Clearance and Pressure on Horizontal Wrappers: What’s the Difference?

Greener’s latest “Tech Bites” video explains how proper clearance and pressure adjustments optimize horizontal flow wrapper performance.

Clearance and pressure settings on horizontal flow wrappers are critical for achieving quality packages, minimizing downtime, and controlling costs. We’ve noticed that the differences between clearance and pressure, and the proper occasions to adjust each of them, are not always clear to those making these adjustments. Greener’s latest “Tech Bites” video and blog post differentiate the function and adjustment of clearance and pressure.

Clearance—the physical dimension between the upper and lower shaft—is dictated by the height of the upper and lower crimpers while the serrations are meshed together. It should be adjusted when crimpers are initially set up and generally left unchanged. (Clearance may need to be fine-tuned when film structures or temperature settings are changed.) Knives and anvils are adjusted separately with shims or adjustment screws, depending on the crimper style.

Greener Corp._clearance and pressure adjustment

The criteria for when to adjust clearance and pressure remain the same for all wrapper makes and models. Adjustment methods, however, may vary.

Pressure refers to the spring tension between the shafts. Adjustments to pressure change the force applied by the crimper serrations to the end seal, and by the knife against the anvil. These adjustments should be made after the clearance is set. The pressure must be great enough to create a quality cut and seal at operating temperatures and speeds, but not so great that it distorts or fractures the packaging film.

Problems arise when the clearance is mistakenly adjusted in an effort to improve seal quality or get a knife to cut. The fine, incremental changes necessary in these situations are quite difficult to obtain using clearance; the resulting over-adjustment, where the shafts are brought too close together, can often be easily diagnosed by a distinct thumping sound and vibration when the upper and lower crimpers meet. In addition to degrading seal quality, over-adjusted clearance causes undue wear to the crimpers, knives, anvils, bearings, shafts, and other critical components.

Clearance and pressure adjustments are an important part of optimizing package quality and wrapper productivity, and should be taught as a basic component of operator and maintenance training.


 

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