What a TDC Flange Forming Machine Does
A TDC flange forming machine roll-forms the TDC (Transverse Duct Connector) profile onto the edge of galvanized coil or blanked strip. In the Preda lineup the machine is a compact line: a coil decoiler feeds the roll-forming main body, and an integrated cutting section cuts the formed flange to length with a small burr and no secondary operation. The output is a continuous flange strip that replaces the angle-iron frame on rectangular duct.
Why it matters commercially: the TDC connection is the strongest of the standard rectangular duct joints. Panels lock at the corners with TDC/G clips and bolt together over a gasket, so the joint stays square and air-tight on large cross-sections and higher-pressure systems, where a cleat-and-gasket TDF joint would flex.
TDC vs TDF: Choosing the Connection System
TDF and TDC solve the same problem — eliminating the welded angle-iron frame — with different corner hardware. The choice drives which machines a shop buys.
| Aspect | TDF connection | TDC connection |
|---|---|---|
| Corner hardware | Cleats locked over the flange | TDC/G clips, bolted through the flange |
| Assembly | Cleat plus gasket, no bolts | Clip, bolts and gasket |
| Joint strength | Standard commercial duty | Higher — large cross-section and high-pressure duct |
| Flange heights | ~20–37 mm class | 20 / 25 / 30 / 35 / 40 mm |
| Flange production | Flange former on each panel edge | Continuous TDC line direct from coil |
| Best fit | Light to medium rectangular duct | Trunk duct, industrial ventilation |
If your work is mainly commercial rectangular duct at standard pressure, TDF tooling is faster per panel. If you fabricate large trunk sections or industrial systems where joint rigidity and sealing class are specified, the TDC line pays for itself in joint quality and assembly time.
How the Line Works
The machine has three sections. The decoiler pays off the coil and feeds it straight into the forming station — the flange strip needs no separate blanking step. The roll-forming main body progressively shapes the TDC profile through a series of roller stations; flange height is fixed by the tooling at 20, 25, 30, 35 or 40 mm, with optional grooves. The cutting section — grinding-wheel cutting or keep-cutting depending on configuration — cuts the formed strip to length automatically and leaves a small burr.
Working speed is 5–7 m/min. That sounds modest next to a TDF flange former at 8–12 m/min, but the comparison is misleading: the TDC line produces finished flange strip continuously from coil, while a flange former processes panel by panel. For flange-strip consumption, continuous coil feeding usually wins on labour alone.
PDT Model Range: 20 to 40
The PDT number is the flange height in millimetres. That single dimension drives everything else — thickness capability, power and frame size.
| Model | Flange height (mm) | Sheet thickness (mm) | Power (kW) | Weight (kg) | L × W × H (mm) |
|---|---|---|---|---|---|
| PDT-20 | 20 | 0.8 | 3 | 2000 | 2800 × 600 × 1150 |
| PDT-30 | 30 | 1.0 | 3 | 2200 | 3000 × 600 × 1150 |
| PDT-35 | 35 | 1.0 | 3 | 3000 | 3200 × 600 × 1200 |
| PDT-40 | 40 | 1.2 | 4 | 3000 | 3200 × 600 × 1200 |
How to pick the flange height
Match the height to your duct size and pressure class, not to the biggest number available. A 20 mm flange suits smaller branch ducts; 30–35 mm is the general-purpose range for trunk duct; 40 mm with 1.2 mm capability is the heavy class for large cross-sections. Taller flange also means more clip and bolt hardware per joint, so oversizing raises consumable cost on every duct you build.
Roll Tooling and Frame Construction
The forming rollers are made from 9CrSi and GCr15 steel, quenched and blackened. That matters: the roller grooves see continuous abrasion from the galvanized coating, and a soft roller wears out of profile within months, drifting flange height along the strip. Quenched tool-steel rollers hold the profile for years and can be re-ground rather than replaced.
The body uses welded steel plate construction, stress-relieved to remove welding stress before machining. Frame rigidity is not a marketing point here — roll forming is a continuous process, and any frame flex shows up directly as flange-height variation that no downstream adjustment can correct.
Throughput and Line Balance
At 5–7 m/min a PDT machine produces roughly 300–400 m of flange strip per running hour. Balance that against corner-clip and punching capacity: the line is designed to work with a 40T series punching machine and TDC/G clip corner molds, and the whole cell — line, puncher, corner tools — should be sized together. A fast flange line feeding a slow corner station simply moves the bottleneck.
Acceptance and Inspection Checklist
- Flange height constant along the full strip — measure both ends and the middle of a 3 m sample.
- Cut-length accuracy and burr size at the cutting section; the burr should be small enough to handle safely.
- Roller material and hardness certificates — ask for the steel grade (9CrSi / GCr15) and quench spec in writing.
- Run a full coil at rated speed: listen for roller knock or bearing heat, and check the decoiler pays off without tension spikes.
- Corner fit — assemble a sample duct with your actual TDC/G clips and check squareness and gasket compression.
- Confirm matching hardware supply — corner molds, clips and bolts — so the line is not idled waiting for consumables.
Common Faults and Usual Causes
| Symptom | Likely cause |
|---|---|
| Flange height drifts along the strip | Roller wear or frame flex — check roller profile and stand alignment |
| Strip edge cracks | Roll gap too tight for the gauge — reduce reduction per pass or change coil |
| Cut length varies | Cutting-section encoder or blade wear — recalibrate the length setting |
| Coil feeds unevenly | Decoiler tension or brake setting — check payout and straightening |
Frequently Asked Questions
What is the difference between TDF and TDC flange?
TDF panels lock with cleats over a gasket; TDC joints use bolted TDC/G clips. TDC is the stronger, more rigid connection and is preferred for large cross-section and higher-pressure ductwork.
Can one shop run both systems?
Yes — many shops run a TDF line for standard rectangular duct and a TDC line for heavy trunk work. Tooling, clips and corner hardware differ, so plan floor space and consumables for both.
What gauge can a PDT machine form?
0.8 mm on the PDT-20 up to 1.2 mm on the PDT-40. Always trial-run your actual coil — coating thickness and temper affect the formed edge quality.
Does the machine need a separate blanking press?
No. The flange strip is formed and cut continuously from coil. Blanking presses are still needed for the duct panels themselves, but not for the flange.