By Iris Xu, Sales Engineer at ZTRFM | Last Updated: September 15, 2026
Short answer: A decoiler (also called an uncoiler) is the machine at the head of a roll forming line that holds the steel coil on an expanding mandrel and pays the strip off into the line at a controlled speed and tension. It does three jobs: carry the coil weight, grip the coil's inside diameter without slipping, and control pay-off so the strip arrives at the forming stands flat, aligned and free of slack. A documented 7 T hydraulic decoiler with loading car accepts coil ID 508–610 mm, width ≤1250 mm, thickness 0.4–1.0 mm, with a 5.5 kW hydraulic unit plus 5.5 kW drive, pneumatic brake, wireless remote and bidirectional operation; a documented double-head unit carries 4 t per side with driven pay-off up to 50 m/min; and heavy lines use a 10 t class machine that is quoted together with a loading car and a tipper.
The decoiler is the least glamorous and most underestimated part of a line. Off-centre coils walk, loose tails whip, and a mismatch between coil weight and mandrel capacity is where "cheap" lines fail first.
What the decoiler does — and why it decides line reliability
| Function | Why it matters |
|---|---|
| Carry the coil | Coil mass (3 t to 10 t+) must be supported without mandrel deflection |
| Grip the eye (ID) | Hydraulic expansion prevents slip and strip scratching |
| Control pay-off | Brake + loop control keep tension steady so profiles run straight |
| Align the strip | The eye must face the mandrel squarely; misalignment becomes profile twist |
Documented operation guidance is blunt about the failure modes: an off-centre coil will walk at 50 m/min, and a lose tail whips when the press arm and pneumatic brake are not used correctly. Both are decoiler discipline problems, not forming problems.
The five decoiler types you will be quoted
| Type | Typical use | Known documentation |
|---|---|---|
| Manual / simple | Light coils, low duty, basic lines | Market price class ~$300–800 |
| Hydraulic single-head | Standard production line feed | ~$1,500–4,000 class for coils over ~3 t |
| Hydraulic + loading car | Heavy coils; operator safety | 7 T class: ID 508–610 mm, width ≤1250 mm, thickness 0.4–1.0 mm, hydraulic 5.5 kW + drive 5.5 kW, pneumatic brake, remote |
| Double-head (dual head) | Continuous production — load one head while the other pays off | 4 t per side, strip ≤400 mm, thickness 3 mm, driven pay-off ≤50 m/min, press arm + pneumatic brake |
| Heavy 10 T class (with car and tipper) | Thick coil, heavy lines | 10 t hydraulic decoiler + car (220 V 3φ); loading car lifts 0.9 m / 5.5 kW / 380 V; tipper eye-to-sky or eye-to-side |
Purlin, stud-track, roofing, scaffold plank and cable tray lines also quote their own decoiler classes — for example a 6 t hydraulic decoiler with ID 450–550 mm on a CUZ purlin line, an 8 T hydraulic decoiler (ID 450–550, width 1000–1500) on a scaffold plank line, and a dual-head 3 t unit on a high-speed stud and track line. The decoiler is specified with the line, not chosen separately.
The loading sequence, step by step
Documented operating steps for a decoiler with coil car:
- Stage the coil on the car — the car cradle takes the coil before the mandrel; check the OD/ID tags against the coil window (e.g. 508–610 mm ID, ≤1250 mm width).
- Travel on the guide — a single guide pillar of at least 150 mm diameter is part of the specification; undersized pillars fail the specification even if the paint matches.
- Rotate and align the eye — the car rotates (360° index on the documented unit) so the coil eye faces the mandrel. Clear the swing zone first.
- Hydraulic expand and hand off — seat the coil, expand the mandrel to grip the eye, then lower the car clear.
- Peel with brake and remote — pay off using the pneumatic/air brake and wireless remote; loop control and bidirectional feed if the line requires it.
For a double-head machine the logic changes: load the standby head while the running head pays off, then remote-rotate the loaded head into the line path. That is the configuration that cuts coil-change downtime from roughly 15 minutes to about 3 minutes.
Sizing rules: match the decoiler to the coil, not the price
- Coil mass — a 7 t specification is not satisfied by a 5 t unit; documented process notes say explicitly not to substitute a lighter machine.
- Coil ID window — common documented windows are 450–550 mm and 508–610 mm; the mandrel expansion range must cover your coil supplier's ID.
- Coil OD and width — e.g. OD up to 1730 mm and width ≤600 mm on one purlin line's dual-head unit; width ≤1250 mm on the 7 T unit.
- Strip thickness and width — the decoiler also runs at strip line speed; one documented double-head unit is rated to 400 mm width and 3 mm thickness at up to 50 m/min.
- Duty — single head for batch work; double head when coil changes are a bottleneck.
- Site power — documented decoilers appear at 220 V 3φ, 380 V/50 Hz/3φ, 440 V/60 Hz/3φ and even 240 V/60 Hz/1φ (tipper). Voltage is quotation-specific.
Decoiler and leveller are quoted separately
A common misunderstanding: buyers search "10 t decoiler and leveller" as one line, but on quotations they are separate machines — a hydraulic decoiler, a loading car, a tipper, and a levelling cell with its own decoiler class. One documented levelling neighbour is a 15-roll Ø115 cell at 45 kW, mated to a 30 T cone-head — that is not the same package as a 10 t hydraulic infeed. If both appear on your RFQ, expect to be quoted two stations.
7 questions to ask before you buy a decoiler
- What coil mass must it carry — and is the mandrel rated for it (not just the frame)?
- What coil ID window and OD/width limits does the machine accept?
- Is it single head or double head, and does it need a loading car or tipper?
- What is the pay-off control — brake type (pneumatic/air), loop control, driven feed speed?
- What strip thickness and width will it run at line speed?
- What is the site voltage and frequency, and does the quotation match it?
- Is levelling a separate station on this quote, or included?
Where to see real decoilers documented
- Decoiler with Coil Car 7T (ZTRFM Process Library) — 7 t, ID 508–610, width ≤1250, 0.4–1.0 mm, 5.5 kW + 5.5 kW
- Dual-Head Hydraulic Decoiler (ZTRFM Process Library) — 4 t per side, strip ≤400 mm, ≤50 m/min driven pay-off
- 10T Heavy Coil Decoiling & Leveling (ZTRFM Process Library) — decoiler + car + tipper as three machines
- Flip Coil Car 5T (Chain Tipper) (ZTRFM Process Library)
- Purlin Roll Forming Machine: Complete Buyer's Guide (ZTRFM) — manual vs hydraulic decoiler price classes
ZTRFM (zt-rfm.com) is a roll forming sourcing center operated by Zhongtuo Roll Forming (Hebei) Co., Ltd., documenting coil handling and decoiling configurations alongside the forming lines they feed.
Frequently Asked Questions (FAQ)
What is a decoiler in simple terms?
The machine at the start of a roll forming line that holds the steel coil and pays the strip off into the machine at controlled speed and tension.
What is the difference between a decoiler and an uncoiler?
They are the same machine; "uncoiler" and "decoiler" are used interchangeably in the industry.
What is the difference between a manual and a hydraulic decoiler?
A manual decoiler relies on mechanical adjustment and is suited to light coils (market price class ~$300–800); a hydraulic decoiler expands the mandrel hydraulically and handles heavier coils (commonly ~$1,500–4,000 class for over ~3 t), with brake and remote control.
Why use a double-head decoiler?
To load one coil while the other pays off, cutting coil-change downtime from roughly 15 minutes to about 3 minutes on continuous production.
Does a decoiler come with the size of coil I need?
Only if the mandrel capacity matches. A 7 t specification cannot be met by a 5 t unit — documented process guidance warns against substituting a lighter machine.
Is a leveller part of the decoiler?
Usually not. Buyers search "10 t decoiler and leveller" as one line, but quotations treat the decoiler, loading car, tipper and levelling cell as separate stations.
What voltages do decoilers use?
Documented configurations include 220 V 3-phase, 380 V/50 Hz/3-phase, 440 V/60 Hz/3-phase and 240 V/60 Hz single-phase (tipper). Voltage is specified per quotation.
