I was doing my usual research around the net, you know... to pass some time very late at night, and I came across a member of cnczone.com building one of Joe's CNC machines, and to my surprise, he was using the design from this site. I was very proud to say the least. This CNC router is setup very nicely, with a vacuum attachment and a few other interesting modifications. Lucan has also been cutting out an enormous amount of parts on this machine. He is in real production.
Since Lucan has had a bit of experience on this design and build, I asked him to give me some feedback as to any possible limitations of the machine, and all that he has learned. I also wanted to know what he would do differently and what aspects of the machine could be improved.
Here is what Lucan had to say: I already had most of it together when I saw your modification about doubling up the MDF on the base, and I left it as is. That is one thing I wish I had went back to do because the weight of the gantry causes quite a bit of variations in the Z depths from the front to the back of the machine. When cutting parts for Joe's, I tried to make any toolpaths that aren't complete cutouts run along the Y axis to minimize it.
Cuts in the X and Y direction seem very accurate (tape measure accurate, haven't checked it with a caliper or anything), and I have no anti-backlash mechanism setup at all... just using the standard threaded rod from home depot.
I decided to use 1/2" though on the X and Y, and couldn't use your method of drilling through the edges since the holes would be too large, so I shifted the gantry to the front of the side walls, and mounted a block to the back with the nut in it. I lost a lot of travel doing this, but I really wasn't concerned at the time since my goal was to just have something that moved so I could learn on.
If I were to do it over, I'd make the sides of the gantry like an upside down L shape, to make enough room for the lead screw bearings to hang off the back. Or maybe a bolt on extension would work. I can draw it up in SketchUp if I'm not making any sense.
The aluminum angle is starting to show some signs of wear where the bearings ride too. I think I saw some steel angle at Home Depot or Lowe's the same size that might hold up longer..not sure.
That's all I can think of that I changed or would change. I was really shocked at how accurate it cuts (excluding the Z problem I mentioned earlier, that you already solved). I threw it together with scraps of plywood, MDF, and I think even some 2X4's lol.
I lived on these forums for a few months throwing around ideas with 80/20, linear rails, just buying a commercial cnc, etc. but they all came down to a hefty investment up front for a hobby I wasn't sure I'd stick with. Then I saw your site, and realized it was possible to build something with inexpensive materials, using common tools. Well, I did use a table saw, miter saw, and drill press for a lot of it, I can't imagine cutting it all by hand like you did.
Glad I did it this way too, once it was done I loaded up the roadrunner file, turned the router on and hit go, then watched with excitement as it positioned the bit....and then plunged it like 2" deep and tried to destroy itself. So glad that Mach's default key for e-stop is escape.
In summary, Lucan was almost finished with the build when I recommended that the bed should be reinforced; however, he found that the deflection was tolerable when orienting the work to be cut in the Y direction, but he felt he would have like to get the bed stiffer. The machine has measurably accurate cuts to the eye. He uses 1/2" threaded rod which is too large to be centered through the back supports. On all threaded rods larger than 1/4", I would recommend offsetting the shaft like Lucan did with the addition of the blocks. You will also see this method when I show the DIY ballscrew coming up in a later post. The gantry and the y-axis rail support can be altered to offset the shaft in the back instead at the bottom of the z-axis assembly. Steel angles will probably last longer since the bearings are also made of steel, hardened steel. He essentially used scraps to put this machine together and yielded great accuracy. The materials used are a great way to show that MDF is not the only possible material. Plywood, birch plywood, also has great properties. Laminated wood will increase the strength dramatically.
My favorite part of this build is the vacuum attachment. He positioned the vacuum hole to the side of the router, which is interesting. In a normal build of this machine, the attachment may pose a travel problem, but in his case, it seems to clear the gantry sides. My vacuum attachment, which you will see will be oriented so that the hose fronts the router. He is also using flexible plastic as opposed to bristles, which is a characteristic of the vacuum attachment that I will show also. I'm still doing research on the pros and cons of bristles over flexible plastic.