This guide covers everything you need to know about Round Flange Production Guide 2026: Forming Line vs Angle Iron Bender vs Welder. Key takeaways: detailed specifications, cost comparisons, pros and cons, maintenance requirements, and expert recommendations from Preda Machine — a leading HVAC duct machinery manufacturer since 2008, serving 60+ countries.
In This Guide
Round Flange: Connecting Spiral Duct
Every spiral duct system needs round flanges to connect duct sections. Whether you're using angle iron flanges, rolled steel flanges, or punched flange rings, the right flange production equipment determines your ability to meet project specifications and delivery schedules.
Preda offers three round flange production solutions for different volume and flange type requirements.
Quick Answer
For high-volume production of angle iron round flanges, the Round Flange Forming Line YFL-40 is the complete solution — it bends, punches, and cuts flanges automatically. For small-batch or custom flange production, the Angle Iron Bending Machine JT-50 combined with a Round Flange Punching Machine offers flexibility. The Round Flange Welder is needed for welding flange ends in continuous production.
Three Round Flange Production Solutions
| Feature | Flange Forming Line YFL-40 | Angle Iron Bender JT-50 + Punch | Round Flange Welder |
|---|---|---|---|
| Automation | Fully automatic line | Semi-auto (2 machines) | Semi-auto |
| Flange Type | Angle iron (L-bar) | Angle iron (L-bar) | All types (welding) |
| Flange Diameter | 100–1500mm | 50–2000mm | All diameters |
| Production Speed | 1 flange/30–60s | 1 flange/2–3 min | 1 weld/10–20s |
| Operators | 1 | 2 | 1 |
| Best For | High-volume flange production | Custom, small-batch flanges | Continuous flange welding |
Round Flange Forming Line YFL-40: High-Volume Production
The Round Flange Forming Line YFL-40 is a complete automatic production line for angle iron round flanges. It takes raw angle iron bar, bends it into a circle, punches bolt holes, and cuts to size — all in one continuous operation with a single operator.
- Fully automatic: Feed angle iron, set diameter and hole count — the line does the rest
- Fast production: One complete flange every 30–60 seconds — 60–120 flanges/hour
- Consistent quality: Every flange identical — same diameter, same hole spacing, same roundness
- 100–1500mm range: Covers most commercial spiral duct flange sizes
- One operator: Minimal labor — load material and collect finished flanges
View Round Flange Forming Line →
Angle Iron Bending Machine JT-50: Flexible Custom Production
The Angle Iron Bending Machine JT-50 bends angle iron (L-bar) into circles or arcs of any diameter. Combined with a separate punching machine, it offers flexible production for custom flange sizes — perfect for shops that produce a wide variety of flange diameters in small batches.
- Wide diameter range: 50–2000mm — covers everything from small fittings to large industrial duct
- Flexible: Produce any diameter on demand — no tooling changes needed
- Simple operation: Manual or motorized adjustment — easy to learn
- Low cost: Fraction of the price of a full forming line
View Angle Iron Bending Machine →
Round Flange Punching Machine: Precision Hole Punching
The Round Flange Punching Machine punches evenly spaced bolt holes around the flange circumference. Used in combination with the angle iron bender, it completes the flange production process.
View Round Flange Punching Machine →
Round Flange Welder: Continuous Welding
The Round Flange Welder welds the ends of bent angle iron to create a continuous circular flange. Essential for high-pressure applications and large-diameter flanges where mechanical joining isn't sufficient.
How to Choose
- Daily flange volume? >50 flanges/day → Forming Line YFL-40 (ROI in labor savings). <50/day or wide variety of sizes → Angle Iron Bender + Punch
- Flange diameter range? Standard 100–1500mm → Forming Line. Custom/wide range 50–2000mm → Angle Iron Bender
- Do you need welding? High-pressure or large-diameter flanges → add Round Flange Welder
- Labor cost? High labor costs → Forming Line (1 operator vs 2). Lower labor costs → Angle Iron Bender + Punch is more affordable
- Can you combine? Many high-volume shops use the Forming Line for standard sizes AND the Angle Iron Bender for custom/odd sizes — they complement each other
Preda Care: Flange Equipment, Lifetime Support
All flange production machines include lifetime technical support. Forming lines include on-site installation and 5-day operator training. Replacement tooling (bending rollers, punching dies) ships free when needed. Remote PLC support available for all automated models. Global agent network provides local service in 40+ countries.
Standard Round Flange Dimensions and Bolt Patterns
Round flanges are specified by tube diameter, flange material section, and bolt circle. Standardising these three numbers across a project is what makes flanges interchangeable on site — and it is the first thing to agree with the contractor before you start production.
| Duct Ø | Angle iron section | Bolt qty | Bolt size | Bolt circle Ø | Gasket width |
|---|---|---|---|---|---|
| 100 – 200 mm | 25 × 25 × 3 | 4 | M8 | D + 45 mm | 10 mm |
| 250 – 400 mm | 30 × 30 × 3 | 6 | M8 | D + 50 mm | 12 mm |
| 450 – 630 mm | 30 × 30 × 3 | 8 | M8 | D + 55 mm | 12 mm |
| 710 – 1000 mm | 40 × 40 × 4 | 10 – 12 | M10 | D + 60 mm | 15 mm |
| 1100 – 1600 mm | 40 × 40 × 4 | 14 – 18 | M10 | D + 70 mm | 15 mm |
| Above 1600 mm | 50 × 50 × 5 | 18 – 24 | M12 | D + 80 mm | 20 mm |
Pitch the Bolt Holes, Do Not Count Them
Holes evenly spaced around the circle matter more than hitting an exact count. On a forming line the punch is indexed by pitch, so specifying "8 holes" instead of "8 holes equally pitched on a Ø+55 circle" is how you end up with flanges that bolt up on three of four sides.
Matching Production Method to Volume
The four production routes have very different economics. This is the break-even picture for a shop running 300 mm to 800 mm flanges.
| Method | Capex | Cycle per flange | Labour per flange | Economic from | Economic to |
|---|---|---|---|---|---|
| Corner mould on a press | Under $1,000 | 3 – 5 min | High | 1 flange | ~300/month |
| Angle iron bender (JT-50) | $6k – $14k | 60 – 90 s | Medium | 200/month | ~2,500/month |
| Forming line (YFL-40) | $45k – $95k | 12 – 25 s | Low | 2,000/month | No upper limit |
| Welder + punch (custom) | $18k – $40k | 4 – 8 min | High | Non-standard only | Special sizes |
There is a genuine gap between the bender and the forming line. Between roughly 300 and 2,000 flanges per month the bender is the right machine; below that, moulds are cheaper; above that, only the forming line keeps up. Buying the line at 300 flanges a month ties up capital for no throughput gain.
Flange Quality Checks Before Dispatch
Flange defects are found on site, not in the shop, and by then the fix is a return visit. Four checks catch essentially everything.
| Check | Method | Tolerance | Consequence if missed |
|---|---|---|---|
| Inside diameter | Tape or go/no-go ring | +1 / −0 mm on tube Ø | Flange will not fit the tube |
| Flatness | Straightedge on the face | Under 1 mm over 300 mm | Gap leaks under pressure |
| Bolt hole pitch | Template or jig | ±1 mm cumulative | Bolts will not line up on site |
| Weld / joint integrity | Visual plus pull test on a sample | No visible crack | Flange opens during handling |
| Gasket seat | Visual, no burrs | Clean edge | Gasket cuts and leaks |
Keep one go/no-go ring per diameter. Checking the first and every twentieth flange takes under a minute and prevents an entire pallet going out wrong.
Planning a Flange Production Setup?
Tell us your flange size range, daily volume, and labor costs — we'll recommend the right flange production solution with detailed ROI calculation.
Get Free Flange Solution ConsultationContinue Reading: Related Guides
Go deeper on this topic, then compare the machines that do the work.
Gorelocker Elbow Machine Guide 2026
Hydraulic vs electric gorelockers: cycle time, gauge range and which elbow sizes each handles.
Read the guide → ProcessRound Flange Forming Guide
Angle ring flange production from coil: roll forming, welding and bolt-hole layout.
Read the guide → ComparisonSpiral Tubeformer Buying Guide 2026
Head-to-head comparison of PD1600, PD1200 and PD2000 — capacity, price band and ideal shop size.
Read the guide → Buying GuideAuto Duct Line Buying Guide 2026
Line 2 through Line 5 compared on labour saved, floor space and payback period.
Read the guide →Machines covered in this topic
Compare specifications, gauge range and output for the machines discussed above.
Round Flange Forming Line YFL-40
Automatic angle ring flange forming line
View specs → MachineSpiral Duct Flanger
Flanging the ends of spiral tube for joint connection
View specs → MachineSpiral Pipe Machine Band Type
Band-type mould spiral pipe forming for large diameters
View specs → MachineCNC Rotary Beading Machine RBM-1600-CNC
CNC controlled rotary beading for round duct
View specs →