A round carbon fiber tube has one structural parameter the OEM engineer controls: its diameter. A rectangular tube has three: outer width, outer height, and wall thickness. That extra degree of freedom allows engineers to distribute bending stiffness independently across each bending axis, which is why rectangular carbon fiber tubes are specified in applications where load direction matters more than symmetry. Robot fork arms predominantly carry downward bending loads. Gantry beams must be stiff in the vertical axis but not the lateral one. Structural automation frames need flat faces for direct bolting to flanges and baseplates. None of these requirements are met efficiently by a round tube.
Xinbo Composites produces rectangular carbon fiber tubes in cross-sections up to 400mm, in Standard Modulus through Ultra High Modulus fiber grades. Manufacturing is carried out by mold pressing, autoclave molding, and pultrusion at Xinbo’s ISO 9001-certified factory in Shenzhen.
Mold Pressing, Autoclave, and Pultrusion: Which Process for Your Rectangular Tube
Rectangular carbon fiber tubes cannot be produced by roll-wrapping, which requires a cylindrical or oval mandrel. mold pressing process for shaped carbon fiber tubes, see the guide to produce carbon fiber square tubes . Autoclave molding applies additional pressure to the cured laminate, increasing fiber volume fraction and wall consistency; it is selected where tighter tolerances are required. Pultrusion is a continuous process suited to structural profiles where axial stiffness is dominant and production volumes are high.
| Process | Wall Consistency | Fiber Alignment | Surface Quality | Best For |
| Mold Pressing | Good on all four faces | UD, 2×2 Twill, or Plain prepreg; 0°/90° or ±45° layup | Raw or clear coated | Standard OEM rectangular tubes; short-to-medium run production |
| Autoclave Molding | Excellent; highest dimensional control | UD, 2×2 Twill, or Plain prepreg; 0°/90° or ±45° layup | Excellent on all four faces | Precision mechanical and aerospace-grade rectangular tube applications |
| Pultrusion | Consistent in longitudinal direction | UD fiber tows; longitudinal (0°) dominant | Good on die-contact faces | High-volume structural profiles; axial-stiffness-dominated applications |
OEM Applications: Robot Fork Arms, Gantry Systems, and Structural Frames
In motorsport and mechanical tooling, rectangular tubes are specified for chassis cross-members and CMM arm structures.
| OEM Application | Typical Cross-Section | Wall Thickness | Fiber Grade | Surface Finish |
| Industrial Robot Fork Arms | 30×15mm to 100×50mm | 1.5mm – 3mm | Intermediate Modulus | Raw or Matte Clear Coat |
| Pick-and-Place Gantry Arms | 40×20mm to 120×60mm | 2mm – 4mm | Intermediate / High Modulus | Raw |
| Fixed-Wing UAV Fuselage Frames | 20×10mm to 60×30mm | 1mm – 2mm | Standard / Intermediate Modulus | Matte Clear Coat |
| Motorsport Chassis Cross-Members | 30×20mm to 80×40mm | 2mm – 4mm | Intermediate Modulus | Raw |
| Mechanical Tooling and CMM Arms | 20×20mm to 60×60mm | 1.5mm – 3mm | High Modulus | Raw |
| Industrial Automation Frames | 40×40mm to 150×80mm | 2mm – 5mm | Standard / Intermediate Modulus | Raw or Matte Clear Coat |
Dimension ranges are typical OEM specifications. Xinbo accepts all drawings within the standard production envelope: cross-sections up to 400mm, wall thickness 1mm–10mm, length up to 3000mm. For UAV-specific arm profiles, see Xinbo’s carbon fiber drone weapons page.
Drawing Specifications for Rectangular Carbon Fiber Tubes
Rectangular tube drawings require three outer dimensions: outer width, outer height, and wall thickness. The most common error in first-time orders is submitting only the outer envelope without specifying wall thickness, or not stating whether the wall is uniform on all four faces. If different wall thicknesses are required on the wider versus the narrower faces, each face must be dimensioned separately. The standard manufacturing tolerance is ±0.1mm on both OD and ID, with ±1mm on length. For assembly applications where the tube fits inside a housing, inner width and inner height also require tolerance callouts. Send drawings to Xinbo’s engineering team with all outer dimensions, fiber grade, and surface finish to receive a production lead time and unit price.
| Drawing Parameter | Required | Notes |
| Outer Width | Required | With tolerance callout if tighter than ±0.1mm |
| Outer Height | Required | With tolerance callout if tighter than ±0.1mm |
| Wall Thickness | Required | Uniform wall assumed unless per-face dimensions are specified |
| Length | Required | Standard length tolerance ±1mm |
| Fiber Grade | Required | Standard Modulus / Intermediate Modulus / High Modulus / Ultra High Modulus; Standard Modulus applied as default |
| Weave Pattern | Optional | UD, 2×2 Twill, or Plain Weave; Twill default |
| Fiber Orientation / Layup | Optional | 0°/90° default; ±45° for torsion-dominated load cases |
| Inner Width / Inner Height | Optional | Required if tube must fit inside a housing or mating part |
| Surface Finish | Required | Raw, Glossy Clear Coat, or Matte Clear Coat |
| CNC Machining | Optional | Drilling, cutting, slotting, and threading available |
| Assembly / Bonding | Optional | Metal insert bonding; aluminum and plastic part assembly available |
Frequently Asked Questions
What cross-section sizes are available for carbon fiber rectangular tubes at Xinbo?
Xinbo produces carbon fiber rectangular tubes in cross-sections up to 400mm on the larger outer dimension, with wall thickness from 1mm to 10mm and lengths up to 3000mm. All cross-section dimensions are specified by the buyer on the drawing.
What is the standard tolerance on rectangular carbon fiber tubes?
The standard manufacturing tolerance is ±0.1mm on both the outer and inner dimensions, and ±1mm on length. Tighter tolerances require a callout on the drawing.
Which manufacturing process does Xinbo use for rectangular carbon fiber tubes?
Xinbo produces rectangular tubes by mold pressing, autoclave molding, or pultrusion, with the process selected based on the application’s mechanical requirements, dimensional precision, and production volume.
Can Xinbo supply rectangular tubes with CNC-machined holes or slots?
Yes. Drilling, cutting, slotting, and threading are available as secondary operations on all rectangular carbon fiber tube orders.
Xinbo Composites supplies custom rectangular carbon fiber tubes to OEM buyers in 100+ countries.
Request a quote with your drawing or specification sheet.
