Stretch Film Wrapping Machine Drive Systems · Industrial Gearbox Engineering · Australia
Technical Specifications
Key parameters for gearboxes used in the three primary drive systems of a stretch film wrapping machine: the turntable or rotary arm drive, the film carriage elevation drive, and the pre-stretch film roller drive.
| Drive / Parameter | Typical Range | Notes |
|---|---|---|
| Turntable Speed | 3 – 15 RPM | Load-dependent; typically 8–12 RPM operational |
| Turntable Drive Torque | 50 – 800 N·m | Varies with pallet load and turntable diameter |
| Film Carriage Speed | 5 – 60 m/min vertical | Chain or lead screw drive |
| Pre-Stretch Ratio | 100 % – 300 % | Set by drive roller speed differential |
| Cycle Rate | 20 – 60+ pallets/hour | High cycle drives demand RMS torque sizing |
| IP Rating | IP54 – IP65 | Food and cold storage environments need IP65 |
The Three Drive Systems in a Stretch Wrapper
A stretch film wrapping machine uses gearboxes in three distinct motion systems, each with a different speed range, torque profile, and duty cycle. Understanding the interaction between these drives — and the consequences of a poorly specified gearbox in any one of them — is the foundation of correct stretch wrapper drive specification.
1. Turntable Drive: High Inertia, Variable Load, High Cycle Count
The turntable drive rotates the pallet while the film carriage applies the stretch film wrap. The turntable starts from rest with a full pallet load — potentially 1,000–2,000 kg on an industrial machine — accelerates to wrapping speed, maintains constant speed through the wrapping cycle, and decelerates to stop before the next pallet is loaded. This start-stop cycle repeats for every pallet, placing the turntable gear motor in a high-inertia intermittent-duty application that must be sized on RMS torque rather than running torque alone.
The acceleration torque required to bring a 1,500 kg pallet from rest to 10 RPM on a 1,400 mm diameter turntable in 1.5 seconds is: moment of inertia J = ½ × 1,500 × 0.7² = 367.5 kg·m²; angular acceleration α = (10 × 2π/60) / 1.5 = 0.698 rad/s²; acceleration torque T = J × α = 367.5 × 0.698 = 256 N·m. This acceleration torque is in addition to the running torque from turntable bearing friction and any eccentricity of the pallet load. The gearbox must deliver this combined peak torque at every start, while the RMS torque over the full cycle (including the deceleration energy returned to the drive) determines the thermal rating requirement.
A VFD-controlled gear motor is the standard for modern turntable drives. The VFD manages the acceleration and deceleration ramp, limiting the peak current and reducing the mechanical shock on the gearbox at each start. Without VFD control, direct-on-line starting produces a torque spike of 5–7× rated motor torque at every start — accumulated over hundreds of thousands of starts per year, this dramatically accelerates gear and bearing fatigue. For machines operating at 60 pallets per hour, 16 hours per day, 300 days per year, the turntable motor starts 288,000 times per year — a regime that demands VFD control and conservative service factor specification as the baseline, not a premium option.
2. Film Carriage Elevation Drive: Bidirectional, Precise Positioning
The film carriage travels up and down the mast column, applying the film in a helix pattern across the pallet height. The elevation drive is typically a worm gear motor driving a chain or lead screw, providing the combination of speed reduction, position hold at any height, and reverse capability needed for the up-down wrapping cycle. The self-locking characteristic of a worm gearbox at ratio above 30:1 holds the carriage at any height — including at the top of the mast where gravity would pull it down if the drive is not self-locking — without requiring the motor to remain energised between wrapping passes.
The elevation drive cycles through a full up-down traverse for every pallet. At 60 pallets per hour with a 1.5-metre mast and 30 m/min carriage speed, the elevation motor traverses 180 metres per hour and reverses direction 120 times per hour. RMS torque calculation for the elevation drive must account for the acceleration and deceleration phases at each direction reversal, which are frequent and brief. The worm gear motor for the elevation drive is typically 0.37–1.1 kW with a gear ratio of 30:1–60:1 on standard industrial stretch wrappers.
3. Pre-Stretch Roller Drive: Continuous Running, Precision Speed Ratio
The pre-stretch assembly uses two driven rollers running at different peripheral speeds to stretch the film before it is applied to the pallet. The speed differential between the upstream (slow) and downstream (fast) rollers determines the pre-stretch ratio: a 200% pre-stretch requires the downstream roller to run at 3× the peripheral speed of the upstream roller. This ratio must be maintained with precision — a 5% variation in the ratio produces 5% variation in film tension, which affects wrap quality and load containment. The drive for each roller is either a separate gear motor or a gearbox with two output stages at the required speed ratio, connected to the film carriage so the pre-stretch system moves with the carriage during elevation. These are continuous-running drives from the start to the end of each pallet wrap cycle, with no direction reversal — but they start and stop with every pallet and must maintain the speed ratio accurately through each start transient.
Gearbox Type Selection
Right-angle compact form; self-locking for carriage position hold; ratios 15:1–80:1 covering all standard turntable and elevation drive requirements. The default choice for both turntable and film carriage elevation drives on semi-automatic and automatic stretch wrappers below 2.2 kW. For turntable drives, the worm motor must be specified for the RMS torque at the machine cycle rate — a unit sized only on running torque will overheat at high throughput rates. VFD control is strongly recommended for all turntable drives above 30 pallets per hour.
Higher efficiency for turntable drives above 2.2 kW on high-throughput machines cycling 50+ pallets per hour. Lower heat generation extends the thermal margin on machines operating in warm environments (food processing adjacent areas, outdoor depots in Queensland summer). Must be paired with a VFD for speed control and soft starting — without VFD, the starting torque on a high-inertia pallet load would require a significantly larger motor than the continuous running torque needs.
Low-backlash inline or right-angle units; precise speed ratio maintenance for film tension control; typically 0.12–0.55 kW; carried on the film carriage and therefore subject to vibration, cyclic loading from carriage direction reversals, and the environmental conditions of the wrapping zone. Sealed bearings and IP54 minimum. On premium machines with electronically adjustable pre-stretch ratio, each roller uses an independent servo gear motor with feedback control.
RMS Torque Sizing: Why Peak Torque Is Not Enough
For a turntable gear motor cycling at 40 pallets per hour, the thermal load on the gearbox is determined by the RMS torque over the full wrapping cycle, not the peak acceleration torque. The cycle consists of acceleration (high torque, short duration), constant speed wrapping (moderate torque, longer duration), and deceleration (regenerative torque returned to the drive, or dissipated in a braking resistor).
RMS torque = √[(T²_acc × t_acc + T²_run × t_run + T²_dec × t_dec) / (t_acc + t_run + t_dec + t_dwell)]. For a typical 60-second wrap cycle with 3-second acceleration at 256 N·m, 50-second running at 60 N·m, and 5-second deceleration at 80 N·m (regenerative), and 2-second dwell: RMS = √[(256²×3 + 60²×50 + 80²×5) / 60] = √[(196,608 + 180,000 + 32,000) / 60] = √6,811 = 82.5 N·m. The gearbox continuous thermal torque rating must exceed 82.5 N·m, even though the peak torque is 256 N·m. A gearbox with 120 N·m continuous thermal rating provides adequate margin for this cycle at the specified ambient temperature.
At higher throughput rates — 60 pallets per hour, 40-second cycle — the reduced dwell time means the motor restarts before the gearbox has fully cooled from the previous cycle. The RMS torque increases toward the peak torque as the cycle time decreases, and the thermal rating must be confirmed at the actual throughput rate, not at an idealised long-dwell condition. This is the most common cause of turntable gear motor overheating on high-throughput wrapping lines in Australian distribution centres — the motor was specified for a lower throughput rate and the actual production rate later exceeded the thermal design basis.
Applications Across Australian Industries
Sourcing Stretch Wrapper Gearboxes in Australia
Stretch wrapper gearbox specifications must address: turntable drive RMS torque at the rated throughput cycle rate (not just peak); film carriage elevation drive self-locking confirmation; pre-stretch roller drive speed ratio accuracy; IP rating matched to the environment; operating temperature range (critical for cold storage); lubricant specification; VFD compatibility for turntable drives; and cycle count-based L10 bearing life at the rated throughput. For right-angle drive applications where bevel gear stages are used in the film carriage or turntable drive system, supplying accurate bevel gear load and dimensional specifications to the supplier ensures the gear mesh is correctly rated for the cyclic reversing loads of a wrapping machine drive. We supply worm gear motors and helical-bevel gear motors for stretch film wrapping machine applications across Australia. Browse configurations on our packaging machinery drive solutions page, or contact our engineering team with your throughput rate, pallet load, environment, and IP requirement for a specification within one business day.
Frequently Asked Questions
Common questions from machine builders, maintenance engineers, and packaging line managers about stretch film wrapper gearbox selection and maintenance.