Router build

i want to cut fast ... i cant sit around all day watching the machine scrape about ....

so what would you recommend to cut 2400x1200 MDF minimum ... my initial design was 76x76 tube which was too small ... so 150x100 is too big ...

im not too bothered on non critical design details right now , if the radii is 5mm or 6mm its not gonna make a difference to the whole concept .... when i receive the steel i can measure what the exact detail is and amend the drawing to be sure any bolts/nuts/washers dont sit on the radius of the tube

I don't see why you would not push this build just a bit up and finish with aluminum cutting machine. I mean a very nice aluminum cutting machine.

I am in the process of making now exactly the same working area machine and one of the ideas is to cut Aluminum precisely. Ignore the third bearing blocks in the middle everywhere.

By pushing a bit up, i mean on the long axis 2510 screws from china and rotating ball nut . I am not expert here, before some time Dean told me not to go RP if i want precision cuts. You would not believe how comparably cheap are 2x 3m / screw + nuts, for what they will offer.

2x 100x100x4 for the gantry , 100x100x3 for sides , front and back. All rest cross sections could be 80x80x3

just received 7x6m 100x100x4mm which i will use on all machine. 500eur with transport here in Spain. So basically my design uses 42m of main material. It doesn't matter if you make it on the floor or raise the legs, its the same.

i am expecting from my machine 20000mm/min, servo driven 1:1.5 , with very good resolution. That at 3000rpm of the servos. Not that they can not be driven at 4500rpm. There were panasonic servos at ebay, that have the same torque up to 6000rpm. that should be pretty frightening though

if you want fast, and heavy you will drive it AC servo, yes? Not that it can not be step driven, though i cant imagine what i would feel if it looses steps when i am doing 2m ali sheet

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Originally Posted by Blackrat

i want to cut fast ... i cant sit around all day watching the machine scrape about ....

so what would you recommend to cut 2400x1200 MDF minimum ... my initial design was 76x76 tube which was too small ... so 150x100 is too big ...

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Ok well if your wanting to cut fast then your concerns are not just strength.? Your main concern will be spindle power and tooling.
You Can build the machine like a tank but ultimately the spindle power and tooling will dictate the speed you can cut at. Any machine using 100x100 steel section for the gantry will more than match most spindles that would be attached to a DIY machine.

Building a successful machine is about balance. No point wasting money on expensive servo's, ballscrews and massive steel structure etc if your going to attach a 1.5Kw spindle at the sharp end.! . . . . . Equally no point attaching 10Kw ATC spindle if the machine is flexing like a jelly fish. The results while differant in practise will still be the same.? . . . Disappointing.!

Balance is required so you need to define what your going to cut with the machine and be realistic regards the feeds/speeds/DOC. Everything needs to match and suit to get a balanced machine and this is where it gets hard and expensive to achieve with a Jack of all trades machine. Esp if your chasing speed.!!

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Originally Posted by Blackrat

so what would you recommend to cut 2400x1200 MDF minimum ... my initial design was 76x76 tube which was too small ... so 150x100 is too big ...

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I never said 76x76 would be too small and 80 x80 would make a decent gantry if design was good so I wouldn't be too concerned using that size section provided it had decent wall size. . . BUT . . Your box on box with no bracing and open ends isn't a good design IMO so I'd be looking to change things in this department.

wahoo

my rails and servo kit has arrived

but now to finalize the design to get building

oops ..

the problem now is how do i do the Z axis

mount the rails so that they move ? or mount the bearings so that they move ?

i realize that mounting the rails so that 'they' move is better as the forces on the rails are consistent and that the bearings are fixed ( as per the drawing) and .. that the bearings are maximized as they are directly bolted ontop of each other

but ... the biggest problem is that the travel is now limited ....

if i google z axis pictures, the majority is showing the rails fixed, and the bearings moving ... is it really worth the effort to do the visa versa ?

i think this render explains it a little better

the gantry bearings are directly onto the Z bearings which is great ... but i can only lift the Z rails until they are level with the bearings, which stops Z clearance .... sheesh i feel like im speaking Chinese now

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Originally Posted by Blackrat

i think this render explains it a little better

the gantry bearings are directly onto the Z bearings which is great ... but i can only lift the Z rails until they are level with the bearings, which stops Z clearance .... sheesh i feel like im speaking Chinese now

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Why would you want to go higher than that you have shown, you can't go higher than the gantry so lower the bed. The Z rails (in my opinion) are better fixed on the plate that the spindle is fixed to as it helps to stiffen the plate etc. ..Clive

to clear the work piece ... the bit will foul if it doesnt retract far enough

dont really wanna lower the bed (or raise the gantry) as this will induce more flex , vibration , resonance and the list goes on

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Originally Posted by Blackrat

to clear the work piece ... the bit will foul if it doesnt retract far enough

dont really wanna lower the bed (or raise the gantry) as this will induce more flex , vibration , resonance and the list goes on

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Well how about moving the z bearing blocks higher up the plate. ..Clive

Its a part of my designs also to be able to move the spindle up to clear for a large work piece. But in real life that would mean realigning vertically the spindle, and its time consuming process. The only proper way to do this without fiddling is to make a custom mount and machine the spindle so they fit perfectly, as i make now on my machine now. But its expensive.

having in mind at which stage are you and the prices of ball screws and rails for Z, if simply you made the error and bought them short, spend now 100 quid and buy new ball screw and rails, instead of compromising the whole investment. If don't have them, all the better. The Z should be made properly, not to speak that you want a high performance Z.