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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Let's go ahead and start the demonstration. We will start it with production machining. We are going to look at basic 3-axis milling, maybe of a billet or of a casting. We will look at 2-axis turning. As you examine a CAM system, some of the technologies to look for include a really low-level of tool control. You need to be able to put the tool right where you want it, at just the right speed. You need to have that sort of APT-level control but have it in an automated CAM system. You need high-speed milling functions. A lot of technology goes into that, as it is not just cranking up the speed. We have to slow down at corners and always round off the corners, functions such as that, so look for that in a system. We want to be able to rough the part out with extremely complex re-roughing - put the tool only where the previous tool left material, don't waste time machining air. Maybe we need multiple levels of re-roughing. And finally, we have to have simulation. We want to know for certain that the toolpath is exactly how we want it before we ever go out to the shop floor.

So, here is the model that we will be working with today, a new design for a skid-steer loader. One of the important things for your CAM system should be the capability to take the entire model from the customer, not just single piece part files. In this case I am going to start with a top-level assembly and drill down in to the bill of materials, and here is our cooling system, a new design with dual pathways for airflow. One of the key pieces of this design is this blue fan blade in the middle, so let's open that model up and examine it. This is the piece we need to work with today. Maybe we need to cut this out of a billet of aluminum to make a prototype for example.

This is the model I want to work with, so again, I don't want to any sort of translation. I want to simply put it inside of a manufacturing assembly, using the same system. In this case I have the design model inside of a workpiece, in this case the billet. I should be able to model any kind of fixtures, any kind of custom holding devices. I start out by defining my machine, and again since I am in one system, I can choose from a mill, a lathe, a mill/turn, or wire EDM, and it can be a 3, 4, or 5-axis mill. I define my starting location, I define my tools, and I am ready to start cutting.

Let's start with just a roughing operation. I just take this tool, a 1 inch flat end mill, and rough out everything that is not part. I have different options I can choose, whether I want to have a spiral motion or maybe lace back and forth or maybe a constant tool load, any number of options. I should be able to simulate that toolpath, speed it up or slow it down or run it block-by-block. I can zoom in on any given area and put the tool just where I need to see it, to insure it is doing what I want.

You can see here that I have started with conventional machining, turning 90 degrees or as needed for corners, but maybe I want to do this as high-speed milling. I should be able to take that operation and say for example every cut has a smooth radius, no hard corners, no hard stops. I might make it a constant radius, or change it based on the angle. I might put in a slowdown function, and as it approaches a corner, have it add additional feedrates. Maybe I will drop it down to 50% and have it increment the change over a couple of steps. I should be able to define all of that, so that I can achieve a good, smooth ramp down and ramp up. Maybe for plunging, I don't want to have any 90° plunges, so I will put in a helical diameter and entry angle, so that every entry is a constant, smooth entry.

So now I have that same roughing motion, but redefined for high-speed milling. Every corner is a nice smooth radius move, and every corner has a feedrate ramp up and a ramp down. I can have exactly the tool motion that I need to achieve very high feedrates with very shallow depths of cuts, and that allows me to do my job, to get this part finished quickly, get it off the machine and out to the customer, and I get to make my softball game at 5:00.

Now that I have my roughing pass set up the way I like it for high-speed milling, I will change tools, to maybe a œ inch bull nose cutter, but all I want to machine is whatever was left. I want the system to look at that previous toolpath, based on stock allowance, tool size, and part geometry. In this case, that means I just need to walk around the part, profiling the outside walls of the blades, machining all the way down but only machining the material that was left during the previous cut. I don't want any air machining or other extraneous motions. Once I have that, I will move in to a finish or semi-finish cut. Let's take a ball end mill and finish out the valleys between the blades. It is made up of several surface patches, but I will treat them as one area, and define the flow as following the outside contours. Not only will that give me a smooth polished surface, it will be exactly the type of surface finish that the aerodynamics guys would prefer. I will choose my ball end mill, set a step over or, in a case like this, maybe give the system a scallop height and set that surface finish, letting the system determine an appropriate step over.

You have seen me playing the toolpath inside of the CAM system. Simulation is really key, and at any time I should be able to take, for example, let's take the first roughing pass, and show it as a solid. I can show the material being cut away, show the scallops and stair steps, all the material being removed, and of course at all times watching for any gouges, especially if I go in and enter some manual moves. I might run just that one sequence, or I might run everything. I might want to set up multiple windows, maybe an isometric view here on the left, but on the top let's do a top view, and over on the bottom let's do a side view. Now I can watch the simulation from all sides. Let's do the roughing, let's do the reroughing, and visually I can see what the operation is doing but also have the system watching for gouges and fixture collisions, things I would really like to know about before I ever go out to the floor. You can see the system changes colors as I change tools, so in this case I have changed to my bull nosed cutter for the rerough, maybe come in with a second rerough, in this case a 1° taper tool since these blades have a taper to them. This will give me a smooth profile finish, again only machining where material was left from the previous cuts.

Once I have that I will take the ball end mill and clean out those valleys. Anything I do once, something like this on the valleys, I can subroutine around so that I don't have to program each valley individually. If my machine controller can handle subroutines, I will output the code as needed, and if not, I will have the system simply output the code in full, as I still only need to program an area once.

So that is looking pretty good, I'm feeling pretty confident about my program. Now I mentioned earlier that we also need really low level tool control. These have been fairly high-level, such as rough out everything that is not part. Maybe I just want to take that ball end mill and walk it down the tops of these blades as a finish cut. I should be able to simply pick an edge, maybe a sketched toolpath or maybe a drive curve, maybe just a wireframe model, and just follow the tool along that edge. A really low level tool control, maybe just a handful of GOTO's, whatever it takes. In this case, let's drive down that edge. I will want to control things like entry and exit, moving in a specific manner. I don't want to plunge down to the start of the edge, so let's add a radial lead-in, maybe a œ inch radius lead in and ramp in to the model. I'll do the same thing for the exit, maybe a delta move or a helical exit, any sort of low level command, even a CL command like an OPSTOP at the end of the motion. That's the kind of control I will have to have to machine truly complex parts like this.

So that looks good, I have my smooth entry and exit, I have the motion I need, so let's close that. Now, what always happens? This part is ready to go to the shop floor, and what phone call do you always get? Well, this is when the customer calls and says, "That 9 bladed model, no, we meant to say 6 blades." It is very easy on their side, with a good CAD system, to change it from 9 blades to 6, but you have already programmed this model. This is where it really pays to have a powerful CAD/CAM system that can go all the way from art to part. Here is the design model, let's change it to only have 6 blades. It might be a big, drastic change like this that you need to accommodate, or it might be a tiny change. Maybe they go to the root of this blade and change the radius from 3.100 to 3.150, something you can hardly even see as you look at the model, but exactly the sort of change that can scrap a part and send the Material Review Board in to action.

What you want is to be able to simply bring that changed model in to your manufacturing assembly, and it knows that it is a 6 bladed design, and it knows that the root of the blade has moved by .050. You tell it to recalculate the toolpaths, redoing the roughing, the reroughing, all of the toolpaths, and just let the system do all of the calculations. I still make the decisions like this is an appropriate tool, maybe choose a larger or smaller tool, but that is where I put in my expertise. I let the system do the grunt work to say this part is changed.

Before we are done here, let's cover one other area of production machining, namely turning. Back at our cooling assembly, I have this shaft that I need to turn. As before, I don't want to go to a different system to cut this out or waste machine time with on-machine programming. Here I have my part, with no translation, and I set it in a fixture like a chuck that can be as simple or as complex as I like. I will put it inside of a workpiece and then put some toolpaths to it. Just as in milling, simulation is key as I need to be able to speed it up, slow it down, maybe rotate it around and put it in the ZX plane, maybe even have multiple views. I need to be able to see that my roughing is good, my grooving is good, my cutoff tool works, with the same needs in the solid display. Simulation is key, and low level tool control is key, just as it is in the milling world.

That's what you want out of your manufacturing system. You want it to be comprehensive to cover all of your manufacturing needs. You want it to be accurate, you want that simulation to tell you for certain that this toolpath will cut a good part, because that is what production machining is all about.