Silage Stretch Film Width and Pre-Stretch Ratio Explained
Silage stretch film comes in three standard widths—250 mm, 500 mm, and 750 mm—at thicknesses of 17 µm, 25 µm, and 30 µm. Most round bale wrappers in 2026 run 500 mm or 750 mm film with a 50–70% pre-stretch ratio. Wider film (750 mm) finishes a bale in fewer rotations, while 500 mm film gives finer overlap control and is the standard for double-roll wrappers like the 4QM-1200, which runs two 500 mm rolls at 50% pre-stretch.
This article covers film width selection, pre-stretch mechanics, and the trade-off between single 750 mm wrappers and double 500 mm wrappers like the 4QM-1200.
Standard Silage Film Widths
| Width | Typical Use | Wrappers | Примечания |
|---|---|---|---|
| 250 mm | Small square bales, mini round bales | Small square bale wrappers, hobby-farm units | Low film cost per bale; multiple passes needed for round bales |
| 500 mm | Standard round bales (Φ900–1200 mm) | Single and double-roll round bale wrappers | Industry default; balanced overlap control and wrap time |
| 750 mm | Large round bales (Φ1200–1500 mm), high-throughput operations | High-speed single-roll wrappers | Faster wrapping; coarser overlap; less common in compact wrappers |
For a Φ1000 × 850 mm round bale—the most common size worldwide—500 mm film is the practical sweet spot. It produces a 50% overlap with every rotation and runs on virtually all mid-range wrappers.
What Is Pre-Stretch Ratio?
Pre-stretch ratio is the percentage the film is stretched between the dispenser and the bale. A 50% pre-stretch means a 1-meter length of film becomes 1.5 meters when applied—thinning the film from 25 µm to roughly 17 µm in the stretched zone.
Pre-stretch serves three purposes:
- Improves cling. Stretched film conforms tightly to the bale surface and self-adheres at overlap points, eliminating the need for glue.
- Reduces film cost per bale. A 1500 m roll at 50% pre-stretch covers 2250 m of bale surface—the same roll at 0% pre-stretch covers only 1500 m.
- Thins weak spots. Microscopic variations in film thickness are evened out during stretching, producing a more uniform barrier.
Pre-Stretch Ratio Comparison: 50% vs 70%
| Pre-Stretch | Bale Coverage per Roll (1500 m × 500 mm) | Effective Film Thickness (from 25 µm) | Bale Seal Quality | Tear Risk |
|---|---|---|---|---|
| 0% (no stretch) | 750 m² | 25 µm | Loose cling, low conformity | Низкий |
| 50% | 1125 m² | ~17 µm | Tight, conforming, standard | Низкий |
| 70% | 1275 m² | ~15 µm | Very tight, optimal for stemmy forage | Medium (over-stretched tears) |
| 100% | 1500 m² | ~12.5 µm | Theoretical max; rarely used in practice | High (film brittle) |
50% is the recommended default for most operations. 70% pre-stretch gives 12–15% more bale coverage per roll but increases the risk of micro-tears on stemmy forage like mature alfalfa or sorghum. Stay at 50% unless your wrapper is calibrated for 70% and your forage is fine-stemmed.
Double 500 mm Rolls vs Single 750 mm Roll
The 4QM-1200 silage wrapper runs two 500 mm film rolls simultaneously—an alternative design to the more common single 750 mm wrapper. Each has trade-offs:
| Feature | Single 750 mm Wrapper | Double 500 mm (4QM-1200) |
|---|---|---|
| Wrap time per bale (6 layers) | ~80–100 seconds | ~60–80 seconds |
| Film control | Coarser overlap; one dispenser | Finer overlap; two dispensers balance film tension |
| Film replacement frequency | 1 roll change per ~40 bales | 2 simultaneous rolls, change at the same time |
| Best for bale size | Φ1200–1500 mm large bales | Φ900–1100 mm standard bales |
| Mechanism complexity | Simpler; one pre-stretch gear set | Slightly more complex; two pre-stretch gear sets |
| Seal uniformity | Good, but one-sided tension | Excellent; balanced tension from both sides |
For most Φ900–1100 mm round bales, the double 500 mm design is faster and produces a tighter seal because two film dispensers apply layers simultaneously from both sides, balancing the pulling force on the bale. The 4QM-1200 finishes a 6-layer bale in 60–80 seconds—about 20% faster than comparable single 750 mm wrappers.
How to Choose the Right Film for Your Wrapper
- Check your wrapper’s maximum roll width. The 4QM-1200 accepts 500 mm rolls; loading a 750 mm roll will not fit. Most single-roll wrappers in this class accept either 500 or 750 mm.
- Match film thickness to forage type. 25 µm is the universal standard. Use 30 µm only for very stemmy or abrasive forages; 17 µm is reserved for low-stress bales under 350 kg.
- Buy UV-stabilized film. All silage film should be rated for at least 12 months of outdoor UV exposure. Cheap non-UV film fails in 3–6 months.
- Stick with one color per batch. Mixing white and green film in the same bale is acceptable, but inconsistent film lots can produce different cling and stretch characteristics.
- Store rolls indoors. Heat and direct sunlight degrade film before it’s even used. Keep rolls in a shaded, dry area between seasons.
FAQs on Silage Stretch Film
What width is silage stretch film?
Standard silage stretch film widths are 250 mm, 500 mm, and 750 mm. 500 mm is the most common for round bale wrappers like the 4QM-1200.
What is the best pre-stretch ratio for silage film?
50% pre-stretch is the industry standard—balancing seal quality, film economy, and tear resistance. Use 70% only for fine-stemmed forage on calibrated wrappers.
Is 25 µm or 30 µm silage film better?
25 µm is the universal standard. 30 µm is slightly more puncture-resistant but costs more per meter; in most operations, an extra layer of 25 µm outperforms thicker film.
Can I use 750 mm film in a 500 mm wrapper?
No. The 4QM-1200 and most 500 mm wrappers have a fixed roll holder and pre-stretch gear sized for 500 mm film. Use 750 mm film only in wrappers rated for it.
How long does silage stretch film last in storage?
Properly stored rolls (dry, shaded, <30°C) keep 18–24 months. UV-degraded film loses 30–50% of its barrier performance and should be discarded.
Run 500 mm Film at 50% Pre-Stretch on the 4QM-1200
The обмотчик силоса 4QM-1200 is built around two 500 mm stretch film rolls running at 50% pre-stretch—the most efficient combination for Φ900–1100 mm round bales. Its 12 V electro-hydraulic control lets operators dial in 4, 6, or 8 layers with a single button press. The wrapper mounts on any 90 HP tractor with a 3-point hitch and a 30 L/min hydraulic remote. Pair it with the пресс-подборщик и упаковщик силоса for a one-pass cut-bale-wrap line. Factory pricing: USD 3,500–5,800 FOB. WhatsApp: +86 136 7368 9272.