School me on the best machine for big hardwood

[bluesking]

I’ve spent a lot of time lurking on this great forum and planing my next machine. I’ve finally accepted the extent of my ignorance and am now totally in a state of decision paralysis - please help!!

I am an electric guitar luthier and for a few years I have used a small and crappy chinese 3018 CNC for inlay work and fretboard carving. Its been a trial but I have learnt a lot. I’m pretty skilled with using both handheld and tablemounted routers and working with wood in general. I also have a software and electronics background, reasonable mechanical savvy but little no metalworking experience.

I’ve decided to take the plunge into using CNC to carve full guitar bodies and necks. I will need a working area of at least 900 x 400 mm to achieve this - whilst bigger would certainly be more flexible (e.g. for occasional bass guitars necks and neck-throughs) I think keeping it smaller is better - for size and weight constraints. In the rare case I need to, I’m happy to tile the work.

Here are some of my initial thoughts which I’d really appreciate a sanity check on:

1) My feeling is that for reasonably large hardwood pieces I need to ensure a high feedrate is possible - at least 5000mm/min if not 10000. Accuracy is important but I think not as critical as for you metalworking guys - my feeling from my handbuilt guitars is that 0.1mm accuracy is totally sufficient. Is my thinking on the right track?

2) Rigidity obviously a key concern as it would be for any machine - I’d like to take as high a DOC as possible. I’ve seen lots of youtube videos of chaps CNCing guitars, and often I’m very surprised by the very small bits they seem to use (often around 1/4”). This seems really strange to me - I’d rarely use such a smal bit in a handheld router. The obvious thing is, I need a spindle capable of taking ER20 collets, but the more difficult problem is finding a machine/design that provides adequate rigidity to do justice to something like a 1” ball nose with a 3mm DOC.

3) Machine weight is a major headache. Its quite possible my workshop may need to relocate and I am concerned about having a 200kg behemoth to drag through doors and around stairs. I appreciate this is going to limit the rigidity I can expect! My best hope I think is having a machine that is straightforward to dismantle (ruling out the relatively attractive full table sized chinese offerings).

4) Cost is certainly a consideration but to some extent it is not the limiting factor - the weight problem dominates.

Here are my options as I see them:

1) Build my own. I have taken great interest in the build described here http://www.mycncuk.com/threads/11266-3-Axis-900x500mm. Similar requirements to my own and a largely modular aluminium design. Machined aluminium sideplates would be the biggest challenge for me but I can potentially access a CNC machine at my local hackspace. I’d look to use 4Nm Nema23 motors and add a pulley coupling mechanism - hopefully allowing me to tune the gearing for a good balance of accuracy/speed (also it seems much more difficult to get hold of 1610/2010 ballscrews compared to 1605 so I see gearing as a way around that). I could perhaps dedicate a full month of my time to this build and have costed it to around £3k - is this mad?

2) Omio 9060 CNC for around £3k all in (https://www.omiocnc.com/x8-2200epl.html). Looks like a generic chinese machine but with all the trimings (2.2kw water cooled spingle, square supported rail, ballscrews, bellows, reasonably quick shipping). Would this be much worse than option 1? In some ways the basic design is very similar to the design for 1, aluminium extrusions with aluminium endplates. Motors are directly coupled though and a max speed of 4000mm/min which seems a little slow. A respectable performance in the following video even using a tiny router cutter for some reason (https://www.youtube.com/watch?v=HyMO89obfmg)

3) A brace of comparatively heavy and rigid machines which utilise at least some steel frame components. These tend to be more expensive and not to use square supported rail and some even use ACME lead screws - on paper this sounds like bad news but I wonder whether the overall machine rigidity is more important than the “sum of the parts”?

a) JBEC 106512
£7k+ and a lukewarm mycncuk reception (http://www.mycncuk.com/threads/6389-...able-in-the-UK)
but I have seen some videos of quite impressive guitar building performance (https://www.youtube.com/watch?v=OCC_4lJcRAI)

b) Kompas H - 1000 GS KIT
Eastern european wildcard, £1.5k for a mechanical only soltuion - could do the electronics myself but max speed seems really low

c) CRP4828
Mechanical only for £2.5k - could do the electronics myself. Seems like old technology, using roller bearings and ACME leadscrews. Still has admirable performance as in this example (https://www.youtube.com/watch?v=1VEebB157G4). Maybe the rigid frame and modular construction make it a winner?

d) I tech K6090T (https://www.scosarg.com/itech-k6090t-q-series-desktop-cnc-router)
£5.5k and seems to have all the right qualities - square rails, ballscrews, fast traverse! This seems to be the pick of the bunch but at 200kg I worry about transportability. How would you move this around if it was yours? Theres an unboxing video of this machine on youtube and they use a chain hoist to get it up on the workbench!

Wow, that was quite a lot. If you got this far I’m really grateful. Any help or advice you can give would mean the world to me at this stage!