Step by step

Step By Step Guide To The FIM Process

The process of in-mold decorating a plastic component using the FIM technique consists essentially of 4 stages: Printing, Forming, Cutting and Molding

Printing: The printing operation is used to create the decorative appearance of the product. A variety of standard technologies can be used for this stage, including silk screen, flexographic and digital printing. The selection of the correct printing technology will depend on the type of image, the required resolution and the quantity to be produced.

A two-dimensional image is printed onto a sheet of plastic material such as polycarbonate. This image may be printed on either the first surface, or the second surface of the material. If first surface printing is used, the image will generally be coated with a protective lacquer to prevent abrasion. This lacquer can be applied either to the flat, printed sheet, or as a spraying operation on the fully molded component. In second surface printing the image is more robust, but may have to be protected from the ravages of having the plastic resin injected directly onto it. Often this protection can take the form of a second layer of plastic material laminated onto the reverse surface.

Ancillary operations at this stage will include the addition of some form of locating mechanism such as pilot holes in the plastic sheet.

Forming: The forming process converts the flat 2D-printed image into a 3D part. This process is sometimes referred to as 'thermo-forming' which is a catchall term to include vacuum forming, hydroforming and high pressure forming. In all three of these techniques, the flat printed image is shaped over a single part tool using negative or positive pressure. The tool can be either male or female, and each type has its own advantages and disadvantages.

All thermo-forming techniques have the advantage that they 'soft form' the image over the tool, rather than stamping it into the required shape. This reduces any potential distortion of the image and maintains the strength of the material on which it is printed.

The forming operation can also be carried out using matched-metal tooling, in which both a male and female die are used. The use of these two part tools can produce acceptable product, but it is often the case that this technique can damage either the plastic sheet or the printed image. In particular, images that are to be backlit for nighttime viewing can suffer from this problem.

Cutting: These 3D images must now be cut out of the waste material in order to create the foils for the molding operation. Generally a die-cutting operation will be used for this stage of the process. The die-cutting tool is similar in operation to those used to stamp out numerous components in a variety of different industries. However, FIM foils have to be cut 3-dimensionally, and must be very accurate if the printed image is to closely match the parting line of the mold tool. Hence this operation requires great care and excellent quality tools. It is often the case that the cutting tool will require a number of iterations to ensure a match to the mold tool.

Molding: The cut foils are then placed in the cavity of the mold tool and the required resin is injected onto them. The foils can be manually or robotically placed into the tool depending on the volume required and the need for a fast cycle time. Robotic placement does have the advantage of a consistent positioning of the foil in the tool. The molding process itself will almost certainly have to be optimized to suit the foil and may be radically different from the process used to produce non-IMD parts on the same tool. Since all IMD techniques are intended to create cosmetically attractive parts, it will be clear that handling of the product is a key issue.

Information kindly supplied by Pressac Decorative Systems Division. For more on the company please visit http://www.advanceddecorative.com/