Another nut-tensioner solution!

[Joham]

Hello All - I started building a JGRO about a month ago and came up with this for a lead-screw nut tensioner, at least on my X axis. I cut two plastic 2" discs with 4 mounting holes on the edge. I bolted these together and bored and tapped the center for a 3/8" - 12 Acme thread. I bolted these on either side of the 3/4" mdf partition. With the 3/8"-12, I had a little better than 1/16 th of a turn to line up the holes. I used a short piece of rod in the one disc and screwed the other down till it was tight. The lead screw seems to spin freely with no play. I don't know if another pitch would work out with the 3/4" spacing but extra holes or elongated holes in one disc could be used for adjustment. The advantage over the stock design is that there is no pressure on the tapped 10-24 adjustment holes and that there is positive pressure on one disc or the other. Now, all I gotta do is figure out how to squeeze this into the Z axis!

[Joham]

Not much progress for a while....what I came up with for the Z-axis is the stock design basically with the nut reduced in size so there is clearance all the way around in the slot so the nut can self-align with the lead screw bearings preventing any binding. I put sliding spacers between the bearing blocks to strengthen the assembly when pre-loading the bearings. Is backlash as critical on the Z-axis? Was hoping the weight of the router would take care of it.

[denz]

Hi joham, How did your z Axis work out?

[Joham]

Originally Posted by denz Hi joham, How did your z Axis work out?

I have had to put my CNC project on hold for the past few months due to needed home repairs. I did get it to the point of installing electrics. When tested with an electric drill it seemed to work smoothly. The nut has about 1/4" of travel in the slot to take care of any wobble or misalignment of the screw. The nut is fairly snug on the screw so I'm hoping the weight of the router will provide enough tension.

[forgetcolor]

hey, nice looking paint job. did you spray or brush? what did you use for primer? i presume you disassembled somewhat to paint, but did you dissassemble everything or did you leave major assemblies in tact (e.g. x axis, y axis)? i'm thinking that having paint on the joint surfaces would screw things up.

[Joham]

After 9 months off for home remodeling, I've 'retired' again and started back on my JGRO. I still had to complete the base. I notched all the bracing, squared it up, and glued it to the top with blocks to hold it square. Having run low on 3/4 MDF (and money), I used some leftover cabinet birch for the rest of the base. I modified my round nuts for the Y (X?) long axis. I mounted the whole thing on a Lowes storage rack (Black Friday sale) that I cut down to table height. Still had enough left over for a counter height work table. Anyhow it's mostly complete now except for neatening up the wiring and enclosing the electronics. Here's a couple of vids of my first cutting attempts. YouTube - DIY CNC 1st test cuts.divx ... YouTube - CNC test chain link.avi