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Profiles of object cross sections are cut from paper or other web material using a laser. The paper is unwound from a
feed roll onto the stack and first bonded to the previous layer using a heated roller which melts a plastic coating
on the bottom side of the paper. The profiles are then traced by an optics system that is mounted to an X-Y stage.
After cutting of the layer is complete, excess paper is cut away to separate the layer from the web. Waste paper
is wound on a take-up roll. The method is self-supporting for overhangs and undercuts. Areas of cross sections which
are to be removed in the final object are heavily cross-hatched with the laser to facilitate removal. It can be time
consuming to remove extra material for some geometries, however variations on this method have been developed by
many companies and research groups. For example, Kira's Paper Lamination Technology (PLT) uses a knife to cut each
layer instead of a laser and applies adhesive to bond layers using the xerographic process. There are also variations
which seek to increase speed and/or material versatility by cutting the edges of thick layers diagonally to
avoid stair stepping.
In general, the finish, accuracy and stability of paper objects are not as good as for materials used with other RP methods.
However, material costs are very low, and objects have the look and feel of wood and can be worked and finished in the same
manner. This has fostered applications such as patterns for sand castings. While there are limitations on materials,
work has been done with plastics, composites, ceramics and metals. Some of these materials are available on a limited
commercial basis.
The principal commercial provider of LOM systems, Helisys, ceased operation in 2000. However, there are several other
companies with either similar LOM technology, or in early commercial stages. These companies are addressing market segments
ranging from concept modeling to very large objects for architectural applications.
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