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Try in-mold decorating for good looks that last.

From the glitz and glamour of appliance and automotive parts to point-of-purchase and promotional products, in-mold decorating has improved design flexibility and appearance while cutting manufacturing costs in dozens of applications.

* In-mold decorating with preprinted film inserts is not a new technology, but its application in many industries is relatively new. Recent technological improvements have made in-mold decorating (IMD) an option for three-dimensional products with complex surfaces. Today, IMD is cutting costs and boosting quality in uses from automobile interior components with compound curves to contoured control panels on appliances and a variety of consumer products.

IMD is used for many products that were traditionally decorated by hot stamping, heat transfers, pad printing, direct printing, or pressure-sensitive labels. It is ideal for parts with complex curves because the insert is formable to the shape of the finished product. It also has an advantage when the application requires consistently registered graphics.

By integrating the graphics into the molding process, secondary operations are eliminated and scrap is typically much reduced. With preprinted inserts in different solid colors, users may also avoid the need to purchase numerous precolored resins. Altogether, cost savings from 5% to 40% can be realized.

'Untouchable' second surface

The in-mold process begins with a screen- or offset-printed plastic sheet or film insert. Graphics can be printed on either the first or second surface of the insert. The "first" surface is that which will be on the outside of the finished part. The "second" surface is where the insert meets the backing resin; it faces inward rather than outward. With a transparent film insert, the graphic can be reverse-printed on the second surface, thereby protecting it from abrasion, scratches, or chemicals by encapsulating it inside the part.

After printing, the insert is die-cut to fit the mold. The die-cutting process can be automated depending on the size of the part, the application, and production volume. The insert can be used as a flat overlay or it can be formed to a 3-D shape after printing. (Thermoforming, hydroforming, or other methods may be used.) Proprietary elastic ink and coating systems have been developed to withstand the rigors of forming and molding.

In the molding process, the decorated insert is placed into the cavity of an injection mold that has been designed for in-mold decorating. Melt is shot behind the insert, bonding its surface to the molding resin and forming an integral finished part.

The durability, particularly of second-surface insert decoration, is well beyond that of other decorating methods because the graphics on the insert are permanently embedded in the product and never exposed to the environment. This contrasts with methods such as labeling or direct printing, which are likely to be exposed to dust, human or mechanical handling, and other potential damage.

The in-mold process often produces significantly less scrap than other methods such as adhesive labels because the decorated insert is shaped to fit precisely into the mold, so the position or registration of the graphic is highly consistent and permanent. During or after secondary operations, labels sometimes shift on a part or collect dust at their edges, making them difficult to clean. In-mold decorating eliminates those concerns because the decoration is fixed on or in the part and there are no edges.

Match up the materials

The most appropriate sheet or film materials for screen- or offset-printed inserts are those with higher surface energy that will cause better ink bonding. Such materials include polycarbonate, acrylic, ABS, PVC, and PS. However, success with some low-surface-energy materials such as polyolefins can also be achieved. But some types of low-surface-energy materials (e.g., acetal), as well as those that are self-lubricating or to which lubricants have been added, do not work well for in-mold decorating.

The most common backing materials used in this process are polycarbonate, SAN, PC/ABS, PVC, nylons, ABS, PS, acrylic, PP, and PE. In general, the insert and backing resins do not have to be the same, but they are usually compatible. If they are not compatible, special heat-activated adhesives may be used to improve bonding.

In-mold decorating does have its challenges and limitations. It is less cost-effective if the decorated area is a small proportion of the decorated surface. It also requires up-front consideration when designing the injection tool. In some cases, an existing tool can be modified for IMD. Die-cutting and forming tools also have to be built before production can start.

Success stories

Examples from three different industries show why IMD is increasingly displacing more traditional decorating techniques.

* Appliances: Maytag in Jackson, Tenn., used in-mold decorating to save labor costs associated with mechanical application of appliques to the fascia of a refrigerator control panel. Using a polycarbonate insert with ABS backing, the in-mold process helped streamline the appliance's appearance by giving it the look of a single part - since the graphic becomes part of the bezel - rather than a graphic applied to the part.

This high-quality look also drove the decision of Frigidaire in Dublin, Ohio, to redesign its top-of-the-line Gallery laundry appliances and opt for in-mold decorating for the control panels - in this case a PVC insert with PVC backing. The process was suited to the control panel because it can be used easily on contoured surfaces. And with no gaps, edges or adhesives, IMD gives the finished product a clean, crisp appearance.

* Automotive: In-mold decorating was determined to be the best option for the automatic-transmission PRNDL (park, reverse, neutral, drive, and low) bezel graphics of the 1997 Chrysler Sebring convertible. Combining decorating and molding in one in-mold step saved Chrysler time and money by reducing the number of components and improving ease of assembly. The bezel consisted of a polycarbonate insert with ABS backing.

For the integrated control panel (ICP) of the 1997 Ford Escort and Mercury Tracer, in-mold decorating provided Ford Motor Co. with flexibility in design and colors as well as durability. The new ICP (a polycarbonate insert with PC backing) incorporates the radio/cassette controls, HVAC system, rear defroster, and clock into a single oval-shaped bezel. The part has six colors, different textures, and a low-gloss finish.

* Specialty products: The Pleasant Company in Madison, Wis., designs and manufactures the American Doll Collection and accessories. In-mold decorating was used for the 19-in. ski accessories, made with a PC insert on PC backing. The manufacturer chose IMD over adhesive-backed decals because of the large part area to be covered, a desire to avoid secondary operations, and the need for sufficient durability to withstand playing with the skis in the snow.

In-Mold Vs. Traditional Decorating Methods

In-Mold vs. Hot Stamping

* Better-quality graphics.

* More economical for multiple colors.

* Durable and tamperproof.

In-Mold vs. Pad Printing

* More economical for multiple colors (pad printing requires curing between colors and a printer for each color).

* Dry process eliminates VOC issues.

* Second-surface graphics possible.

* Greater ink opacity possible.

* More design versatility (e.g., tinted windows) because of better color control and opacity with screen printing.

In-Mold vs. Pressure-Sensitive Labels

* Eliminates secondary operations.

* Eliminates problems with adhesive.

* Offers "no label" look.

* Durable and tamperproof.

* Eliminates need for recessed label area where dirt can collect; no edge lift.

In-Mold vs. Direct Printing

* Eliminates secondary operations.

* No capital investment for auxiliary equipment.

* Dry process eliminates VOC issues.

* Saves cost of shipping parts to printer.

* Can decorate in multiple dimensions. (Can't do this with direct printing on 3D objects.)

* Graphic flaws eliminated prior to molding.

In-Mold vs. Heat-Transfer Labels

* Second-surface graphics on opaque parts possible.

* Less scrap.

* Can mold part with laminated protective mask (later removed by the consumer).

* Can decorate on subtle curves and embossings.

Michael Terlizzi is v.p. of research & development for Serigraph Inc. in West Bend, Wis. The company specializes in industrial screen and offset printing for plastic decorating. Serigraph has been active in in-mold insert decorating for a number of years and has worked with Bayer Corp. and GE Plastics in their efforts to advance this technology. Serigraph supplies molders with preprinted, die-cut, and flat or formed shells to be used as decorative inserts.
COPYRIGHT 1998 Gardner Publications, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1998, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

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Author:Terlizzi, Michael
Publication:Plastics Technology
Date:Aug 1, 1998
Words:1337
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