Hydroforming

Tube hydroforming forms hollow metal tubes with high-pressure fluid inside a die, enabling complex, lightweight shapes with fewer welds and good repeatability.

Overview

Tube hydroforming expands and shapes a metal tube by sealing the ends and applying high internal fluid pressure while the tube is constrained by a hard die. It produces smooth transitions, variable cross-sections, and integrated features (ribs, bulges, bends) with minimal seams, often replacing multi-piece weldments.

Choose hydroforming for structural tubes where stiffness-to-weight matters and you want consistent geometry across production runs: frames, rails, substructures, and fluid-handling tubes with formed ends. Tradeoffs: higher upfront tooling and development (die, sealing, pressure path), tighter constraints on material formability, and part geometry limits driven by thinning, wrinkling, and end-feeding. Holes and trims are usually secondary ops, and final dimensional control depends on die quality, tube spec, lubrication, and pressure control.

Common Materials

  • Aluminum 6061
  • Aluminum 5083
  • Stainless steel 304
  • Stainless steel 316L
  • Low carbon steel
  • DP600 steel

Tolerances

±0.010" to ±0.030" (formed); tighter features typically after trim/pierce

Applications

  • Automotive roof rails and structural members
  • Motorcycle/bicycle frames and swingarms
  • Exhaust components and formed tube ends
  • Roll cage and chassis tubes with integrated nodes
  • HVAC/refrigeration manifolds and headers
  • Industrial machine frames and supports

When to Choose Hydroforming

Hydroforming fits parts that start as tube and need non-round sections, bulges, or smooth multi-axis shape changes while staying hollow and lightweight. It makes sense when reducing welds and improving repeatability offsets the tooling cost, typically in medium to high volumes. It’s also a strong choice when surface continuity and fatigue performance matter.

vs CNC tube bending

Choose tube hydroforming when you need cross-section changes, local bulges, or integrated features that bending can’t create. Hydroforming can consolidate multiple bent and welded pieces into one formed tube, improving repeatability and fatigue performance. Bending is better when you only need centerline geometry changes with constant cross-section.

vs Welded tube fabrication

Choose tube hydroforming when weld count, distortion, leak risk, or fatigue at joints is driving cost or performance. A single hydroformed tube can replace multi-piece assemblies and reduce fixturing and inspection load. Welded fabrication stays attractive for very low volume or when geometry is too aggressive for forming limits.

vs Stamping + welding (sheet metal assemblies)

Choose tube hydroforming when a closed-section structure is needed for stiffness and you want a smooth exterior without multiple seams. Hydroformed tubes often deliver better torsional rigidity and cleaner airflow/exterior surfaces. Stamped assemblies can win when you need large planar features, many attachments, or very high volumes with established press lines.

vs CNC machining

Choose tube hydroforming when the part is primarily a thin-wall hollow structure and machining would waste material and time. Hydroforming creates the macro-geometry in one operation, with machining reserved for localized interfaces. Full machining is typically reserved for thick-wall blocks or tight-tolerance prismatic features.

vs Metal additive manufacturing

Choose tube hydroforming when you need a production-ready hollow structural tube with predictable material properties and cycle time. Hydroforming scales economically with repeatable tooling and avoids internal support/removal issues. Additive is better for very low volume, extreme topology, or complex internal lattices/manifolds.

Design Considerations

  • Hold wall thickness, tube OD/ID, and weld seam location consistent; variability drives split lines, wrinkles, and thinning risk
  • Use generous transition radii and avoid sharp section changes to reduce thinning and improve die fill
  • Minimize extreme expansion ratios and long unsupported bulges; plan end-feeding paths to control thinning
  • Define trim lines, pierce locations, and datums early; most holes/slots are secondary ops and need fixturing strategy
  • Specify functional tolerances on critical interfaces only; allow looser tolerances on free-form surfaces unless post-processed
  • Provide tube length, straightness, and end-condition requirements (square cut, deburr, preform bends) to get accurate quotes and stable runs