Where does the stable flow rate come from?

From a trial or a logged infusion, after the front is moving steadily. Startup surge and final wet-out are faster and slower than the stable rate, so use the middle section of the run.

What happens if the estimate beats the gel time?

The margin goes negative and the page warns, because the flow front can stall before the fill completes. Add flow media, warm the resin or mold, or switch to a slower hardener.

Is the setup and monitoring allowance part of the fill?

No. It covers vacuum checks, debulk stops and flow front monitoring around the fill. Keep it in the total you compare with gel time, because the resin is aging throughout.

Does the allowance make the estimate conservative?

It makes the compared time longer, which is protective. The fill itself still uses the base time, so cut the allowance only when your records show the stops do not happen.

Composites, Fiberglass & Advanced Materials calculator

Resin Infusion Time Calculator

Work out how long resin takes to fill a dry preform from the volume to infuse and the stable flow rate. The page adds a setup and monitoring allowance and checks the result against the resin gel time.

What this calculator does

Estimate vacuum infusion fill time from volume and stable flow, then compare it with the resin gel time.

Formula used

Base infusion time = resin volume ÷ stable flow rate
Estimated infusion time = base time × (1 + setup and monitoring allowance ÷ 100)
Setup and monitoring hours = estimated infusion time − base infusion time
Margin to gel time = resin gel time − estimated infusion time

Inputs explained

Resin Volume to Infuse: Resin drawn for the fill, from the pot draw or fill line.
Stable Flow Rate: Steady fill rate after the preform wets out, from a trial.
Setup and Monitoring Allowance: Percentage for vacuum checks, debulk stops and front checks.
Resin Gel Time: Working time at the resin and mold temperature used.

How to use the result

Best suited to planning an infusion day, checking a fast hardener choice, sizing a slow fill from low permeability media.
Fill rate falls as the front advances and permeability drops; a single stable rate is an idealization. Exotherm in thick stacks can shorten gel time, so confirm the margin against a trial.

Current U.S. benchmarks

The producer price index for plastic resins and materials stands at 280.569 (BLS, Aug 2026), up 6.6% from a year earlier. Quotes priced off last quarter's material cost miss this move.
Steel mill PPI stands at 381.162 (BLS, Aug 2026), up 23.4% from a year earlier. New factory orders are up 8.5% year over year (Census).

Common questions

Where does the stable flow rate come from? From a trial or a logged infusion, after the front is moving steadily. Startup surge and final wet-out are faster and slower than the stable rate, so use the middle section of the run.
What happens if the estimate beats the gel time? The margin goes negative and the page warns, because the flow front can stall before the fill completes. Add flow media, warm the resin or mold, or switch to a slower hardener.
Is the setup and monitoring allowance part of the fill? No. It covers vacuum checks, debulk stops and flow front monitoring around the fill. Keep it in the total you compare with gel time, because the resin is aging throughout.
Does the allowance make the estimate conservative? It makes the compared time longer, which is protective. The fill itself still uses the base time, so cut the allowance only when your records show the stops do not happen.

Last reviewed 2026-10-01.