In-Mold Assembly - The Next Advance in Manufacturing Efficiency

Honda Rear Window In Mold Assembly

The elimination of secondary operations is pushing multi-shot plastic injection molding and compression molding into a new level of manufacturing efficiency. CS Tool Engineering is an expert in designing assemblies that combine separate components in the tool via snap-fits, welding, and co-molding of incompatible materials.

For example, we recently re-engineered the rear side window for an automotive manufacturer. Our process successfully joins the glass window with the window frame, the interior trim, exterior trim and the weather proofing, without the use of fasteners.

It’s called “in-mold assembly” (or IMA) and it represents an exciting new frontier in manufacturing technology.

How Does In-Mold Assembly (IMA) Work?

With IMA, separate components which are traditionally assembled outside the mold are put together inside the mold through welding, snap-fits or adhesive bonding. In other words, the end product is pre-assembled right out of the mold.

The result is a significant reduction in part count and improved overall productivity through the elimination of several assembly operations.

Special technology for IMA is found in the tooling, rather than in the molding press. That’s because the tooling also acts as an assembly fixture, by holding the previously molded parts during subsequent molding stages.

In-Mold Assembly (IMA) Implementation Methods

There are a variety of ways to implement IMA. For instance, single-face tools with sliding or rotating plates may be used to change cavity configurations between shots. Traditional linear or rotary table designs, which use multiple parting-line stack molds, can also be employed.

Another older method involves producing hollow parts by molding two separate halves and joining them together, using sliding plates.

Both the single-face and stack-mold processes can be made more versatile with one or more turning center turrets. Each of these turrets can have four faces that perform different functions.

IMA can also be used to mold interlocking hinges and joints using dissimilar materials that will not bond to each other. (This is different from “over-molding,” where the objective is for the two parts to adhere to each other.) The point of using IMA in this case would be to shoot one material against another without them sticking together.

Today, many of these applications utilize robot technology to transfer parts between cavities, or even between machines.

The Benefits of In-Mold Assembly (IMA)

AdobeStock 44346342 PreviewIn addition to the economic advantages of IMA, increased product quality is the major benefit. In-mold assembly develops a more consistent component. The component assembly is not subject to the same warpage or shrinkage issues seen when secondary operations are used.

IMA also:

  • Eliminates work-in-progress inventories.Reduces the need for separate presses and molds.Reduces labor and floorspace requirements.Improves registration or alignment of a part for assembly.Reduces the total time to produce an assembly.Allows production of parts with features that would be cost-prohibitive or impossible to produce by conventional assembly process.
  • IMA eliminates the need for conveyors, bowl feeders, fixtures and ultrasonic welders. It removes potential sources of scrap parts caused by mishandling, misalignment, process variations or contamination.

At CS Tool Engineering, we are proud to be a part of developing the innovations that power our future.