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Concept modelersConcept modelers

Concept modelers, often called office modelers, and are class Of RP systems are specially to make models quickly and inexpensively without a great deal of effort.

The systems are usually small and inexpensive, quick and require very little or training operator.

For these reasons, the systems are targeted to reside in design office environments, where they can ideally be operated much like a standard printer, only the prints from these systems are in 3 dimensions.Types of concept modelers:

Thermal jet printerSanders model maker3-D printerGenisys Xs printerJP system 5Object quadra sysemJP SYSTEM5The JP system 5 is patented by Schroff Development Corporation. it is an inexpensive RP system that requires only a personal computer and a cutting device.

The system produces prototypes using paper sheets and so the material cost is very low

In the layer slicing and gluing operation, the solid model is sliced by software into cross sections of desired thickness.

The cross section data are output to a sign making plotter that cuts the slices and automatically adds registration holes to each slice.

The slices are assembled manually on a registration table and backing paper is removed to expose the adhesive material which glues the slices to form the solid object.

The final solid object's surface can then be coated if desired.

It uses a Roland Digital PNC 900 cutting machine, registration board, all needed software, and a supply of startup material (label paper and plastic foam board).

The model is sliced into layers at a given thickness, the layers are registered manually, and one-on-one adhered to each other.

The typical build time for a nominal model of 60 slices is 2-3 hours. Once the model is completed, it can be held for physical inspection and compared to the rendered computer model.

While the resolution of 60 slices may seem rough for real engineering applications, it may be adequate for some purposes.

Indeed, the models built with the JP System 5 compares favorably with the real models .Hence, this simple and economical approach to rapid prototyping, which in many ways manually mimics what the "big" systems do, may be an acceptable candidate for small firms and model makers. It also functions nicely in an educational environment.

PROCESSA proprietary software package is used to slice the model into a series of cross sectionsThe software then converts the slices to a HPGL plot file format which is sent to a plotterThe sheets are layered by aligning specially cut orientation holes.The sheets are positioned on a registration board.

PROCESSAn adhesive is sprayed on the first sheetThe support backing is removed exposing the adhesive layer. Each subsequent sheet adheres to the exposed adhesive surfaces of the previous sheetSections formed by the nesting operations are cutThe final model is assembled

Fig: Slicing the model into series of cross sections

LENS

Company

Optomec Inc. was incorporated in 1992.

Since 1997, Optomec has focused on commercializing a direct fabrication process, the Laser Engineered Net Shaping (LENS) process originally developed by Sandia National Laboratories.Products

Models

The latest Optomecs products are the LENS750 and LENS 850 systems.

These two systems feature the Laser Engineered Net Shaping (LENS) process, a technology that builds or repairs parts using metal powders to form fully dense objects to give excellent material properties.

This technique can be used with a wide variety of metals including titanium, tool steels, stainless steels, copper and aluminum.Process:The LENS process builds components in an additive manner from powdered metals using a Nd:YAG laser to fuse powder to a solid as shown in Figure. It is a freeform metal fabrication process in which a fully dense metal component is formed. The LENS process comprises of the following steps:

A deposition head supplies metal powder to the focus of a high powered Nd:YAG laser beam to be melted. This laser is typically directed by fiber optics or precision angled mirrors.

The laser is focused on a particular spot by a series of lenses, and a motion system underneath the platform moves horizontally and laterally as the laser beam traces the cross-section of the part being produced. The fabrication process takes place in a low-pressure argon chamber for oxygen-free operation in the melting zone, ensuring that good adhesion is accomplished.When a layer is completed, the deposition head moves up and continues with the next layer. The process is repeated layer by layer until the part is completed. The entire process is usually enclosed to isolate the process from the atmosphere. Generally the prototypes need additional finishing, but are fully dense products with good grain formation.

Principle

The LENS process is based on the following two principles:

A high powered Nd:YAG laser focused onto a metal substrate creates a molten puddle on the substrate surface. Powder is then injected into the molten puddle to increase material volume.

A printing motion system moves a platform horizontally and laterally as the laser beam traces the cross-section of the part being produced. After formation of a layer of the part, the machines powder delivery nozzle moves upwards prior to building next layer.Applications

The LENS technology can be used in the following areas:

(1) Build mold and die inserts(2) Producing titanium parts in racing industry(3) Fabricate titanium components for biological implants(4) Produce functionally gradient structuresAdvantages

Superior material properties. The LENS process is capable of producing fully dense metal parts . Metal parts produced can also include embedded structures and superior material properties. The microstructure produced is also relatively good.

(2) Complex parts. Functional metal parts with complex features are the forte of the LENS system.

(3) Reduced post-processing requirements. Post-processing is minimized, thus reducing cycle time.Disadvantages

(1) Limited materials. The process is currently narrowly focused to produce only metal parts.(2) Large physical unit size. The unit requires a relatively large area to house.(3) High power consumption. The laser system requires very high wattage.