illeboc-r's first cnc build in pics and diagrams

[neurofen]

Hi, I thought as i go along i'd post some photos and specs as i build my first 3 axis cnc.

fs.. Just clicked the back button on my mouse and lost everything i typed in the last 15 minutes, so until i sleep abit and muster the energy to type it all again there's 4 pics attached.

Since at present i only have 2 ballscrews and a naples coombe slide table which i picked up cheap on ebay i was toying with the idea of running the y axis screw under the table. Now im not to sure, ,looks like i'll get another one machined when i can afford it so that theres a ballscrew running either side of the y axis. i dont know if this is over kill.

The z-axis doesnt have much travel: 50mm, but should do for the time being, until i can build one from scratch.

Will post back tommorow with specs and pics of the rest of the pieces that i have so far and some sketches.

[neurofen]

been trying to make some structural decisions. not sure wether to have the y axis beams face down and plate them with 10mm al. bar with the ballscrews mounted on top: layering may cause vibration issues. Or have them standing upright which should be better in terms of flexing in the z direction and mount the rails and ballscrews in a different configuration.

off to the machine shop tommorow at any rate to start drilling holes in the frame, and to maybe mill some support plates, time allowing

[neurofen]

not sure if this is a good idea or not, i've sandwiched some 10mm al. flatbar between the bottom of the y axis support beams and the perpendicular supports below, to add a bit of weight to the frame:

vibration might be a problem, and maybe rigitity can be gained elsewhere.

[neurofen]

is having 2 sets of linear rails per beam overkill?

any help would be appreciated.

i've got a feeling one per beam will be enough

[neurofen]

one possibility : y axis support beams face down , 2 linear rails and ballscrew on top

[neurofen]

second possibility is: 1 linear rail with ballscrew positioned on top of the carriages with the mounting plate sandwiched between them

[greenb_60097]

is having 2 sets of linear rails per beam overkill?

any help would be appreciated.

i've got a feeling one per beam will be enough

I'm running THK sr15 (15mm rails) on my machine atop 80/20 extrusions and that is fine. I'd say save the money and rails as the paired as draw would certainly be overkill for something this small.

Good luck and keep the pics coming

Brian

[neurofen]

with the beam standing on end, the base plate isnt to scale.

[neurofen]

I'm running THK sr15 (15mm rails) on my machine atop 80/20 extrusions and that is fine. I'd say save the money and rails as the paired as draw would certainly be overkill for something this small.

Good luck and keep the pics coming

Brian

thanks for that. will stick with one rail per y axis beam, i had a feeling 2 was too many. good to here from someone with a similar rig.

[neurofen]

20mins to get that sucker back in..

[hemsworthlad]

Hi,

Those rails will be fine with one rail per side, I run the same on my machine and my Gantry is 78lbs(36kg).

What do you plan doing with this machine.?

Those hollow Alu beams will resonate something horrible when cutting anything hard which will produce cutter chatter, I would consider capping and filling them with dry sand or concrete. Esp the gantry.

Dont be put off by the weight, with twin ballscrews you have lots of mechanical advantage and good efficency so with the right size motors they will move far more weight than you probably realise.
Mass is helpfull to a cnc machine and with this setup you have lots of potential for a really strong well built frame work with a massively strong gantry. . . . Dont chase weight with this setup it's not required and will actually give you a lesser machine with poorer results than the components are capable off providing.!

The long beams will need supporting in the middle else you will get deflection at the centre and even without filling they would still need supporting IMO to prevent sagging due to gantry weight. . . . . Being honest this layout of long beams on top of short basicly creating a bridge from end to end is a weak area I would seriously consider changing.

Hope this helps.!

[neurofen]

Hi,

Those rails will be fine with one rail per side, I run the same on my machine and my Gantry is 78lbs(36kg).

What do you plan doing with this machine.?

Had to have a good re think on this r recently, started getting the bits and researching about 3 years ago, and at the time was to be honest thinking more of the technologies and that i could actually own one at home, than the actual practical uses of the machine i was going to build.

I was building custom computers at the time and often needed some engraving done, and could never afford to get al. flat bar milled to create for instance objects like the macbook pro unibody.

So Basically to start with engraving and light millinglastics and aluminium. though the more i look the more i realise i can do a lot more on the milling side if i have some weight in the frames, and a decent motor spindle.

Those hollow Alu beams will resonate something horrible when cutting anything hard which will produce cutter chatter, I would consider capping and filling them with dry sand or concrete. Esp the gantry.


ive got to admit i was a bit worried about using the box section for the frame and was thinking of someway to reduce the vibration. I bought 5 metres of it about 2 years ago and didnt like to think of it going to waste.

From what i'd read sandwiching metals together (specificly inserting weighted rods inside the box section) would more than likely cause more vibration.

filling them with sand seems like sound advice though this may be impractical, this might do for th etim ebeing until i can aford some profile retrofit framing, or whatever its called.

Dont be put off by the weight, with twin ballscrews you have lots of mechanical advantage and good efficency so with the right size motors they will move far more weight than you probably realise.
Mass is helpfull to a cnc machine and with this setup you have lots of potential for a really strong well built frame work with a massively strong gantry. . . . Dont chase weight with this setup it's not required and will actually give you a lesser machine with poorer results than the components are capable off providing.!

The long beams will need supporting in the middle else you will get deflection at the centre and even without filling they would still need supporting IMO to prevent sagging due to gantry weight

The plan is to have another 1 meter length in the middle to stop the sag, just havent picked it up yet, i getting the bits as and when i can afford them


. . . . . Being honest this layout of long beams on top of short basicly creating a bridge from end to end is a weak area I would seriously consider changing.

could you expand a bit on this? which way around would you reccomend?or maybe an alternative.

I've got the use of milling machines etc tommorow but have to travel quite a way. if i can get this machine up and running with the bits i have already, then making the necescary changes and drilling holes in a new and improved frame i could do from home a lot quicker


Hope this helps.!

thanks al lot