Resin Infusion vs Autoclave: A Practical Cost and Cycle Time Guide

What drives the price difference between infusion and autoclave

The gap in cost between resin infusion and autoclave curing is not a single line item. It spreads across labor, tooling, energy, and schedule risk.

For a typical structural composite panel, autoclave curing requires a pressurized chamber. That chamber must be rated for the cure chemistry and the part size. The chamber itself is a fixed capital cost. Every part that enters the chamber consumes a slot in that capacity. If the cure cycle runs longer than planned, the chamber is unavailable for other jobs. That downtime multiplies the per-unit cost.

Resin infusion removes the chamber. The part cures in an open mold or a bag. The equipment footprint is smaller. Labor hours drop because the resin is placed by gravity or low-pressure pumping rather than by manual layup inside the mold. The tooling for infusion is often the same mold used for hand layup, though infusion molds are typically more precise.

The material cost is similar for both. The same epoxy or vinyl ester resins are used. The same carbon or glass fibers are available. The difference is in how much skill and time the factory spends on each unit.

How cycle time changes with process choice

Cycle time is where scheduling gets complicated.

An autoclave cure is a closed loop. You load the part, close the door, pressurize, heat, hold, cool, and unload. The total time is fixed by the resin system and the part thickness. A thick beam section takes longer to cure than a thin skin. The chamber cannot be opened early to check the part. If something is wrong, you wait for the full cycle to end.

Infusion is more flexible. The resin can be pumped in stages. If a section is not wetting correctly, the operator can adjust the flow. The part can be bagged and cured in an open oven or a vacuum bag without the pressure constraint of a chamber. This means shorter cure times are possible with some chemistries.

However, infusion has its own timing risks. If the vacuum breaks, the cure is incomplete. The operator must monitor the bag and the vacuum line. A failed infusion often means reworking the part. That rework adds labor time that does not appear in the nominal cure cycle.

For a production schedule, autoclave is predictable. Infusion is variable. The factory must plan for both the nominal cycle and the probability of a rework event.

How to write a clear RFQ for these processes

A vague request for quotation returns a vague quote. To compare resin infusion and autoclave fairly, you must define the quality targets in the request.

The first line of the RFQ should state the part geometry. Provide a drawing with tolerances. Specify the fiber type and layup sequence. State the resin system if it is fixed, or list the preferred classes.

The second line should define the quality standard. Do not just say high quality. Specify the maximum void content percentage. Define the visual acceptance criteria for the surface. State whether the part must be radiographed or ultrasonically tested.

The third line should define the quantity and schedule. State the number of parts per week or per month. State the delivery date. If you need a first article inspection, include that in the scope.

The fourth line should ask for the process. Require the supplier to state whether they use autoclave curing, vacuum infusion, or a hybrid. Ask them to explain how they achieve the stated void content. Ask them to provide the cure cycle time per part.

If the supplier does not answer these points, their quote is not comparable to another quote. You are comparing two different products.

How to compare quotes fairly

Suppliers often quote a single number. That number hides the assumptions.

Look at the tooling cost. If the supplier owns the mold, the tooling cost is amortized over the first few parts. If they are buying a new mold for your project, the tooling cost is a fixed fee. Make sure that fee is listed separately.

Look at the material cost. Is it included in the unit price or billed separately? If billed separately, check the unit price of the resin and the fiber. Different suppliers buy at different prices.

Look at the quality cost. A quote that includes ultrasonic testing will be higher than one that does not. If your application requires the test, add it to every quote. If it is optional, decide whether the cost difference justifies the added confidence.

Look at the schedule cost. A cheaper quote that takes longer to deliver may cost more in inventory holding and project delay. Normalize the quote to a per-week rate.

Do not compare a quote that includes tooling with one that does not. Do not compare a quote with full testing to one with no testing. Strip the quotes to the same scope before looking at the price.

When autoclave curing is the practical choice

Autoclave curing is not always the best process, but it wins in specific situations.

The first situation is when the part has high structural demand. If the part carries flight loads or heavy machinery loads, the fiber wet-out must be consistent. Autoclave pressure forces the resin into the fiber bundle and squeezes out the air bubbles. The result is a denser, stronger composite. The void content is lower. The mechanical properties are more predictable.

The second situation is when the part geometry is complex. Internal ribs, thin skins, and sharp corners are hard to wet with gravity infusion. The pressure in the autoclave helps the resin reach those areas. The operator does not have to fight the flow.

The third situation is when the customer requires a certified process. Some standards and qualification programs expect autoclave curing for the primary structure. If the audit trail must show pressure and temperature records from a chamber, infusion may not meet the requirement.

When resin infusion is the practical choice

Infusion is the default for many production environments.

The first reason is cost per part. For a moderate volume of parts, the labor savings are significant. The operator does not need to place each layer by hand. The resin is pumped in. The mold does the work of shaping the part.

The second reason is tooling flexibility. If the part design changes, the mold may still work. Autoclave molds are often more rigid and more expensive to modify. Infusion molds are often simpler.

The third reason is schedule. If you need a small batch quickly, the infusion line can be set up and running before the autoclave chamber is free. The chamber is a bottleneck. Infusion can run in parallel with other processes.

The fourth reason is part size. Large panels that would not fit in a standard autoclave can be cured by infusion in a larger oven or in a vacuum bag on a flat bed. The equipment is easier to scale.

A table of cost drivers

The following table lists the main cost drivers for each process. The values are relative, not absolute. A specific part will shift the balance.

Cost Driver	Autoclave Curing	Resin Infusion
Labor	Higher, due to chamber loading and curing time	Lower, due to automated pumping and less manual work
Equipment	High, due to chamber capital cost and maintenance	Lower, due to simpler molds and vacuum pumps
Tooling	High, molds must withstand pressure and heat	Moderate, molds are standard molds
Material	Same as infusion for the same resin and fiber	Same as autoclave for the same resin and fiber
Quality Control	Lower void content, less rework	Higher void risk, potential rework cost
Schedule	Fixed cycle time, chamber availability bottleneck	Flexible cycle time, parallel processing possible
Part Size Limitation	Limited by chamber size	Limited by oven or bag size, easier to scale

Final selection advice

The choice between resin infusion and autoclave curing comes down to three questions.

First, what is the quality floor? If the void content must be below a certain percentage, and the part carries a high load, the process must be able to meet that floor. Autoclave curing is easier to justify for that floor. Infusion can meet it, but the process control must be tighter.

Second, what is the volume? If the volume is low, the tooling cost is a bigger part of the total. If the volume is high, the labor cost dominates. Infusion usually wins on labor. Autoclave may win on consistency.

Third, what is the schedule? If the schedule is fixed and the chamber is booked, infusion may be the only option. If the schedule is flexible, the quality requirement may tip the scale toward autoclave.

Write the RFQ with those three questions in mind. Ask for the process. Ask for the quality data. Ask for the schedule. Then compare the quotes on the same scope. The lower price is not the best answer. The best answer is the process that meets the quality floor within the schedule at the lowest total cost.