Z-axis design woes

[samualt]

Machine Info
------------------
Size: 4'x8'
Motors: 1500 ozin Servos
Controllers: Rutex
Construction: Aluminum tslots and plate.



Here is my ball-screw for my Z-axis and one of the small THK rails. The ball-screw already has a pully on it so that is the top.
1. Are my small THK rails too small? I haven't seen anyone use rails with carriages that small on their z-axis. It feels really sturdy.



Here is a close-up of my ball-screw. You'll notice there is a rounded lip and a flat side. The round side has a metal protrusion.
2. What is the metal protrusion? It looks like it can unscrew. An oiling hole for the ball bearings?
3. I have no idea why they designed a ball-screw with a rounded lip. It really gets in the way of most designs I might use. The curved piece is taller than the end mounting blocks. Do you think the rounded side of the ball-screw should be facing toward or away from the router? How is it usually done?
4. I'm not exactly sure how to attach the plate for the router onto the ball-screw. None of the gallery pictures show this. Anyone got a picture of that?



Here is a picture I got from THK. It would be nice to build a z-axis this way except the rounded lip of the ball-screw gets in the way.
5. Any other pictures? Any suggestions?



broncosis:
I'll be watching how you do your Z-axis. Looks great so far!

[Hobbiest]

Make it a little taller (from the carriage to the bottom), and put the nut in there.

[dmgdesigns]

Looks like a grease zert (SP) to me. The small hole on the side of the flange goes to the threads and the zert goes to the small hole.

What hobbiest said. Get a block with a hole the same size of the round part of the nut. Add holes to attach the nut to the block and holes to attach the block under the table. and you will have the exact thing in the picture
.

[Hobbiest]

To clarify what I meant in my post, add risers underneath your rails, to make the space bigger for nut mounting and clearence (did I spell that right?)

[samualt]

Hobbiest:
I got ya. I just bought some AL 6061 bar that is .5x1.75x48" for the rail risers. I figure I'll cut it into a couple foot long pieces. That will make my thickness of z-axis about 1.75 (screw standoff) +.5 (extra ball length)+.5 (back plate)+.5 (front plate) = 3.25" thick x 4" wide x 14" long (abouts). That's not too bulky I hope, cause it's what I got. I might make the front plate a little wider for the router. I'll have to see.

Anyone use epoxy as well as bolts on this stuff? I'm kinda afraid of "just" bolting it together. Perhaps a little industrial epoxy would help. Basically, I'm making an elongated U out of 3 different pieces of aluminum. A little epoxy as well as bolts wouldn't hurt, right?

[trubleshtr]

You could take a piece of angle iron (aluminum) and bore a large clearance hole in it for the nut, and drill and tap 5 holes for it to mount securley to and then mount the angle to your carriage/slide assembly.

[Hobbiest]

Epoxy would help, but bolts should be just fine. Even the professional, industrial pieces I have come accross are just bolted together.

[signIT]

Use Loctite 330 if you want to glue it together it is a very nice product Aston Martin use it when making cars.

[NEATman]

If you are interested in how many types of these stages are built, take a look around the following website:
www.neat.com
This is where I work, and the last project that I designed is a linear stage just like what you are describing. The DS4 stage is based on size 9 linear rails, and a 16mm ballscrew. It is based on custom made extrusions and is offered in several different configurations. For more info on this product, take a look at the following link:
http://www.danaherprecision.com/ds4/
There is a manual, with calculations that you can use for stiffness and load calculations, there is a product configurator where you can view and download a simplified version of the stage, there is even an excel spreadsheet that will calculate the moment loading and tell you the life of the stage with thw load that you apply.

Hopefully this will give you some ideas on how to construct your Z axis.

Regards,
Keith