CIMdata PLM Industry Summary Online Archive
4 December 2007
Events News
Delcam to Show Aerospace/Automotive Machining at Southern Manufacturing
Delcam will highlight special modules in the company's PowerMILL CAM system for the aerospace and automotive industries at the Southern Manufacturing exhibition to be held in Farnborough on 6th and 7th February. The aerospace module makes the machining of blisks and impellers much easier and faster, while the automotive module automates the programming of engine port machining. Delcam will also feature the latest versions of its FeatureCAM and PartMaker CAM software on its stand, O61.
Typically, the new aerospace option will allow even complex blisks and impellers to be programmed in around 30 minutes, compared with the many hours of work that would have been needed previously. To generate the CAM program, the user simply has to divide the CAD geometry between the shroud, hub and blade, plus the splitter blade if appropriate. Then, the tools to be used have to be chosen from the tool database within the software and the type of leads and lifts specified. Next, the user needs to decide whether to undertake the roughing either by pocket or level by level. The latter option involves more air moves but avoids deflection of thin blades that can result when machining pocket by pocket. A further choice may be made between finishing the blades either by machining the opposite faces of the pair of blades across a pocket or by machining around each blade. Finally, the predominant tool angle must be set. This will usually be normal to the hub, or to the shroud or to the centre line of the part. During the calculations, PowerMILL will automatically adjust this angle by the minimum amount required to maintain adequate clearance at all times and also to give smooth tool axis movement.
PowerMILL will then calculate the three type of toolpath needed to machine the item - a roughing toolpath to remove the bulk material, plus separate finishing toolpaths for the blade and the hub. A warning is given automatically if the cutter chosen for roughing will not remove sufficient material so that finishing can be undertaken safely. In these cases, a stock model can be produced showing the material remaining. This allows the user to choose either to reduce the size of the roughing cutter and so enable better access and increased material removal, or to create an additional semi-finishing toolpath to leave a safe amount of material for finishing.
To further speed the calculation times, if the blades are evenly spaced, PowerMILL will automatically count the number of blades and produce a complete set of toolpaths in a single operation. When the blades have different spacings, toolpaths must first be produced for a single blade and then copied around the hub at the appropriate angles.
PowerMILL's port machining module automatically optimises the overall machining sequence so that as much material as possible is removed with three-axis and positional five-axis operation, and that continuous five-axis machining is only used where necessary. This reduces the overall machining time, while maintaining the required level of surface finish. With most machine tools, using three-axis or positional five-axis cutting offers greater rigidity and so allows more accurate machining, with less vibration of the cutter, at higher speeds. However, engine ports usually require continuous five-axis machining for part of their manufacture.
The module uses a spiral motion for the roughing cuts but gives the operator a choice between using a spiral or a plunging approach for the finish machining. Using a spiral approach produces cusps across the flow of gas and so increases turbulence, while using the plunging technique gives cusps parallel to the flow direction and speeds the passage of the gas mixture through the port.
PowerMILL also divides the CAD model of the port automatically to create the surfaces that will be machined from either end of its length. The user can specify the length of the overlap between the two sets of toolpaths to ensure a smooth transition between the two areas.
PowerMILL supports the full range of cutter types, including the lollipop cutters that are frequently used to access difficult to reach areas of the port. The software can be used either to machine ports directly from solid material or for the finish machining of cast engine blocks.
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