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Advances in CAD/CAM enable faster, efficient cutting, longer tool life

By Karen Haywood Queen Contributing Editor, SME Media

More powerful software plus better math equals faster tool paths

CAD-CAM-photo.jpg
Daniel Remenak, product manager for GibbsCAM at 3D Systems, using GibbsCAM software.

Advances in CAD/CAM algorithms have improved tool paths, resulting in more speed and efficiency and less stress on both the tool and the objects being cut. Because these new algorithms help tools cut more efficiently and faster, operators save time and the tools last longer.

These advances also allow parts to be cut that couldn’t be cut in the past.

Simulation technology also has evolved and can now be integrated within a CAM system as opposed to a machine-specific, third-party add-on.

“At its core, CAM is a very mature product line,” Vynce Paradise, director of product development for manufacturing engineering software at Siemens PLC Software, said. “It’s astonishing that after so many years there are still so many areas where we can improve the technology to improve the path that drives the cutter, optimizing for speed and tool life. ”

Daniel Remenak, product manager for GibbsCAM at 3D Systems, said machine and tooling manufacturers “have the same core objectives as we do: improving our customers’ productivity. As a result, they are constantly innovating, and it’s important for CAM systems to keep up—whether it’s with new tooling geometrics like barrel mills or new machine configurations for improved automation.”

In the past, manufacturing cutting worked as a step-by-step, straight-ahead process, Ben Mund, senior market analyst at CNC Software, said. The tool typically made a cut and then moved a uniform distance to make the next cut—even if the material it was cutting along that path wasn’t consistent.

The path of the cutting tool remained constant even if the material changed. If a material void loomed ahead, the tool still continued cutting along the predetermined path, which reduced efficiency, caused variations in heat and increased stress on both the tool and the part being cut, he said.

“The limitation was the tool path and the software were not material aware,” Mund said. “Traditionally, a tool path works off offsets. It looks at the geometry next to it, then offsets by a certain amount that the tool is going to get, then offsets again. You end up with a lot of tool motions that look very parallel.”

Over the last eight years, software manufacturers have used these high speed machining (HSM) algorithms to develop software that enables the tool to adjust itself to the material being cut—to become material aware.

“Anyone who cuts anything with a three-axis machine gets a dramatic benefit from this,” Mund said. “It’s a major shift. It’s the most widespread tool path advancement we’ve had in a long time.”

When a single cutting tool costs $100-$200, extending tool lifespan is significant, Paradise said. “Buying tools is a big cost for machine shops.”

A more accurate tool path also is important so as not to damage the product being cut, according to Paradise.

CNC Software coined the term dynamic motion to describe the way its Mastercam software suite works with CAD tools to make sure the amount of material it is cutting remains as consistent and close to ideal efficiency as possible, Mund said.

Cutting only appears chaotic

At first glance, it’s hard to believe the tool running Mastercam software truly is helping a tool cut more efficiently.

Results, however, showed that what appeared to be chaotic actually was faster.

“From a top view, it can look a little chaotic,” he acknowledged. “It looks like the tool path is going all over the place, [as it] constantly changes motion to make sure the chip load and tool path are consistent. We had a race and the dynamic motion tool finished in one-fifth of the time.”

First cut is the deepest

“Dynamic motion looks at the tool and the object and changes the motion of the cutter path to consistently provide the ideal cut parameters for that tool and keep a consistent chip load on the tool,” Mund said. “It looks ahead and knows the material coming toward it and looks at the tool to make sure it’s engaging the same amount of material at all times.”

He said it is a much more efficient tool path, speed-wise. It also allows the machine to use all or most of the cutting surface on the tool. Instead of going straight through, it might move around a little to make sure the amount of material is as consistent as possible.

“This allows you to cut all the way down with the tool,” he added. “It’s much faster, smoother and there’s less stress on the machine tool. The tool is working closer to its ideal condition. You’re cutting a lot faster and a lot deeper.”

Other manufacturers have developed products with similar goals and results.

“The specific mechanisms (and the names) vary from provider to provider. Some such mechanisms are common while others are unique to one of the providers,” 3D Systems’s Remenak said. “The goal of all these high speed machining algorithms is to produce parts with shorter run times and longer tool life.”

It’s not just the cutting algorithms getting an efficiency boost. GibbsCAM 12’s newly revised interface was designed to improve programmer productivity, streamline workflow and optimize and customize the work environment, he said.

“We’ve seen great improvements in cut times and tool life from high-speed milling technologies like Volumill and we’re now applying the lessons we’ve learned in those technologies to turning withVoluturn,” Remenak said. “We’re also applying new, smarter clearance strategies to reduce the amount of machine time that is wasted transitioning between cuts.”

The new algorithms are making the difference.

“We have more powerful computer hardware—that’s the easy piece,” Paradise said. “As we develop new functions on one side, we are also looking at different functions to re-factor them—different techniques and different mathematics. We can introduce different ways of doing the mathematical calculations.”

“We’ve been doing open-heart surgery in the CAM systems to introduce new technology under the covers that people don’t see. If you change the algorithms that calculate the tool path, it can be a factor of 10 faster or even more.”

The quality of the tool path is “much better now because of the way the software generates the surface we’re trying to machine and controls the tool path on that surface,” Paradise said. “We can accurately calculate and check the orientation of the tool at every point.”

Consumer electronics makers adopt early

Manufacturers of high-tech consumer electronics, such as the casing for phones, tablets and televisions are early adopters of this HSM algorithm technology, he said.

“They are really pushing hard, looking for faster programming and faster machining times because time and a perfect finish are critical,” Paradise said. “There are factories with 10,000 machine tools producing the case of your cell phone. Programs have to run very fast. The difference in machining times makes a difference in cost.“

Simulations integrated into CAD software

“Having machine-specific simulation inside the CAM system eliminates the need for similar but external capabilities provided by third parties as separate add-ons,” he said. “Equally important is that accurate simulations should be driven by the code that will be sent to the machine tool.”

Until now, manufacturers who wanted to have the most accurate simulations had to buy third-party products, Paradise said. “Creating a model in a different system led to extra effort, extra translation time and the potential for more errors.”

Now these simulations can be done within the CAM system itself.

“We’re now able to simulate inside the CAM system with the G-code—the code that goes to the machine tool to form the machining system—so the programmer can see what is going to happen on the digital twin,” he said.

“As you program the digital twin, you can see the cutting motion—not just some estimation of what we think it’s going to do, but a higher level visual based on being able to read back the code. You can do that inside the CAM system; you don’t have to have the third-party product. It means the digital twin is more accurate.”

Better cutting

Creating a smoother tool path is more possible now, Mund said, with software and tools that allow machinists to temporarily fill holes in a part or product.

“That creates a solid plug without changing the inherent geometry of the part. Normally if there are holes, the tool has to make additional considerations, try to avoid the hole. By removing the holes from the equation, the resulting tool path is more efficient. You temporarily fill the holes so you can cut over them quickly.”

Getting systems to play nicely together

Manufacturers are still challenged by interoperability, as well as backward and forward compatibility. But they are working to address those issues, too.

Having an open architecture will help shops achieve a key goal: the ability to work with and analyze data from different sources, accommodate a variety of software and hardware and then release data that is usable by others, Mund said.

Vendor-neutral formats such as IGES, STEP and STL can help with interoperability, Remenak said.

But these are not always the best solutions.

GibbsCAM can import directly from many source CAD systems, which helps preserve design information such as hole data, geometric dimensioning and tolerances, he said.

As for compatibility, even without an update the GibbsCAM software often can support new machine kinematics—such as live B-axis tooling on Swiss-style lathes—and new tooling functions such as Y-axis parting tools, Remenak said.

New shapes for cutters

Another CAD/CAM advancement is taking full advantage of emerging specially-shaped cutters that can cut with the sides, not just the tip, to enable better multi-surface finishing, Mund said.

This multi-axis approach works well on any large exposed surface area.

“These multi-axis applications are good for certain areas of mold-making—especially in aerospace, where you have exposed large surfaces. With multi-axis capability, you can go in with one of these shaped tools and cut faster with better surfacing.”

Biggest needs now

Industry wide, the biggest need is continuing to support new advanced machines and tooling, Remenak said.

Mund said shops need access to CAD tools to make incoming files machinable.

“Engineers don’t always think about what is needed to make a CAD model machinable—the moving features to make things more cuttable, the variety of things that impact the person running the machine,” he added. “Those aren’t things that design engineers always think of.”

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