My baby 15" x 15" machine

[wilfy]

I've done it!!!

that is designed the whole machine using only 50x25x3mm box section..... oh and a little bit of 25x5mm flat bar as very helpfully recommended above... i had to give in somewhere as i needed 60mm spacing in a few places which using 50mmx25mm box section wouldn't allow... the fact is the flat bar adds on £4 to my total order so i cant grumble about that.

so the picture below is obviously missing a bed, but i have basically spent the last week or maybe longer re-designing this whole machine within the limits of the screws and rails I've already received. the reason for this was due to me using the drawings from another site for the rails and bearings making basically all measurements out.. but it actually worked in my favour as it reduced the need to have 60x40mm box section in my build.

the colouring is purely to make it easier to count the lengths and for me to picture which bits move together, so purple is the x axis and the bed when its done, blue is the gantry, yellow is the y axis carriage and green is the z axis carriage. i am also yet to design a spindle mount as i am planning to do this in another program so that i can export it to dxf and have some lucky member from here cut them pieces for me, the plan is to mount it to the 2 pieces of box section that the rails are mounted to.



the biggest changes to this from my earlier designs are the x axis screw is now located a hell of a lot closer to the bearings which if i understand right should reduce any racking, my only concern here is do i need to add a length of box section on the outside of the screw bearing mounts to reduce flex here? in my mind they don't go under any stress when the screw turns but if someone tells me i'm wrong it'll be the next change.

I've also reduced the height of the machine which is one of the reasons there is no bed at present as the current z axis would smash straight through the previous design, the height now from x axis bearing center to y axis bearing center is 265mm.

all the bearing spacing's are as follows

z axis center of bearings on rails 120mm
z axis rail spacing 175mm ( should be 180mm actually)
y axis rail spacing 180mm
y axis center of bearings on rails 198mm
x axis rail spacing 804mm
x axis center of bearings on rails 255mm

this gives a total cutting area of x = 400mm, y = 529mm, z = 100mm which considering i originally said 15"x15" and its now more like 16"x20.5" i'm very happy.

the total length of steel up to here is around 8mtr's of 50x25x3mm and 1mtr of 25x5mm flat bar so i have around 7mtr's left to make the bed with which i know will take most of that 7mtrs. that brings the total cost of steel to £76.31 and the only other things i need to fabricate are the spindle mounts and stepper mounts which i have a feeling both will come from alu but i'm not sure yet.

so provided i dont need any more steel the total to date is £629.18 and thats for spindle, rails, bearings, screws, ball nuts, screw bearings plus all the steel to fabricate the frame