Setting Up Sealing Jaws on Horizontal Flow Wrappers

Proper sealing jaw setup is critical for producing consistent quality packages; even slight misadjustments can damage the package and cause leaks that prevent you from meeting seal quality standards.

This Greener Tech Bite explains nine essential procedures for accurately setting up sealing jaws on horizontal flow wrappers.

1. Clean the Shafts

Begin by removing the old sealing jaws and cleaning the shafts of any product buildup.

2. Sealing Jaws

Replace all sealing jaws on a wrapper at the same time, and make sure all the jaws come from the same packaging machinery supplier.

You may be tempted to replace only one seal jaw, or just one of multiple pairs, to save time or reduce costs. But running sealing jaws with different wear levels or different designs causes inaccurate setups that create sealing problems.

3. Insert Heaters and Thermocouples

For heat seal applications, coat heaters and thermocouples with heat sink compound before inserting them in the jaws. This will fill in air gaps to improve heat transfer and sensing accuracy.

4. Install Sealing Jaws on Shafts

Install sealing jaws with new mounting bolts and washers. Wear and damage to used bolts and washers, which can easily go unnoticed, can cause inaccurate mounting and make sealing jaws difficult to remove in the future. 

 To help ensure that the jaws are accurately seated and don’t shift out of alignment, use hardened, flat washers on flat shafts and split washers on round shafts.

If possible, tighten bolts while the sealing jaws are meshed.

5. Heat the Sealing Jaws

For heat seal applications, bring the jaws to operating temperature before making adjustments.

6. Adjust Clearance

Begin by adjusting clearance, the narrow gap between the upper and lower sealing jaw serrations.

Many wrappers utilize clearance adjustment rods, as illustrated here. Some makes and models use wedges, shims, or other methods.


Rotate the sealing jaws together by hand to make sure they’re not hitting each other, and then run carbonless paper between them.  Adjust clearance just wide enough to create an interference fit for the paper—about the same thickness as a double layer of your packaging material.

Check the carbon impression to make sure that the clearance is even from end to end and adjust accordingly.

7. Adjust Serration Alignment

Also use the impression to evaluate alignment and adjust the sealing jaws as needed so that the serrations mesh properly.

Our previous post on carbon impressions diagnoses examples of misadjusted clearance, alignment, and other issues.

8. Remove Backlash

Next check for backlash, or independent movement between the upper and lower sealing jaws.

With even minor backlash, the resulting misaligned serrations can damage and split the package and reduce seal quality.

On gear-driven wrappers a split gear on the non-drive shaft is used to remove backlash. Belt and chain-driven machines utilize a tensioner. Over time, worn gears and stretched belts and chains contribute to backlash, so periodically inspect these components and replace them when needed.

Learn more about backlash from these Tech Bite posts and videos.

9. Adjust Sealing Pressure

The next step is to adjust spring pressure. On most wrappers springs are adjusted and locked to create the pressure required to seal and cut packages. Some wrappers utilize compression washers.

Springs and compression washers often go unrecognized as the source of package sealing problems. Since evaluating their condition can be difficult, it is well worth replacing them on a regular basis.

Run five to ten packages through the sealing jaws, with product if available. Cut the packages with scissors and check seal integrity using your current testing method.

Adjust spring pressure as needed to meet your seal quality standards.

If you’re not producing quality seal jaws after following these procedures, discover the problem-solving solutions on our Technical Resource Blog and contact Greener Corporation for technical support. We provide integrated parts and technical services worldwide.



Carbon Impressions

Seal Quality

Sealing Jaws

Set-Up & Adjustment

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