Continuous Fiber FDM

Continuous Fiber FDM deposits continuous fiber strands within a thermoplastic matrix to create 3D printed composite parts with high, directional strength and stiffness.

Overview

Continuous Fiber FDM is a composite 3D printing process that lays continuous carbon, glass, or Kevlar fibers inside a thermoplastic matrix as the part is built. The result is a laminate-like internal structure with metal-like strength and stiffness along the fiber directions, while keeping the weight and design freedom of polymer 3D printing.

Choose it for low- to medium-volume parts that need high strength-to-weight ratio, good fatigue performance, and complex geometry that would be expensive to machine from metal. Typical use cases are structural brackets, arms, fixtures, and tooling that must survive real loads, not just prototyping. Tradeoffs: anisotropic properties (much stronger along fiber paths than across layers), limited part size, moderate surface finish, and tolerances driven by FDM fundamentals. Machining critical faces or bores after printing is common when tight fits are required.

Common Materials

  • Onyx (nylon with chopped carbon)
  • Nylon 6
  • Nylon 12
  • Carbon fiber tow
  • Fiberglass tow
  • Kevlar fiber

Tolerances

±0.005"

Applications

  • Lightweight structural brackets and mounts
  • Robot end-effectors and gripper fingers
  • Drone and UAV arms or spars
  • Assembly jigs, fixtures, and soft tooling
  • Custom tooling inserts and nests
  • Motorsport and racing hardware brackets

When to Choose Continuous Fiber FDM

Use Continuous Fiber FDM when you need high strength-to-weight, directional stiffness, and real structural performance from low- to medium-volume 3D printed parts. It fits small to medium components where you can align fibers with known load paths and accept FDM-level surfaces and tolerances. It’s ideal when metal would be overkill for cost or weight, but standard plastics are too weak.

vs Chopped Fiber Infusion Printing

Choose Continuous Fiber FDM when you need maximum strength, stiffness, and fatigue resistance along specific load paths, closer to metal-like performance. Chopped fiber processes give more isotropic reinforcement but cannot match the directional strength and stiffness you get from continuous strands. Use continuous fiber when structural behavior and weight reduction are more important than print speed or cost per part.

vs Standard FDM 3D printing

Choose Continuous Fiber FDM instead of standard FDM when a part must carry real loads, replace metal brackets, or survive impact and fatigue. Standard FDM works for housings and cosmetic or low-load parts; continuous fiber is for structural members, fixtures, and tooling where failure is unacceptable.

vs CNC machining

Choose Continuous Fiber FDM over CNC machining when geometry is complex, volumes are low, and weight reduction matters more than perfect surface finish. It eliminates multi-axis setups and difficult workholding while giving you strength comparable to some aluminum parts, though with less dimensional precision and more anisotropy.

vs Resin (SLA/DLP) 3D printing

Choose Continuous Fiber FDM instead of SLA/DLP when mechanical strength, impact resistance, and long-term durability matter more than fine detail and surface finish. Resin prints are great for appearance models and small, intricate parts; continuous fiber prints are better for brackets, arms, and fixtures that will actually be loaded.

Design Considerations

  • Align primary load paths with fiber direction; communicate this so the shop can orient the part and fiber routing accordingly
  • Keep walls and ribs thick enough to contain fiber strands, typically ≥2–3 road widths, to avoid weak, resin-only regions
  • Avoid sharp internal corners; use generous fillets so fibers can follow the geometry without kinking or stopping
  • Concentrate fasteners and interfaces in thicker, reinforced regions; plan for metal bushings or inserts where bolts clamp or pivot
  • Limit extreme overhangs and thin unsupported features; design for printed or sacrificial supports that won’t interfere with fiber routing
  • Call out critical dimensions and mating faces for optional post-machining so the shop can plan stock and fixturing