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Program a part once, machine it many times over

By Karen Haywood Queen Contributing Editor, SME Media

Advances in CAD/CAM design and modeling save time, improve accuracy

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Generative design has advanced significantly since its introduction in 2018, Autodesk’s Kimberly Losey said. Above, she tests a Veemo at the opening of Autodesk’s Toronto Technology Centre. VeloMetro Mobility used Fusion 360 to design and prototype the enclosed, electric-assisted bicycle.

Until 2018, a West Coast manufacturer of gaming headsets and peripherals used approximated mesh CAD/CAM to size parts, tightening tolerance parameters up to 10 times smaller than the standard setting. Then the company spent hours to fine tune the calculations to the desired geometry, smoothness and aesthetics. In other cases, a company might machine as accurately as possible with available technology and then use a polisher to achieve the desired quality and consistency.

Now, the manufacturer activates the high-precision mode available in many finishing strategies from Open Mind’s hyperMILL CAM software, obtaining the desired surface quality and reducing calculation time by 75 percent, said Alan Levine, managing director, Open Mind Technologies USA.

Calculation time to check the millions of mesh elements for one part can shrink from 12 hours to less than one hour.

Reducing calculation time is especially significant because every time an engineer or floor technician wanted to change a single parameter, the calculation time clock restarted, he said.

“Ultimately, it leads to a higher quality part and saves the engineer’s time calculating at the desk,” Levine said. “The engineer programs the part once and may machine it 10,000 times.”

Mixed-mode, or hybrid, convergent modeling technology enables 3D product modeling using both mesh and surface data sources in a single environment, while eliminating the complexity, potential errors and delays due to data conversions, said Vynce Paradise, head of NX CAM development for Siemens. Siemens’ Convergent Modeling capability is included in NX and Solid Edge.

Traditional solid modeling systems do not operate well, or at all, to edit models that have faceted surfaces, he said.

A model can be converted from a true solid model, also known as fully mathematically defined or analytical surface, to a faceted model that is simpler and gives acceptable data when approximate surface definitions are needed. But then it’s not always easy or even possible to convert back to do true solid model and do more modeling.

The value of convergent modeling is two-fold: The process chain is no longer one way (from solid model to faceted with no way back); and designers can take output from scanning systems, which is nearly always faceted, and use it in a modeling environment, Paradise said.

“The big savings is not having to remodel,” he added. “You don’t have to spend time doing a remodel of the component to use tools that work in only one mode.”

Convergent modeling is being increasingly deployed in aerospace in use cases dependent on repeated optimization using stress analysis, as well as in the medical industry to create customized artificial joints, Paradise said.

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Mixed-mode, or hybrid, convergent modeling tech enables 3D product modeling using mesh and surface data sources in a single environment, while eliminating the complexity, potential errors and delays due to data conversions, said Vynce Paradise, head of NX CAM development for Siemens.

Generative design catching on

Generative design, in which designers input the performance parameters of a product and the software produces hundreds or thousands of design options, has advanced significantly since its introduction in 2018, Autodesk’s Kimberly Losey said.

“Since Autodesk commercially launched generative design for manufacturing, significant advancements include the addition of 2.5-axis and 3-axis machining, which makes this technology even more applicable for the manufacturing industry,” she said. “We also integrated costing and made it possible for our customers to connect with third-party solutions, like simulation from Ansys, to further enhance and validate their outcomes.”

In January, Autodesk added an electronics workspace to Fusion 360, breaking down age-old siloes between electrical CAD and mechanical CAD, Losey said.

If there is a design change after the handoff from the mechanical design team to the electrical design team, the model updates immediately and the software either updates the model or flags areas that need to be modified, she added.

“The days of spending time fine-tuning outdated models are a thing of the past.”

Fusion 360 also can translate different file formats throughout the product development process, making it possible for customers to go directly from design to making on a single integrated platform, Losey said.

Over the last two years, generative design has become more accessible in standard CAD/CAM packages, said Scott Green, director of product management for 3D Systems.

Initially, generative design had been mainly available as a third-party plug-in for CAD/CAM systems with use cases mainly in high-end aerospace applications, he said.

“Now generative design is integrated directly into CAD systems as a standard package or a modest upsell.”

Pursuing form and function simultaneously

Manufacturers can pursue both form and function of a part at the same time instead of separately. When done separately, the final appearance can be less than ideal.

That is because improvements in software have allowed designers to integrate form and function into initial designs, Green said.

In the past, designers working to create an aesthetically appealing product worked separately from those designing for function—sometimes yielding a beautiful product that didn’t work as intended alongside a functioning product that looked less appealing, he said. Then at the end of the process, the two designs had to be reconciled.

“You may have a Porsche design that ends up looking like a Kia,” Green said. “Generative design allows communication between design groups to be much tighter and more efficient. Not only are you able to design something that’s functional, it may also look nice and you can make it with additive manufacturing.”

Extending tool life

In addition to greater accuracy and less computing time, these and other advances in CAD/CAM software are helping manufacturers lengthen the life cycle of factory tools, computers and high-end machines.

One Midwestern company that makes molds to produce food packaging was able to avoid replacing its $500,000 milling machine, Levine said.

“They had a seven-year-old milling machine that was overall serving them well but quality was degrading,” he said. “They said, ‘Can we make a tool path that would be insensitive to the machine’s inaccuracies?’ We said, ‘Sure.’ Now they’re keeping the machine.”

“Using a new generation of toolpaths, we can optimize the cutting forces exerted to the tool during the cutting process, minimizing tool wear and extending tool life,” Paradise said.

Open Mind’s hyperMill software allows customers to choose between a high-precision mode and a standard mode, Levine said. “In some industries, close enough is good enough.”

When using high-precision mode, the calculation uses the standard solution against a normal mesh model instead of a highly refined mesh, he said. Then the procedure continues to locate the cutter on the exact surface model geometry.

“The initial phase of the calculation against the mesh has a predictable calculation time,’ Levine said. “As mathematicians, we know when we’re that close to the mesh that the calculation from mesh to surface is fast and robust.

“Though sometimes the tool path is moved by only a few microns, there is a marked improvement in the visible resulting surfaces with no remaining witness marks (visible flaws) from the approximated mesh surface.”

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Initially, generative design was mainly available as a third-party plug-in for CAD/CAM systems with use cases mainly in high-end aerospace applications, 3D Systems’ Scott Green said. “Now, generative design is integrated directly into CAD systems as a standard package or a modest upsell.” Here, he presents to a software user group meeting held in Tbilisi, Georgia.

“Some day soon,” he predicted, “the high-precision mode will become the new standard for finishing operations.”

The latest version of hyperMill contains enhanced modules that improve tool paths and identify error conditions, and offers a collision check engine. Any design changes are automatically updated; no need for hours of additional calculations. The software also eliminates errors that can arise, for example, when “three different operators all use a different zero point,” Levine said.

“We as a company have tried to make it easy for the user and provide a strong mathematical basis,” he said.

“The customer doesn’t have to manipulate their geometry,” Levine added. “We have made this apply to any geometry. There is no extra work to set it up. Users do not have to learn programming languages. There is no preparation. It is easy to explain. Just turn the switch.”

Codifying senior workers’ expertise

With the constantly evolving hyperMill software, manufacturers also are able harvest the knowledge that highly skilled senior workers have and codify that wisdom into automated best practices available daily to all staff long after these senior workers retire. Highly skilled workers are free to focus on challenging tasks, he said.

“One customer told me he feels his senior employees are doing senior level work only 15 percent of the time,” Levine said. “If we can automate the mundane and rote processes, or speed up processes, the business owner is happier because his senior employees are doing highly skilled work more often.”

With the Open Mind Automation Center, clients can customize hyperMILL for their needs. “We are giving them the ability to write their own automation, to show steps they do on a repeated basis,” he said. “By following this script, employees meet the company standard and reduce the chance of errors.”

One senior employee at an automotive OEM in the Midwest wrote a five-page script showing everything he does when he gets a new piece of geometry.

“We have hundreds of available automation commands; he found the ones that match what he does and built a sequential script of step one, step two, step three,” Levine said. “Some of the commands are conditional and prompt the user for a value. He has a way to share it with his colleagues. They’re capturing best practices and institutional knowledge. As the older guys and gals retire, some knowledge gets lost. We’re trying to let the user capture that knowledge.”

Driven by time savings

Siemens’ NX CAM automates programming with software that quickly recognizes and learns the shapes and features getting more data from the model, standardizing the programming process, Paradise said.

“For our customers, the big driver is the time savings,” he said. “The time savings can be 70 to 90 percent in programming time—from several days to a matter of hours. For us as a vendor, this is transformational. This is one of the big reasons a company would look at buying a new CAD/CAM system.”

Manufacturers also use NX CAM to harvest data from the model to automate the inspection process, Paradise said.

The software looks at the model, reads the features and data, and creates an inspection program, resulting in big time savings, he said.

Minding the curves

Open Mind first applied its process to optics involving surfaces, such as car hoods or bumpers, with a large radius of curvature. The next applications include turbine blades, Levine said.

“In some industries, appearance is critical,” he said. “The visual may be more important than the positioning. On the hood of a car, the look is the most important quality. Attaining a high-quality surface is easier when you can machine the surface model. Optics also push the limit to surface smoothness, for example in an automobile head lamp. If a car is coming at you, the light should not be distracting. A rippled or faceted view on the headlamp of a car is not acceptable. The smoothness of optics becomes critical.”

Another feature of hyperMill is its smooth overlap feature to blend where a mold or part is cut in two different steps, Levine said. A two-step approach can cause problems.

For example, milling machines don’t always measure the cutter to exact specs, different cutters may be programmed from different orientations, shop temperature and machine temperature may vary, and cutter wear may vary. The smooth overlap process adds some passes to overlap adjacent paths but avoids double-cut surfaces. The result leaves nearly imperceptible marks where adjacent cutting paths join, he said.

“The two cutters and holders are different shapes, one is in a different orientation, one may have been running three hours and the next one is coming in cold,” Levine said. “That makes getting smooth overlaps an interesting process.”

These issues can result in parts with creases between the machining processes where cutters changed. Manufacturers then have to blend the crease by hand with a smaller cutter. “In demanding applications, customers want to reduce post-machining processing,” he said.

As software continues to evolve, “the quality of the digital manufacturing world can increase,” Levine said. “What people accepted in 1990 is nothing like what they accept today. We’re raising the bar again. In five years, the bar will be higher.”

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