The Art of Handcrafting Custom Game Calls > CnC Discussion Area
CNC's and Call Making - info
Wade@WEBFoot:
Wanted to start a post with some info about CNC's and Call Making. Ill try and follow sort of an order with the posts, so that they are in some sort of logical arrangement. But I cant promise Ill do very well at it :D
Ill start with some back ground info and see where it leads us :eek:
Obviously, CNC (Computer Numeric Control) machines are not things youll find in every home shop, and there are a lot of reasons for that.
The benefit of a CNC machine, is to do the same thing over and over, efficiently. That is why they are generally considered "production machines". That is where CNCs shine... the more parts to be made, the more economical they can be.
I think some people have the beliefs that a CNC will just "make a call with the press of a button". And that is far from true. A CNC will only do what you tell it to do. And in many cases, you have to know even more about what youre telling it to do, because you have to "speak" to the machine in a language it understands, and use measurements, geometry, and mathematical calculations to express just about everything you want it to do. In terms of call making, there are two basic machines that come into play - a CNC lathe (many times called a turning center) and a CNC Mill (many times calls a Vertical Machining Center). The lathe gets the majority of the work since the majority of the call is actually made on the lathe. Much like a hand wood lathe, CNC turning is relatively fast, and really, all youre doing is making a shape with a hole in the middle. Then VMC would probably only handle the soundboard portion of the call. But there in lies the complexity of using a CNC to make a call. You will have to specify in actual measurements and geometry, and if you havent already made one on a hand wood lathe, that you want to duplicate then you will likely have a pretty big battle figuring out what you want to do. But it gets really intricate when you get to the soundboard. Sure, once a program is written, you can get a sound board cut with the push of a button, but to get that program, you have to base it off of something. The best way I feel, is to build your prototype, and get it right where you want it, and then you have something to measure and reference. And of course, just like a jig, youll have a little hand work to do once its done, squaring the cork notch, and of course the fine tuning.
With a CNC, there is no "take just a little bit off here, and a little bit more there..." It is very specific... and must be quantified. In some ways, a CNC is the exact opposite of a wood lathe... (not in every regard, but many). With a wood lathe, its easy to "take a little off here and there". Youre looking at it, and you just grab a tool, put the tool where you want it, and do it. But with a CNC, it cant see, it doesnt know what "a little bit" is, and it cant choose the right tool to do what you want. In addition, with a CNC, you dont have one HUGE benefit that you do with a hand wood lathe, and that is the ability to reposition the tool on the tool rest on the fly. CNCs have the tools mounted rigidly to the machine, be it a tool post, turret, or slide. You literally bolt the tool to the machine. So some of those nifty things you can do on a hand lathe (like beads or undercuts) can be a nightmare on a CNC, not because of programming, but because of the tool to do it. And going the opposite direction... On a CNC, its super easy to change the tenon diameter from .620" to .624", or to change a bore from .625" down to .619" provided you have the proper tool. Thats hard as heck to do repeatedly on a wood lathe. Or shaping a perfect hemisphere on a CNC can be pretty easy, were as doing it by hand can be quite a challenge.
Another benefit of CNC, which is likely one of the main reasons it has become a big part of call making is Acrylic... Acrylic is a temperamental material... It doesnt like heat, it doesnt like vibration, it doesnt like sudden tool movements, and so on. Those of you that have worked it are, Im sure, familiar with how acylic likes to "throw shards" if your tool catches, or bubbles when youre drilling. A CNC can alleviate a lot of those problems because of a couple of the main benefits of CNC equipment. The first being the enclosure and flood coolant system. Usually a water soluble oil that when mixed with water turns milky white, and has rust preventative properties as well as lubricating the cutting tool/material. Well, that coolant system helps to keep acrylic cool, so it doesnt bubble. And with the tool being mounted rigidly to the machine, as mentioned earlier, you effectively eliminate any sudden moves of the tool, therefore the tool cant "catch" unexpectedly. A CNC also controls the RPM of the lathe (Speed) and the rate at with the tool moves (Feed) - and since acrylic is primarily sensitive to the feed of the tool, you can effectively eliminate "throwing shards" once you identify the proper feed for the tool and depth of cut you are making. Another benefit (though this is also a benefit if one has a manual metal lathe and not just limited to CNC) is being able to use a boring bar for the bores. And since acrylic does not like heat, a boring bar allows for coolant to be sprayed in the hole while cutting. Of course all of this can apply to any material, but since acrylic calls are so popular, one can see why CNCs became so popular for making calls out of acrylic.
To be continued....
Michael @ Foster Calls:
Great info, thanks just one question can you also turn wood on a cnc lathe.
Wade@WEBFoot:
Certainly can, the catch is if one is willing to... depending on the machine design etc... it may be a non issue, or it could be a big problem in the making.
I personally wont run wood or any other "dust making" material on my one and only CNC lathe, because I only have the one, and with the coolant tank, ways with auto lube, ball screws etc... I cant easily set it up to protect everything from the dust - so I opt not to run anything like that on it. Dust and oil are a bad combo... and when you add "precision" to that... it gets even worse.
I have been trying to find another machine that I can afford, so that I can set the better of the two up for metal/acrylic, and then the lessor of the two will get drained, and all sorts of dust shields etc... to protect it, along with a dust/vac system so that I can in turn run wood on it.
As far as a mill goes, Id be more willing to do that because it is easier to "dust proof" it just because of the lay out of the machine and the ability to catch almost everything with a dust collector/vacuum. Plus, since its small tools, it doenst throw chips like the lathe does.
Wade
Aaron at Wingerts Woodworks:
Good info so far. I'm intrigued by the process but have very little exposure to it, so this is very informative. Would love to see pics of how calls can look right off the machine without any further polishing.
Michael @ Foster Calls:
Do you sand the calls on a lathe after being turned on a CNC?
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