By Ann Mazakas
The vice president of product design at Surfware thinks outside the box to solve the problem inherent in machining today.
Glenn Coleman’s career in manufacturing has spanned 25 years. He worked as a machinist and NC programmer for six years before moving into CAD/CAM software. Prior to joining Surfware in 2000, he held various positions at PTC, Manufacturing and Consulting Services (MCS), and Gerber Systems Technology. After realizing that many of the enhancement requests he received from SURF-CAM customers were actually requests to treat symptoms of a problem rather than to fix the problem itself, Coleman decided to take a fresh look at CAM technology and spearhead a revolutionary new approach to machining parts. As a result, the SURFCAM product line is said to offer improved speed, accuracy, and cost efficiency.
Where will new CAM technology have the largest impact on manufacturing?
Coleman: The three main areas where CAM software can affect the profitability of a company come down to saving time by automating user interaction with the CAM system, speeding up the calculation of toolpaths, and reducing machine cycle time. In general, the cost to machine a part far outweighs the cost of creating the NC code, or the cost of the computer used to calculate the toolpaths. So we weight these three areas, putting the heaviest emphasis on reducing cycle time. Particularly with large-lot runs, a little extra programming time pales in comparison to saving several minutes per part when you’re producing hundreds or thousands of parts.
What are some new technologies you’re developing?
Glenn Coleman Surfware, Inc.
Coleman: Staying with the theme of reducing cycle time, we have a new toolpath engine called TrueMill that precisely controls the tool’s engagement with the material. This patent-pending technology will be part of our release of SURFCAM Velocity, which will ship this summer. Through our maintenance program, all qualifying customers will receive SURFCAM Velocity when it is released.
TrueMill toolpaths are very different from any tool motion you’ve seen before. We’ve effectively eliminated all corners, all the sharp directional changes. The tool never plows into a corner. This algorithm, this technology, works on all part shapes. Rather than generating toolpaths based on a given stepover value and the shape of the geometry being machined, we manage tool-engagement angles and effective feed rates to produce toolpaths that are far superior to anything currently on the market. The net result is that much more aggressive cutting parameters can be used, resulting in dramatically reduced cycle times. The concepts behind TrueMill are pretty simple, obvious even, once pointed out. The implementation of the solution, however, was not.
It seems to be a trend, where the software adjusts to how much material is removed.
Coleman: Adjust is the commonly used description, but that doesn’t apply here. Adjust implies that you take a standard toolpath and modify it to avoid burying the tool in areas with excess material, or just slow the feed rate down in those areas. That’s what you see with the so-called trochoidal toolpaths, morphing toolpaths, feed rate optimizers, and other similar processes. Such adjustments seek to address specific symptoms of the overall problem without treating the problem itself, and have achieved little success. We’re not doing that at all.
A standard toolpath simply offsets the shape of the part boundary, producing a sharp transition every time the tool needs to change direction. This causes excess wear on both the machine tool and the cutter and produces an undesirable dwell mark on the floor of the part every time the tool slows down to change direction.
We believe that the core problem in milling has always been the inability to control the cutting tool’s engagement with the material. This makes it impossible to keep the load on the tool constant, and forces machines to be run at far less aggressive cutting parameters than they are capable of, resulting in slower cycle times. TrueMill solves this core problem. The motion of the toolpath is designed such that, as it’s calculated, the tool will never be over-engaged. We don’t need to adjust the toolpath because the tool will never be buried in the first place. We stay as close as possible to the desired engagement angle without ever exceeding it.
That sounds totally different.
Coleman: It is totally different. If you look at these toolpaths on the screen, you will instantly notice that they don’t look like anything you’ve ever seen. The toolpaths are engagement-angle driven, not geometry driven. In other words, the shape of the geometry doesn’t dictate the flow of the toolpath. Rather, each cut is made such that the next cut can be made at the desired engagement angle. The part shape is ultimately produced, of course, but it doesn’t really become apparent until the final passes of the tool. Because of this smooth, flowing, engagement-controlled motion, we’re able to run at feedrates, spindle speeds, depths of cut, and stepovers that at first glance might seem crazy. The cycle time reductions are dramatic.
And perhaps the most impressive characteristic of these toolpaths is the way they sound on the machine. The even tool load produces a quiet, constant pitch that seems out of synch with the aggressive material removal rates. When you look at the current approach to high-speed machining you’ll notice that they’re taking very light cuts. TrueMill enables you to run at high speeds with much heavier cuts. Also due to the even loads, there is less stress on the machine and the cutting tool. Tool life is actually extended while cycle times are reduced. Those two concepts used to be mutually exclusive.
Can this toolpath replace all other specialized toolpaths?
Coleman: Yes, TrueMill replaces them all. Specialized toolpaths are usually the result of treating a symptom of the problem, rather than solving the problem itself. Some CAM systems offer eight or ten ways to machine a pocket. Each of these options addresses one symptom of the problem, but more often than not introduces other problems that didn’t exist before. For example, adding self-intersecting loops in sharp corners is one popular method of allowing a stepover of greater than 50 percent of the cutter diameter without leaving uncut material. But doing this adds length to the toolpath, forces the tool to be engaged at 180 degrees for extended periods of time, and cuts conventionally when exiting the loops. So it treats one issue, but introduces three new problems to the toolpath—each of which is detrimental to the machining process. With TrueMill, we have solved the core problem that produced all of these symptoms in the first place. Since there are no symptoms to treat, there is no need for multiple, gimmicky toolpath options. There’s just one strategy that works in all cases. It even removes the distinction between pocketing and contouring, or profiling. You just select your geometry and TrueMill knows what to do.
TrueMill toolpaths don’t rely on the shape of the boundary. Cutting passes are calculated based on the desired tool engagement angle. This smooth engagement-controlled motion can run at higher feedrates, spindle speeds, depths of cut, and stepovers while producing superior finishes.
This sounds like a great way to run machines unattended.
Coleman: Right. Since the tool engagement angle is accurately managed, the tool load never exceeds a known threshold. Therefore, the machine operator no longer needs to stand there with his hand on the feed-override control, enabling him to do something productive while the machine is running. With current technology, since there is obviously no operator standing by when running unattended, shops tend to back way off on the cutting parameters when running lights-out. This is because they don’t want to risk breaking a tool in the middle of the night and come back in the morning to find they wasted the whole shift. With TrueMill, you can run lights-out with even faster speeds than you would today with an operator standing by.
Will this new toolpath work on a standard machine lacking high-speed capabilities?
Coleman: It will enhance the productivity of any machine. Historically, the limiting factor in material-removal rates has not been the machine tool or the cutting tools, though that has been the popular belief. The toolpaths themselves have been the limiting factor. Traditional toolpaths force tools into corners; they plow into excess material, spiking the tool engagement angle. These toolpath flaws have dictated the cutting parameters that can be used. The oldest, most basic numerically controlled machine you can find is capable of producing the motion of a TrueMill toolpath. That’s good news; shops can increase their throughput with their existing equipment. The even better news is that the better the equipment you invest in, the higher your productivity will be. TrueMill will match the capability of your hardware, not limit that capability. The toolpath is no longer the limiting factor in material removal rates.
What are some of the things you’re looking at beyond this release?
Coleman: Moving forward, we’re going to continue to expand TrueMill technology. The first release will support 2-1/2 axis milling only. In a follow-on release we will plug this technology into our complex, multiple-surface roughing routines like our patented Step Reduction Milling. That’s going to increase the speed of the already advantageous SRM roughing process. We’ll then extend the concepts into 3-axis and even 5-axis milling. We’ll also increase our focus on streamlining the NC programming process, the next big opportunity for time savings.
I hear you’re looking at a new strategy for the direct machining of solid models.
Coleman: Yes, this is actually what I was just referring to. We’re taking a completely different approach that we can’t talk about right now, since we will be seeking patent protection for this technology as well. It won’t be like anything else on the market today. Suffice it to say that it will be as different from current solid-model machining technology as TrueMill is from current toolpath technology, and will have as big of an impact on the part-programming process as TrueMill will have on the part-machining process.
Ann Mazakas is the owner and president of Intelligent Creations LLC. You can send her an e-mail about this Q&A to firstname.lastname@example.org.