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Tips for Trimming the PVB Interlayer

Tips for operating and maintaining your glass laminating assembly line

Written by: Billco Manufacturing Service Department

To maximize your laminating line production and protect the emitters, proper PVB trimming techniques should be used. If trimming of the interlayer is not done properly, the result can be damaging to the oven emitters, press rollers, and conveyor rollers in the heat and press sections. Improper trimming can also cause delays in the overall production and quality of the finished laminates coming off the line. Here are some tips on navigating common issues when trimming the PVB interlayer:

LEAVING TOO LITTLE INTERLAYER – This can cause a condition called “snap back” where the interlayer edge will shrink to a point where it is actually behind the glass edge. This will result in a laminate that will not seal, therefore allowing air to seep between the glass and the interlayer during autoclaving. The final result is air bubbles along the edge, improper sealing of the glass to eh interlayer material, and ultimately rejection of the laminate after autoclaving.

LEAVING TOO MUCH INTERLAYER  – This will cause too much PVB to hang over the edge and will cause melting of the interlayer in the laminating ovens. When the excess interlayer melts in the ovens, it will drip onto the heating elements, conveyor rolls and press rolls. This can cause serious and costly problems to the equipment, reduced production and possibly poor quality laminates. Here are three examples of how dripping PVB can cause issues:

  • PVB Dripping onto the Heating Elements in the Ovens – PVB will cause uneven heating by the elements, and eventually require costly and time consuming cleaning or replacement of the elements.
  • PVB Dripping onto the Conveyor Rolls in the Ovens – The melted PVB on the roll will get transferred to the glass surfaces as the glass passes over the rollers. It will then be necessary for operators a the unload end of the laminating line to scrape and clean these marks off prior to loading the laminates on the racks for autoclaving. It will also be necessary to stop the line conveyor and clean the dried PVB drips off the rollers.
  • PVB Marks Tracking on the Press Rolls – When PVB gets on the Press Rolls, the consequences are similar to the Conveyor Rolls however the marks become even more compressed and difficult to remove. Cleaning the Press Rolls is also a laborious and possibly dangerous process if proper safety procedures are not followed.

How much PVB should be left sticking out past the glass edge after trimming? A rule of thumb in the industry is no more than 5mm (0.197”), however it is best to consult with your PVB interlayer supplier for their recommendation.

If you have any questions, please contact the Billco Service Department at 724.452.7390 or

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