Airtac SEJ Adjustable Cylinder SEJ125X80-20S
The AirTAC Airtac SEJ Adjustable Cylinder SEJ125X80-20S is a genuine double-acting ISO 15552 double-rod cylinder with a mechanically ADJUSTABLE stroke: a back-rod stop screw lets you fine-tune the retract end over a 20mm window, so this Ø125mm unit covers an effective stroke of 60–80mm without changing cylinders. Force is equal in both directions.
- BoreØ125 mm
- Nominal stroke80 mm
- Adjust window20 mm
- Effective stroke60–80 mm
- Port sizePT1/2
- CushionAdjustable, 40 mm
About the Airtac SEJ Adjustable Cylinder SEJ125X80-20S
The AirTAC SEJ125X80-20S is a double-acting, double-rod ISO 15552 profile cylinder featuring an adjustable retract stroke. A rod exits both ends, yielding identical annulus areas so the drive force is equal in both directions at 5734 N each way at 0.5 MPa. The integrated -20 stop screw on the back rod lets you dial the retract end position over a 20 mm window, giving an effective stroke range of 60 to 80 mm.
This 125 mm bore pneumatic cylinder includes a magnet for position sensing and uses a PT1/2 port. The extruded aluminum barrel contains no external tie rods, and field-adjustable air cushions at both ends decelerate the heavy 1169 kgf maximum load near stroke end without acting as a mechanical lock.
Airtac SEJ Adjustable Cylinder SEJ125X80-20S Technical Specifications
| Model | Airtac SEJ Adjustable Cylinder SEJ125X80-20S |
|---|---|
| Series | SEJ ISO 15552 adjustable-stroke cylinder |
| Bore size | Ø125 mm |
| Nominal stroke | 80 mm |
| Adjustment window | 20 mm (60–80 mm) |
| Configuration | Double rod, double acting |
| Port size | PT1/2 |
| Rod thread | M27×2 |
|---|---|
| Operating pressure | 0.15 – 1.0 MPa |
| Proof pressure | 1.5 MPa |
| Temperature | -20 to +70 °C (0–150 °C with FKM seals) |
| Speed range | 30 – 500 mm/s |
| Cushion | Adjustable, 40 mm |
Specifications follow the official AirTAC SEJ datasheet and ISO 15552 / VDMA 24562 dimensions. The adjustment screw shortens the retract end only; do not exceed the 20mm window. Port options: PT (standard) / G (BSPP).
Theoretical Output Force (Ø125mm)
| Pressure | Force (both directions) |
|---|---|
| 0.5 MPa | 5734 N |
| 0.7 MPa | 8027 N |
| Max (@1.0 MPa) | 1169 kgf |
A rod exits both ends, so extend and retract force are identical. Actual usable force is lower than theoretical; size with a safety margin.
Model Code: Airtac SEJ Adjustable Cylinder SEJ125X80-20S
| SEJ | ISO 15552 double-rod double-acting cylinder with adjustable stroke. |
|---|---|
| 125 | Bore size in mm. |
| ×80 | Nominal stroke length in mm. |
| -20 | Adjustment stroke window in mm (options: 10/20/30/40/50/75/100). |
| -S | Optional built-in magnet for CMSE / DMSE sensor sensing. |
Rod material: carbon steel (blank) / SUS420J2 (A) / SUS304 (B). Seals: TPU (blank) / FKM high-temp (H) / NBR (N). Thread: PT (blank) / G. Mounting (SEJ): Basic, LB, FA, TC, FTC, TCM1, TCM2. Related: SED (double rod, fixed stroke), SE (single rod).
Where the Airtac SEJ Adjustable Cylinder SEJ125X80-20S Is Used
Heavy Press Tonnage Calibration
Dial in the exact 60-80 mm bottoming position during stamping press setup, utilizing the 5734 N both-way force to firmly seat heavy dies without reconfiguring hardware.
Automated Pallet Changeover
Adjust the retract stop on the fly to match varying pallet thicknesses in CNC machining centers, using the equal double-rod force to smoothly shift heavy 125 mm bore loads.
Injection Mold Ejection Tuning
Fine-tune the ejection stroke window during commissioning to prevent mold damage, leveraging the 1169 kgf max capacity and 40 mm adjustable air cushions to arrest high-momentum plastic ejection.
Is the Airtac SEJ Adjustable Cylinder SEJ125X80-20S the Right Cylinder?
Confirm the 20 mm adjustment window covers your exact end-position tuning needs for this 125 mm bore cylinder, providing an effective 60-80 mm stroke. If sizing force, this model outputs 5734 N both ways at 0.5 MPa. Stepping down to the 100 mm bore yields 3681 N both ways, while no larger standard SEJ bore exists. If fixed end positions are sufficient and you do not need field adjustment, a standard SED double-rod cylinder is enough. For drop-in ISO 15552 replacements, match the 80 mm stroke, 20 mm window, PT1/2 port, and desired mounting from the SEJ set (Basic, FA, LB, TC, FTC, TCM1, TCM2). Remember that a plain SEJ does not hold position on air loss; the adjustable cushion only decelerates near stroke end, so specify an external rod lock for fail-safe holding.
Quick checklist
- ✓ Need on-machine stroke fine-tuning?
- ✓ Adjustment window (20mm) covers your range
- ✓ Equal force both directions OK
- ✓ Port/thread type (PT/G)
- ✓ Magnet (-S) for CMSE/DMSE sensors?
Installation & Maintenance Notes
- check Use clean air filtered to 40µm or finer.
- check Keep within 0.15 – 1.0 MPa operating pressure.
- check Set the stop screw within the 20mm window; lock it after adjusting.
- check Adjust end cushion screws for smooth stops.
- check Use correct mounting accessory (LB/FA/TC/FTC/TCM1/TCM2).
- check Installation by qualified personnel per AirTAC docs.
Airtac SEJ Adjustable Cylinder SEJ125X80-20S FAQ
A mechanical stop screw on the rear rod lets you dial the retract end position over a 20 mm window. This shortens the nominal 80 mm stroke down to a minimum of 60 mm, giving an effective stroke range of 60-80 mm. You lock the screw after setting the exact end position.
Because it is a double-rod cylinder, the force is identical in both directions: 5734 N at 0.5 MPa, 8028 N at 0.7 MPa, and a maximum of 1169 kgf at 1.0 MPa.
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