Why LRTM Is Ideal for Medium to Large Batch Production

Ryan Franklin
June 5, 2025

Scaling composite production can be a massive financial strain and a scheduling nightmare. As order quantities and scale grow, manufacturers need to be able to ramp up production while keeping material costs predictable and meeting rising targets for standards and delivery dates.

Light resin transfer molding (LRTM) has the potential to keep that delicate balance. By blending the finish of high-end closed mold techniques with lower investment in tooling, LRTM makes an ideal solution for medium to large-scale batch production demand without sacrificing profit margins.

A Closer Look at Light Resin Transfer Molding

LRTM is a closed-mold composite method where the dry reinforcement is placed into a rigid fiberglass mold and sealed with a lighter counter-mold. Then, it’s infused with catalyzed resin in a vacuum chamber. In traditional open-mold hand lay-up, the laminate cures inside the mold, creating both an A and a B side. Both sides’ surfaces are smooth, repeatable, and almost completely void-free—all while using less resin mix and releasing fewer VOCs during the process.

How the LRTM Process Works

The basic LRTM process can be broken down into four parts:

  1. Gel‑coat application: Spray the rigid mold with a controlled layer for a class‑A finish.
  2. Dry lay‑up: Position fiberglass reinforcements and any core inserts, ensuring fiber orientation for strength.
  3. Mold closure & vacuum: Clamp the lightweight counter‑mold, connect feed and vent lines, and then draw a full vacuum to compact the stack.
  4. Resin infusion & cure: Inject catalyzed resin until it reaches the vents; maintain vacuum as the laminate cures, after which the part releases cleanly with minimal trimming.

Biggest Benefits of LRTM Production

LRTM molds are typically made from fiberglass and resin instead of being cast or machined from steel or aluminum. Therefore, any initial tooling investment will usually only be a fraction of those needed for traditional RTM.

Fiber-to-resin ratios also stay much more consistent, and voids are minimized because the laminate cures inside a rigid cavity under a full, powerful vacuum. Not only is part quality consistently repeatable, but the counter-mold can be opened, cleaned, and rewaxed relatively quickly, helping to hasten cycle times.

Associated Manufacturing Advantages

Since resin is pulled only until every strand of reinforcement is fully wetted, over‑infusion essentially becomes impossible. Operators can dial in flow rates with a simple vacuum gauge, which gives incredibly predictable resin use from part to part.

The sealed cavity also keeps a lot of the shop dust and debris from settling on the tacky laminate, keeping surfaces smooth without additional reworking. LRTM’s closed‑mold design sharply limits styrene fumes and messy overspray, allowing facilities to satisfy strict OSHA exposure thresholds without investing in large paint‑booth exhaust systems.

Lower odor levels boost morale and help attract skilled labor, while reduced emissions lighten the paperwork needed for air‑quality permits. These advantages compound as operations ramp from pilot runs into full production.

Industry Applications

LRTM’s scalability is evident across a huge range of sectors and industries. Transit OEMs can mold lightweight bus and truck panels and fairings that can cut fuel costs. Marine yards can infuse cockpit liners and deck hatches with coatings that provide considerable protection from blistering and the harsh effects of saltwater.

Theme park outfitters can create production lines of intricately contoured ride seats and vehicles with show-quality finishes. Architectural firms can specify curved facade panels that arrive pre-primed and ready for final installation. Even renewable energy suppliers rely on LRTM for nacelle and spinner covers on mid-range wind turbines.

Let's Talk About Your Production Needs

When demand has grown beyond prototypes and into true production space, LRTM delivers incredibly consistent quality, shorter lead times, and lower costs on a per-part basis, which is exactly what your growing organization needs. If you’re ready to expand your composite production capacity, reach out to Painted Rhino and tell us about your project.