SecretSpy711 published a new build:

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Working on re-designing the Z axis. There are some aspects of the CNCnewbie units that I don't like, so I now plan to make my own using probably 20mm profile linear guide (same as used on X and Y), and 3/8 leadscrew (using the excess cut from my Y screws possibly).

Haven't decided whether I want to go for the full 4 bearing setup, or use 2 of the long variety bearings.

 

Also reconsidering my bearing setup to capture the leadscrew. The bearing blocks I bought from servocity are looking pretty wimpy.

Here's the bearing blocks I bought for the X axis:
1/2" Bore, Face Thru-Hole Pillow Block

I believe it uses this bearing:
http://www.product-config.net/catalog3/output/82052925/specsheet.pdf. Static load rating of 71 lbs, and I have 2 of them. Should theoretically be enough but I'm more worried about the fact that they are so thin and I am not planning on turning down my leadscrew

Considering something more like this, and I wish I had seen it sooner:
1/2" Two Bolt Flange Bearing UCFL201-08

 

Creo

 

Sorry for the delay, I hadn't checked the thread in a while since I haven't been able to work on this recently. I will see about posting files when I get some time.

The Z axis long-version bearings and rail just arrived, so I can make some more progress soon. I was waiting until after the holiday bills had passed before buying the motors and drivers, then the machine will be mostly complete. I also still need drag chain, a motion controller and Mach3 software. I was also considering getting some more extrusions for the base instead of mounting it directly to my wood torsion box.

 

sure, I'll take some pictures when I get home. CAD might be easier since I can hide parts. Basically it's the reverse of many designs here. The Z rails are bolted to the back of the Z plate, and the linear bearings are mounted to the X carriage plate. So the entire Z plate and motor move up and down. This makes the Z axis taller overall, but more rigid. Thanks to Florian Bauereisen for that suggestion.

 

Here's a view looking at the back of the Z axis. You can see the rails bolted to the plate which act like stiffening ribs. The 2 bearings and short piece of 80/20 that holds the lead-nut (actually 1"x2") bolt to the X carriage plate. Since I only have 2 bearings here instead of 4, I am using the "long" versions which are about 3.5" compared to the standard length (about 3") everywhere else on by build. I am using a piece of 3/8-8 4-start leadscrew (0.5" travel/rev), and the Z carriage *almost* falls down when power is removed from the motor, but not quite. A small spring, or a slower leadscrew would fix that.

There is a flaw in this design that I've found, which is this: if there is enough force in the Z direction, the piece of 80/20 could potentially slide up and down, causing lost steps. It is mounted using sliding T nuts. You can barely see those T nuts here:


That means I need to really, really make sure that these 4 bolts are tight, and if that's not enough then I might bond the piece of 8020 to the X carriage plate or try to machine a different lead-nut bracket that doesn't use sliding T nuts.

 

I also have several sets of holes on my Z plate so I can mount the router clamps at various heights.

 

Yes, on my old machine, very slowly.

 

They were from 1/2" stock but the piece they were made from was bent a little, so they are probably more like 0.45" now since I faced it first.

3/8 should be fine if they are spaced apart. If they are close together go thicker.

What I don't like about these mounts is that the mouting holes are behind the router, so I can't remove the mounts unless I first remove the router. (They were originally made to fit a Shapeoko 2's Z plate and I cannibalized them for the new machine.) Also, tramming is difficult with this arrangement, and tightness of the clamp affects the tramming. I plan to re-design these mounts at some point.

 

Yep, pretty much. I did most of the outside profiles with a sliding miter saw, then filed the corners round.

 

Yes it would be more rigid if I swapped X and Y, but I really liked the access that was provided with the long gantry.

The -8 and -10 is threads per inch.