Join Taylor Hokanson for an in-depth discussion in this video Pocketing for the control cavities, part of Creating a Guitar Body with RhinoCAM.
- A pocket toolpath is slightly more complicated then a drilling toolpath. Both drilling and pocket operations are known as two axis and that the CNC does not move an X and a Y during C travel. Unlike drilling, however, a pocket pass also cuts an X and a Y during predetermined stops along the travel of the Z axis. So, pocketing is gonna make up quite a bit of the interior cuts that we perform right here although each of these different areas will, we're gonna treat slightly differently. So, I'll show you how. Let's start over here on the neck.
And just like when I make any new machining operation I wanna new map set and I can title this as you might imagine Pocketing and then within Pocketing I'll make a two axis and pocketing pass and then I'll get this somewhat familiar parameters window. So, first off we select the drive and containment regions. When making a pocket, it's often convenient to actually just select a curve within which the pocketing will take place and these curves can be found on the layer top pockets, enter when done.
For the tool, I'm gonna pick a half inch flat mill because we want the bottom of our pockets to wind up flat. We'll leave feeds and speeds, and clearance plane alone, and cut parameters is the first place where we'll make some significant edits. So, by default, under Global Parameters, right now the machine is set to leave a little bit of stock behind but we want these pockets to be the exact right size after only one operation so I'll tell it to leave 0 stock. We also have an opportunity to pick our stepover distance which is basically the resolution of the cut.
So, if I make the stepover distance larger, the cut'll go faster but sometimes I'll get a bit of a grungier detail on the bottom. So, I'll leave that at 25%. Now, in terms of cut levels, we need to take a look at where our bounding area geometry is in relationship to the model. So we can see here that it's actually at the bottom of this cut as opposed to this curve which is at the top of this cut. So, we'll set that up at the bottom and then we also need to measure our total cut depth. So, I'll do that with this tool.
Snapping to these two knots and that's revealed to be .625. Now, when it comes to the rough depth of cut automatically that's been filled in by the overall rough depth and this means that the machine would try to make this cut happen in one pass which probably isn't a good idea. So, the harder your material is the less material you can take on with each subsequent pass. A good rule of thumb is to start with a depth pass set at about half the overall thickness of the bit. So, we have a half inch bit.
So, I'll make this a .25 inch depth of cut. We're gonna skip entry and exit, advance cut parameters, and sorting. So, let's go ahead and generate that. And here we've got a tool path that routes out that neck. Okay, the next ones we can do a little bit faster. So, there's our neck and I'm gonna copy and paste. So, for this one, we want our drive and containment regions to be this area here. This is where the pickups will go. Under cut parameters, we have 0 stock, 25% stepover, great.
For overall cut depth, I believe this is slightly different. So, I'll measure that and sure enough it's .812. We're gonna leave the rough depth of cut the same but also keep in mind that geometry is at the top and not the bottom of this particular cut. Go ahead and generate that and those are looking pretty good. It's a little hard to tell but right now this cut is giving out at this ledge so we actually need to route this lower area as a separate pass. So, I'll call this Pickups.
This can be Pickups 2. So, for Pickups 2 now we have this as our drive and containment region. For cut levels, I wanna double check on the total cut depth which is again slightly different. Rough depth of cut, everything else looks good. I'll generate that. Okay. Second to last, I'll have this spot where the jack connects. Remove my drive regions, select this fellow, measure the cut levels, and generate, and then finally we have this spot here where the strings travel through to the anchor on the back of the guitar.
Now, we're actually gonna cut this hole from two different sides and so each of those will have to be slightly different. If I take a close look at the model too you can see that I've got a little bit of a rim here on the inside. So, to get this one done I'll make one more copy. And call it Strings. And select that drive and containment region. Now, this time when we assess our cut levels I'll take this initial measurement which is .391 and so forth.
So, maybe I'll just select this and make it .45. So, we'll make that a little deeper and when we come back and cut this thing from the bottom on the flip side, that'll get resolved. As you can see, all pockets are not made equal. Even though all the guitar elements we just tool pathed required the same machining operation. They all required it in a slightly different fashion.
- Setting up and editing the model
- Adding bridges for flip milling
- A variety of two-axis and three-axis machining operations
- Simulating and troubleshooting multiple toolpaths