Watch Advanced 3D Solutions For Manufacturing Engineers This MMS inMotion presentation from Parametric Technology Corporation (PTC) demonstrates the latest techniques and technology in production and multi-axis milling, moldmaking, and sheet metal programming.
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The next key component of an advanced manufacturing system is multi-axis machining. More and more, companies are saving time by eliminating refixtures, eliminating moving parts from one machine to another, and often multi-axis machining is the method to achieve that. It is not enough however to simply add a rotational axis to pivot the tool. You need specialized machining strategies, depending on the type of geometry being cut. You need precise tool motion control, to say where is the first cut, where is the last cut, what does it do for entry and exit. All along those cuts, you need complete tool axis control. If you are cutting a turbine blade, you need to specify exactly the appropriate entry motion. All the way down the cut you want to control that tool axis. And then you want to have exactly the right exit motion, making sure at all times it is cutting what you want to cut.

And of course, you have to have top level simulation to be able to say that this cut goes where you want, it cuts what you want, and just as important, it doesn't hit anything along the way. The tool holder doesn't hit a fixture or gouge the part, all of those things that can end up scrapping a part or, even worse, damaging the machine. This becomes all the more important in multi-axis machining.

Let's explore this technology, we'll go back to our fanblade milling model. You will remember we took a ball end mill and drove it down the valleys between the blades, but doing this in a 3-axis motion with this particular tool, there is a problem. I have turned off gouge checking to show this, and you will see that if I position the tool over on the right side, we have a problem. I don't have enough tool length, and the tool holder is actually contacting the blade. I want my system of course to tell me about this, and you can see that if we run this in the solid simulation, I get the nice clear red line, and I get a line of code that says the tool holder has contacted the part surface, all warnings that I need.

So, what can we do about this? Obviously, I could just go buy a longer tool, but maybe in this instance we need that small radius at the bottom and that long of a tool would chatter and break. Instead, 5-axis would be another way to do this if I can control the tool vectors. There are a lot of complex ways to do this, but I want something fast and easy. One good method is shown here. I am up at the retract plane and I am going to sketch a drive curve, basically down the middle of this valley. I am not seeking any exact values; I am just free handing a spline that basically bisects these two blades. Then I will use that as a drive curve.

So I select that curve, and what was a 3-axis cut is now a 5-axis cut. I will go ahead and play it, and what you will see is that now my tool stays away from the blades. As it starts cutting on the left side, the tool vector always goes through that curve, and that achieves my goal of keeping the tool holder away from the walls. This gives me a 5-axis cut, but I didn't have to make any calculations or figure out a lead or a tilt angle. I simply free handed a curve that would approximate where I want to keep that tool vector, and with that very simple sketching effort, now I have a very complex 5-axis tool cut that, as I rotate it around, gives me exactly what I want. That is the type of control you need, but you don't want to have to say that at this point, I want a vector at this angle, and at this point I want another angle. You should have those options, but you should also have some fast and easy options that give you exactly the type of cut you need. You should be able to use drive curves or maybe a pivot point if you are doing spherical work, also a powerful way to control the tool vector. You can see here in our solid simulation, the tool stays away from the blades, no big red marks, no flashing warnings. In this case I was able to use the same tool and make use of my 5-axis capabilities to finish that part.

Let's look at couple of other industries such as automotive, maybe an engine manufacturer using tools such as a lollipop cutter down inside of an intake manifold casting. Obviously I can't machine normal to the interior surface, but what I can do is draw a pivot curve up top, or maybe a pivot point, I need to be able to really see what I am doing, so I might apply a cross-section to this part. Now I will play that toolpath again, and I can really see how that tool is moving as it rotates around, pivoting around as it cuts. I can see there are no gouges as it walks down this intake manifold.

Maybe let's look at one more industry, the aerospace world. A bulkhead like this is almost always going to have an outside contour following the contour of the aircraft surface. Moving to a different strategy, I might want to cut this as a ruled surface, simply taking the side of an end mill and run across the outer surface, but let all of the tool vectors be determined directly by the part surface. I want to simply lay the tool up against the side, and let the system determine its own vectors and follow it all the way around. I'll add a good entry and exit motion, and maybe even do multiple cuts if I need to.

I have to have the strategies to cut the parts I need. I have to have the tool motion control to tell it how I want to cut each area. And then I have to have the tool axis control to specify how I want to orient the tool as it cuts along. Finally, and obviously, it is so important to have good simulation to show exactly what this cut is going to do out on the shop floor.