In-mold Basics
Getting Started Guide
Designing a new product or upgrading an existing product from direct print, glue-on, pressure sensitive or heat transfer labeling to IML or IMD can be a difficult decision. How hard will it be to produce in-mold labeled or decorated products? How expensive will it be to implement and operate? How will our decision affect operational efficiency and profits?
In-mold labeling and decorating require an investment of both time and financial resources but it does pay off in enhanced products, increased market share and cost savings. Whether you are making packaging or durable products, this getting started guide will help ease your entry into the world of in-mold labeling and decorating.
What is In-Mold Labeling (IML)?
A “pre-decorating” technique for injection molded or blow molded plastic containers.
“Pre-decoration” means the container is decorated by the molder before it is shipped to the filler and filled with product.
Container is produced with a fully integrated label which is imbedded in the wall of the object.
Does not require any secondary operations for labeling.
How Does It Work?
- Label is inserted into the open mold via robot.
- The label is held to the mold surface by static electricity or vacuum.
- The hot plastic is injected or extruded into the mold under pressure.
- The plastic conforms to the shape of the mold, embedding the label in the container wall.
- The cooled parts are removed from the mold (most often, via robot).
Types of Packaging Containers Produced with IML
Blow Molding
- Laundry Detergents and Fabric Softeners (liquids)
- Household Cleaners
- Food, Drinks, Liquors (juices and squeezables)
- Automotive (anti-freeze, lubricants, cleaners)
- Personal Care (shampoos, soaps and hand lotion)
- Agricultural and Garden Products
Injection Molding
- Food packaging tubs and lids
- Wipes containers
- Household cleaners
- Agricultural and garden products
Thermoforming
- Yogurt cups and Margarine tubs
Why Use IML?
Lowers the cost to manufacture by:
- Reducing wall thickness in the label area, saving plastic usage
- Reducing scrap rate
- Faster label changeovers
- Increasing overall productivity and efficiency
- Eliminates all secondary labeling operations, including equipment, labor, utilities and floor space.
Improve part appearance and quality:
- High quality of decoration, high brilliance
- Single operation process – logistic advantages, less risk of contamination
- All 5 sides of a container can be decorated in a single step
- IML film improves the part rigidity
- Label allows for even thinner molded wall due to insulation effect of label
- Flexibility in changing decoration
Improve product integrity:
- Product can go right from molding machine to product filling.
- Eliminates sterilization
- Makes for leaner enterprise
- Much harder to counterfeit package
- IML labels cannot be applied after the product is molded
What is In-Mold Decorating (IMD)?
IMD commonly refers to durable, higher value products.
Process is essentially the same as for IML
Labels or decorations are thicker and higher cost, sometimes pre-formed
Label die cutting and placement tolerances are more exacting than for IML.
When Should IMD Be Used?
Life of product may be many years under adverse conditions:
- Temperature extremes and abrasion
- Outdoors in all weather conditions
- In contact with harsh or corrosive materials
Permanent, legally required product warning or caution labels
Labels for toys that must not come off and become a choking hazard to small children
Decoration that must not fade or degrade in any way
Types of In-Mold Decorated Durable Products
- Automobile dashboard and engine components
- Truck mud flaps and bed liners
- Serialized bar code labels for truck tires
- Major appliance control panels
- Recreational products and sporting goods
- Toys and playground equipment
- Cellphone face plates
- Medical devices
- Beer and soft drink beverage crates
Major Considerations for IML
In-Mold Labels
IML-Capable Molds
Label Handling Robotics
Molding Machine
Label Considerations
In-mold labels are die-cut and stacked similar in many ways to labels used for glue-on or pressure-sensitive applications. They are printed by gravure, offset, flexo, letterpress, screen or digital.
Blow Mold (IML-B)
- Unsupported polyolefin or paper
- Three to five mils thick
- Heat-activated adhesive on back side.
Injection Molded (IML-I)
- Unsupported polyolefin or other plastic
- Two to three mils thick
- No adhesive layer on back side
- Die cutting tolerance more stringent than for IML-B
Thermoformed (IML-T)
- Similar to IML-B labels
Label Shape
- May Affect Cycle Time
- May Affect Cavity Count
Label Thickness
- May Affect Ease of Handling
- May Offer Cycle Time Benefits
- May Allow Molded Wall Thickness Reduction
Label Quality
- May Affect Scrap Rates
Injection Insert Molded (IMD)
- High-temperature films such as PC or PC-alloy, acrylic, PS, ABS
- Seven to 20 mils thick
- Usually pre-formed
- Can be 10X the cost of packaging in-mold label
- First or second surface (reverse) printed.
Label Characteristics
- FDA Approval Requirements
- UV or Heat Resistance
- Labels Containing Metal May Not Accept Or Hold A Static Charge
Make sure that the label printer has a proven track record in the kind of IML/IMD production you plan to do. This is especially important with regard to die cutting accuracy and tolerances.
Label Positioning – Electrostatic vs. Vacuum
Some means are needed to pin or position the label on the mold wall before the plastic melt enters the mold.
Electrostatic
- Lower maintenance cost
- Most common method for IML-I – should be used whenever possible
- Eliminates vacuum holes in mold
Vacuum
- No label discharging & charging required
- Ambient conditions have less influence on label positioning
- No dummy core required (from label rack directly to split level)
- Slightly shorter label insertion time
- Hologram, metallized and paper labels can be used
Vacuum is most commonly used for IML-B in North America but the system may require frequent cleaning to prevent clogging by dust, dirt, or offset drying powder.
Injection Mold Requirements
- Molten plastic injected under high pressure into closed mold through gates
- Capable of fast cycles
- High level of cooling
- Robust construction
- Designed to be used with side entry robots.
- Competent design
- Moldmaker should be experienced with stack molds.
- Moldmaker should be experienced with the IML process.
- Able to be serviced without removing it from the machine.
Gate Locations
Inside
- Advantages compared with outside gating
- Uninterrupted decoration of bottom
- No gate mark on part outside
- Smaller dome is required
- Disadvantages compared with outside gating
- Cooling time approximately 0.5 sec longer
- Mold manufacturing costs approximately 15% higher
- Difficulties in multi-stage stripping systems such as tamper-evident containers
Outside
- Advantages compared with inside gating
- Approximately 0.5 seconds less cooling time required
- Mechanical stripping off core by machine ejector is possible
- No restrictions by IML for multi-stage stripping systems such as tamper-evident closures
- Disadvantages compared with inside gating
- Interrupted decoration on bottom surface (hole in label)
- Gate mark on outside surface of part
- Special dome needed for label centering
IML Foot
- Used to hold the label against surface of the mold.
- Prevents melt from getting under label.
- Must be used with wrap-around labels.
- This detail makes using existing molds not configured for IML impossible without rework.
- Requires special venting.
Blow Mold Requirements
- Mold closes around and “bites off” section of extruded hollow parison
- Vacuum ports in mold or static charging system needed to pin label on wall
- Mold wall may need adjustment for label volume
- Higher level of cooling than for non-IML
Degree of Difficulty for IML-I Containers
In general there is a progression in the degree of difficulty depending on the shape of the part. The least difficult are flat parts such as lids, more difficult are rectangular parts with three sided or five sided labels and even more difficult are round conical parts. The difficulty increases more for a four-sided rectangular part (with no label on the bottom) or for round parts with zero or little draft such as cartridges for silicone caulking tubes.
Although the multi-compartment, double-wrap around product includes two different labels per cavity with completely different shapes, this “7 difficulty” part is produced every day with a scrap rate of less than 1%. Moreover, it is a unique container only made possible by IML!
Product | Label Type | Degree of Difficulty |
Lid | Flat | 2 |
Square or Rectangular Container | 3 Sided | 3 |
Square or Rectangular Container | 5 Sided | 3 |
Round – Conical | Wrap Around | 4 |
Square or Rectangular Container | Wrap Around | 5 |
Round – Cylindrical (Zero Draft) | Wrap Around | 6 |
Multi-Component with IML | Flat | 6 |
Multi-Compartment | Double – Wrap Around | 7 |
Automation Requirements
Picking labels from the label magazines and placing them into the molds quickly and accurately is one of the keys to successful IML and IMD operations.
- Capable of fast cycles
- Very fast in and out time
- Complete label “re-charge” within the cycle time
- Must be able to handle labels – this is not a regular insert loading application.
- Must work seamlessly with label magazine to dispense labels one at a time.
- Should be designed for quick label change over.
- Should be integrated with the part removal equipment.
- Supplier should be experienced in the nuances of the in-mold labeling process.
IML-I Machine Requirements
- High injection speed with accuracy and consistency
- High plasticizing rate
- Clamp must be fast, responsive, and accurate
- Rigid construction required to support mold – look at the machines weight
- Tight control over process
IML-B Machine Requirements
Rotary (wheel) blow molding machines for high volume production
- Single or double parison
- Changing molds takes longer than on shuttle machines.
- Favored for long runs of the same product.
Shuttle machines for shorter runs
- Capable of making calibrated finish
- Mold change-over faster than wheel
- Multi-parison designs can provide versatile, high volume production
Although starting an in-mold labeling or decorating project may seem daunting, a great deal of help is readily available from highly experienced and qualified suppliers.