Already used for some cheese products, in-mold labeling is poised for more domestic dairy applications

Consumers are noticing a new style of packaging that is appearing on store shelves around the country. It is in-mold label (IML) decoration on injection molded containers and lids. The high resolution graphics that are a signature of IML are improving the looks of many products in grocery stores, and more are arriving on shelves everyday. IML is a manufacturing process where a label is inserted into a plastic molding machine; the container is then formed, and out of the mold is born a finished decorated container! This amazing process is only possible with close coordination between the five elements of the IML package: container design, the mold tool, the molding machine, label insertion automation and precision label manufacture. Each of these elements is vital to successfully manufacturing containers and lids that are functional as well as beautiful.

IML containers are quite common in Europe. The dairy case in a typical EU grocery store will have a variety of products that are in thin IML decorated containers. Plastic molders in Europe have been typically molding containers in lower numbers than domestic markets require. Recently however, U.S. plastic molders are taking the plunge, starting to manufacture IML containers and lids in the higher cavity molds required for the U.S. container market.

There are many benefits to IML decorated containers, from an aesthetic and performance viewpoint and from a container manufacturing viewpoint.
  • Superior Graphics are achieved using IML decoration. Photographic quality graphics can be achieved when Offset Lithography is used to manufacture the labels. This gives a premium look and feel to IML containers and packages.

  • The IML process eliminates secondary decorating process. The container ejects from the mold completely decorated. This eliminates post molding print processes, pressure sensitive label application or heat transfer labeling.

  • Odd shapes are possible. Square, sqround, wedges, pyramids and other unusual containers can be fully decorated. A square container on a retail shelf provides better utilization of the shelf compared to a cylindrical container. A cylindrical container wastes 45% of the shelf space.

  • IML containers can be fully wrapped with a label, thus providing a no-label look. This continuous decoration allows every available square inch of container to be decorated.

  • Container handling is minimized, thus reducing work in process. Since the containers are ejected from the mold fully decorated, there is no need for handling or storing the containers prior to the secondary decoration processes. A natural benefit of eliminating handling is cleanliness. The containers have reduced exposure to dirt, dust and other contaminants.

  • These containers are fully recyclable. A polypropylene container with a polypropylene IML label can be completely recycled in most domestic municipalities.

  • IML is a permanent, tamper proof decoration method. Labels are permanently fused onto the container and cannot be removed without destroying the molded container or lid.

    Partnering with an experienced IML container molder will ensure that the five elements of successful IML containers are achieved. A successful IML project begins with properly designing the container or lid for the IML process. There are certain subtle design characteristics that will control the flow of the molten plastic to ensure that the plastic stays behind the label and does not flow over the label. If the plastic flows over the label this of course will bury the label behind the plastic and create a bad container - scrap. The correct container design translates quickly into the mold design - the second element of success. The mold has to be designed with proper clearances for the label automation equipment, part retrieval equipment as well as the critical cooling lines to protect the labels while in the mold.

    The mold fits into the third and fourth IML element, the mold machine and the label insertion automation. The molding machine and the label automation work in close synchronization and are closely integrated via modern electronics and sensors. Below is a simplified sequence of how the process works:

  • The IML robot retrieves, forms and stages the labels while the mold is closed.

  • When mold opens, the decorated parts are retrieved.

  • While the mold is open the IML robot quickly inserts a label into each cavity of the mold.
All this is happening in a matter of seconds. If the labels are placed in the mold askew, bad containers will be created. The label automation is precisely manufactured to form and insert the labels as quickly as possible. Accurate label manufacture is the last element of the successful IML project.

There are a number of valid print methods for printing IML labels. Offset Lithography, Rotogravure, Flexography, Screen and digital printing are all possibilities. Each has it own benefits in terms of print quality, durability, longevity, cost, prep charges and finishing capabilities. Precise label diecutting is critical in the IML process. The label size must be exact; this will ensure it fits into the label automation and into the molding cavity. The tight tolerances in the label, robot and mold will ensure perfect containers are made with minimal scrap.

If you have a container or project that you feel might be a candidate for the IML process what should you do? A good starting point would be to ask your current container vendors where they are at with the IML decoration process. Many domestic molders are involved in the process. Some are beginning and others are farther along, however most are aware of IML and eager to learn and get involved. Each project needs to be explored fully to determine its IML economic viability. For an IML container to be economically feasible it will take the right combination of annual quantity, label size, type and size of container, and marketing desires. In-mold labeling may seem like an impossible endeavor, but for those dairy brands that have the foresight to get involved now it will be a very worthwhile investment because of the advantages gained over today's current packaging.

Sidebar: IML Technology Update Printing Methods

Offset Lithography -Sheet fed printing yields some of the highest possible quality reproduction. Prints with aluminum plates. A variety of inks and coatings are available.

Rotogravure - Material printed off of a roll. Excellent for high volume stable graphics. Prints with engraved cylinders.

Flexography - Material printed off of a roll. Graphics are improving. Prints with a soft photopolymer plate.

Screen Printing - Sheet fed printing with the most durable, light fast printing available. Prints method uses ink squeezed through holes in a fine mesh screen using a squeegee.

Digital Printing - Material printed off rolls or sheets. Great for multiple sku's and prototyping. Minimal preparation and pre-press expense. Somewhat limited in IML materials available.

IML Supply Contacts:

Airlite Plastics

American Fuji Seal

Berry Plastics

H.S. Crocker



Smyth Companies