Small workshop CNC router, steel base, planning on ATC

[spresv]

Hello!

This is not so much a build thread as the machine is mostly complete and operational, but i wanted to share and document any further development. There are so many people over here with much more experience than me, so i'm open to criticism, suggestions, anything.

A bit of backstory, i started with a chinese 3040 router frame, which was mostly horrible. I started upgrading and reinforcing it here and there but soon realized that it was a lost cause, so i started building a machine from scratch. Goal was to have a machine rigid enough to mill aluminium somewhat reliably, but since i'm a student currently without a job, it had to be as budget minded as possible.

First thought was to make the entire frame out of 80x80 aluminium extrusions, but that thought quickly went away due to cost and the fact that i somehow got it in my head that it wouldn't be rigid enough. So i made a frame from 10mm mild steel plates with a 12mm mild steel top, with holes for mounting a vice or an aluminium t-slot table. The base ended up weighing about 50kg alone. Complete machine comes about 75kg.

Then i adapted the gantry i had made for my previous machine. Double ball screws for the x-axis, 16mm ball screws and 16mm supported shafts all round, coupled with 270oz stepper motors. I'd love to have gone with hiwin rails or something like that, but it was more than double the cost and i really couldn't afford it. I really regret it now though. Spindle is a generic 2.2kw chinese spindle. Travel ended up being 550mm x 250mm x 125mm.

Now at that point i intended to get the steel frame stress relieved and the top skimmed but the machine shop wouldn't be available for a few weeks, so i couldn't hold myself from assembling and testing it. First impressions are really satisfactory. There is a bit of ringing from the steel frame, but much less than expected. I'll probably be filling the base with epoxy granite, or something to that effect. I've made a couple of samples (like the carburetor mounts you see in the pics), and i'm quite pleased with the result. These were made with a 2 flute 8mm carbide end mill on ~12k rpms, with a 6.8mm depth of cut and 0.7mm width of cut and 1600mm/min feed rate with no chatter. That's not the limit, it's just the first combination i happened to use randomly, and worked good.

Next step is to disassemble the whole thing, get the base relieved and skimmed, put it back together and square everything up for good. I'll then fabricate some sort of enclosure, because i intend to use both mist cooling and flood cooling. I haven't made up my mind if it'lll just be a plain polycarbonate enclosure, so that the flood cooling won't be making a mess, or if it will be a substantially larger double-walled wooden soundproof cabinet. Also, i played around a bit with the VFD's torque boost function, which does make a difference and will definitely be of use, but the spindle gets really hot really quickly, so a proper water cooling system is in order, instead of just a bucket with a recirculating pump.

I'd love to hear your thoughts! Excuse the crappy quality pics, i'll be posting better ones.
Steve