Greetings, :wave:
I have come to humbly prostrate myself before the gods of DIY CNC with what I'm hoping is not a stupid idea. :banana:
So basically I live in a rental and want to build a giant CNC router table which at this stage looks like it will have a cutting area of 2500x1300x120 / 7.56'x4.27'x4.72". I plan to make the table out of two sub tables with self leveling feet which I can *hopefully* align with the space between being spanned by sections which bolt onto either table. Each sub table will measure 1380x1000x650 / 4.53'x3.28'x2.13' (715 / 2.35' with leveling feet installed) and weigh approximately 50kg / 110lb which means two people should stand a chance at a) moving the bloody thing and b) fitting it through a standard doorway (am I asking too much?). The top spanning section weighs in at 15kg / 33lb.
75x50x2 / 2.95"x1.97"x5/64" RHS is used for the main structure with 65x35x2 / 2.56"x1.38"x5/64" RHS for the centre spans and 50x25x2 / 1.97"x0.98"x5/64" ribbing for the table surface. I will clad each section in plywood and then attach an MDF wasteboard to the top later..
I want to use 2800 / 9.19' long 8080 sections resting on 18x brackets cut from 75x75x5 / 2.95"x2.95"x13/64" equal angle section which will bolt to the side of the table *hopefully* allowing me to finely adjust the straightness of the 8080 section in both the Z axis and parallelism in X and Y.
After speaking with the owner of a local steel merchant he supported the idea of cutting the angle section into brackets so that when I'm trying to get the 8080 level I won't be fighting the angle section itself. Yes there are a million holes to drill but I'm a patient man. (Last year I built a 3m / 9.84' tall 6m / 19.68' diameter 4v geodesic dome with 3D printed hubs and 250 lengths of PVC conduit cut using various jigs, ended up having to use a heat gun to flare the ends of most of the pipes to fit on my hubs as we all know the ID of PVC conduit is not a spec'd dimension @#$@#! haha)
Compared to a lot of the builds I've seen, mine certainly seems to be on the light weight side of things but I've tried to optimise the usage of the RHS steel sections to give it strength where it needs it / reduce the length of spanning sections etc. The local steel guy who built his own CNC plasma table pointed out that you're paying for metal by the tonne more or less and so RHS with narrow top is ideal for spans where square section is just wasting metal etc.
I've conducted a gazzilion stress/strain simulations and the ones pictured show the table itself loaded with 300kg (2943N) along with an additional 200kg (1962N) load held by the side brackets (100kg per side) with only one foot fixed on the floor and the rest of the feet on a friction-less sliding surface. Max simulated deflection is a little over 0.1mm / 0.004" and my gantry assembly at this stage will be around 45kg / 100lb including spindle etc so as far as I can tell this will be well and truly strong enough for a wood router.
It's easy enough to add gussets later down the track if rigidity proves to be insufficient.
The 8080 will support HGR20 w/ HGW20CC blocks for the gantry which will be a section of 80160 - driven by a moving omega drive using 25mm / ~1" AT5/ATL5 belt but I'll post more about that later as my primary focus at the moment is on the table itself.
I'm a humble electronic tech / tinkerer who's welding is good enough to join @#$# together but by building in the adjustment I hope to save myself from disaster down the track.
Normally I'm pretty shy / lurker but this has been a dream of mine for a long time and I have a patron who is paying for more or less everything to make it happen so it's time to make this dream a reality!
I really appreciate the opportunity to engage with all of you lot so let the constructive criticism begin! (flame2)