Newbie- Z axis design, help me out here?

[killahbeeze]

Hello! I'm currently working on my first JGRO build, with plans for using that machine to cut out the second. I'd like to reuse most of the parts however, so before I can cut the leadscrew to length, I need to know how long it will have to be for the second machine (I'm designing this one); thus, I build, I learn, I (re)design and repeat.

I'd appreciate it if someone would look at my z axis, and tell me if i'm on the right track here. I've seen a lot of similar designs out of aluminum, but that's expensive, so I'm trying to build it around MDF. It only needs about 3" of travel, but the x and y axis's will be 25" and 49" respectively, all using the similar skate bearing/gas pipe system on the JGRO. Thanks!

[ger21]

Al those screws in the edge of narrow pieces of MDF will cause it to split, or be very weak. The bearings need to be extremely tight on the pipe, and I don't see how that design can achieve that.
It would also need to be built to extreme precision.

Have you looked at the Joes 2006?

[killahbeeze]

Points well taken, and I will definitely be using the 2006 if this doesn't pan out. I will have to see how the aluminum angle holds up on my Jgro, but just looking at it, i'm a little uncertain, that's why I'm trying to shy away from it here.

[CarveOne]

I agree with Gerry. The MDF is going to need pre-drilling and probably soak the holes with thin CA adhesive to maintain any kind of split resistance. I would recommend using poplar or red oak instead. They would need pre-drilling also, but not the CA adhesive treatment.

CarveOne

[PaulRowntree]

Have you considered using cross-dowels (like the knock-down furniture uses, available here in Canada at Lee Valley among many others)) instead of end-on screws into the MDF? For good work a jig for drilling the perpendicular holes is a good idea.

Using the MDF in the single-piece split-ring clamp is tough. Could you arrange to have two of the three bearing mounts (each with 2 rollers) mounted in one MDF assembly positioned on one side of the rails, then squeeze the final bearing strip up against it. That way you are cinching two independent pieces together to bind the pipe, rather than trying to deform one piece (without breaking it) as shown in the drawing.

Cheers!