This image shows how the print plates work on the printing press
July 31, 2017 Uncategorized No Comments

Print plates are a one time added cost when purchasing custom polybags. Once print plates are made, they can be used over and over again with no added fee (plates do wear over time but typically plates last at least 20+ runs). How are print plate costs determined? Why do some prints with seemingly small coverage have more costly plate fees than expected? Why can’t plates be used for any size bag? What are things to look for in trying to save money on print plates? Before we attempt to answer these questions, we will first provide a brief explanation of the print process.

Print Process: Print plates are made using photo-polymer flexible material. Once made, print plates are mounted on the appropriate sized cylinders (or sleeves) corresponding to the desired width of the bag. The cylinders are then loaded into a flexographic printing press. As the polyethylene material moves through the print press,  the plates pick-up ink and apply it to the poly (see pictorial). The rolls of printed poly are then moved to the bag-making machine for custom bag manufacturing.

How are print plate costs determined? Print plate costs are directly related to the amount of polymer needed to make the plates. Each color has its own cylinder and its own plate. (5 color print will be mounted on 5 separate cylinders and have 5 plates). Cylinders are used over and over again for various jobs. The plates mounted to the cylinders creates the print on the bag. Each plate is made as a full step and repeat (for widths under 13″) “wrap” of the cylinder in order to maximize quality and limit waste. Key to understanding “full wrap” of a cylinder is knowing we do not carry any cylinders smaller than 13″. Print presses are not made to accept small cylinders. Larger cylinders also allow multiple width repeats on one common cylinder size (a 16″ cylinder can make a 2″ wide bag (8 around), a 4″ wide bag (4 around), an 8″ wide bag (2 around) or a 16″ wide bag (1 around)). In each case, a plate is made to fully wrap the cylinder and the width will determine the number of impressions on the plate. Knowing the width of the bag and the length of the print will allow a determination of the photo-polymer needed to make the plate(s).

Why do small print coverage at times result in seemingly high plate costs? As mentioned in the previous question, we step and repeat all prints to a full wrap of the appropriate cylinder for best quality and less waste. For example, a 5″ wide bag will have plates stepped and repeated to the smallest cylinder we stock that fits a multiple of the width: 15″. The 5″ wide bag will have a three-impression plate made to allow a full 15″ wrap around the cylinder. One revolution of the cylinder will create three impressions on the poly. Each color has its own cylinder and own plate. A 5×10 bag with a 3×3 print size on 1 side of the bag will translate to a 15×6 plate size per color (full wrap of the 15″ cylinder plus 1.5″ on each side of the length for relief). In this example, a 9 square inch (3×3) print size translates to a 90 square inch (15×6) plate size.

Why can’t plates be used for any size bag? The previous questions outline the process of “full wrap” plates around cylinders based on width. Each width will have plates specific to the cylinder it will run on. Each width will have its own print plates. Two scenarios allow for sharing of plates. First is when bags have the same width. Second is when widths are over 13″.

How do save money with regard to plates? Most prints are custom and it is difficult at times to change the look and feel of the desired appearance but here are a few things to keep in mind as art is developed.

  • Less print coverage will result in less cost. (on a 15×15 bag, 5×5 coverage will result in far less plate costs than 14×14 coverage)
  • Each color has its own plate so less number of colors will have less cost.
  • For multiple variety prints,  maximizing common plates for all varieties will save plate costs
  • Sharing plates for common widths under 13″
  • Widths over 13″ can share plates

Thanks for reading!!

Written by Trent Romer