New CNC router 8x4 For Cutting Multiple Materials

[ciscoeuk]

Hi all

i am not new to cnc, i have built a small version once before from mdf but scrap it

i now need a requirement 8 x 4 cutting area actual size will 1500mm x 2500 with 450mm z axis for carving vac form plugs, prominently used for wood, ply, etc and for cutting alloy sheet to 12mm, where possible, plastics, foam etc basically an all rounder!

i will be starting this build in march, most of the stuff is on order and awaiting delivery

build consist of

hiwin/equivalent rails all round
4 nema 34 motors kit with breakout and stepper drivers 1600 oz
rack and pinion, - near help hear please with mounting brackets and gear reduction ideas????
2.2kw water cooled spindle er20 with vfd, but looking into a 3kw

this is where i have dilemma, i am not sure what to build the y and x base from as i need as much rigidity as possible to cut alloy/metal sheet

welded steel box for the base (x) ali on verticals

all from 8020 extrusion ( x and Y)

a hybrid of steel and 8020 and ali y/z verticals

and optimal height of gantry from table? as i need to be able to carve plugs up to 125mm in height from router tip

what grade/thickness of ali to use for the y/z gantry? and ali thickness

and help hear would not be rejected!

my main concern is frigidness of the gantry

i am also looking for volunteer/pay to help with cnc parts to be cut, i can help with any related IT issues as i am an IT engineer/Admin, no charge?

look forward to hearing from you all and all the suggestion and advice

would be great if i could meet up, or skype, i don't mind travelling, i live in Newark Notts

i will be posting design after i have got some advice

[ciscoeuk]

forgot if any member got any spare parts to sell or swap let me know, if the fit my needs, i will buy/swap

[ciscoeuk]

this is what i had in mind for the gantry y axis after do some basic calcs and using the spread sheet on here

the deflection for y and z had a tolerance of 0.054, this being 2 x 4 " ali u channel and 1 6 " channel with y axis = to 1500mm but this may get reduced to 1350mm this may be wrong

my calcs may be wrong as i may have use the ss in the wrong way

please put me right

ric

[Jonathan]

Good to see someone using the spreadsheet. You'll find that if you change to similar size box section the deflection due to bending will be similar, but the bending due to torsion will be substantially lower. That's because the torsional stiffness of a channel cross section is very poor. Also put the rails for the Z-axis on the plate that moves up and down, so swap them round. It's much stronger this way since the distance between the supporting bearings and the tool is minimised. The best thing you could do to that design is loose the tall gantry sides, as they're invariably weak compared to the machine frame.

[ciscoeuk]

Good to see someone using the spreadsheet. You'll find that if you change to similar size box section the deflection due to bending will be similar, but the bending due to torsion will be substantially lower. That's because the torsional stiffness of a channel cross section is very poor. Also put the rails for the Z-axis on the plate that moves up and down, so swap them round. It's much stronger this way since the distance between the supporting bearings and the tool is minimised. The best thing you could do to that design is loose the tall gantry sides, as they're invariably weak compared to the machine frame.

i take on board the board the issue of u channel and move over to box are recommending ali box on the y vertical as well

the z axis is one i pick off the net to try the nema 34 motor to see where i could put the pinion drive? my version is similar but to take a nema 23 or 34

the z axis i am building is using hiwin rails and a lead screw set up

can you send me a photo the z axis u spoke about please or threads

on the height, i need to clear 6 " 150mm from tip of router to base and some of what we intend to d, is carve forming plugs, ie engine cowls what do you suggest? as this cnc is going to be used got mixed materials,

hope to speak soon


ric

[ciscoeuk]

hi all this is an update of build i am in the design process stage here's what i been up to!

the cnc base (bed) is steel constructed from 75mm, 50, & 25mm steal box

i would like your thoughts please and weather this is up to the task?

if anyone wants anything welding in steel from Pm a line, not to bad at welding, new 200 amp Welder on its way



have a look

all welcome to comment

[Jonathan]

Not a bad start, but a few changes will make it a lot easier to construct and stronger. The most important factor is how do you intend to fix the box section for the bed (25mm) to the rest of the frame? It looks like it's just welded on at the moment, which makes the bed nice and strong, but the issue is with such a large Z-axis (450mm) you want to be able to adjust the height of the bed. The general idea is for sheet material you put the bed high up, so where it is in your drawing, then for the occasions where you need more Z-travel you drop it down. This is easy enough to do if you drill a series of holes in the 6 vertical pieces, support the cross pieces for the bed on two 8' long prices of box section, then attach them to the frame with M12 bolts. If that's not clear then look at my build log. You've got no chance of cutting 12mm aluminium and having 450mm Z-travel, without having an adjustable height bed.

It'll be a lot easier to make if you use 50mm box section, or something bigger than 25mm, for the bed and use less of it. Also add in some diagonal pieces to the main frame since without them it will skew relatively easily.

Since you want to use this for cutting aluminium, if only occasionally, I wouldn't use rack and pinion since the resolution and rigidity will be worse than with ballscres. You can easily use a ballscrew and 3Nm nema 24 motor on the 1500mm axis, however to use ballscrews on the 2500mm axis requires a large ballscrew and big motors, or rotating nuts.

[ciscoeuk]

oooooops i missed

idea 3

as idea 1 but using 2 or 3 stacked bearing and holder boc ali and direct drive nema34

ric

[ciscoeuk]

xyz
idea

Please comment on this idea i do like the design, but i not sure if this is going to had too much deflection so please advise?

i have reduced the hight y gantry from 400mm to 175mm from the bottom of the z axis

y gantry virtical and mount box section is welded steel, or welded ali

all comments welcome

[ciscoeuk]

THE FINAL DESIGN

I THINK????? suggestions welcome please

for x y and z

the z axis is not final i need help hear please

using hiwin rails and ball screw, spindle using 2.2kw water cooled, clearance to table 165-175mm



using nema 34 motors, but not sure i should use a high torque nema 23 on the z axis

rack and pinion x and y

the y axis can with take a reduction drive or should i go direct drive


help please!


ric