- Hello and welcome to
another Haas Tip of the Day. Right now we're gonna cover mill chatter and we're gonna give you some general tips on how to avoid it. I promise, if you stick around
to the end of the video, we're gonna show you what
these tuning forks are for. (melodic hum) (upbeat music) Okay welcome to the chatter zone. While this is running, you
can make your best guess as to the cause of this chatter. Okay do you wanna hear the most
annoying sound in the world? (humming) (buzzing) Okay so we know what chatter sounds like, let's see what it looks like. Oh, oh, nice. The turn chatter is
almost always a misnomer, it means something different
to lots of different people. For our purposes, chatter is simply when a tool or a workpiece vibrates enough to give us surface problems, and we definitely see that now. The solution to our chatter problem always comes down to these
three aspects of our setup. I'm talking about our workholding, our tooling, and our part program. Think about these aspects
as interconnected, right? If one of these aspects of
our setup is compromised, the other two need to step
up and pick up the slack. As an example, if we're
forced to use a tool that is crazy long, then our workholding better be really strong to compensate. Along those same lines, our program is gonna have to be perfect. We're gonna have to use modern toolpaths and really ideal feeds and speeds to compensate for using that odd tool. Now let's take a look
at our workholding here. Clearly, our part is not
being supported well. With this part hanging out so far, when the tool is in the cut, it's really gonna be bouncing around, giving us a lot of chatter. (buzzing) So we have to dampen this. We could go with a larger vice like an eight inch curved vice. Right off the bat, we're gonna
wanna center up this material but even when I've done that, I still get some chatter on both ends. What I'm gonna do in this situation is just go ahead and make some wider jaws. I'm gonna change out these jaws right now and we'll go from there. (ding) This workholding setup
is a problem we can fix. In fact, we did fix it, right? We centered up our material
and we went with wider jaws that get a better hold on our
part along its entire length. If we couldn't touch our
setup for some reason, then we would have to
look at strengthening our program and our tooling. Now let's take a look at our tooling. Typically if we wanna dampen vibration when it comes to our tooling, we wanna shorten up those
tools, but what part of it? Well, all of it. We wanna shorten up our
holders, our flute length even, shorten up everything you can. Now sometimes you have no choice, you've got a deep pocket
you have to go into to make some type of feature. In that case, go with the
shortest flute length possible. You've got a solid carbide tool here that only has the flutes necessary for the pocket that you have to create. Now these are some unique tools, right? If you look at the end of this guy, it actually has variable flute spacing. This interrupts our cut
and cuts down on chatter. Along these same lines, the
Widia that I'm using or will use along the outside of our
part has a variable helix. It's not a constant helix and it has variable pitch teeth on
the end, variable flute. These interruptions in the cut keep us from finding a sweet spot
where things tend to chatter. Going with some special tools can also get you out of trouble faster. By going with ideal tools for our job, we were able to get rid of chatter. But what if we couldn't change our tools? What if we had to use a long holder or if we had to use a long end mill? Again, in that case, we
would have to strengthen our workholding or strengthen our program. Now we're gonna go back to the
tuning forks now, as promised and give you a little physics experiment that'll help illustrate how
small changes to our program can help erase chatter. With these two tuning forks, we're gonna demonstrate resonance. Resonance is when the natural
frequencies of two objects combine and they amplify each other. Sometimes you'll hear
that on a CNC machine, when you hear that little twinge, that little high pitched squeal and it builds and builds until
it gets away from itself. I'm gonna set this tuning fork
up against our ping pong ball and give the second tuning fork a whack. (melodic hum)
(dinging) Pretty amazing, right? It's like remote control. Okay now watch this. If I adjust this tuning
fork so it no longer creates the same C note
as this tuning fork, and I tap it,
(melodic hum) it now creates a slightly different sound and it's no longer exciting
the second tuning fork. In this same way, sometimes the natural
frequencies of our tooling vibrated just the right frequency
to excite our workholding or our part that might be
hanging out a little bit. If we can just change
our tooling in some way, adjust that tool up or down
like we adjusted our tuning fork we can change the natural
frequency of our tooling and stop our chatter. A CNC machine is not
a tuning fork, though. We've got a whole lot of
things we can play with from within our program. Our feeds and our speeds, our depth of cuts, both axial and radial, and also just our toolpaths in general. We've got these modern toolpaths that can give us a
constant tool engagement. Now the closest thing to a
magic button on our machine is this spindle override button. We've all walked up to the machine when we hear that chatter start
to build, start to resonate, we've pressed the minus
10% spindle button twice and seen that chatter disappear. But sometimes that's not good enough. Now remember, looking at our tuning fork, when we adjusted this down, (melodic hum) we got out of the resonance zone. In the same way, I can
adjust this tuning fork up. (melodic hum) No resonance. Again, moving it back down to the middle, we can end up in the sweet spot (melodic hum) where we create that resonance. In the same way, on a CNC machine, moving the RPM down will
often fix our problem, but sometimes, especially
with the longer tools, moving our RPM up can get us
out of that area of resonance and stop the chatter. So I've lowered my RPM
and my chatter goes away for about three seconds, right? And then we hear it, we hear
the chatter come right back as that tool runs into the inside corner. Let me grab my part here and
show you what's going on. What happened here is
that our tool engagement, the percent of the tool that's engaged in the material at any one
time is constantly changing. At one point in the pocket, we might have a 15% tool engagement, and the tool is happy
running at 3,000 RPMs. At another spot on the pocket, we might have a 40% tool engagement, and at that point, we
would need to lower our RPM to 2,000 RPM to get rid of the chatter. Here in this slot or this channel here, with a very long tool, we
might have to lower the RPM to 1,000 RPMs because we've got 50% of the tool engaged in that cut. It's impossible to find
a perfect feed and speed that's gonna work in every single corner of this old style pocket. You have to slow down your entire program to avoid chatter in just
a few of those odd spots. This is a beauty of the newer toolpaths. We're using adaptive
toolpaths, dynamic toolpaths. There's toolpaths like a
volume mill that actually base a toolpath based on
the size of the chips, but what we're doing
here is giving ourselves a constant tool engagement. This is a game changer, this has changed the world of machining. This is using an adaptive
or dynamic toolpath. Our tool engagement is constant throughout the entire pocketing machine. I don't even care what that
engagement is, 10%, 30%. What I care about is that that tool load, the engagement, isn't changing. Once I find the perfect RPM
or the perfect feed rate, I can stick with it
through the entire pocket. If I only had one bit of
information to give you today, it would be this, find
yourself a canned system that has a modern high
speed machining toolpath that has constant engagement. Well this has been a 10,000
foot overview of a giant topic. Remember, your workholding, your tooling, and your program are linked. If you're weak in one area, the other two are gonna have to step
up and pick up the slack. Now if you've learned
something in today's video, be sure to subscribe to this channel. You don't wanna miss what
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be a part of your success and for watching this,
Haas Tip of the Day. (upbeat music)
