Continuous Fiber 3D Printing With Void-Free Reinforced Filament

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Solution Overview

Problem

Existing three-dimensional printing methods face challenges in producing durable and UV-stable parts due to weak bonding between deposited materials, air pockets, and voids, leading to reduced strength and durability, as well as inefficiencies in handling and feeding composite materials.

Innovation Solution

The use of a continuous core reinforced filament with a preimpregnated thermoplastic resin, which is substantially void-free, allows for improved bonding and strength by eliminating the need for subsequent vacuum steps and enabling deposition in concave shapes, with a cutting mechanism to control material length and direction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional three-dimensional printing methods are used to deposit successive layers of material, then parts can be built layer by layer, but weak bonding between layers and presence of air pockets reduce strength and durability

Engineering Contradiction:
Improvepart strengthVSAvoidbonding quality
Core Design Contradiction:
StrengthVSReliability

Solution Approach 1:

The filament is preimpregnated with thermoplastic resin before deposition, so the bonding action is prepared in advance rather than relying on layer-by-layer bonding during printing. This preliminary impregnation ensures strong bonding without requiring subsequent vacuum steps.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The invention uses a composite filament structure combining continuous core reinforcement (carbon fiber, Kevlar, or basalt) with thermoplastic resin matrix material. This composite structure provides both strength and durability while eliminating air pockets through the preimpregnated void-free construction.

Inventive Principle:
Principle #40Composite materials

2Reliability

If towpregs with continuous fiber reinforced materials are deposited in green state and then placed under vacuum, then air voids can be removed and parts cured, but the process is time-consuming and complex

Engineering Contradiction:
Improvevoid-free constructionVSAvoidprinting speed
Core Design Contradiction:
ReliabilityVSProductivity

Solution Approach 1:

The void-free construction is achieved through preliminary impregnation of the filament with thermoplastic resin before deposition. This eliminates the need for subsequent vacuum steps, directly resolving the contradiction between achieving void-free construction and maintaining high printing speed.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The vacuum step is extracted and removed from the printing process entirely. The patent achieves void-free construction through the preimpregnated filament design, eliminating the time-consuming vacuum and heating steps that were previously necessary.

Inventive Principle:
Principle #2Taking out (Extraction)

3Strength

If preimpregnated composite construction uses sheets of fabric layered into a mold, then durable parts can be formed, but the method is not three-dimensional printing and requires manual handling

Engineering Contradiction:
Improvepart durabilityVSAvoidhandling complexity
Core Design Contradiction:
StrengthVSEase of operation

Solution Approach 1:

The invention changes the physical form parameter from sheet fabric to continuous filament, enabling automated three-dimensional printing while maintaining the durability benefits of preimpregnated composite construction. The filament can be automatically fed and deposited by robotic systems.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The manual mechanical process of layering fabric sheets into molds is replaced with an automated extrusion and deposition system. The continuous filament is fed through a print head and deposited layer by layer under computer control, eliminating manual handling complexity.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

4Shape

If filament winding uses strands of composite wound around a mandrel, then concave shapes can be formed, but convex shapes cannot be produced due to fiber bridging

Engineering Contradiction:
Improveconcave shape capabilityVSAvoidshape flexibility
Core Design Contradiction:
ShapeVSAdaptability or versatility

Solution Approach 1:

The invention uses a dynamic, adaptive deposition process where the continuous filament can be precisely controlled to follow any toolpath geometry. Unlike fixed mandrel-based winding, the print head can dynamically adjust to create both concave and convex shapes with the same continuous material feed.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The continuous core reinforced filament system provides universal shape capability, enabling the production of both concave and convex geometries through a single automated printing process. The same system that creates concave shapes can also produce convex features without requiring separate winding operations.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach results in stronger, more durable parts with reduced voids, enabling faster printing and the ability to tailor directional strength, and facilitates the integration of functional components like printed circuit boards and sensors.

Implementation Method 1

heating the core reinforced filament to a temperature greater than a melting temperature of the matrix material and less than a melting temperature of the core

Methodology Applied
Scientific EffectHeating: Heating

Implementation Method 2

heating the core reinforced filament to a temperature greater than a melting temperature of the matrix material

Methodology Applied
Scientific EffectMelting: Melting

Implementation Method 3

extruding the core reinforced filament to form the part

Methodology Applied
Scientific EffectExtrusion: Extrusion

Data Source

PatentEP4406739B1Three dimensional printing
Publication Date: 2026.03.11 MARKFORGED INC
  • EP4406739B1 patent drawingFigure 1
  • EP4406739B1 patent drawingFigure 2
  • EP4406739B1 patent drawingFigure 3A~3F

AI summary

Various embodiments related to three dimensional printers, and reinforced filaments, and their methods of use are described. In one embodiment, a continuous core reinforced filament is fed into a heated extrusion nozzle. The continuous core reinforced filament is extruded from a nozzle outlet of the heated extrusion nozzle. A compressive force is applied to the extruded continuous core reinforced filament with the nozzle to adhere the continuous core reinforced filament to a surface. The nozzle is displaced relative to the surface to drag the continuous core reinforced filament from a nozzle of a printhead.