Build #2: 3 axis open table, Baltic birch

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 :)

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

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

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

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

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.

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

Quote:

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Originally Posted by ger21

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

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

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

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.

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.