New CNC Mill on the horizon

[fvfdrums]

Ok I'm going with profile rails on all x,y & z 4 blocks on each rail.

My thoughts are going towards a low level gantry eg minimum deflection in relation to the x axis with the adjustability of the bed. I have access to a fair bit of 100mmx100mm off cuts and was thinking of using this as the base for the machine. Would this be too extreme for the gantry?

[Jonathan]

My thoughts are going towards a low level gantry eg minimum deflection in relation to the x axis with the adjustability of the bed. I have access to a fair bit of 100mmx100mm off cuts and was thinking of using this as the base for the machine. Would this be too extreme for the gantry?

Excellent. Nothing's too extreme. The worst that will happen is you might need bigger motors, or have to accept lower feedrates (which is irrelevant for aluminium cutting). Design the machine then select the electrics to suit. Don't start trying to make things lighter to optimise the feedrate since a rigid slower machine is much better than a fast weak one.

[JAZZCNC]

Excellent. Nothing's too extreme.

Design the machine then select the electrics to suit.

Completely 100% agree on both counts. . . . If you then filled it with concrete you still wouldn't be extreme, Infact if you mainly intend cutting Aluminium I recommend you do exactly that has it makes a big difference to resonance and quality of finish.!!

[fvfdrums]

Right I have had an hour to play in solidworks so this is not very detailed its just an outline of the idea I am thinking of once I have ironed out any potential problems I will go in a bit more detail.

So once again 1200mm x 800mm bed current z axis 200mm ? good bad ugly?

z axis is based on 4 blocks sitting on a 200mm square footprint eg one on each corner of a 200mm square.

Adjustable bed for altering depths of material / things to machine.

twin ballscrew on the x axis, single on the y and z

concrete/ sand etc in the box section taken on board I will give that a go.

[JAZZCNC]

concrete/ sand etc in the box section taken on board I will give that a go.

Ah so you've seen me mention sand before.!! Yes dry kiln sand works good and is easily removed.

Like the chunky frame look forward to the detailed version.!

[Jonathan]

Ah so you've seen me mention sand before.!! Yes dry kiln sand works good and is easily removed.

That or seen someone else mention it - it's a well documented solution.

I'd go for epoxy granite over concrete. Concrete moves/warps after it's set and since you're using profile rails any movement in the piece they're mounted to could cause serious problems. If the rail is bent ever so slightly the slide coefficient of friction increases dramatically, so if this happens over a long period of time you probably wont notice until the machine stalls due to the greater power needed to move each slide. By that point some serious wear could have occurred to various parts in the system.

Frame looks appropriately sturdy, but I'd be inclined to add some smaller box section to link the legs. It wont cost much compared to the rest of the frame and could help with resonance, since at the moment you have a large mass supported by legs (rather like a cow which wobbles a lot if you push it!)

[JAZZCNC]

That or seen someone else mention it - it's a well documented solution.

I'd go for epoxy granite over concrete.

Ye but seemed logical has I mentioned concrete and he added sand which I've mentioned and recommended many times in the past.!! . . . . But does it matter.!!

Personally I wouldn't go with Epoxy or concrete.!! Sand is cheap the concrete example was to make a point that heavy or dense is good.!
Epoxy is not a good solution either has the heat from the large qty of epoxy could and will warp the steel.!! . . .Plus the cost of epoxy it would be just has cheap to buy plate steel.??