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Method of insert molding auto and truck bumper, rocker panel parts

Method of insert molding auto and truck bumper, rocker panel and chin spoiler parts


A paint film laminate is co-molded over a desired plastic substrate to produce an automobile bumper member, chin spoiler or rocker panel part. Along a desired surface of the part, such as, for example, a border between a part surface having one segment covered by paint film and a second segment comprising the exposed substrate, the edge of the paint film is embedded in the plastic substrate along a surface discontinuity such as a recess or ridge so that an aesthetically pleasing sight edge having a desired contour exists along this surface portion. The sight edge is formed during the co-molding process via the provision of an incline or ramp along a desired mold cavity surface. When the co-molded part is installed in its intended application, the paint film edge is substantially hidden from view by the surface discontinuity.


The present invention pertains to an improved method of insert molding of a laminated film or the like over a plastic substrate to produce a part such as a bumper, chin spoiler or rocker panel for an automobile or truck.


A variety of injection molded parts have been made and used for auto or truck body and trim parts. For example, bumpers, body panels, doors, filler panels, wheel covers, dashboards, arm rests and other parts have been made via injection molding techniques. Additionally, with regard to automobile exteriors, body side moldings, beltline moldings, roof moldings and window moldings are made via injection molding of thermoplastic olefin (“TPO”) or acrylonitrile-butadiene-styrene copolymer (“ABS”) or from other thermoplastic materials.

In order to provide a painted surface for these parts, film lamination techniques have been successfully employed. In accordance with these processes a paint film laminate is insert molded with the desired thermoplastic to fuse the film over the injection molded part. The resulting injection molded part is ready for assembly without subsequent painting.

The paint film laminate used in these insert molding techniques may comprise a backing sheet of about 0.020″ in thickness to which paint layers are adhered. Typically, the backing sheet comprises an extruded thermoplastic sheet.

In such paint film laminates, a paint film, comprising a cast dried continuous paint coating, is provided over the backing sheet. The paint film may consist of a monocoat, a clear coat over a base coat or a clear coat and a base coat with interposed print or design. The paint film, including base coat, clear coat and print or design, if desired, may range from about 0.5-4 mil. in thickness.

The laminated paint films are available, for example, from Avery Dennison, Decorative Films Division, Schererville, Ind., or Rexham Decorative Products, Charlotte, N.C. The films are typically provided in a roll, unwound, then trimmed to a proper “preform” size and shape, ready for insertion into the injection mold. The preform is usually placed along the cavity side of the mold with the painted side thereof facing the mold cavity surface. In some instances, the preform may be placed along the core side of the mold. The mold is then clamped and the desired molten resin is injected into the mold cavity. Heat and pressure conditions in the mold partially melt the backing sheet and a melt bonding or fusion of the injected resin and film occurs. Injection molds used for these processes are rear or edge gated so that the molten resin is directed along the backside of the film. The process leads to a finished plastic part with the paint film fused over the underlying plastic substrate. The painted or decorative side of the paint film laminate is exposed over the surface of the substrate to exhibit the desired aesthetic appearance.

It has become increasingly popular to insert or co-mold bumper, rocker panel, and chin spoiler parts for autos and trucks. Conventionally employed co-molding techniques however often result in the unsightly disposition of one of the paint film laminate edges over the substrate plastic in such manner that the laminate edge is exposed on the surface of the part and presents an uneven or non-uniform border with the plastic substrate material. This not only detracts from the physical appearance of the edge, but the exposed edge then serves as a site for peeling back and eventual separation of the film laminate from the underlying substrate.

Furthermore, the border between the film laminate and plastic substrate may have a wavy or uneven appearance. This may be caused by non-uniform dimensions or shrinkage of the paint film laminate during molding.

Accordingly, there is a need for a method for co-molding bumper, rocker panel, and chin spoiler parts wherein a uniform border is provided between the film laminate and plastic substrate. There is a more specific need for a method in which the paint film edge is located in a recess or relief area so that it can not be readily peeled back from the underlying substrate. Additionally, there is a need for a manufacturing process that will place the laminate-plastic border on the far or remote side of a raised area of the plastic part so that it will be hidden from sight and not normally seen from the vantage point of an ordinary observer.

Taizhou Huangyan Pro Mould Co., Ltd

No.32, Gongxin Avenue, North Industrial Area, Huangyan,Taizhou,Zhejiang,China

Tel: + 86 (0) 576-84360788
Fax: + 86 (0) 576-84360788




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