[gthomann]

I wanted to build a jgro for the experience. I live in a condo so space is limited and wanted to make it smaller. The first thing I did was cut the y-axis travel by about 12 inches. I made the regular sized gantry, but to cut the width so it easily fit on a table I flipped the bearings to the inside of the gantry. My bed end pieces are now narrower than the gantry itself. I am using 3/4 and 1/2 inch plywood and cutting out windows where I think I can get away with it. I have also made quite a few changes to the y-axis bed. I have attached a photo of the gantry, please forgive the busy background (condo again). I will attach a photo of the bed later.

[jckstrthmghty]

Interesting build. What kind of cutting area are you predicting? Are you not concerned about deflection with the holes on the gantry walls and base?

[gthomann]

The travel on the y-axis is about 22.5 inches, on the x- and z-axis the travel is the same as regular build. The cutouts are being made based on judgement, not any real analysis. At present I am not worried about deflection, I guess ignorance is bliss. If I have a problem it is pretty easy to replace the plywood parts, I haven't glued anything.

And I might as well post the other photos. The left photo shows the bed part. I made the end pieces out of two pieces of 1/2 inch plywood, with 1/2 inch spacers between. So the width is the same as regular build. I didn't see what the purpose of all that wood in the base was, so I just removed it, and replaced it with two T beams that you see running along the sides. The top grid also adds stiffness. The dowels thru the grid are an attempt to add torsional stiffness. I would rather have used a flat board instead of the dowels, but I can't run a noisy router in my condo but can run the drill press. In any case when I bolt down the top piece it will also add a lot of torsional support. The one place I might have some flex is under the y-axis lead screw. If so, I thought I might place a box beam made from 1/4 inch plywood there and prestress it with a threaded rod. Or just place another T beam there would be another possiblility. The pipes are gray primer. I was not happy with the surface finish on the large gas pipe. I sanded it down as good as possible, then primed it and sanded again. Next I am going to spray with appliance epoxy and sand some more.

The right side photo shows the gantry mounted. Just like a regular build except running on the outside edge of the pipe. The ruler in the front is two feet long, it shows the width. Electronics, lead screws and couplings have been ordered, just waiting for the mailman.

[DeadTom]

Nicely done especially the bearing inside/outside swap on the gantry.
And remember it's not the size of your tool but how you use it.
My slightly modified JGRO has been going for many years, have fun.