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STEP

STEP is acronym of The Standard for the Exchange of Product Model Data , is a wide and strong set of ISO (International Organisation for Standardisation) standards, all under ISO 10303. The overall objective of STEP is to provide a mechanism that describes a complete and distinct product explanation throughout the life cycle of a product. STEP provides both generally convenient data modelling methods and data models focused on specific industrial uses. The STEP standards contain numerous dozen separate documents. STEP advanced from earlier efforts in building data standards for CAD, particularly the Initial Graphics Exchange Specification (IGES), the first version of which was released in 1980.

(Andrew Y.C. Nee, Xun Xu; Advanced Design and Manufacturing Based on STEP; Page: 1)

Three-Dimensional Printing

Three-Dimensional Printing (3DP) was invented at MIT and has been licensed to

more than five companies for commercialization. 3DP prints a binder into a powder bed to

fabricate a part. Hence, in 3DP, only a small portion of the part material is delivered

through the print-head; most of the part material is comprised of powder in the

powder bed. Typically, binder droplets (80 mm in diameter) form spherical agglomerates

of binder liquid and powder particles as well as provide bonding to the

previously printed layer. Once a layer is printed, the powder bed is lowered and a

new layer of powder is spread onto it (typically via a counter-rotating rolling

mechanism), very similar to the recoating methods used in powder bed fusion

processes. This process (printing binder into bed; recoating bed with new layer of powder) is repeated until the part, or array of parts, is completed. Because the printer head contains several ejection nozzles, 3DP features several parallel one-dimensional avenues for patterning. Since the process can be economically scaled by simply increasing the number of printer nozzles, the process is considered a line-wise patterning process. Such embodiments typically have a high

deposition speed at a relatively low cost (due to the lack of a high-powered energy source), which is the case for 3DP machines. The printed part is typically left in the powder bed after its completion in order for the binder to fully set and for the green part to gain strength. Post-processing involves removing the part from the powder bed, removing unbound powder via pressurized air, and infiltrating the part with an infiltrant to make it stronger and possibly to impart other mechanical properties.

The 3DP process shares many of the same advantages of powder bed processes. Parts are self-supporting in the powder bed so that support structures are not needed. Similarly to other processes, parts can be arrayed in one layer and stacked in the powder bed to greatly increase the number of parts that can be built at one time. Finally, assemblies of parts and kinematic joints can be fabricated since loose powder can be removed between the parts.

(I. Gibson, D. W. Rosen, B. Stucker; Additive Manufacturing Technologies; Page:195)

Paper Lamination Technology (PLT)

This technique is a variation on LOM and was developed by Kira Corporation. 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. The Paper Lamination Technology (PLT) uses an additive/subtractive process by which layers of paper (for use with copy machine) are bonded together by high heat and pressure and then uses computerised cutter to cut to desired profiles. Similar to the LOM technology, the part does not go through a phrase change. Products are made by paper lamination as follows:

Paper Feed Unit: A sheet feed mechanism orients the one sheet on the target block.

Hot Press System: Using high pressure, the hot press moves the target block with sheet up a hot plate. All the area of the sheet is applied adheres to the target block. The amount of movement up to the hot plate is measured. If deviation in sheet and resin thickness is identified, automatic compensation is made to insure dimensional integrity of the completed 3D model.

Cutting Process: The PC generates plotting data based on section data of the target shape. A mechanical cutter cuts the top layer of the target block along the contour of the section.

Processes are repeated rapidly and accurately. Unnecessary partions are removed.

(Miltiadis A. Boboulos; CAD-CAM & Rapid Prototyping Application Evaluation; Page: 157,158)

Multijet Modelling(MJM)

One example of the technology variations available in these so-called phase change inkjets is provided by 3D Systems. This company produces an inkjet machine, called the ThermoJet Modeler (formerly Actua), based on MultiJet Modelling (MJM) technology, which utilises several hundred nozzles. The completed CAD solid model is transferred to a STL file, ready for the build process. Parts are built by an innovative process that uses a MultiJet Modelling (MJM) head to apply a thermopolymer material in three dimensions. The print head comprises multiple jets that build the model layer by layer. If the part is larger than the MJM head the build platform will reposition within the Y-axis such that the process may continue. The material deposition process of the 3D printer is very similar to that of the ink jet printer. As the development stage processes near manufacture, costs of change increase accordingly. Changing a functional prototype has the disadvantage of high cost and delay to production. Desktop 3D printing is the best solution to concept modelling where changes can be introduced early within modelling. Introducing a change in the concept phase can be easily absorbed.

(Miltiadis A. Boboulos; CAD-CAM & Rapid Prototyping Application Evaluation; Page: 154,155)