March 2011 eNews
Research Shows Innovative Tool Path Program Produces Metal Removal Rates as Much as 10 Times Faster
Tests Prove That Combination of Tool Path Software and the Right Tool Can Increase Milling Efficiency By 75 Percent or More
Cutting tool and machine tool technologies have become more sophisticated over the years, but some experts believe full productivity gains have not been made because of the inherent shortcomings in the off-line generation of tool paths.
Ongoing research at Phoenix, AZ’s GateWay Community College involving tool path software provider Celeritive Technologies and high-performance tool manufacturer Helical Solutions clearly shows that a high-quality cutting tool, driven by innovative tool path programs can increase metal removal rates as much as 10 times.
Helical Solutions’ HEVR-SR five-flute, variable-pitch carbide end mill with A1TiN coating and a .030” corner radius directed by a VoluMill tool path cuts Stainless Steel without the benefit of coolant.
“No matter how sophisticated a machine tool is, it can’t do anything without a tool and a tool path,” says Glenn Coleman, chief product officer and co-founder of Celeritive Technologies, designers of the VoluMill tool path software used in the Gateway testing. “The tool path has always been the weak link in the chain, typically forcing the use of cutting parameters that err on the side of caution rather than productivity.”
According to Scott Tiehen, Helical Solutions’ national sales manager, “These cautionary tool parameters are detrimental to the tools’ performance and fate. High-performance geometries are designed for optimum speeds and feeds and ensure a customer a heightened return on their cutting tool investment. With the use of VoluMill, we have discovered that not only does our tooling experience all of these characteristics, it also takes on a whole new aspect of affordability, consistency and predictability allowing for maximum return on investment.”
Helical Solutions’ HEVR-SR five-flute, variable-pitch carbide end mill with A1TiN coating and a .030” corner radius.
When numerical control came along some five decades ago, programmers tried to replicate what a skilled machinist could do turning crank handles. Problems become obvious every time there’s a sharp corner in the tool path, where the load on the tool increases because the tool is bearing into more material.
“There have been many attempts over the years to improve upon the traditional tool path,” Coleman says. “Most of those, however, are still based on the fundamental pick-geometry-and-offset-it method. There are detect-and-adjust approaches out there that try to help along a path that has flaws, but the VoluMill approach is to generate the tool path so that the flaws are never there in the first place.”
There are four problem areas that limit machining throughput when using traditional tool paths:
- The initial full cut
- Stepping over between cuts
- Feeding into new areas of the part
- Overloading in corners
A side-by-side illustration of a VoluMill tool path (left) and a traditional tool path (right).
Celeritive Technologies’ VoluMill is revolutionary new programming tool path technology that catches up with the cutting tools and machine tools. VoluMill utilizes existing CAD/CAM functionality for geometry and input/output functions, allowing customers to continue using their CAM system of choice. It dynamically manages cutting strategies, feed rate and depth of cut, and minimizes force and heat build up in both the part and the tool by maintaining the programmed material removal rate. VoluMill is 100 percent compatible with all geometries and part/stock boundaries, cutting styles, materials and cutting tools with support for an unlimited number of islands, tapered walls, variable pocket depths and variable island heights found in the most widely used CAD/CAM software.
“What we have done with VoluMill,” Coleman says, “is devise a different way of driving the tool through the material. We’ve developed a path that will ensure a consistent load on the cutting tool. We’ve embedded ways to address all instances of the problem areas indigenous to traditional tool path technology. As necessary, VoluMill makes dynamic adjustments to the depth of the cut and/or the feed rate so as to never exceed the pre-set volume of material being removed at any given time,” he continues. The results are metal removal rates that are five or 10 times faster than traditional tool paths.
A completed 6061 aluminum part cut by a Helical Solutions’ HAL-C-SR three-flute carbide end mill with a Zirconium Nitride (ZrN) coating for improved lubricity and a VoluMill tool path. This was achieved with an SFM of 1,560, RPM of 12,000, IPM of 1,000 and 100 CIM MRR.
To prove VoluMill’s claims, Celeritive Technologies joined forces with Helical Solutions, a Maine-based manufacturer of high-quality, high-performance cutting tools at GateWay Community College (GWCC), where the two-year-old Manufacturing & Design Technology Department prides itself on being available to industry for research of this type. “We call our program ‘integrated technology’ as it combines the disciplines of design, CAD/CAM, CNC programming and operations, tool holding and work holding,” says Gateway’s Program Director Dave Zamora. “We are fortunate to have a variety of machine tools to work with ranging from two-axis to simultaneous five-axis models. We enroll approximately 300 students each year, primarily in our technology certification programs for new students and those interested in upgrading their manufacturing skills.
“With these resources, we’re able to benchmark machining technology more than someone in the industry because they’re hard pressed to make parts every day,” continues Zamora. “We are an educational research facility for area companies to benchmark manufacturing processes and tooling, and my students learn extreme material removal parameters and they learn variations in work holding to create an optimal setup, which can then be transferred to the production shop. We love this environment to be able to share this technology with our students and our industry.
“VoluMill and Helical challenged us to use the new high-speed machines that we have and we wanted to push the machining envelope,” Zamora adds. “We found the VoluMill software to be straightforward and highly productive for generating part programs. Helical Solutions advised us on how aggressive we could be in speed and feeds and provided the coated carbide test tools.”
A completed 304 Stainless Steel part cut by a Helical Solutions HEVR-SR five-flute variable pitch carbide end mill with Aluminum Titanium Nitride (A1TiN) coating for heat resistance plus a .030” corner radius and a VoluMill tool path. This was achieved with an SFM of 1,144, RPM of 8,800, IPM of 110 and 3.44 CIM MRR.
The students conducted three separate milling tests using two different materials -- stainless steel and aluminum. In all three cases, the combination of VoluMill and a tool from Helical Solutions significantly outperformed a typical setup.
VoluMill, is a new way of thinking about machine tool programming. By using a machine’s optimum metal removal rate, it can increase productivity while removing unnecessary stress and strain on the machine, cutter, tool holder and fixture. These benefits lead to longevity of equipment, cutting tools, increased cutting precision and more. Moreover, there is no need to “tweak” part programs on the machine and one-off runs become productive as well.
“Don’t overlook other items like coolant, high-quality, balanced tool holders and well-designed fixtures,” offers Helical Solutions’ Tiehen. “Eliminating vibration and adding lubricity go a long way toward higher metal removal and longer life. In all, testing at Gateway proved that milling efficiency can be increased by 75 percent or more by using the right tools and programming techniques. Depending on how much milling the work-piece requires versus drilling, tapping, boring and so on, overall cycle times can be reduced by one-quarter or more. That’s a great payback for a small investment in quality cutting tools and efficient programming.”
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