Vacuum Infusion - A Complete Process

Vacuum Infusion

Composite Processes

A vacuum infusion process makes use of vacuum pressure to drive resin into a laminate. It also applies pressure to impregnate the reinforcement with resin while using negative pressure to extract air.

This system efficiently produces high-performance composites, ideal for carbon fibre parts in marine and automotive industries. If completed correctly, infusion parts provide incredible strength, appearance and consistency across multiple components.

When infusing resin, base the part design on the specific resin you’re using. Using epoxy resin on a polyester-based mould can damage both the part and the mould. Our technical sales team helps you choose the right products and optimise your moulding process—saving time, costs, and waste. Get in touch to see how we can support you.
 

Beginning the Vacuum Infusion Process

The process begins by preparing the mould with your preferred release agent, ensuring an even coverage. A gel coat can be added at this point if required, ensure it is fully cured before moving on to the next step.

To begin the infusion, vacuum tape gets placed on the perimeter of the mould. The operator will cut the fabric, usually carbon fibre, Kevlar or fibreglass, to ensure full coverage. Multiple layers can get added at this point.

Confident that the reinforcement layers are in place, the mould is ready for the peel-ply layer. This is a single layer and unlike the reinforcement, will not need to overlap the edges of the reinforcement, but instead cover it. As a rule, we recommend that it is cut just fractionally larger than the reinforcement.

Applying the Infusion Mesh

Once the operator confirms that the peel-ply fits properly, they can move on to laying the infusion mesh. Like peel-ply, the operator applies this mesh in a single layer, but they can overlap multiple layers if needed—especially in corners or divots in the mould. They should cut the mesh to match the size of the peel-ply layer, leaving excess at two ends to feed in the vacuum and resin lines.

Fit the resin feed to the edge of the infusion mesh to ensure a consistent flow across the mould. Most undertakings will only require one feed, but complex parts may require more. Double-check that all components are in place: ensure the operator attaches the feed connector to the feed tube (usually in the middle) and secures it with vacuum tape if needed. Connect the vacuum to the feed connector on the opposite side of the mould, above the infusion mesh and secure with tape.

Adding the Vacuum Bag to the Vacuum Infusion Process

Prepare the vacuum bag, selecting one 50–70% larger than the part. Press it firmly into the tape around the mould, avoiding wrinkles or folds that could cause air leaks.

Make a small incision in the bag to insert the resin hose into the feed connector, ensuring a secure fit. Seal the hose and incision with tape for an airtight seal. Repeat on the opposite side for the vacuum and resin catch pot.

Connect the resin feed hose to a secured resin pot. Attach one vacuum hose to the catch pot, securing it if needed, and the second hose to the vacuum pump, ensuring airtight connections. Clamp the resin feed.

When the pump is on, the bag will tighten over the mould. Pause if needed to adjust the bag and prevent wrinkles. Once air is fully removed, the vacuum gauge should read 100%. If not, turn off the pump and reseal any leaks, especially around incisions.

Adding Resin to the Mould

It is now time to add in resin. With infusion projects, the norm is to aim for a 60/40 fibre/resin ratio. Mix the resin and catalyst as accurately as possible, and thoroughly stir the mixture—paying close attention to the edges and bottom of the pot.

Once the resin is ready, and the tube is in place, ensuring that the vacuum is on the operator can unclamp the resin feed and begin to see resin travelling through this line and into the mould.
Depending on the size of the mould, this can take up to one hour. Observe the part closely; once the resin fully impregnates the reinforcement, clamp the resin feed and begin the curing process.
The vacuum should remain on during the curing process. The temperature will affect cure time. If planning to cure at a higher temperature, ensure that all products can withstand this temperature elevation.

Finishing the Process

Checking the mould is fully cured, the vacuum can be turned off. At this point, the operator will remove the bag, tape, mesh and peel ply. Peel ply can be challenging to remove and may require force. We don’t recommend using tools to remove peel ply. The part is now ready to be trimmed and finished!

If you are looking to introduce Infusion processes into your business, why not take advantage of our Technical Support and book in for a free audit of your procedures.

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