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CNC 101
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10106&t=19655		 Page 1 of 1
Author:  LRegnier [ Thu Nov 13, 2008 10:51 pm ]
Post subject:  CNC 101
Hi Guys,

I just in the process of purchasing a CNC router, it should arrive in the New Year.

In the mean time I need to do a some learning. I was hoping that you guys may be
able to put me onto some websites with good tutorials.

I'm going to be using Solidworks for component design, Camworks for the part programming
and most likely Mach 3 as the machine interface.

Any help or tips you can offer would be great.

Thanks - Luc
Author:  Parser [ Fri Nov 14, 2008 8:22 am ]
Post subject:  Re: CNC 101
What type of guitars are you making? How much guitar building experience do you have? CAD experience? Do you have Jig designs yet? What type of CNC router are you getting?

I think you have to answer that stuff first before anyone can help you out!

SW is great, I use it all the time at my 9 to 5. I've done a lot of surfacing work in there and am very happy with it.
Author:  Bob Garrish [ Fri Nov 14, 2008 8:00 pm ]
Post subject:  Re: CNC 101
There are a lot of books on SolidWorks; it's pretty popular. I'd start there on that. Can't comment on CAMWorks as I don't use it and haven't known anyone who does. There's a much bigger community for Visual Mill, MasterCAM, and RhinoCAM (which is Visual Mill plugged into Rhino).

Besides that, I think answering the questions Parser asked will most help us to help you.
Author:  LRegnier [ Fri Nov 14, 2008 11:27 pm ]
Post subject:  Re: CNC 101
Hi Guys,

One of the main reasons I purchased a CNC is to make better fixtures and jigs for building
both acoustics and eventually electrics. I have only build classical and steel string using
traditional hand tools and power tools. CNC opens a whole new world of capabilities and
that is why I decided to take the next step.

I have plenty of CAD experience, Catia, Solidworks, Autocad, and others. Just no CNC
experience. So what I'm really looking for is some basic how to get started stuff. For
example types of cutting tools that should be used for different operations, cutting speed
and feeds etc. Stuff for working with metal is pretty easy for me to find in some of
my engineering books. But wood is a different ball game and I was hoping that someone
could point me in the right direction to some good tutorials.

Thanks - Luc
Author:  Bob Garrish [ Sat Nov 15, 2008 1:35 am ]
Post subject:  Re: CNC 101
Use end mills for everything. I use carbide flats and balls nearly all the time, though I have some cobolt tooling for some special applications. Cutters for aluminum work best as they have sharper edges and pull out chips better, but be careful with that as if you have weak fixtures they're also better at pulling your work off!

Although you'll ignore this as soon as you price one: a good face mill is worth getting.

Start with the speeds and feeds for aluminum and work from there (at router RPMs you'll have to really pare back your feed rates as the machines aren't rigid enough to feed at full relative speed with larger cutters)

The hardest part of working with wood as compared to metal is holding it down. Steal fixture ideas from Taylor and Jim Olsen to get you started.

As a general rule, CAM software is easy. Making really good toolpaths is much more dependent on your understanding of how your cutters work, how your fixtures hold, and how the material reacts than being super-proficient with your CAM software. Understanding how the cutters and the materials interact is a weird one, but it's important with wood because your biggest problem at the start (and maybe forever!) will be chipping on your parts.

Oh, and learn your G codes. You should be able to read the G code for a program and know what it's doing. As an example, a pro should be able to watch a program run and then find a specific move in the G code if it needs changing (ie: if you needed to slow down a finish pass at just one point to prevent a recurring chipout, etc). Watch the programs run, read the manual and learn your G-codes, etc, and this'll come over time.

CNCZone.com is your friend, as well.
Author:  LRegnier [ Sat Nov 15, 2008 1:04 pm ]
Post subject:  Re: CNC 101
Hi Bob,

Thank you for the advice and the link to cnczone. Had a chance go throught
some of the topics on the forum. Lots of good info.

G Code...ah yes it's been a long time since I used it. I learned APT (McDonald Douglas)
nc programming language over 25 years ago it will come back, I hope.

Cheers - Luc
Author:  Parser [ Sat Nov 15, 2008 9:23 pm ]
Post subject:  Re: CNC 101
I'd recommend drawing and cutting a bridge first. You can practice with pine or something equally cheap.

As Bob mentions, most routers aren't that rigid so you should probably plan on using smaller tools than you would prefer to use. In general, keep an ear and an eye on your machine while you are running your parts. you can hear/see if you are running into problems. If the wood starts smoking, your feed rate is too slow and/or your spindle speed is too high. If the wood starts tearing out or if you see or hear vibration then either slow down your feed rate or speed up your spindle.

Double stick tape will be your friend unless you decide to go for it and get into vacuum fixturing. You can also screw parts down if you need to. No matter how you fixture it, another good trick i've learned is to not cut all the way thru the part, leaving an "onion skin". With both double stick and vacuum, it is also a good idea to locate parts using pins or dowels. This helps absorb the lateral forces from the cutter.
Author:  Bob Garrish [ Sun Nov 16, 2008 4:35 pm ]
Post subject:  Re: CNC 101
Those are some good points I forgot to mention! Double stick tape is the machinist's secret weapon (most of the time...see below). The advice on listening is huge; if you have a really good ear for what the machine's telling you then you can get an amazing amount of mileage out of what you hear!

On the DST: I once had a contract programming customer who kept coming back getting me to slow down a program I'd made for them to cut some composite parts. I made the program and told them they could run it dry with DST for holddown. After the second time they came back and insisted I needed to slow down the feeds as they were having parts get thrown, I went down to see what they were doing. Sure enough, they were running the program with a garden-hose worth of coolant running on the part (dissolving the adhesive!). I asked why they hadn't run it dry like I'd said to and they said 'coolant can only help, right?'. [headinwall] [headinwall]
They cleaned off the table, turned off the coolant, and all the parts came off perfect using the original, full speed program. idunno
Author:  LRegnier [ Sun Nov 16, 2008 10:24 pm ]
Post subject:  Re: CNC 101
Hi Bob,

Thanks for your tips. The double sided tape is one of my favorites, use it quite a bit.
I checked out the CNCzone website, wealth of information.

Thanks - Luc
Author:  Jeremy Vonk [ Mon Nov 17, 2008 8:07 am ]
Post subject:  Re: CNC 101
DST is great for small stuff...inlays and even fretboards. These days I feel a lot better having things like electric guitar bodies and necks bolted down. I had a neck come loose using dst and the cutter spun it around a couple of times before it threw it into the side of the mill enclosure. Scared the crap out of me. I'm in the process now of making all my body and neck fixturing a bolt down situation.
Author:  mikebrittain [ Mon Nov 17, 2008 9:05 am ]
Post subject:  Re: CNC 101
You may want to check out :http://www.allstaradhesives.com/

They are the best source for gasket material for vacuuam fixtures.

Mike Brittain
gmbrittain@gmail.com
myspace.com/mikebrittain
Author:  LRegnier [ Wed Nov 19, 2008 9:02 pm ]
Post subject:  Re: CNC 101
Hi Mike,

That douple side tape is pretty cool stuff with two adhesive strengths.

Thanks - Luc
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