New CNC router 8x4 For Cutting Multiple Materials

[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]

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.

JONATHAN
thanks for the advice and taken on board,

i have decided to cut the z axis height down to 400mm ballscrew as the y gantry is 2x8 ali box

decided this after i found out the you can mill sections at a time and glue together to for a fibreglass/vac form plug i think mach 3 has that ability or was it artcam????

at a later date build a cnc router for carving vac form plugs,the later cnc 800 x 800 from ali extrusion and plate this does not have to so stiff and rigid as it only carving foam/plastics and MDF and pine

since i posted i have modified the frame to be very rigid, see pics




i know that using 50mm box would be better and save some pennis but i decied to stick to the 25mm as a way of spreading the weight and of course it looks nicer but this may change

as for the x axis and using rack or ballscrews the jury is out on that at the mo , thanks for the spanner by the way LOL

i will post my idea for using rack and pion and a lock plate,

i will have that idea up soon

speak later, buy the way i am on skype if u want to face to face pm me

ATB

ric

[ciscoeuk]

PART TWO

Y GANTRY IDEAS

IDEA 1



hiwin rails, nema 34 x 2, rack and pinion, aluminium plate not to sure what thickness to use or use box section and mill a lap joint, bolted and ali welded


Idea 2


hiwin rails x 2, nema 34 on spring drive plate, ali box section, rack and pin, use box section and mill a lap joint, bolted and ali welded

Ideal 4

using ballscrew and thread 20mm or more use box section and mill a lap joint, bolted and ali welded

Idea 5
ball screw & tread moved to bottom 2 X NEMA 34 use box section and mill a lap joint, bolted and ali welded

this might be over engineered???????

let me know what you think

advice please

ric