Simulation software that checks for potential collisions between machine components and AM equipment is especially important for expensive hybrid machines. The ability to verify laser on/off and power settings, shielding gas, powder-material feed, and delivery gas flow helps ensure parts are made as expected on the machine tool. Shown is a simulation for a Lasertec 65, a 5-axis hybrid milling/laser deposition welding machine from DMG MORI. Credit:CGTech
If you’ve invested in toolpath simulation, verification, and optimization software for your CNC lathes and machining centers, chances are good that you’re a big fan. That’s because the ability to accurately simulate machining processes prevents crashes, improves part quality, increases machine uptime, and provides opportunities for process optimization that would otherwise never exist.
But maybe you’ve made an even bigger investment in a 3D printer or hybrid machine tool recently and are now wondering: Do I really need to simulate additive processes, too? After all, there are no rotating cutting tools, no speeding turrets or flying bits of metal, and the progression of the build seemingly moves at glacial speed.
Besides, the build preparation tools that come with a printer have some pretty nifty graphics, so why bother with yet another software package?
It’s a fair question, one to which you probably already know the answer: It depends on your 3D printer and what you’re printing.
If you own one of those relatively inexpensive “toaster” printers—where a CAD file goes in and a mostly finished part pops out, there are minimal programming options, and no way to alter process parameters—feel free to skip buying simulation software. For everything else, though—especially a hybrid machine loaded with cutting tools and a printhead that must peacefully coexist—additive manufacturing simulation is every bit as valuable a tool as its subtractive counterpart.
Subtractive and additive simulation software both detect collisions. Both give programmers the ability to optimize manufacturing processes. Both identify differences between the finished part and its intended design. Both display operating parameters—laser power, gas flow, and material deposition rates for additive, and feeds and speeds for subtractive. Both prevent costly mistakes.
Granted, additive simulation doesn’t identify certain printing-specific failures, such as layer delamination or the presence of material stuck to the recoater blade that could topple the workpiece. Nor does it help with part orientation or the nesting of parts in the build chamber, although it does display them.
But it does improve quality and throughput by monitoring build parameters as they relate to part geometry, alerting the programmer to things like improper focal distance and potential problems with droop or overhang.
How thoroughly simulation software verifies additive NC code can be the difference between applying corrective actions or calling in a costly repair order for an AM or hybrid additive/subtractive machine. Shown in red is a representation of the deposition head on a BeAM Machines DED (directed energy deposition) 5-axis additive system buried into the part by a rogue “Z0” command. Credit:CGTech
Simulation software also provides an idea of where the build surface sits in 3D space at any given time, a feature that’s particularly important with hybrids. With an additive/subtractive machine, the programmer will often stop the printing process long enough to allow a cleanup cut, in effect “zeroing out” the workpiece’s top surface before depositing more layers or machining the surrounding features. Because simulation software can effectively predict what’s going to happen during the build, there are fewer guessing games while the part is being manufactured.
Another thing that often occurs with hybrid machines is programming software is used that’s not designed for the printing phase of the process. Some NC programmers modify their coding for subtractive toolpaths for additive. Modifying code works, but it’s a less effective option than a CAM package designed specifically for 3D printing. And in some instances, operators might be forced to hand-edit various parts of the machine program, with unpredictable and occasionally disastrous results.
There’s also the question of postprocessing. Most CAM systems offer a form of toolpath simulation—enough so that some in industry feel confident that nothing more is needed. The problem with this assumption—reflected by the old adage “what you see is what you get”—is that it’s frequently false.
The postprocessor may produce unexpected machine movements or activate machine functions not visible in the CAM simulation. Simply put, CNC machines and controls have their own rules governing how they respond to NC program commands, completely independent of—and often very different from—internal CAM system routines.
This, perhaps more than anything else, is why adherents of stand-alone toolpath simulation software feel so strongly about their investment and will tell you the only accurate simulation is one that reads the same code as the machine tool control.
Whether additive or subtractive or a mix of both, machine tools are expensive. So doesn’t it make sense to invest a small fraction of the equipment price in software that not only safeguards the machine from damage but makes it run more efficiently? This is the “optimization” piece of these multifaceted software packages. Optimization turns what would otherwise be a black box into a high-definition color TV with tuning knobs galore.
As mentioned, greater visibility to printing parameters means the programmer can more easily identify what works and what doesn’t, increasing the possibility of “first part, good part.” And where machining is involved, operations can be easily resequenced and cutting values adjusted to maximize material removal.
Finally, because all 3D-printed metal parts and many polymer ones are sent to the machine shop after being printed, simulation software also eases the handoff between these sometimes disparate departments. CNC programmers know what to expect and can more safely and efficiently perform the secondary machining operations needed to complete what is by now an expensive workpiece—a result of many hours, or even days, being invested in its production. There’s never any doubt about what was printed and what needs to be machined, what locating features should be used, and whether the finished part meets the customer’s criteria.
Bottom line: Whether you’re printing parts or cutting them or some combination of the two, simulation software is the least expensive insurance policy you’ll ever buy.
Post time: Sep-29-2019