CAM SYSTEM TOOLPATHS PREVENT EXCESSIVE LOADING ON TOOL AND MACHINE
System options optimize tool loading that helps maximize productivity while ensuring safe speeds that will not break the tool.
Delcam‘s (Birmingham, UK) 2011 version of its PowerMILL CAM system for five-axis and high-speed machining makes the programming of safe toolpaths easier than ever thanks to new stock-model-engagement options that protect both the cutting tool and the machine from excessive loading. Other enhancements include new editing capabilities to simplify the machining of duplicate items; more versatile control of feed-rates for leads and links; and extra functionality for sketching, plus the completion of the move to the new clearer forms for the complete range of strategies.
The options to optimize tool loading will help overcome a constant conflict for programmers. On the one hand, they want to maximize productivity by setting feed-rates as fast as their machines will allow; on the other hand, they need to ensure safe speeds that will not break the tool. The need for safe machining has, of course, become more critical as a growing number of companies are introducing lights-out, unmanned operation overnight or during weekends.
A number of CAM programs incorporate strategies based on the extent of cutter engagement to give more consistent loading on the tool and so allow higher feed-rates. However, these options are usually limited to the initial roughing operations, or to only roughing and rest-roughing. PowerMILL’s new stock engagement technology can also be employed with all of the system’s finishing and rest-finishing strategies so ensuring that the safest-possible toolpaths are run on the machine at all stages.
The key to this more comprehensive solution is the accuracy of the stock models produced within PowerMILL after each machining stage has been completed. These models give a precise representation of the material still remaining on the part and are used to ensure that the cutter is never asked to remove more material than it can safely cut. At the same time, the stock models also ensure that toolpaths are not produced where there is no material remaining so the machine tool is never left cutting air.
The new toolpath editing options in PowerMILL will make it easier to produce multiple copies of any duplicated item, for example, when machining a series of cavities into a mould tool. The user can now specify an array of multiple copies in one operation, using approaches such as a number of rows and columns or a radial spacing around a central point. Once the copies have been produced, the complete series of toolpaths can be re-sequenced to minimise tool changes.
Enhancements to feed-rate optimisation have been introduced to give better control of leads and links at the points of cutter engagement and exit. Typically, the feed rate as the cutter enters and exits the material needs to be slower than that set for the main length of the toolpath. Setting the entry speed too high will risk damage to the cutter and the spindle, and can even move smaller parts on their fixtures. Exit speeds are critical when machining brittle materials, such as graphite electrodes, since the cutter can chip the surface of the part if it is moving too quickly. PowerMILL users can now avoid these problems by setting specific entry and exit feed-rates, either as percentages of the feed-rate for the main toolpath or as absolute values.
PowerMILL has incorporated sketching functionality for several years, for example to draw boundaries within the model to limit individual machining strategies to particular areas of the part. This has been enhanced with a number of new editing options, including the ability to offset or transform curves, and to flatten 3D curves into 2D curves, or to project 2D curves onto 3D surfaces.
About the Author: John Dymale
