"What tension should I use?" is the question we get most after "which machine". The honest answer is it depends on the package, but there are good starting points, and a two-minute test that gets you the rest of the way.
What tension is doing
Tension does two jobs: it pulls the load together so nothing can shift, and it pre-loads the strap so a bump in the truck does not go slack. It is not what holds the weight — that is the strap's break strength. So the goal is "snug enough that nothing moves", not "as tight as the tool will go".
Too tight, too loose — the signs
| Too tight | Too loose |
|---|---|
| Carton corners crushed or cut | You can slide a finger under the strap |
| Strap snaps during tensioning | Load has shifted by the time it reaches the dock |
| Weld peels (strap stretched past its limit at the joint) | Strap has gone slack overnight (PP relaxes; too little tension to begin with) |
| Bundles bow in the middle | Strap can rotate around the package |
Starting points by machine
RCV2 handheld (levels 1–10, about 450–4,500 N / 100–1,011 lbs)
| Load | Strap | Start at |
|---|---|---|
| Single-wall cartons | 1/2" PP | Level 2–3 |
| Double-wall cartons, bundles of cartons | 1/2"–5/8" PP or PET | Level 3–5 |
| Palletised cartons, crates | 5/8" PET | Level 5–7 |
| Lumber, pipe, machinery on pallets | 5/8"–3/4" PET | Level 7–10 |
Press F once (tension icon flashes), then + or –. Change one level at a time. Weld time is a separate setting — press F again — and higher tension on PET usually wants a slightly longer weld.
RCV3 tabletop and RCV9 arch (11–110 lbs)
Both are carton machines, so the range is deliberately low. Light single-wall cartons live in the bottom third; heavy double-wall cartons and bundles of printed matter in the middle. If you are at the top of the range and still want more, the package is a pallet job — use the RCV2 with PET. The RCV9 ships set at 4 on its 1–10 dial; that is the right place to start.
The three-strap test
- Strap one package at the starting level. Tug the joint hard; press the strap with your thumb. It should not move and the corners should not be dented.
- Go up one level and strap a second one. If the corners start to crush or the strap marks the box, go back down.
- Strap a third at the level you settled on, leave it overnight, and check it in the morning. PP relaxes a little in the first hours; if it is now loose, go up one level or switch to PET.
Write the number on a piece of tape on the machine. New staff will thank you.
Why PP goes slack and PET does not
PP strap stretches and slowly relaxes after tensioning — fine for cartons that ship today, a problem for a pallet that sits in the yard for a week. PET holds tension for weeks and takes far more of it. That is the real reason we say PP for cartons, PET for pallets; see PP vs PET vs steel.
Things that look like a tension problem but are not
- Strap snapping on a corner: a sharp edge, not too much tension. Use edge protectors or route the strap differently.
- Weld peeling at moderate tension: dirty strap or weld time too short. See the RCV2 troubleshooting guide.
- Strap slipping in the tool: layers not loaded parallel, or a worn tension wheel.
- Cartons crushing at low tension: the carton is under-spec for the load. No tension setting fixes a weak box.
Safety
Stand beside the strap line, never in line with it, while tensioning. A strap that snaps at 1,000 lbs of tension moves fast. Cut strap with a proper strap cutter, and cut it away from you.
If you would like us to set a starting point for a specific carton or pallet, send us a photo and the weight — it is a five-minute answer.