Techspex

Nov 2017

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3 Just because a non-prismatic part has holes, angles or features that are not normal to the surface or machine axis does not mean that full five-axis capability is required. techspex.com | The Machine Tool Search Engine techspex.com | The Machine Tool Search Engine to a flat, static surface correctly located on a certain spot on the part shape so that the tool can be perpendicular at that point. Move to the position, rotate, then cut. Not all 3+2 machines are designed to move and cut at the same time. In this case, activities take place only in the static work plane established before cutting begins. No other machining or processing is going on during part rotation. Programming for 3+2 may require a kind of a multi-operation-by- workplane approach. The control on a 3+2 machine is not nearly as sophisticated as the control on a full five-axis machine, and the software need not be as powerful. Therefore, the initial price tag of the 3+2 machine is far lower than that of a full five-axis machine. Increased Cost for Full Five Axis There's a big price difference between a full five-axis machine and a three-axis machine, and many factors contribute to this higher price. The construction and quality of the machine itself are costly. Five-axis machines are built for high precision. Ultra-precise, high-accuracy rotary tables and trunnions are essential, and these devices are expensive. With full five-axis machining, the machine's movement is limited by the speed of the slowest rotary axis, so high-accuracy, high- speed rotary devices are installed. This is a big factor in the machine cost. Likewise, high-performance, long-lasting spindles with high-speed capability often are used to produce very smooth surfaces, such as those required for mold work. Often, when machining complex surfaces, cut times can be quite lengthy. Over time, heat can build up inside the machine. To compensate for the effects of this heat (such as thermal expansion of key components), machines are likely to have cooling systems integrated into their casting, machine bed, ballscrews and spindles. These systems ensure and maintain machine accuracy, whether cutting the first part in the morning or the last part at night. Some five- axis machines are designed with a separate, isolated electrical cabinet to help prevent heat from power lines and circuits moving to the machine. Highly responsive servomotors and servo loops are also necessary to control the exact position of the tool center point at all times. These components also add to the cost of the five-axis machine, as do the highly sophisticated machine control, processor and software mentioned above. Some Extras Required Generally speaking, five-axis machining is complex and requires a lot of expertise and substantial investment, not only in the machine itself, but also in CAM and simulation software. Some machine builders also offer the required software, but others do not. With some machines, it is included as part of the standard package; with others, it is an option at an added cost. Many customers jump into full five-axis machining only to discover later that the CAD/CAM and simulation software were not included in the initial package. Options such as 3D cutter compensation are also available. This option enables the user to insert a tool offset into the control, say 0.002 inch, rather than change each tool- diameter setting. For years, you couldn't use cutter compensation once the program

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