cnc metal frame

[georgebarr]

I am planning to build a CNC using steel square tubes. I plan to weld the pieces to form a frame. The question is what thickness of steel square tube should I use and the dimension of the tubes. For example, I could use a 1.75" x 1.75" x 0.095" steel tubes. I can go thicker, lighter, or use a bigger beam.. What is your opinion?

[thielert]

How big will the machine be?
What style of machine? Gantry?
What will the framing look like? Long open streches or frequent supports?

What type of welding?
Stick burns through thin metal, MIG does a nice job.

1.75" sq tubing is rather rigid, for most apps you'll be fine.

Tim T

[georgebarr]

Here is how the frame looks. It has a 60" x 57" length/width dimensions. This will be a gantry style CNC machine. I will install a THK slides and bearings along the 60" side. My question is is 1.75" x 1.75" square steel tube appropriate or should I go for a 1.5" x 1.5"? Also, the thinkness is important. I can use 0.065, or 0.095 thickness. The 0.095 cost almost twice as much as 0.065.

Any and all suggestions appreciated. I will be building this thing soon. Since I am not an experienced welder, I plan to pay a welder $52/hour to weld the stuff for me. How long does it take to weld this frame?

Thanks,

[georgebarr]

I am having problems uploading the JPG picture of my frame.

[Hawkeye]

With a table that size I would go at least .125. If it is for cnc'ing metal you may even look at .25 depending on the actual supports of the table.

Just my opinion,
George

[georgebarr]

Here is the picture for the cnc frame I was talking about:
http://home.mminternet.com/~georgeb/cnc_frame1.jpg
It is 60" x 57". I just need to know what a good mild steel square tube thickness would be. I could use 0.065", 0.095", or 0.125". Also, instead of 1.75" x 1.75", I am thinking of using 1.5" x 1.5". Someone said to use 0.125" since I will be using it for metal/wood projects. To save cost, maybe I can use 0.125" on the top part of frame and use 0.065" or 0.095" for the bottom part of the frame. Since I will be going to my local welding/metal store place, any quick suggestions before I pay to make this project is desired. The welder charges $52/hour for welding. How long do you think it takes to weld this plan?

Also here is my gantry plans:
http://home.mminternet.com/~georgeb/...l_assembly.jpg

The gantry dimensions are:
48" x 1" x 3" for vertical rectangular bar
5" x 3.5" for bottom plate with 6 holes is

What do you think of these crude plans? This is my first experience with CNC and CAD work.
Thanks,

[georgebarr]

Here is a picture of my new and different cnc frame which measures about 4' x 5'. I originally designed it to be 3' x 4' which explains why the bottom frame looks small. The Z axis is about 3.5' high since I plan to mount a 5-axis head, etc. This is my first cnc machine. I wanted it to be very rigid for milling metal and large enough for wood projects. Any suggestions is appreciated.

thanks,

[jphagen]

I am building a similar machine.
I used 1.5x1.5 x .093 wall.
It measures 60x56 total width.
The final gantry weight will be about 130#.
If all goes well I will attach a pic.

[georgebarr]

jphagen,

Looks good. How high will your z-axis be and how much height movement will it have?

Thanks,

[Hobbiest]

If you use something heavier, live 1.5 by 2 by .125, you could bolt it together. Lay the crossmembers on their long sides, and sides on the shorts. Two 7/16" holes will allow plenty of adjustment with 1/2" bolts and washers. This not only cuts out the cost of welding, but also allows for easier adjustment to ensure a square frame. One midspan crossmember should take care of material support and rigidity, and only four legs will be needed. That is how I woul built anyway for lowest cost and highest strength. Just my two cents.

[ezland00]

VERY NICE

[jphagen]

The Z axis is set at 6 in. in the picture.
It is adjustable, as the left and right sides can be indexed up and
down. I usually keep it at this level because twisting forces on a
long arm.
The z travel on the carrage is 10 in.
The frame is also made to fold up the legs, so it can be mounted
on the wall, and operated there to take up less space.