Hi all,
I am in the middle of designing a 3 axis CNC mill/router and eventually a 4th axis to make out of T-slot extrusions, 40x80, 80x80 etc plus partially encased in 16mm thick aluminium plate. I need the machinable bed to be 1400mmX x 620mmY x 250mmZ minimum and have designed the table/bench/stand to be 2000L x 860W x 950H + lockable castors and levelling foot pads which should give me more than enough space for the machine and a little bench for items and the ability to bolt it down to a concrete slab eventually. I'm going to be making the main frame of the "stand" using 50 x 50 x 2mm SHS which will be fully TIG welded. It will have a draw for the computer/touch screen, a slide out section for all the electronics for easy serviceability, coolant tank for when I need it, place for a vacuum, tooling draws etc etc...
I'm planing to machine timber (with a vac head on just the 3 axis), some composites, acrylics etc. but mainly I'll be working with aluminium (6061-T6/T651, 7050-T7651, 7075-T6 etc...) and some small parts I want to make out of mild steel, 4130, 4140, 4340 and G5 Ti (if it's possible with a coolant feed)... It'll only be a small bit of steel alloys until I can build a dedicated 5 axis machine that will be solely for these materials... (Baby steps lol )
I do have some drawings of what I am thinking but I think I'm on the wrong path with the linear bearings and rails of my first design. I initially designed it with those 25mm DIA fully supported rails and trucks from the CNC shop, but I am unsure they are going to be rigid enough for what I want to do with the machine.
I am now looking at THK bearings and rails for increased rigidity?
I'm thinking:
SR35W's for the top of the X axis rails (running 1800mm long) and for the top of the gantry's Y axis.
HRW60CA's for the 2 outer, lower X axis rails and the lower Y axis rail.
Then maybe 2 HRW27CA or CR rails/bearings for the z axis.
Does all that sound good and solid??
I'm thinking ballscrews for travel. 2 on the X axis and 1 for the Y and Z axis'.
Would it be better to use rack and pinion for this machine because I want to use a lot of aluminium and the occasional steel alloy? I know I need it to be as rigid as possible if I want to think about milling steel at all. (The steel will be 400mm x 400mm x 20mm max steel alloy at the moment... And some 125mm max OD on the 4th axis)
The gantry risers (sides) will be 25mm thick aluminium plate mounting off of 4 trucks (2 lower tucks on edge and 2 on the flat horizontal) with the rear of the gantry being 25mm thick aluminium plate. The main section of the gantry will be 2 lengths of 80x80 T-Slot stacked on top of each other and bolted to the rear 25mm plate then the rest is housed in 16mm aluminium plate (front, top and base).
The Z axis will be 25mm thick aluminium plates and will hold a single 2.2kw water cooled spindle to start off with, with the possibility of upgrading further down the track if it doesn't have enough grunt.
4th axis... Still searching...
Steppers I'm still thinking about what would be the best for it along with drivers etc...
Basically I'm wanting to build it right (solid, beefy, rigid etc...) from the start rather than spending even more money later on down the track trying to make it better or wishing I had done it differently from the get go. Please pick my plans (or lack of, I'll get actual plans up soon...) to pieces as in if this isn't going to work well for what I want to do with it. This is my first machine and first CNC build so all the help, advice and info is more than welcome and much appreciated! I hope to get some progress reports up soon!
Cheers
Steve