The Shrink Process How shrink works The essential ingredients of a great seal Time Temperature Pressure The #1 enemy of great seals- film tension The roles of: Proper bag sizing Air evacuation/perfing Proper tunnel choice Film tracking- system setup Film tension- sources, detection Equipment maintenance Product orientation The effects of product properties such as temperature, color, weight, texture

Tunnel Basics The job of a tunnel is to impart sufficient energy to the film for it to begin shrinking causing the envelope/bag to “balloon” and then collapse snugly around the product. Ballooning is not caused by the air inside the bag expanding. Rather it is the result of the shrinking film trapping the air already present in the bag and only letting it escape through the perforations. Air flow- Both air flow and temperature are critical elements of good shrink. Olefin films generally require large amounts of turbulent air impacting the package while polyethylenes require high temperatures and very little air movement in the tunnel.

Product Considerations Weight- very light or very heavy Fragility- tendency to curl or crush Color- black or highly reflective Stability- tendency to shingle or fall over Shape- regular or oddly-shaped Voids/bridging- film does not touch product Temperature sensitivity- eg. Chocolate, vinyl, aerosol cans. Surface characteristics-smooth, tacky, etc- film sticks to the surface or slides easily across it. Importance of appearance Purely functional- appearance is not important Point-of-purchase- typical retail look Extremely important, no imperfections allowed, precise seam placement critical Desired rate- fast or slow < 1 ounce Super critical appearance Oddly shaped 6.5 pounds Heat sensitive Film bridging/voids

Film Considerations Polyolefin Polyethylene- based Polypropylene- based Shrink polyethylene PVC Plain or pre-perfed High or low shrink force Light or heavy gauge Shrink %- ease of clean up

Other Factors Bag size relative to product size- Bag must be large enough to allow the film to balloon away from the product and shrink so that, during collapse, contact with the product does not stop the shrink prematurely. Tall products require very large bags- resulting in significant dog ears Amount of perforation- Letting the air out too fast does not let the film shrink completely resulting in wrinkles, crows feet, fish eyes Letting the air out too slowly causes bubbles and potential burn outs Placement of perforations- controlling which part of the bag retains the air longest can help control the shrink-eg. in the dog ears Hole punch typically used with heavier films Adjustable perforating wheels

Common Shrink Problems Crows feet Fish eyes Cloudy near burnout Burn out Dog ears Pin holes in seal

Ballooning/Bag Sizing 25” 25” W=10” L=10” H=10”