A flanging machine (rotary flanger) forms a clean rim on the edge of round or cylindrical sheet-metal parts—think lids, tanks, cookware, drum ends, HVAC rings. Instead of a press hit, it rolls the edge with hardened rollers against a mandrel, so the metal flows gradually. That rolling contact is why the edge and face finish stay smooth (no die lines, no chatter marks).

How it works (quick cycle)

1. Clamp on mandrel – the disk, cone, or cylinder is centered on a copy mandrel.
2. Pre-flange pass – a forming roller turns the edge up/down to ~30–60°.
3. Final flange/hem – the roller follows a guided path to 90° (flange), 135–180° (curl/hem), or into a bead.
4. Planish – a polished planishing roller “irons” the surface to the final thickness/finish.
5. Trim/calibrate – optional rotary trim knife sets exact OD after forming.

Key components

• Headstock & tailstock with servo RPM control (typ. 200–1,500 rpm).
• Forming/planishing rollers (polished, 58–62 HRC or PCD-tipped) on CNC slides.
• Copy mandrel (steel or aluminum, mirror finish for visible parts).
• Backup/anti-wrinkle rolls to hold the wall and prevent buckles.
• Lube & cooling to avoid galling (especially on SS/Al).

What makes the surface “smooth”

• Rolling deformation (not stamping) + polished tools.
• Low feed per rev (≈0.1–0.6 mm/rev) and constant-radius tool paths.
• Planishing pass that evens thickness and reduces Ra (≈0.8–1.6 μm common).
• Correct edge radius (min ~2–4× sheet thickness) to prevent micro-cracks.

Typical capability (rule-of-thumb)

• Materials: mild steel, stainless, Al, Cu, Zn-coated.
• Thickness: ~0.3–4.0 mm (up to 6 mm with higher power and large diameters).
• Flange height: up to ~3–5× material thickness (before hemming).
• Diameters: from ~80 mm to >2,000 mm depending on model.

Common operations

• 90° flange for bolting/welding.
• Curl/Hem (180°) for safe edges or gasket seats.
• Beading to stiffen shells.
• Joggle for step joints.
• Edge calibration & rotary trimming.

Quality pitfalls & fixes

• Wrinkling (compression buckles): use backup rolls, higher clamp force, pre-flange in steps.
• Cracking at outer fiber: increase bend radius, anneal if needed, reduce feed/RPM, add lube.
• Galling/tool marks: polished/PCD rollers, correct coolant.
• Ovality: good mandrel fit and synchronized tailstock pressure.

Where it shines vs. press-brake/stamping

• Superior surface finish and visible-grade edges.
• Fast changeover (swap mandrel/roller) for short runs.
• Less tonnage; better for large diameters and conical parts.

Buyer’s checklist (sheet-metal shop)

• Thickness & diameter range you actually run.
• Number of CNC axes (at least X/Z; Y/tilt gives better profiles).
• Power & torque at low RPM (SS needs it).
• Quick-change mandrels/rollers, programmable anti-wrinkle rolls.
• Integrated trimming and planishing if you need cosmetic parts.
• Proven samples on your material (SS 304/430 and Al 5xxx behave differently).

In short: it’s a roller-forming machine that turns, curls, or hems the edge of round sheet-metal parts while keeping the face and rim cosmetically smooth—ideal when you need both strength and a showroom-grade finish.