Adjusting Backlash to Improve Quality and Performance

The first video in Greener Corporation’s “Tech Bites” series explains how adjusting backlash on horizontal flow wrappers helps prevent problems such as fractured end seals and premature failure of knives and anvils.


Loose play between the upper and lower crimpers on horizontal flow wrappers, known as backlash, can cause problems with seal quality and packaging line performance. Backlash can build up gradually, unnoticed, and is often diagnosed only when it causes the crimper serrations to pinch the packaging film and fracture the end seals. Left unchecked, this condition will also damage the crimpers.

There is good reason to look for and adjust even minor backlash. By causing the knife to swipe across the anvil, or leave inconsistent impressions (see photo below), it can lead to premature knife and anvil failure. Backlash can also be a hidden cause of inconsistent and inferior seal quality.

Greener Corp. anvil Impression showing backlash Greener Corp. sealing head backlash

On gear-driven sealing heads, a split gear on the non-drive shaft is used to adjust backlash. On chain-driven machines backlash is adjusted with a chain tensioner. Over time gears wear and chains stretch, so in either case these components should be periodically inspected and replaced when needed.

Inspect for and adjust backlash as part of your regular checklist when setting up crimpers, knives, or anvils, as well as when troubleshooting. Be sure to adjust the clearance between the jaws first, since this influences backlash by changing the physical dimension between the crimpers.

By regularly monitoring and adjusting backlash, you will help maintain consistent seal quality, reduce downtime, and reduce parts costs for crimpers, knives, and anvils.




Knives and Anvils


Sealing Jaws


Set-Up & Adjustment


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