In this lesson, we'll be creating a pencil toolpath. After completing this lesson, you'll be able to Identify pencil toolpath requirements and create a pencil toolpath. Let's carry on with the file from our previous example and let's explore the 3D pencil toolpath. To get started, we're going to navigate to 3D and select Pencil. The pencil toolpath is one that can be used for finishing of internal fillets. This is a great toolpath to allow us to go back and create a pass that goes over and clears out a fillet after some other operations have been run. We're going to get started by taking a look at our 8 inch ball end mill which was used in the previous operation. And we're going to try to create a pencil toolpath that follows along this fillet on this edge, goes into the pocket, and comes back out. Remember, there's a lot of other geometry here that needs to be finished. And this doesn't necessarily mean that this is the best time for this operation or the best strategy, but we want to at least learn how to apply it. So to get started, we're going to navigate to the Geometry section. And I'm going to change my machining boundary to be a bounding box. Now, if you hold the cursor over this bounding box option here, you'll see that it gives you a tooltip of what each of these will do. A bounding box will be a box that represents the overall size of the part. The silhouette will be the silhouette of the part or a selection in which we can use either selected faces, edges, or a sketch if needed. We're going to be using bounding box because we're going to use another option called avoid touch surfaces. Using the touch surface option, we're going to focus specifically on the fillets we want to identify. So I'm going to work my way around. Again, holding down the left mouse button will allow me to select through those geometry faces. And if we have any issues, we can always rotate the model around to get a little bit better idea and access to those faces. Once we have them selected, we don't really have to worry about the heights because it's going to go all the way to the bottom of the part, but it's going to stop at those faces. Then in the passes section, we have a couple options here. We can limit the number of stepovers, and we'll use just a single stepover. We can use the stepover amount, and remember, we're going to use one-tenth, 0.125, as the finest resolution that we want to focus on, and then we'll leave the rest of the options on. So one thing I do want to make note of is this bitangency angle, this is one that's a little bit hard to understand. And if we hold the cursor there, again, we get a tooltip and it helps you understand a little bit better in terms of the angle, the degree that is actually representing the contact point of the tool. So the smaller this degree, the smaller the contact point of the tool is when it's calculating these passes. This can be anywhere between 0 and 90 degrees. So if it goes higher than 90 degrees, you will get a warning. For example, if I put 100 degrees in here, it's going to turn red and tell me that it needs to be 90 or less. We'll leave it at the default 20 degrees for now, and we'll say OK. So you'll notice in this case that we get a warning and there's no toolpath. What's happening with the pencil toolpath is we actually need to have a tool that matches the radius of our filling. So we're going to modify this, select Edit and select a different tool. This file already contains a few additional ball end mills. Tool number one is a quarter inch ball end mill. And if you remember, when we measured this, we had a quarter inch diameter on this fillet. So now that we have the right tool, if we say OK and allow it to regenerate, we can now see that there is actually a pass that's created here. If we select all of our Setup1 and go to Simulate, we're going to use go to next to go past all of our previous operations. Then we're going to take a look and play through the pencil operation to see what it looks like. So with pencil, you can see the tool comes in here, works its way back, and it cleans out that fillet. So if we rotate this around, you can see exactly what we have here. We've got a nice representation of that fillet, and the tool has gone from side to side, all the way down into that pocket, and around and back up. So there are many other options that we can use for this toolpath, but let's explore it on one more section, on the fillet that goes around the outside. Because this comes up to a sharp corner, and we want to see how it works in this situation. So we're going to go to 3D, and again, down to Pencil. But this time, knowing that we have to use the appropriately sized tool, we're going to grab tool number two, the three-eighths ball end mill. Then we're going to go to our Geometry section. Again, I'm just going to use the bounding box and focus specifically on certain surfaces. We'll use the touch option, then we're going to grab each one of these faces that belong to this fillet. And we're not going to adjust any other options, we're simply going to say OK and let it create this. Then I want to select the entire Setup1, again, I'm going to simulate, going to go back, navigate through all the previous toolpaths. Making sure everything is clear, through that last pencil, and then we'll play through this final one. So it's coming in, tracing along that fillet, and then it's cleaning it out. If we zoom in, you can see that there is a minor lip here. We will have to take the tool and do a couple other passes to clean that up. But for the most part, it's taking that tool and it's going along the fillet, like we would expect, and cleaning it up. So now let's explore some of the options inside the toolpath. We're going to edit, we're going to go to Passes. And notice that we have some options in here for tolerance values, for an over thickness value, which adds an additional thickness to help detect the tool passes. So this is going to be if we have a difference in the tool radius and the actual fillet, we can increase this value here and we can actually get into the area where we have a discrepancy between these. We're not going to be using that since we have an appropriately sized tool. For the link inside to outside in the inside/outside direction, we're not too worried about the direction because it's just going along this fillet from side to side. We can add additional stepovers, and we can add an amount here. And again, we're going to be looking at 0.35, so it's going to be a tenth, roughly a tenth of our tool, so it'd be 0.375 if it was exactly a tenth. We can cut in both ways if we want. The up/down milling, it's currently set don't care, which is fine. But this allows us to determine whether or not we're only going to go a single direction if we're going down geometry. And again, we're only moving in x and y in this case. We're going to go into linking parameters, and for linking parameters, all these values should be fine. However, if we want to increase the amount of leads, we can increase these values. And I'm simply going to take out the three and go to 0.75, and we use that value for all four of them. Once we're done, we're going to hit Enter, okay the operation, and now you can see we've got multiple passes here. So again, we'll select Setup, we'll go to Simulate, we'll traverse through all the previous toolpaths. This is ensuring that we are removing all of the stocks so we're not getting any warnings about collisions. We're just going to be looking at this final pencil toolpath. So now it starts at the top, works its way down, does a secondary pass, comes back and does a third pass, and then it's finished. So everything looks pretty good here in terms of the geometry. If we want to extent the areas that we're working on, we will need to modify that toolpath. And if you remember in the geometry section, we have Avoid Touch Surfaces. If we want to include this face and we want the tool to go a little bit farther, then we can do that and allow it to smooth out that little transition between the flat face and the fillet itself. So for the last time, let's select Setup1, let's go into Simulate, and let's traverse through all the operations until we get to Pencil5, and then we'll play through it one last time. So now you can see again it's starting at the top, it's working its way down because we didn't specify whether it was going to go up or down. And it's cutting all the geometry, and then it's going to do that final pass to smooth out that lip between the flat face and the fillet. And again, we can add additional stepovers or we can manipulate the values if we need to. But in the end, this pencil toolpath is a great option for coming back and clearing things like this fillet. We will need to focus on other toolpaths in order to clear out these pockets, to finish this face, as well as go down into this area here. But for right now, make sure that you save your file, then we can move on to the next step.
