways to provide them are compression molding in a hot press and curing in an autoclave. Both make high-quality parts, but they suit different shapes, sizes and volumes.
Hot-press compression molding
In compression molding, the prepreg layup is placed in a matched metal mold, usually with two or more parts. The closed mold goes into a heated press, which applies heat and pressure directly through the tool.
- Accurate thickness and dimensions on both sides of the part
- Good surface quality on all molded faces
- Efficient cycles, suited to repeat production
- Requires matched metal molds, which are a larger upfront investment
- Part size is limited by the press
Autoclave curing
In autoclave curing, the layup is placed on a single-sided mold, covered with a vacuum bag and cured in a pressurized, heated vessel. The gas pressure presses the laminate evenly against the mold.
- Excellent consolidation, widely used in aerospace
- Suits large and complex single-sided parts
- Only one side is molded; the bag side is less controlled
- Longer cycles with bagging, and high equipment cost
Comparison
| Hot-press molding | Autoclave | |
|---|---|---|
| Mold | Matched metal mold | Single-sided mold + vacuum bag |
| Surfaces controlled | All molded faces | Mold side |
| Thickness control | Very good | Good |
| Cycle efficiency | High | Lower |
| Part size | Limited by press | Limited by vessel |
| Typical parts | Foil wings, masts, fuselages, plates | Large shells, aerospace parts |
Why we use hot-press molding for foil parts
Hydrofoil wings, masts and fuselages need both sides of the part to be accurate, with controlled thickness and repeatable dimensions. Hot-press molding in matched metal molds is well suited to these parts. See our process on our Manufacturing page.
Planning a carbon fiber project?
Send us your part and we will advise on the best molding approach for it.