Common Film Blowing Machine Problems: 5 Issues I've Fixed in 30 Years

I've been in this business since 1996, and I can tell you: no film blowing machine runs perfectly forever. The good news? Most problems aren't machine defects—they're adjustments that take 10 minutes once you know what to look for.

Here are the 5 issues I get asked about most often, and what I tell customers to check first.

1. Uneven Film Thickness

This is the #1 complaint I hear.One side of the film is 40 microns, the other side is 55. The customer thinks the die is worn out and wants a new one.

What I check first:The die gap. More often than not, the gap isn't centered. I tell customers to use a feeler gauge and check 4-6 points around the die. If the gap varies by more than 0.05mm, that's your problem—not the material, not the machine.

Another common cause:Uneven cooling. If one side of the air ring is blowing harder than the other, the bubble cools asymmetrically and the film stretches unevenly. Clean your air ring outlets. I've seen machines "fixed" with a $50,000 upgrade when the real problem was dust blocking half the air holes.

2. Bubble Instability or Bursting

A stable bubble is everything in blown film extrusion. When it starts shaking or bursts randomly, production stops.

What I tell customers:** Check your nip roller pressure first. Too much pressure pinches the bubble and creates back-pressure. Too little lets the bubble wander. I usually suggest starting at 2-3 bar and adjusting in 0.5 bar increments.

The other culprit:** Tower height. If your bubble is collapsing before it reaches the frost line, either your cooling is too aggressive or your haul-off speed is too high. I've seen customers run their film blowing machine 15% faster than the material can handle, then blame the machine when the bubble breaks.

3. Vertical Lines or "Streaking"

Longitudinal streaks running down the film look ugly and make printing impossible.

Most common cause:Damaged screw or barrel. Even a small scratch on the screw flights can create dead spots where material burns or stagnates. If your streaks are consistent and in the same positions every roll, I tell customers to pull the screw and inspect it. A worn screw costs you more in scrap film than a replacement screw costs.

Second possibility:Contaminated material. If you're switching between LDPE and recycled blends without purging, residual material can degrade and cause lines. Purge for 20-30 minutes when changing materials. It's boring, but it works.

4. Winding Problems

The film looks perfect coming out of the die, but the finished roll is lopsided, has wrinkles, or telescopes off the core.

What I check:Tension. Inconsistent tension is the root cause of 80% of winding problems. I tell customers to check their tension sensor calibration every 3 months. A sensor that's off by 10% will give you rolls that look like cones instead of cylinders.

Also:Core quality. If your cardboard cores aren't perfectly round, the film will wind unevenly from the first layer. It sounds obvious, but I've seen customers spend weeks troubleshooting their film blowing machine when the real problem was cheap cores from a new supplier.

5. Hazy or Cloudy Film

The film should be crystal clear, but it's coming out milky or hazy.

First thing I ask:What's your melt temperature? If you're running too cold, the material doesn't fully fuse and you get haze. If you're running too hot, you get degradation haze. The window is usually 10-15°C wide. Check your thermocouples—I've seen machines where the display reads 180°C but the actual barrel temp is 195°C because the sensor drifted.

Second:Moisture. LDPE and LLDPE absorb moisture during storage. If your raw material has been sitting in a humid warehouse, dry it for 2-4 hours at 70-80°C before running. This is especially common for customers in coastal areas or tropical climates.

When to Repair, When to Replace

I tell customers honestly:If your machine is under 10 years old and these problems are new, it's probably an adjustment issue. If your machine is 15+ years old and you're fighting multiple problems at once, the cost of downtime might justify upgrading.

For a guide on what newer film blowing machines offer compared to older models, see our Single vs Multi-Layer Comparison. If you're dealing with recurring material cost issues, our ABA Machine Guide explains how three-layer technology can reduce raw material waste.

Jiangyin Yuexing Machinery has been troubleshooting film blowing machines since 1996. If you're stuck on a problem that isn't in this list, send me a message—I might have seen it before.

Email: ryanzhang911222@gmail.com  

WhatsApp: +86 13771616165