What a Pneumatic TDF Bender Does
A pneumatic TDF bender — also catalogued as a pneumatic TDF folding machine or pneumatic folder — bends the fold lines on rectangular duct panels that already carry a formed TDF flange. Where a manual TDF folder depends on the operator's strength, the pneumatic version replaces that effort with air cylinders driven by shop compressed air: the panel is clamped, the folding beam is powered by the cylinder, and the fold is made in one consistent stroke. There is no electric motor and no drive train — just air.
It occupies the middle ground of the TDF folding lineup. It is faster and far more repeatable than a manual folder, yet simpler, lighter and cheaper than an electric bender. For a duct shop that already runs air tools, it is usually the most rational first powered upgrade.
How the Pneumatic System Works
The Preda pneumatic folder uses a four-cylinder arrangement: two cylinders perform the folding stroke while the other two press and hold the plate against the bed. The operator controls the raise, fold and release cycle with a foot pedal, so both hands stay on the panel. Rated supply pressure is 0.6 MPa (about 87 psi) — the same pressure class as standard pneumatic tools.
Why air instead of an electric motor
- No electrical supply beyond a simple control circuit; the machine runs off the air pump the shop already has.
- Cylinder force is inherently limited, so the bend cannot be over-forced — thin galvanized sheet is protected from cracking along the fold line.
- Maintenance is a cylinder seal kit and a valve, not a motor, gearbox or frequency drive.
The trade-off is flexibility: a pneumatic stroke is quick but not programmable, and bend angle is set by mechanical stops rather than a CNC axis. For 90° TDF corner folds — the vast majority of work — that is entirely adequate.
Model Range: Reading the WSQ Code
Preda lists the family as the WSQ series, and the model code encodes the capacity: WSQ-1.5×1020 means 1.5 mm maximum sheet thickness at 1,020 mm working width.
| Model | Bending capacity (mm) | Min. bending angle | Rated pressure | Weight |
|---|---|---|---|---|
| WSQ-1.5×1020 | 1.5 × 1020 | 80° | 0.6 MPa | 350 kg |
| WSQ-1.5×1310 | 1.5 × 1310 | 80° | 0.6 MPa | 400 kg |
| WSQ-1.5×1515 | 1.5 × 1515 | 80° | 0.6 MPa | 450 kg |
| WSQ-1.0×2000 | 1.0 × 2000 | 80° | 0.6 MPa | 550 kg |
| WSQ-0.8×2525 | 0.8 × 2525 | 80° | 0.6 MPa | 600 kg |
Read the capacity column as a product, not as two independent numbers. The same frame that folds 1.5 mm sheet over 1,020 mm is only guaranteed at 0.8 mm once the width grows to 2,525 mm. That is beam deflection in practice: the longer the span between supports, the more the bed and upper die flex under load, and the fold line drifts. Sizing a pneumatic folder is always a thickness × width decision, never a thickness decision alone.
A note on QTDF export codes
On export markets the same family is catalogued as QTDF-1.5×1300 / 1500 / 2000 / 2500, rated for 0.5–1.2 mm galvanized sheet with a 45° minimum fold angle, weights of 450–650 kg and footprints from 1,950 × 650 × 1,550 mm to 3,100 × 650 × 1,550 mm. When a quotation mixes both naming systems, compare the thickness × width capacity, the cylinder count and the die design — not the badge on the side.
Choosing the Right Width for Your Shop
Match the folding width to your largest recurring duct panel, not the largest duct you have ever quoted. A 2,500 mm folder that spends most of its life folding 1,200 mm panels costs more, weighs more and consumes more floor space for no return. The reverse mistake — buying narrow and forcing wide panels through in two passes — shows up immediately as a visible kink at the overlap of the two folds, which becomes a leak path once the duct is pressurised.
Also check flange clearance along the bed. The machine must clear the formed TDF profile across the full fold; on the Preda design the upper die is a detachable segmented die, so worn or damaged fingers can be replaced individually instead of scrapping a one-piece die.
Sizing the Air Supply
A pneumatic folder is only as consistent as the air feeding it. Three points decide whether the machine performs to spec:
- Pressure at the machine, not at the compressor. The 0.6 MPa rating must be present at the cylinder during the fold. Long or undersized hose runs and worn quick-disconnect fittings are the usual culprits when pressure sags mid-stroke.
- Filtration and regulation. A filter-regulator-lubricator unit upstream keeps moisture and scale out of the valve and seals — the cheapest reliability upgrade on the machine.
- Compressor headroom. Four cylinders cycling on a foot pedal draw more air than a small piston compressor can recover. Size the compressor for duty cycle rather than average consumption, or fold speed will fade by the fifth panel.
Throughput: Pneumatic vs Manual Folding
The honest comparison is not seconds per bend but consistency per shift. A skilled operator on a good manual folder can approach pneumatic speed on light gauge, but bend angle starts to wander as fatigue builds — and every drifted fold becomes a corner that will not close square, a rework panel, or a leak call-back on site. The pneumatic folder removes that variable: the same stroke, the same angle, panel after panel, independent of who is on the machine. For shops running more than a few boxes a day, that repeatability is the real productivity gain.
Common Faults and What They Usually Mean
| Symptom | Likely cause | First check |
|---|---|---|
| Fold angle varies panel to panel | Pressure drop or worn cylinder seals | Gauge pressure at the cylinder during the stroke |
| Sluggish or incomplete stroke | Restricted air line or sticking valve | FRL condition, hose diameter, valve exhaust |
| Crease marks on coated sheet | Damaged die surface or debris | Clean and inspect the die fingers |
| Panel slips during clamping | Worn clamp pads or low clamp pressure | Pad condition and clamp line pressure |
Factory Audit and Purchasing Checklist
- Ask for the capacity table in writing — thickness × width, never a single thickness figure.
- Confirm cylinder brand and seal-kit availability, with part numbers, before ordering.
- Verify the bed clears your TDF flange profile with a sample panel, not a drawing.
- Check the detachable die design and the price of replacement fingers.
- Watch a live fold: listen for valve chatter and watch for bed deflection on your thickest gauge.
- Confirm warranty terms (Preda offers 24 months) and that the machine ships in a wooden case on a steel chassis skid.
Frequently Asked Questions
Does a pneumatic TDF bender need electricity?
No. The power comes from the air cylinder; only a minimal control circuit is involved. The machine runs on the shop air pump alone.
What air pressure is required?
0.6 MPa rated, with a working range of roughly 0.6–0.8 MPa on the export QTDF machines. A standard tool-air supply is sufficient provided the compressor has duty-cycle headroom.
Can it fold stainless steel or aluminium?
Within the same gauge limits, yes — but always trial-fold your actual alloy and temper. Stainless work-hardens at the fold and needs a slightly wider radius allowance than galvanized sheet.
Pneumatic or electric — which should I choose?
If daily volume is modest and shop air is already in place, pneumatic is the lower-cost, lower-maintenance choice. Move to electric only when you need programmable bend angles or cycle rates a single pneumatic stroke cannot reach.