Questions on CNC lutherie capabilities

[Victoria Hewitt]

I build mountain dulcimers & I cut a silhouette through the scrollhead, which is about 2.5"-3" thick. I currently use a scrollsaw for that, which is a total nightmare! I get burned wood, broken blades, injuries, all that fun stuff. I'm looking to see if there are better alternatives.

What I know about CNC machines could fit on a postage stamp, so I'm asking the community:
Can a CNC cut through 3" of hard wood?
Can a CNC cut triangular points, such as stars have? (I've only seen round shapes done so far.)
What type (if any) machine would do that job?

Any input, answers, or direction would be greatly appreciated!

[Jim Becker]

1) The ability to cut deep is a combination of the machine's capacity/capability and the length of the cutter. To realistically cut 3" deep, you'd want at least 7" or so of gantry/Z-height (the vertical dimension of the thee direction coordinates, x, y and z) so you can clear your material with a cutter that can reach that deep. The cutter, itself, would likely be something that is designed specifically for deep work with a relieved shank to avoid burning. I have a 4" bit like that which I bought for things like cutting out electric guitar bodies and other objects which are thick enough that a typical cutter of 2.5" or so would be able to handle

2) Inside Corners will always be "round" because the cutter is round. The smaller diameter of the cutter, the tighter the corner. There's no rule that says you cannot go back and manually take a corner to a sharp point if that's what your end result requires. Outside corners can be sharp as sharp can be.

3) Because of point number 1 above, you will want to consider a machine that is beefy and also has the vertical hight if you want to cut the scroll head in once piece. If you're willing to laminate it left and right, you will not need quite as much height for obvious reasons. For the work you describe, you do not need a huge machine relative to x and y (left to right and front to back) because your components are not huge for such instruments. Height is the factor for you here. Many hobby level machines don't offer that so honestly, you'll want to consider machines from manufacturers like Camaster, ShopSabre, etc., who have smaller, but industrial type machines. There are also folks like Gary Campbell who build beefy machines that are small but industrial in strength. While initial cost is always eye opening, if you have a business, you have to take into account return on investment, which considering the value of your time, could be relatively short if you can increase production and increase sales. Talk to your accountant because tax savings figures into cost, too.

[David Falkner]

Victoria, can you post a photo of the area you're cutting? I work on guitars, am building them when I can get shop time away from my regular work, and have played some dulcimers in the past. But often a photo helps to get more ideas on solving your cutting needs.

Jim's suggestions are on point, btw.

David

[Gary Campbell]

Victoria...
You may have found one of the "Catch 22's" of CNC. Reality is that most luthiers have small shops, but require high quality cuts. Most mfgr's don't put high Z clearance and the rigidity to cut with long bits on smaller format machines, and luthiers don't have room for big ones. Jim makes some good points above. The ability to use large diameter long bits and cut aggressive enough to maintain a good chipload in hardwoods is very rare in branded machines in the size that is attractive to luthiers.

The pictures below show some parts cut by one of my customers, who is a fine craftsman.

This video shows 3D cutting of a small neck, if you look about 2 minutes in it shows multiple toolpaths cutting ~3" deep: https://www.youtube.com/watch?v=LHKHqkKT4aA

IMG_0538.jpgIMG_0535.jpg

[Tony Leonard]

Wow! I'd like to see that finished!

[Brady Watson]

I am pretty sure I scanned the original and set up the toolpaths on that body if it's the one I am thinking about...Came out great!

Regarding CNC capability for instruments... there's some work involved setting things up, but once you do you'll make fewer mistakes and scrap less of that precious lumber. Plus you'll be cranking out parts in hours or days compared to weeks or months by hand.

[Gary Campbell]

Brady...
Sure thing. Those are your scans. Nice job on the double sided 3D plus 2D setup! I would guess that there is more work setting up a complicated file for this type of double sided machining is rewarding. This customer had not owned a CNC machine prior to his purchase of one of my "UWM" ATCs. His progress is amazing, thanks for pitching in.