ADVANCED MANUFACTURING NOW David Conigliaro
How to Reap the Most Benefi t from Advanced Cutting Tools a Q:
What do typewriters, telephone booths and toolpaths for conventional CNC roughing have in common?
A: They are all obsolete. In their day, they were boons to mankind. Today, each has been replaced by technologies that are far more acces- sible, easier to use and economically benefi cial: computers with word processors, cell phones and CAD/CAM programs incorporating advanced dynamic motion control algorithms. Now I may be a little premature in heralding the com- plete demise of conventional roughing toolpaths. It took about a decade for typewriters and telephone booths to overcome status quo inertia and become historical rel- ics. Dynamic CAM algorithms that replace conventional toolpaths with automated, material-aware tool motions have only been commercial for a few years now. So if the same pattern holds, conventional roughing toolpaths may hang on until about 2022, although that’s doubtful. Near universal adoption of these dynamic mill and lathe roughing strate- gies is likely to happen at a very fast pace because they are being promoted by a large core of technical experts, such as applications engineers representing major cutting tool vendors. They want to demonstrate their latest tools in con- junction with CAD/CAM programs that automatically adjust tool motion to maintain the best possible cutting conditions for the tool in question. This makes before and after far more impressive.
Cutting tool vendors have developed a range of prod- ucts with advanced materials, coatings and geometries that deliver better cutting performance and longer tool life at a lower per part cost of ownership. They are more expensive but well worth the price if used appropriately. It all boils down to maintaining a specifi c constant chipload that easily can be picked off a table or sometimes found using a calcula- tor provided within the CAD/CAM software itself. Once the appropriate chipload for the tool has been established, the user can set the desired width and depth of cut. A CAD/CAM program like Mastercam with Dynamic Motion technology
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AdvancedManufacturing.org | January 2016
will automatically adjust cutting motions based on material conditions ahead of the tool to maintain the desired chipload. These adjustments allow the user to combat the two great- est enemies of cutting tool performance and longevity: heat and vibration. In applications where the rigidity of equipment, workholding solutions, or walls and other part features is not an issue, constant chipload machining will allow some tools to power through material up to several times faster with very deep and wide cuts without breaking the tool. If there is too much vibration, the programmer can reduce the width of cut to fi nd a “sweet spot.”
Near universal adoption of dynamic mill and lathe roughing strategies is likely to happen at a very fast pace.
Other applications benefi t from using a smaller tool with a shallow (less than 50%) stepover. In these instances the phenomenon of RCT (Radial Chip Thinning) kicks in. As stepovers decrease, lateral stresses on tool and part decrease, but considerably higher feed rates must be achieved to take heat out of the process by way of the disproportionately smaller chips being produced. Using this approach, one customer recently reported doubling his roughing productivity while reducing cutting tool use by a third. Productivity gains and cost reductions of this magnitude are allowing adopters of constant chipload machining strategies to compete more effectively based on the improved productivity of existing equipment and manpower along with lead time and cost reductions. There is, of course, a small but not prohibitive learning curve. It’s comparable to what we had to learn in order to adopt word processors instead of typewriters and cell phones instead of phone booths. To put the value of this small effort in perspective, here is
one fi nal question: Where are all those businesses today that refused to give up on typewriters and telephone booths?
Product Manager CNC Software Inc.
www.mastercam.com
MODERN MANUFACTURING PROCESSES, SOLUTIONS & STRATEGIES
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