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I'm looking at getting a CNC, mostly for making fingerboards and definitely for carving necks.

I'm thinking a 24x48 should be ample for guitar making. However, a 48x48 is only 200$ more.

Anyone have any insight as to whether the larger machine would be useful? No point getting it if all it does it chew square footage...

I'm using a 24x48, and have found nothing that I want to cut that is too big for the machine. My shop is small, and I didn't have room for a bigger machine, but I did replace a 24x36 machine that just missed being big enough for some things I wanted to cut. I use mine for fingerboards, archtop guitar and uke plates, necks, lap steels and other miscellany.

Dave

Mine is 48"x 48" and I use an area about 24"x 36" for luthiering. I'm cutting fretboards, bridges, headstocks, plus all my inlay work. I went bigger for cutting sheet goods, plywood etc. 24"x 36"-48" is plenty for most operations.

Think I'll save the real estate then...

I'm looking at a Zenbot. Anyone have any experience/comments on them?

I have no experience with that machine, but I would avoid a machine whose structural members a made from HDPE. It might work ok for a small machine.

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Jim Watts
http://jameswattsguitars.com

I know little of these beasts. However, a friend of mine, the CNC department head from my old life has one and recommended it to me. His is the smaller 24x24. The gantry's on the one I want are twice the thickness than on his machine, and he says he's getting .001 tolerances.

Can you recommend a better option, cause I'm still in exploratory mode here?

I can't make a recommendation but it's good to hear they made the material twice as thick. A quick search in a materials database tells me that hdpe is about 1/3 the stiffness of mdf, just as a reference point. Of course you can overcome that by making everything thicker and that sound like the approach they took.
I have a cheap machine that has a 20 x 30 work area which would be fine, but the machine is so poorly built that it has no repeatability and is only useful for small parts such as bridges etc.. It really should be better than it is. It's from a company/guy that sold them under the name pcnc. One of these day's I'll make myself a new one or rebuild that one.
I hate to see someone buy a machine that doesn't perform to their expectations and basic requirements. But knowing someone who has one like you're interested in is a big plus.

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Jim Watts
http://jameswattsguitars.com

My first machine used HDPE extensively, and it worked OK as long as I took very light cuts at fairly slow speeds. Pushing the envelope on either of these factors resulted in deflection of the HDPE parts, and poor quality cuts. The bigger the machine, the bigger problem flex will become. The small size of your friend's unit, even with the thinner material, is less likely to have problems due to flex.

The machine I had was fine for fingerboards, if cut slowly, and things like that. It would have never been adequate for cutting necks or something else that requires some heavy hogging (or many many hours of cutting time). Even on fingerboards, when I compare work that I did on that machine to current work, the fret slots are a bit loose (probably due to a combination of a not-so-rigid machine and runout on the router collet). I can push very hard on the current machine's spindle and not measure any appreciable deflection. If I did the same to the old machine, I could create visually detectable deflection.

The machine I'm running now is still not a "heavy duty" router by any means, but it's made of thick aircraft grade aluminum primarily, and is well engineered to be very rigid. 3/4" thick aluminum on a small machine, if all the parts fit together precisely and if the linear bearings are good, can make a surprisingly solid machine. A machine made of HDPE, even with good bearings and good design, is still going to be pretty flexible and I think it would have to be run considerably slower than it's capable of running in order to avoid problems due to flex.

Dave

What machine do you have currently?

Can you recommend something better than the Zenbot? I'd love to know...

Head to the AWFS in Vegas this July, the have every woodworking machine you can imagine, most functioning on the convention center floor.
Yea, July in Vegas = stay inside.

B

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My memory is so good, sometimes I remember things that never happened.

No way I could make it...

I'm using an Xzero Raptor with a Colombo spindle and G540/Mach 3. It came as boxes of parts and no instructions--pretty much a semi-kit, but it wasn't hard to figure out. The spindle was used. I have a small CNC milling machine too for doing metal parts, running G540 wit UCCNC/UC100. I may well switch the Raptor over to the same controller. It's been working quite well so far.

Since I've never seen a Zenbot, I won't comment along that line, but for my needs, my current machine has been very acceptable.

Dave

Shopbot we own three ---- top notch company, I have been dealing with them for about 15 years -- BTW the 1st machine 96x48 is still running like a top. The drive systems are super powerful nema 34 geared stepper rack and pinion design .0005 resolution .001 accuracy. The included 3D software is amazingly simple to use. Shopbots may be a little more expensive than the hobby machines but the completeness of their packages, robust construction, durability, and the fact that help/support is an email or call away in my view actually makes them a bargain.

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Ken Cierp

http://www.kennethmichaelguitars.com/

Another perspective

There is something to be said for not dropping $10k+ on your first machine. My first machine was a base model CNC Shark that I found on Craigslist for $1500 including a computer and copy of Vcarve pro. It was 6 months old. I learned so much over the 2 years that we owned it, Sure, you can't carve a neck with it, you have to go slow and take shallow passes, but with the tiny bits that are being used you need to go slow anyway. My first 18 guitars were built using that little thing. I made two modifications to it. I added an 8020, extruded aluminum work surface, and better quality collets. It's now making Mandonators in San Jose. I sold it for $1400 with no computer or software. I'm not suggesting that the shark is a good machine, only that it was an excellent learning tool.

Vcarve pro is an excellent product for doing inlay, cutting fret slots, and many other guitar related operations. It's a very easy program for getting started with CNC. I'm about to upgrade to aspire.

One advantage to HDPE is that it flexes when you crash the machine, and you will crash your machine!

Best, M

The only real reason I was looking at it is because of the price point. A shopbot is simply out of reach. Full stop, end of story.

The Zenbot, delivered to my door, is under 3500$. Another 300$ for a router and 300$ for software puts a functioning machine in the garage for about 4k$. Graspable...with on the ground support from someone who knows cnc's...maybe I'm thinking wishfully...

A good thing about having a larger table is that you can mount and leave several holding fixtures in different locations and simply move the XY origin point to accommodate each fixture.

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Ken Cierp

http://www.kennethmichaelguitars.com/

That was something I was wondering about. But in theory, changing fixtures shouldn't take -that- much time...

I have a friend that bought the Joe4x4 kit. He says it's a white elephant in his small shop and that he wishes he hadn't gotten such a large machine.

BTW I assume you know that the footprint of the machine in your shop is MUCH larger than the actual cutting envelope. A machine with a 24x48 cutting envelope will probably consume floors pace closet to a full sheet of plywood. Keep that in mind when deciding where it will go in your shop and how much real estate you want to devote to a single tool.


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Exactly, gonna stick with a 24x48, and park it in the garage. And hope that RH control is not needed for CNC...