Large aluminium profile build

[jeronimo]

Hello everybody,
first off I would like to say thanks to the dwellers of this fine forum for the amount of information Iv’e learnt during the countless hours of reading about and going through various build logs and threads!


SHORT VERSION:
I tend to write a lot, so feel free to skip the long preview and just take a look at my questions below, bottom line is I need a machine that will be able to cut wood and plastic at reasonable speed, have the option to cut aluminium (even at slower speeds as this will not be the main job) and have the option to modify later on if needed.



LONG VERSION:
I run a small product design/collaborative design space (kinda like an invitation only makerspace) and am now at the stage where I could really use a CNC.


I’m hoping to build a semi-modular machine that will allow me to swap out parts and change the stuff it can do according to the type of job/material I want to work with:


Mainly it should cut up wood, from ply to harder stuff, it should do this well. I will also need to work with plastics and foams and I might want to extend the Z later to allow for larger blocks or add a 4th axis at some point.
It would be great to work with aluminium as well (until I have the chance to buy and convert a dedicated vertical mill).
I would like to be able to work with full sheet material so I’m thinking of a 1300x1500x150 format (total size not workable area)


I’m guessing it will work only a couple of hours a week.


due to the modular nature of the build I think alu-profiles are probably the least worst material for the bed/gantry as this will allow me to bolt on and swap out parts as projects change.


so here’s the part list I’ve got so far:


PART LIST:
80x120 profile for the Y axis
80x40 profiles for the cross sections
80x160 for the X gantry beam
300mm Z axis with 150mm travel
20mm alu machined parts to bolt everything together and for the Z axis
HIWIN 20mm linear guides all over with wide carriages
Belt driven 1610 ball screws with FK/FF type supports
HTD/GT3 15mm wide belts / pulleys + idlers
Nema 23 420 oz motors (have these from another project) coupled with maybe a Gecko 540 for simplicity?
2.2Kw water cooled Chinese spindle with a hitachi or similar VFD


For now the machine bed will sit (bolted to) a heavy 3000X1500 table (steel frame and quartz surface that i already use as one of the working tables in the studio. does the table have to be perfectly levelled out if the machine itself is squares?


QUESTIONS:

• single large profile for the X gantry beam like it is now, or rather break it up into an L shape as i see is popular?
• iv’e seen some threads in which the Z axis was designed in a way that the bearing carriages are stationary and the rails move with the spindle - could anyone point clear this up or point me to the right thread?
• are the alu profiles rigid enough for my expectations of the machine (i think maybe machining aluminium would be pushing it)?
• bolting linear guides directly to the aluminium profiles - is this possible at all? It seems I’ve seen some have been successful at doing so and others have ended up placing ground bar stock in between the profiles and the guides. I could theoretically do the epoxy self levelling method on one face of the profiles, it would leave it modular yet levelled. I’m just not sure it theres enough material for threading later on as i will not be able to use the T-nuts anymore..?
• can I swap out the machined 20mm aluminium parts (such as Z assembly, gantry ‘risers’ and motor brackets for welded 6mm steel?
• 1610 ballscrew or 2010 for the Y axis?
• filling the gantry profile main cavities with epoxy to add rigidity/dampening material, silly and messy or good idea and messy?
• which axis should be planned with wide and which with long bearing blocks?
• to keep things simple I was hoping to use the ready made ballscrew end supports, with the design I have now it seems the FK/FF type would work best, but I have also seen that there are the BK/BK type with mounting holes parallel to the ballscrew - so similar to FK/FF, is there any difference between the options?

I’ve got a thread going on at cnczone, and have used some of the info there to iterate the design - I would love to get some feedback from you guys as well regarding the design/expectations/selected parts before I begin my actual build(i'm in no rush to order parts).