Build #2: 3 axis open table, Baltic birch

[nicanor76]

From following bought plans on the 1st build, I was unsatisfied with alot of stuff. But I learned enough to know how things work, etc. So starting my 2nd build using my own design this time. I scrapped the DIY skateboard bearings, etc and using precision bearings. Also decided to use Baltic birch for the majority of the build

The Z axis will have fully supported 1/2" linear rods/bearings. The other axis will have (unsupported) 3/4" rods/bearings. Will be using 4x 269oz motors (2 for the X axis) on a 5 axis board (potential future 4th axis upgrade), 1/2" 10 acme threads with CNC Dumpster anti-backlash nuts. Will be roughly 16"x16"x9" cutting size.

I'm finished most of my Z axis. The Y axis bearings mounts is integrated into the Z axis to maximize strength and minimize wasted space and materials (ie: instead of "attach part A to part B", why not design both as one unit from the beginning). The carriage is about 10" wide to give you proportion ideas. Any feedback/comments welcome

[tajord]

Looks to me like you'll have a bit of flex from those unsupported rails, can you alter that design anyhow?

[ger21]

Use 1/2-8 2 start instead of 1/2-10, you'll get double the speed.

[nicanor76]

tajord: How exactly do you mean I'll have flex on the unsupported rails? The bearings for those aren't installed in the pictures. The bearings are supported by 2 layers thick 3/4" Birch ply (will be 95% enclosed inside the ply) with a 3.5" space in between them. I haven't made the X or Y axis yet. I'd liek to know if I missed something. Thanks

[ger21]

Unsupported rails always flex. But it may be acceptable due to the short axis lengths.

[tajord]

I looked at your first image where i saw the rods behind the z carriage, the holes in the back didn't look like it'll be carrying those open type linear bearing blocks like the ones you got for the z axis, and with the size of your carriage along with the weight of the router and the forces applied as the machine go might subject it to a "bit" of flex, not trying to be a critic here.

[nicanor76]

Oh ok, I knew they're not as great compared to fully-supported rail. But I can't redesign the precision rails/bearings I bought so can't do anything about that. That's also why I went with a thicker 3/4" rails, and also only 24" long each. Because of my budget, I can't afford fully-supported rails all through-out (just got a good deal for the Z axis). The X and Y won't have an open type bearing. They're definitely a great improvement from my DIY skate bearings still. I appreciate your feedback

[tajord]

Originally Posted by ger21 Unsupported rails always flex. But it may be acceptable due to the short axis lengths.

this too i took into consideration, that's why i stressed on a "bit".

[Cartierusm]

I think so far what you have in the pics looks good. Did you epoxy the wood, seal it or is that fiberglas?

[nicanor76]

It's sealed right now. Also just glued but about to put screws on specific locations. I'm just about done designing the Y axis so I can finally continue the build, so more progress coming soon.

[nicanor76]

slow progress but progress nonetheless. Here's most of the Y axis finished. Will be doing the X axis soon and how the X + Y will be attached.

My plan will be to have the Y + Z parts (pictured) to be securely bolted onto the two X axis so it can be unbolted for transportation/storage. But will also have an adapter section in between them; so with the adapter on, the Z axis will have maximum cutting height above the table, and when removed it'll have a maximized cutting capacity below the table.