Long Fiber Injection (LFI)

September 13, 2017

High & Low Gloss LFI

In 1999, Romeo RIM was the first company to bring a new material technology to North America called Long Fiber Injection (LFI) which is a sprayed slurry into open mold based on simultaneous pouring of Polyurethane resin together with chopped fiberglass at various lengths (1/4” to 2”).

LFI is a new production technology, wherein a robot is used to spray a mixture of polyurethane and chopped fiberglass onto a mold, which then uses low compression to form the part, such as roofs and body panels. This process is similar to SRIM, but in this molding operation, the original two-step method is condensed into a single-stage procedure that is robotically applied.

Our LFI operations provide parts with several product advantages, including lower tooling and production costs, dimensional stability, and optimized weight and strength – among other benefits. From mass transit to agriculture and construction, our ISO-compliant LFI services have met the needs of multiple industries.



Material/Process Benefits Applications To Consider Use of LFI
Excellent Stiffness to Weight Ratio Roof Inner/Outer – Falling Object Protection
Low Cost Single Tool Process Medium-Large Size Body Panels
No Post-Applied Paint Required Interior Cladding
Class-A Finishes (right out of mold). Textured or Glossy Textured Int/Ext Applications
Optimized Properties Glossy Int/Ext Applications
Ability to Change Composite Density Structural & Semi-Structural Reinforcements
Glass Content 0-50% by Weight
Dimensionally Stable – Low CLTE
Design Freedom
B-Side Features – Bosses, Ribs, Etc.
Thick & Thin Wall Features
Near ZERO PPM Process
100% Robotically Controlled
65 PCF (1.02d) – 83 PCF (1.33d)
High Impact Resistance
Large Complex Parts
12′ x 12′ Double Shuttle system (The Largest LFI Press in the World)

LFI up to 40% lighter than SMC

Mechanical Properties LFI SMC LFI SMC
Weight (specific gravity) 1.02 1.2 1.3 1.8
Flexural Modulus (PSI) 1,100,000 1,000,000 1,300,000 1,600,000
Tensile Strength (PSI) 9,700 9,000 16,500 12,000
Elongation (%) 1.3 1.1 1.5 1.2
Notched Izod Impact (ft-lb/in) 13 13 17 16
% Glass Content 35 41 35 30

Weight reduction, strength, durability, good aesthetics and processing efficiency. These desirable traits are critical for a multitude of applications spanning across many markets, and they can all be achieved with Long Fiber Injection (LFI) utilizing Baydur® polyurethane from Covestro LLC. Romeo RIM is an LFI leader and innovator, with a long, successful track record.

The company brought LFI, an automated process for producing structural polyurethane composites, to North America over 15 years ago. Using Baydur® polyurethane from Covestro, Romeo RIM successfully established LFI in North America with its first commercial application – interior sleeper cabs for heavy trucks. Romeo RIM has collaborated closely with Covestro for over a decade. Covestro’s versatile Baydur® polyurethane allows for cost-efficient production of large moldings and accurate reproduction of surface details.

Collaboration with Covestro on part design and structural analysis techniques enables Romeo RIM to achieve optimal part designs, which translate into superior end products for OEMs. In addition to supplying the polyurethane, Covestro also provides Romeo RIM with material development and process technology support. The lightweighting value proposition of polyurethane LFI positions it as an attractive alternative to steel, aluminum and other polymers, such as sheet molding compound (SMC) or fiber reinforced plastic (FRP).

Long Fiber Injection Markets

With LFI it is possible to achieve 40 – 50 percent weight savings over competitive technologies while maintaining the same performance level, according to Romeo RIM. Polyurethane LFI is ideal for large components requiring a stringent balance of strength and stiffness to weight, such as roofs, body panels, spa cabinets and entry door skins. Key markets include mass transit, agricultural and construction, heavy trucks and spas.

Long Fiber Injection Process

During the LFI process, long glass fibers (typically 12.5 mm to 100.0 mm or 0.5 in. to 4.0 in.) are cut and injected along with polyurethane resin in a one-step process. A fiberglass chopper works in tandem with the polyurethane dispensing mix-head, both of which are attached to a robot arm. The robot is programmed to move over the open mold cavity while simultaneously dispensing both the long glass fibers and the polyurethane resin in an open-pour method.

The mold, which is capable of incorporating complex three-dimensional shapes, integral stiffening and structural elements and deep draws, is then closed and compressed to form large, glass-reinforced parts. Managing the process through robotics reduces production variation, thus improving part consistency and quality. Romeo RIM houses one of the largest double shuttle presses, along with one of the fastest production LFI presses in the world.

Romeo RIM & LFI

This combination enables the company to provide customers with a continuous part as large as 11.5ft by 11.5 ft, a size beyond traditional injection molding, but also the ability to produce high gloss painted composite parts directly out of the mold in less than 120 seconds. Unlike a traditional molding process that requires multiple parts, with the versatile double shuttle press Romeo RIM can manufacture a large part in one mold, reducing cost and improving efficiency.

Alternatively, the company can use the double shuttle press to simultaneously produce multiple parts as small as 2 ft. by 2 ft., offering another productivity improvement. While LFI boasts a lower cycle time and more streamlined process than competitive techniques, it does not compromise the performance or aesthetic quality of the resulting parts. In fact, the technology offers a variety of attractive Class-A surface finishes achieved through a barrier coat and in-mold painting method pioneered by Covestro and Romeo RIM.

By applying the paint directly to the open LFI mold before dispensing the Baydur® polyurethane and chopped-glass material, a decorated part can be formed in one step, eliminating secondary operations, increasing manufacturing efficiency and lowering cost and waste. Baydur® polyurethane’s ability to replicate intricate tool surface effects allows high gloss, fine wood grain and other surface textures to be achieved in the same one-step LFI process.

At the heart of Romeo RIM’s successes are LFI and its collaboration with Covestro. It’s a proven, winning formula for pushing the boundaries of what’s possible, and in doing so, expanding market adoption and industry awareness to bring the next generation of LFI to market.

LFI Mechanical Properties

Material Density (pcf) Tensile Strength (psi) Tensile Modulus (psi) Compressive Strength (psi) Flexural Strength (psi) Flexural Modulus (psi) Unnotched Izod (ft-lbs/in) Dart Impact (ft-lbs) Dart Impact (ft-lbs)
83 16,331 1,132,373 22,205 38,391 1,302,088 19.28 11.28 8.66
70 10,833 861,614 11,458 35,774 1,207,804 14.68 10.82 7.18
60 8,593 626,539 6,561 33,354 1,044,759 13.88 9.52 7.2
50 6,663 524,709 4,321 15,196 576,638 10.58 10.07 5.6
40 4,431 382,998 2,784 11,067 382,836 8.46 9.08 3.7

LFI Design Considerations


  • Matched metal mold tolerances, use sliding scale
  • +/- .0015” per each inch of part size
  • Remember CLTE between dissimilar materials
  • Trim edges require larger tolerances

Wall Thickness

  • Thickness as low as .060”
  • Thickness greater than .5” possible
  • Can vary within part

Draft & Vertical Walls

  • Minimum draft 1.5°
  • Lower draft angle results in lower glass content

B-Side Features

  • Ribs & Bosses
  • Design correctly based on fiberglass content required


  • Boss Clusters
  • Bonding of Brackets & Hardware

LFI Design & Properties at work

Falling Object Projection Systems (FOPS)

  • FOPS Roof Requirements
  • 100lb ball drop from 3 meters
  • No headliner deflection greater than 9”
  • Ball cannot penetrate into cab area

Romeo RIM Solution

  • Structural foam Inner Roof
  • LFI In mold painted Outer Roof
  • Localized composite stiffener between roofs

Customer Benefits

  • Reduced cost – 35% Assembly Cost Reduction
  • Eliminated the need for steel plate
  • Reduced weight – 50lb lighter roof system


LFI Market Acceptance

Agricultural Roof Assembly

  • Support 300 lb Loading
  • Class A Finish Out of Mold
  • B-Side Mounting of Cab Equipment
  • 4mm Thick
  • ~30lb Assembly
  • High Gloss In Mold Painted
  • 8’ x 7’ Assembly

LFI Market Acceptance

LFI Spa Cabinet Assembly

  • Reduced Assembly Time
  • Eliminated Wood Frame
  • Superior Weatherability
  • 3mm Thick
  • ~65lb Assembly
  • Texture In Mold Painted
  • 94” x 94” Cabinet Assembly

LFI Market Acceptance

Hull for Personal Watercraft

  • 25% Weight Savings
  • Better Impact Properties
  • Functional Mounting on B-Side
  • Variable Thickness
  • ~100lb
  • High Gloss Finish

LFI Market Acceptance

Shield on Agricultural Baler

  • Consolidated Frame into Part
  • Better Impact Properties
  • Functional Mounting on B-Side
  • 4mm Thick
  • ~8lb Molded Part
  • High Gloss In Mold Painted
  • 36” x 29” x 6”

LFI Market Acceptance

  • Smart Car Roof
  • 3 Pc Tractor Hood
  • Residential Siding
  • Structural Door Inners & Dash Carrier
  • Residential Entry Doors
Romeorim design guide