Hi folks!

It was a busy week. Since I was about to get some days off due to a deserved vacation, I tried to get rid of the piled work and leave my colleagues in a comfortable situation as much as I could. Although it was a lengthy week, I admit it was hard to decide what would be the next subject I was going to write about at CAMZone.org. I picked a technical one today (again), but for sure we’ll talk a bit about the industry, some names behind High-Speed Machining and the new super cool high-speed / high performance toolpaths developed in the recent years… my original plan was to write twice a week here… but time will say how this is going to be… Anyway, my primary goal is to write high level articles about manufacturing technology, and unfortunately, this take quite some time…

The roots of High-Speed Machining

Due the popularization of high performance machine tools in the last 20 years, HSM has become widely adopted, and I don’t think that there’s any reason to say this trend will change for years to come. This technology changed our world so deeply for better (Or for worse, if seen from other points of view) that I doubt we will have any regression. In 1924, a German dude named Carl J. Salomon started a series of applied experiments that were the beginning of the R&D in HSM. In 1931, a German patent was granted for his work in this area.

I think every one reading this already saw a movie showing a blacksmith hitting the incandescent metal with a hammer in order to shape it. If you are not an IT guy and had some education in the metal working trade, then you know at least the basics of metal handling… (I presume)

Well, the thing here is that Solomon connected the dots and realized that the metal could be cut/shaped more easily when the temperatures were higher than usual (The principle used by the blacksmith) – He also realized that within a certain temperature range, with the increase of cutting speed, the cutting temperature increases up to a maximum value close to the melting point of the material and then decreases with additional increase in speed. This showed that the advantage of high speeds without the limitations caused by the heat generation. The graph shown below shows some known figures about HSM temperatures.

The problem back then is that the machine tools did not have technology to meet high speeds, so he used circular saws with big diameters to carry out his experiments. In some experiments, he was able to achieve 16500 m/min of cutting speed, mostly while machining Aluminum, although Solomon tests were also conducted with several other metal types. Solomon was smart, with very limited spindle technology, the circular saws with big diameters were conclusive to define a key element often misunderstood in HSM: High Speed Machining is not about high RPM, but instead, about high cutting speeds – You can get a very high cutting speed with a big circular saw – The RPM will be very slow because of the saw diameter, but the cutting speed will not. Many people do not realize this – They think that in order to have HSM in their shops they need to have high performance / high speed spindles. This is not always the case. It’s a common sense in among the academics that high-speed machining starts when conventional cutting speeds are exceeded by a factor of 5 to 10. Beyond this range they call it UHSM – Ultra High Speed Machining.

Unfortunately, circular saws posed lots of limitations, and the machine tools back then were not suitable for other types of tests either. Solomon’s R&D was limited to tools with big diameters, and for this reason, the research was interrupted after Solomon for at least two decades. In the fifties, the USA Air Force re-started the research and  conducted ballistic tests in order to achieve higher speeds. Since at that machines with higher speeds of rotation were not available, the period of ballistic tests began. These were performed either by passing the tool over the specimen workpiece by means of a rocket slide or by shooting a projectile-shaped specimen workpiece along a stationary cutting edge. From these tests the new findings were derived that at high cutting speeds the chip formation conditions are different from those found in conventional metal-cutting.

The HSM Milestones:

More two decades later, high performance spindles were invented and then what we see today started to be studied.I won’t dig deeper into details about HSM here. I just wanted to talk briefly about the roots of HSM before starting to talk about the CAM side of HSM. Anyway, we’ll talk more about HSM in the next sections…

Trochoidal toolpaths – The first generation of modern HSM toolpaths

The trochoid word was created by Gilles de Roberval to explain a curve described by fixed point as a circle rolls along a straight line. Trochoidal toolpaths are relatively recent in the modern manufacturing… although some researchers found its potential 40 years ago in the research centers in Germany. Back then, the servo motors, controls, drives and many elements of the CNC machines were not fast enough to deal with the mechanical/computational demands posed by trochoidal moves and these toolpaths did not take off… as far as I know (And please correct me if I’m wrong) PTC and UGS (Now Siemens PLM) were one of the first CAD/CAM companies to offer trochoidal toolpaths in commercial CAM systems… François Lamy and Charles Farah from PTC conducted intensive researches to understand and develop the first HSM toolpaths of Pro/NC – Those were (And in their essence, are still being – They did not re-engineered the algorithms ever since) trochoidal toolpaths without the full intelligence found on modern adaptive toolpaths … that was around 1998 (Maybe a bit earlier) – I also remember Mastercam introduced them around V9.x – UGS (Unigraphics developers back then) also introduced these HSM toolpaths in their product… I remember to have read many marketing white papers from UGS with pictures of their trochoidal toopaths…

Trochoidal toolpaths were a fever but soon they started to show their limitations… As the tool engagement was not taken into account but merely the trochoid pitch, often one realized the waste of time because the CAM system was creating the toolpaths taking only the trochoidal pitch into account, not considering the part topology and the pre-machined areas…a clear benefit of these toolpaths is that they were the first ones to allow the usage of the entire tool flute at high speeds… unfortunately they were very dumb and limited to specific geometries like slots or simple pockets… there was an excessive number of arcs in the toolpath and the machine acceleration/de-accerelation was massive… it was clear that the technique was a good start, but the same principle could be better explored…

Soon the customers started to ask for enhancements and smarter toolpaths, which should use the same principle plus the ability to adapt themselves to the current topology, keep a constant engagement area, thus avoiding air cuts… the tool manufacturers also saw the potential of the machinery and the technology and started to develop new hard metal powders which allowed the creation of new grades with more toughness and wear resistance… two important elements in HSM…

Adaptive toolpaths – The kickoff

Well, soon some smart dudes started to develop new approaches for the trochoidal concept… it was not a totally bad approach… I think it only needed more work to become a comprehensive solution and the developers quickly got this… I’d say that all modern HSM toolpaths are still using the trochoid principle, totally re-written though… I may be wrong, but as far as I know the fathers of adaptive toolpaths were Martin Dunschen and Julian Todd who formerly worked on Machining Strategist at NC Graphics. These dudes started the core of what would become adaptive clearing in the end of the nineties… they developed an algorithm that could manage the engagement angle of the tool, thus creating a toolpath that dynamically changed the moves so that the chip section was constant… the trochoidal toolpaths, that were essentially loops following a constant pitch to keep the cut section constant, were then part of past… their algorithm used the good ideas of trochoidal plus a ton of other approaches to keep the engagement angle constant… according to Bob Warfield developer of G-Wizard, “The problem with Peeling and Trochoids is they’re special case “hacks” for corners rather than general purpose ways of controlling tool engagement angle. Eventually, CAM vendors solved the problem of how to generally create toolpaths that keep constant tool engagement angles. The productivity when roughing with such paths is huge.”

Martin and Julian developed an algorithm that could apply a toolpath to a given STL model, taking into account the shape of the workpiece… therefore they could find out the best linking and entry/exit moves with the minimal air cut… this was a breakthrough technology since even today 90% of the cam systems do not take the stock condition into account… and this causes the creation of stupid and unnecessary moves because the system does not know where the stock is… adaptive clearing was the first roughing toolpath to break this paradigm in order to offer the full potential of their solution… Martin and Julian licensed their technology to CIMCO Integration, a Danish Mastercam reseller with many customers in the mold and tooling industry in Europe and Americas… their customers were asking for more speed and reliability from Mastercam… as CNC Software was not delivering what was needed, CIMCO, with its long experience developing add-ons for Mastercam among other products, came-up with a product called HSM Performance pack… an add-on for Mastercam that literally smoked Mastercam HSM toolpaths… the product was using Mastercam models as the basis for the STL meshing used by Martin’s/Julian’s algorithm, plus a lot of other options added by CIMCO – Some of these options are still not available in Mastercam till these days… CNC Software took years to develop similar technologies… and many other companies followed the wave, as far as I know, started by Martin and Julian…

By the way, the STL meshing was a smart way to tessellate the geometry, as a roughing strategy is almost always supposed to leave some stock… the STL model allows the toolpath computation to be faster due to the simplified geometry… a small deviation caused by the triangulation tolerance would not be perceived due to the stock to leave… very nice… many companies copied their idea after that…

Current adaptive toolpaths

Well, after the kick-off many started to develop their own implementations of the so-called adaptive clearing… Surfware, a CAD/CAM vendor in California had a team of geniuses who started around the year 2000 the development of a new adaptive toolpath: Glenn Coleman, Dr. Evan Sherbrooke (Now owners at Celeritive – Volumill) together with Pat Patterson and Alan Diehl (Surfware assets) – The interesting thing is that Surfware website does not mention Coleman and Sherbrooke as co-inventors… maybe because the Surfware family filled a lawsuit against Celeritive folks…

Fortunately, they reached an agreement and the lawsuit was settled after Celeritive agreed to pay royalties to Surfware…

Because the foundation of most CAM systems in the market is broken due to the fact they do not carry out geometrical updates in the stock in order to represent the material that was removed by previous steps, the implementation of these adaptive toolpaths took a very long time… the fact is that most companies are licensing Celeritive’s technology these days…

Surfware is still working hard to make their best with TrueMill, (Even with that Windows 3.11 interface – I think they are working in a new UI written .NET though) but the truth is that Volumill is becoming more and more popular day after day… so far Gibbs Associates (GibbsCAM), Siemens PLM (Unigraphics NX), Geometric (CAMWorks), DP Technology (Esprit), SigmaTEK Systems (Sigmanest), OpenMind (HyperMill), NCCS (NCL-CAM) are licensing Volumill. And this is just the beginning.

Conversely, CNC Software (Mastercam) recently dropped the partnership with Celeritive as they are working to have something as good as Volumill in X6… so far they have lots of bugs to deal with and a bunch of frustrated customers who bought the Volumill add-on and were shortly informed that it would not be continued in future versions… anyway, I think they are in the right track with most of their toolpaths and I see a great value in Mastercam OptiRough capabilities as well…

In today’s world, it’s imperative to have a system with these capabilities. It’s impossible to machine a piece of ICONEL like in the video above without this…

The good thing about these adaptive toolpaths is that they lead to a wave of innovation in CAM roughing toolpaths and this is very good. Volumill for example added a lot of value to the products where it is currently licensed and I love that! It’s great to have options… the companies I mentioned above quickly grasped how important efficient roughing is and they are offering it to their customers… some others are not even considering this in their products and you should keep away from them in case you need a CAM system to machine parts efficiently…

Martin and Julian adaptive clearing turned into the kernel of HSMWorks, and it is still being further developed. As far as I know, CIMCO HSM Performance Pack for Mastercam is still being marketed… and the team behind the algorithms of both products is essentially the same…

I won’t write here guidelines to select a CAM system that offers adaptive toolpaths… I’d say that the adaptive roughing technology is awesome, but the CAM system needs to offer the whole deal… roughing is just a part of the big picture and you should select your CAM weighting all factors and not only because it offers adaptive roughing toolpaths… if you pick one that licenses Volumill they will be very much alike in this field… even the competitors are offering similar technology.. so the CAM UI and the elements that matter to your company are the most important weighting factors I believe… It’s also important to ask your vendor about their plans to develop their own adaptive roughing  technology… Mastercam customers put a dead money on Volumill because the company dropped the partnership with Celeritive Technologies without any formal explanation to neither their customers nor Celeritive… so you better be careful when choosing your CAM system…

Celeritive and Surfcam are also famous by their outstanding support in recommending values to be used with a wide range of materials.. and because of this they’re truly making their customers happy with their purchases… SolidCAM is now offering their iMachining technology which is also supposed to offer in an a blink of an eye lots of proven parameters for a wide range of materials and scenarios…

Another positive example would be Mastercam partnership with ISCAR tools. Together they walked the extra mile and implemented ISCAR’s HEM (High Efficiency Machining) in Mastercam’s tool libraries… what is nice in this partnership is that if you say to the system that you are using an ISCAR milling tool, it will load proven parameters that will get the job done very well in the first shot… I saw this in a trade show recently and I liked it… Mastercam customers are saying good things about this deal with ISCAR…

All these mentioned above are nothing but adaptive roughing toolpaths that are being continuously streamlined.

Well, I hope I was able to share a bit about the HSM and adaptive roughing technologies on this one… I’m currently enjoying some days off in vacation with my family, so I apologize for the big interval between the posts…

Best,

Daniel