Newbie- first design, after constructive criticism

[Ste Hughes]

hi guys

i saw my first CNC machine 2 days ago, i didn't know these thing could even be made!!!

i am fascinated by them and i need one in my life - the machine will be mainly to cut in letting on gun stocks and maybe the entire thing at a latter stage - the spindle (is this the cutting part btw???) will be a rotorzip but i have heard they have a p poor casing so may remove it from that and get one more suitable made (or just buy a proper one lol)

the smooth cylinders are meant to be threads but i just learned google sketch up yesterday, what programs do you guys use to design these in?

the machine will be made from 18mm MDF, may move it up to 25mm i will see. the machine base is 1200mm x 600mm, i am aiming to be able to cut on at least 1000mm x 500 x 400Z (sorry about mm, i am from the uk lol)

the side wall idea is to keep the sawdust in one place allowing easy clean up, i realise i may have to sit there with a shop vac while the machine works but thats no problem, it also keeps the dust off the angle bar that the top bit slides on.

so this is my design so far, its just the X or Y axis (not sure which is which lol)

am i on the right track so far?

i am currently scaning the forum for idea's about how to do the other across axis and Z axis











i will be using the biggest steppers i can afford when i get to this point

i will be making my own drivers and using a custom arduino based controller. (electronics is one of my hobbies so its all gooood )

let me know what you think

Cheers

[ger21]

Make the base of the gantry sides 4x wider, and make the gantry 1/4 as high.

[veteq]

Aren`t those machines nice my friend...... I know

For some advice, the basics off construction are important, youre design looks nice but isn`t going to perform that well i think.

Maybe i have a few hints for you to go further with optimising your design:

Lets look at the verticale beam off your design (off the moving assembly)

You cann look at it in 3 ways, the front, side and the top plane.
If you look at it as a structural part on itself it is only stiff in 1 direction

(If you try to bend a ruler, you cann do this in 2 ways, 1 is stiff 1 isn`t.)

imagine:
if you bend a part and look at it in a 2d way the bending axle is in the middle off the part, try to get more material away from the bending axle, then it gets stiff.
(so for the vertical beam, make it as wide as it is deep, also try to make it a lot less heigh)

Also, a bigger stepper isn`t always better, a bigger stepper is bad for fast acceleration. (google for inertia principle)

A good and easy software package is solidworks, you cann get a student version for 100 bucks. you can learn designing parts and assemblies in 1 weekend, i use it to.

Kind regards.

Roy B.

[ahren]

Agreed with ger that you are likely going to have flexing problems with the gantry as high as it is. Additionally, I'm not sure I understand your bearing system. It appears to only constrain the system in one direction, and that you are relying on the faces of the bearings to keep your gantry constrained side to side. This really doesn't work -- you'll have a system that either binds, moves in directions you don't want it to, or both.

I'd recommend checking out the linear carriage system I offer for ideas. You're welcome to use the design, or some modified version of it. Cold rolled steel makes a very effective bearing surface.

Best regards,

Ahren
www.cncrouterparts.com