Looking for ideas/concepts for a 3 axis mill

[pminmo]

I'd like to eventually build a cnc mill mostly for aluminum, if possible would like it to be sturdy enought for mild steel small cuts. I'm probably totally out in left field, but am pondering, looking for input and if it's reasonable and ideas and concepts. This would be a dedicated workbench top machine. But would need to be able to be assembled and dissasembled to make a reasonable moving weight up and down stairs. Would consider concrete or lead to be able to add weight for dampening.
I have two 30" 1" Thompson rails with their support shafts and four of their companion open pillow block bearings.
I have two 43" 1 1/4" diameter Thompson rails unsupported, I am open on bearings for these.
I'm thinking I would have a frame welded of 3 or 4" square steel tubing, and plate. Secondary parallel steel plates that would be supported via heavy bolts and nuts to get these plates in alignment for the shafting supports.
Assuming I can pickup some decent shafting and bearings for Z, any thoughts on how to use the other two set of shafts and a frame arrangement?

[joecnc2006]

Originally Posted by pminmo I'd like to eventually build a cnc mill mostly for aluminum, if possible would like it to be sturdy enought for mild steel small cuts. I'm probably totally out in left field, but am pondering, looking for input and if it's reasonable and ideas and concepts. This would be a dedicated workbench top machine. But would need to be able to be assembled and dissasembled to make a reasonable moving weight up and down stairs. Would consider concrete or lead to be able to add weight for dampening. I have two 30" 1" Thompson rails with their support shafts and four of their companion open pillow block bearings. I have two 43" 1 1/4" diameter Thompson rails unsupported, I am open on bearings for these. I'm thinking I would have a frame welded of 3 or 4" square steel tubing, and plate. Secondary parallel steel plates that would be supported via heavy bolts and nuts to get these plates in alignment for the shafting supports. Assuming I can pickup some decent shafting and bearings for Z, any thoughts on how to use the other two set of shafts and a frame arrangement?

I have been thinking of designs using 80/20 heavy duty, 1.5"x3"

[Enraged]

just a note, i found www.5bears.com to be very helpful in many aspects of figuring out my own home built cnc mill.

[High Seas]

Phil! You gona cut? Man - I'm gonna hope you keep working wire too!
Seems like you're be in the 48x36 inch range - xy surface. Probably want to keep that pretty rigid, so kinda big up and down stairs. Even 8020 gets to be a lug and a lot of tweak and setup if you disassemble too much.
How about hanging it on the wall downstairs and just taking gantry/bridge up the flight with the spindle and electronics? May be a compromise. Hang it from the ceiling?
Best of luck. Cheers - Jim

[pminmo]

Jim,
Yes I still plan on doing wire. Actually you should see more stuff coming in the next 6 months. PMinMO.com is undergoing a facelift in the background, and a few new surprises.
I'd like to keep the frame intact to move. I.e. pull the spindle, heavy plate...
I'm not sure 80/20 is strong enough.

[kdoney]

3060 is what I'm using and it seems more than up to it. A six foot member clamped at both ends has a critical buckling load of ~45,000 pounds. The deflection with a 200lb load is .005 with a strong orientation (3in side down) and .018 with a weak orientation, if the weight is evenly distributed. If you need more than that you should be bracing the center of your table like they do with the bridgeports. They do have 3075.

Part No. Finish lbs. / Ft.
3060 Clear Anodized 7.4801

Moment of Inertia Area weight
IX= 6.5164"^4 IY= 22.0300"^4 6.4262 Sq./In.

[pminmo]

Ok,
It's time for me to start getting more serious about the design of this machine. Got my last axis (I think). My debate is to use a traditional mill type design with the 1" supported Thompsons the Y )31") and the 1.25 Thompsons (43") the X. Or maybe have a steel frame constructed the would use the 1" at the base for a table, with the 1.25" pair supporting a moving Z. The Z if I keep it together is 3/4" x 9" x 18" AL tool plate (NSK LS15 bearings). It's heavy. I would assume that a fixed column Z would give me the best accuracy? Suggestions? Thanks.