A corner crimper for aluminium window and door fabrication usually works with around 6 bar at its inlet, sometimes a little more depending on the model: the exact value is in its manual. What matters most is that this pressure stays stable during crimping, because the press force is directly proportional to it. A compressor set to 7 or 8 bar, with a regulator at the machine, ensures evenly crimped corners.
The crimper is only one of the stations in an aluminium window shop. Our page on the compressor for PVC and aluminium window fabrication covers all the machines; here, we deal with the presses: corner crimper, copy router and punch presses.
Why does pressure matter so much on a crimper?
A corner crimper assembles aluminium frames: the two profiles cut at 45° are fitted onto a corner cleat, then knives deform the profile wall to lock the cleat in place. It is this deformation that holds the corner for the whole life of the window or door.
The force of the knives comes from a pneumatic cylinder, or from an air-hydraulic booster on more powerful machines. In both cases, the force is the product of the pressure and the piston area:
force = pressure × piston area
Example, as a rough guide, with a 100 mm diameter cylinder:
- piston area: 3.14 × 5 × 5 = 78.5 cm²;
- at 6 bar, each cm² receives about 6 kg of force: 78.5 × 6 ≈ 470 kg;
- at 5 bar: 78.5 × 5 ≈ 390 kg, or 17% less force.
An air-hydraulic booster amplifies this force, but it amplifies the loss too: a 1 bar drop at the inlet still costs about one sixth of the crimping force. The corner is then less tight, the frame may move, and the defect only shows at installation or after a few seasons.
What pressure should you set for a corner crimper?
Read the manual: it gives the supply pressure, often around 6 bar, and sometimes the range within which the machine guarantees its rated force. Then:
- Set the compressor above this value, adding about 1 bar for losses through the dryer, the filters and the pipework: 7 to 8 bar in most workshops.
- Fit a regulator with a pressure gauge at the crimper inlet, set to the value in the manual. The machine then always receives the same pressure, whatever the compressor's load state.
- Check the pressure during a crimp, not at rest, at a moment when the corner cleaner or the saw is also running. That is when you see whether the network keeps up.
If your manual asks for more, for example 8 bar at the inlet, the compressor must be set to around 9 to 10 bar. The K 75 is available in a 10 bar version: it then delivers 0.95 m³/min. Our article on how to calculate the pressure of a compressor explains this margin in detail.
How much air does a crimper use?
Little, on average. On each stroke a cylinder uses the volume of its chamber, multiplied by the absolute pressure:
- cylinder of 100 mm diameter and 100 mm stroke: 78.5 cm² × 10 cm = 785 cm³, or 0.785 litre;
- at 6 bar, the absolute pressure is 7 bar: 0.785 × 7 ≈ 5.5 litres of free air per outstroke;
- out and back: about 11 litres per stroke.
With 30 frames per hour, 4 corners per frame and one stroke per corner, that gives 120 strokes, or 1,320 litres per hour, or 22 l/min. Even doubling it for the clamping cylinders and an air-hydraulic booster, you stay at around 50 to 100 l/min. Our article on the air consumption of a pneumatic cylinder sets out this calculation.
So the crimper is almost never what sizes the compressor. It is, however, the machine most sensitive to a drop in pressure.
What about the copy router and punch presses?
The copy router machines the lock, espagnolette and drainage recesses in aluminium profiles. Punch presses with dedicated tooling cut repetitive shapes in a single stroke. Both work on the same principle as the crimper: a cylinder, sometimes air-hydraulic, whose force depends on the pressure.
As a rough guide, a copy router uses around 30 to 60 l/min. Too low a pressure does not give a weaker punch but an incomplete one: burrs, a cut that does not go through, a tool that strains. The same rules apply: the pressure in the manual, a regulator at the machine, a check during production.
The step-by-step calculation for an aluminium workshop
Take an aluminium workshop with four operators: a double mitre saw, a corner crimper, a copy router, a screwdriver and a blow gun.
- Double mitre saw, continuous: 150 l/min.
- Crimper, intermittent, counted at half: 80 ÷ 2 = 40 l/min.
- Copy router, intermittent, counted at half: 50 ÷ 2 = 25 l/min.
- Screwdriver and blow gun, intermittent, counted at half: 100 + 75 = 175 l/min. With four operators, keep the four hungriest stations: saw, screwdriver, blow gun and crimper.
- Subtotal: 150 + 100 + 75 + 40 = 365 l/min.
- Margins of 25% then 20%, as in our configurator: 365 × 1.25 × 1.2 = 548 l/min, or about 0.55 m³/min (around 19 CFM).
The K 75, with 1.1 m³/min at 8 bar, covers this need with a large reserve, and includes the dryer and filtration. For a small manufacture-and-install business that only crimps a few hours a week, a piston compressor such as the E 75, offered on quote in 8 or 12.5 bar with a 180 L air receiver, remains an option. As soon as there is a profile machining centre or a complete line, the K 110 takes over.
The pitfalls to avoid with presses
- A hose to the crimper that is too narrow. The pressure drops during the stroke, just when the force is needed. The pressure drop calculator checks the diameter.
- No regulator. Without one, the force varies with the compressor's cycle.
- Water in the cylinders. It wears them and makes movements jerky. A refrigerated dryer at the compressor outlet removes it.
- Raising the compressor to 10 bar to compensate. If a press lacks force, check the network and the regulator first. Raising the pressure everywhere costs you in electricity and leaks.
To choose your compressor, run the calculation with the configurator or send us your crimper's manual with a quote request.
For your trade: Compressor for PVC and aluminium window fabrication.