The next and final version.
I needed to address some of the problems that I noticed from before. Complexity needed to be reduced. Some of the racking and shifting needed to be addressed. I wanted to remove the concept of keeping all the skate bearings so tightly pressed against the rails. And it needed a face lift. So I came up with a new (is anything new?) design.
I kept the leadscrew and motor combination along with the torsion boxes. I got rid of the box below the gantry to let the bed lay flat on the table top. The sides were to lose the stiffeners by using a different strengthening technique. The wrap-around Y carriage was to turn into a flat plate. And I went with V-bearings for the linear rails. These bearings are actually fancier than they look. They have two rows of ball-bearings to be able to take both lateral and radial pressure.
They were to ride on angle iron as the official V-rails were beyond my pocket book.
I spent a fair amount of time trying to find a way to make the gantry wall stronger. I actually tested various plys and MDF combinations. I found out that 3/4 inch MDF skinned with laminate on both sides yielded a very strong panel. I also found that yellow glue was better than contact cement at holding it all tight. This combination actually makes a small torsion box, which is a substrate tightly coupled to skins on both sides. I edge banded them in maple to keep out moisture.
I went with dual motors on the long axis to virtually eliminate any racking and more tightly couple the drive mechanism to the bearings. I used wooden standoffs to attach the motors.
The leadscrews where coupled to the anti-backlash nuts with wooden holders on each side of the gantry.
I attached the Y leadscrew to the carriage underneath the Y torsion box to get it out of the way.
I used the removable Z from the last machine and mounted it on this one.
And then added dust collection. A must needed addition.
It was all working pretty darn alright. But there were a few things that I decided to upgrade. The V-bearings for the Y carriage were digging into the edge of the angle iron. I solved this by adding a few wooden strips and mounted the angle iron with the angle facing up. This vastly improved its ride. I had also noticed that sometimes the steel rods and brass bushings for the Z were sticking, so I switched them over to V-bearings as well.
And finally I cut the plate across the front of the machine and added an end vise for vertical board routing.
To those who are still hanging in there: On a different note, before I had the money to buy a CAM program, I needed something to use for test cutting. So I wrote SpiroCNC. I think alcohol was also involved. It would generate G-code for spirographs and other geometric designs. It was kind of stupid fun and is still used a bit by people in that same situation. I did also use it to generate some rosettes.
-- -- I'm no rocket surgeon