Fused deposition modeling & laser engineering net shaping

Fused deposition modeling

In this process, a plastic filament is unwound from a coil and supplies material to an extrusion nozzle. The nozzle is heated to melt the plastic and has a mechanism which allows the flow of the melted plastic to be turned on and off. The nozzle is mounted to a mechanical platform, which can be moved in both horizontal and vertical directions. As the nozzle is moved over the table in the required geometry, it deposits a thin bead of extruded plastic to form each layer. The plastic hardens immediately after being squirted from the nozzle and bonds to the layer below. Several materials are available for the process including investment casting wax. Some FDM systems utilized to extrusion nozzles- one for the deposition of a building material, and second for the deposition of washable material to make support environment. In one of this techniques, a temporary support structure is dissolved with water jets, rather than removing it by hand or with a chemical solvent.

A large range of FDM materials are available that include ABS (acrylonitrile butadiene styrene), polycarbonate, polypropylene, PMMA (polymethyl methacrylic), and various polyesters. ABS is by far the largest used material in FDM.

Fused deposition modeling

One of the major problems with FDM machines is the surface finish of the built part. Since the build material is melted and extruded through the nozzle, the minimum feature size that can be expected is about 0.4 to 0.6 mm, while with SLA it is possible to get as small as 0.08 to 0.25 mm.

Another problem associated is the removal of support structure material, particularly for parts with complicated interiors. Since the water-soluble support structure material is available, this problem is taken care of. Also since these parts required very little cleaning and no post-processing, it is most preferred for functional parts. Also, the materials provide better stability for the part dimensions with time and environmental exposure. This process is widely used for concept models, form, fit and function models, along with patterns for the creation of moulds and tooling. The size ranges of the Machines range from a low build envelope of 200 x 200 x 300 mm to a high of 600 x 500 x 600 mm.

Laser engineering net shaping

So far, this is the most advanced process in terms of the level of achieved Mechanical properties of generated metallic parts among all commercialized processes based on layered manufacturing build principle.

Laser engineering net shaping

The process uses a high power laser focused onto a substrate to create a molten puddle on the substrate surface. The metal powder is then injected into the stream of an inert carrier gas into the melt pool to increase its volume. The Powder ejection head moves back and forth according to the geometry of the first layer. After the first layer is completed, new layers are then built upon it until the entire object represented in the three dimensional CAD model is reproduced. Employment of a substrate makes this process different from others considered so far.

This method can utilize a wide range of metals and alloys including superalloys as build materials. Relatively high cost of operation and of produced parts on the one hand, and very high Mechanical properties generated by this method objects on the other do not allow considering the method as a plane RP technique or as a means of visualization. This technology became efficient only in case of functional part or tooling production.

some of the uses of rapid prototyping are

• checking the feasibility of new design concepts
• conducting market test evaluation
• assessing the fit of the complex mechanism
• promoting concurrent product development
• making money exact copy simultaneously
• making moulds for wax cores in castings
• use as a master for Silicon and epoxy  moulds