Newbie- Tough Enough?

[hiedadam]

As a 23 year old college student I'm finding it's really easy to get good software for free. So a couple weeks ago I got my hands on Autodesk inventor and decided to finally put pen to paper(err... mouse to screen) and start tackling a persistent desire to build a cnc router that has been following me for almost 10 years. I've never used it or any other CAD program before so I am still learning, but i think what I've come up with is a usable outline.



The motor mounts are something I have on hand that were machined locally as well as the leadsrews. The leadnuts will be tossed and replaced with anti-backlash derivatives. The leadnut brackets will also be simplified. The less I need to source out the better and cheaper this project will be.



The work envelope will be about 29 x 40 x 5, and the structure will be made hopefully from as much aluminum as possible. I would like to be able to move it relatively easily. Too my questions....

Taking the loads that will be put on the bearing blocks and linear rails into consideration should I re-orient the rails in any way. Also, I tried to use the rails to strengthen the gantry. Should more re-reinforcement be added? The stand kinda has me at a loss. I don't want too much reinforcement because I would like to access stuff down there, and maybe store sheets of wood or aluminum. Whatever I may decide to cut.

Actually building the beast is a ways off. Probably the start of next semester or so.

Thanks in advance.


Now for the pics...

[multiplex]

looks like your design is off to a good start.

the orientation of your rails seem good. Its one thing i wish i could change on my design, as i have the rails and bearings hanging down and they don't seem to be as rigid as they could be.

i would however box in your gantry a little because you will get some flex in the middle

[DIYaholic]

hiedadam,
Looks like a stout machine, so far. I agree with multiplex, box in your gantry. Two other things to keep in mind:
1) With a 40" X-axis make sure your lead screws are beefy enough to prevent whipping at higher motor RPM.
2) You may want to design in some protection from dust and debris, for your X-axis rails and screws.

Remember, when you do start your build, everyone here NEEDS to see pictures and video.

Randy,

[hiedadam]

Okay I think I'll get on that ASAP. I wasn't sure if I needed to box it in because I plan on using half inch think steel for the gantry. I've also been trying to find a dust shield. I remember seeing one that looks like an accordion, but can't seem to find it again.

I already have the lead screw and did a simple test to check for whipping. Without the leadnut it whips when its turning as fast as my drill can get it to go. With the lead nut on and just a little pressure to keep the nut from spinning it works fine. the leadscrew is a 1/2-10 single start. I know, bad choice. I'll just have to deal with it for a little while.

I'm trying to make the design kinda of modular, and farm out as little as possible to one of my local machine shops.

[stangtjk]

Using 1/2 steel plate is going to be extremely heavy and a flat piece of steel isn't going to be near as stiff as a piece of square tubing.

[hiedadam]

Makes sense. I'll switch to aluminum. I'm using a standard width for that plate making it so the linear guides are flush with the edge. Which is why I went with plate instead of tubing. Would aluminum channel be a happy middle ground? or adding angle to the plate to reinforce it. Kind of how spars are built in some aluminum airplanes. Just replacing the sheet metal with plate and not having a taper.

[multiplex]

here is what i used for my gantry.. obviously just one possibility



i believe it was 8" tall, and about 2.5" of return on each side. 1/2" thick, so there was enough meat to drill and tap into the ends

back



front



If i did my Z again, i might also choose supported rail - as i get some vibration coming through the shafts.

[hiedadam]

Thanks multiplex. I think that will be a great solution. What size rails are you using?