Conventional machining processes

Bannerjee, J.K., Some Effects of Molybdenum Disulphide (MoSj) - Based Cutting Fluids on the Workpiece Surface Finish in Grinding and Conventional Machining Processes, Proc. Conf. Wear of Materials 1981, New York, (1981), p. 496. 

Example Solid freeform fabrication (SFF) techniques such as selective laser melting (SLM) and sintering (SLS) are often prized for being much cleaner than conventional machining processes and being able to fabricate products with minimum waste (e.g., Bourell et al. 2009). 

The majority of commercial blend grades has been developed specifically for injection molding and thus can be processed in conventional machines as long as the processing conditions recommended by the blend manufacturer are followed. Reciprocating screw machines are preferred over plunger-type ones. 

Elastomer-modified PA compositions Zytel , UltramicF B, UltramitF C, TechnyF, Grilon A) are easily processable on conventional machines with single flight, with three-section screws, and... 

With the implementation of CAD/CAM technology, it is possible to produce prototypes direcily based on a virtual model. The generation of the geometry using RP processes takes place quickly without the requirement of molds and machine tools. The main feature of the process is the formation of the workpiece. Rather than the conventional manufacturing process of a clamped workpiece and material removal techniques, RP processes entaU the layering of a fluid or powder in phases to form a solid shape. 

Unlike other subtractive machining processes, Generative Processes buUd parts by a layer-by-layer technique using form neutral substances like fluids, powders, foil-or wire-shaped materials by chemical and or physical reactions. In general the process, as shown in Fig. 79, results directly from a 3D model, which is sliced into thin cross-sections typically with a thickness of 0.1-0.4 mm. Depending on the kind of process, parts that may be difficult or even impossible to fabricate by conventional methods, can be produced out of polymers, metal, ceramic or composite materials [101]. A selection of RP-processes is described below, but due to the complexity of the processes readers are referred to the cited references. 

The tool diameter is in every case smaller than the bore diameter. This results in a free space between the bore waU and the tool which allows a better chip transport and a more effective process cooling compared to a conventional boring process. Furthermore, different bore diameters can be machined using the same tool geometry. 

Furthermore, the tangential uncut chip thickness varies according to a conventional milling process. The maximum value is then equal to the tangential feed per tooth. However, for the continuous cut, the undeformed chip thickness as well as the undeformed chip width is constant. The undeformed chip width is equal to half of the tool diameter. These values have to be known to calculate the machining forces. 

The drill milling process leads to a low burr formation and a low delamination of the CFRP layers (Brinksmeieretal. 2008). Furthermore, the produced chips are small compared to conventional drilling processes. Because the bore diameter is bigger than the tool diameter, the chips can be evacuated easily. In conventional drilling, the chip transport in the flutes of the tool leads to friction at the wall of the borehole. Especially when the CFRP layer is machined prior to the titanium or aluminum layer, the hot chips of the metallic material can destroy the surface in the CFRP layer. This can be avoided using the drill milling process. 

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