Finally finished my machine!

[oodanner]

I've mostly been a silent observer on these forums but, just wanted to say thanks to everyone who ever posted questions and answers that helped me along the way. I think most every question I've ever had was satisfied with a search of the forums. Below is a small summary of my machine and some things I did during the build.

Also, don't want to detract from anyone else's machines with this post. I'm just extremely happy that it is now complete and that I'm able to make some of the first pieces on it.

The usable cutting area on it is X = 45", Y = 25", Z = 9.5"

I also built this in mind with using it as a combo table for a plasma cutter eventually. I think I've laid most all of the ground work aside from the water below the table but, have yet to thoroughly investigate a proper THC and how to go about mounting, electrically grounding the plasma cutter etc...

Here is a link to a youtube video of my machine cutting out a very basic circular pocket(you may want to turn down the volume as it may be a bit loud):

YouTube - CNC is Complete

YouTube - CNC is Complete

I used a lot of ideas on this forum for the build of my machine. I've spent about 3 years building towards a machine that I would be happy with. Since the only engineering I know is hillbilly engineering I messed up two other machine builds first and then tore them down to build the one in the video. Nothing was designed on a computer so it was a lot of trial and error until I got what I wanted.

So far the basic circles and rectangular pockets I have cut appear to be the exact tolerance I specified in the wizards(haven't learned Gcode yet) so I'm pretty happy with that. The resolution is .000 and I don't have any tools that can measure better than that.

The gantry on it weighs in around or over 300 pounds. I wanted something very sturdy and it is very sturdy. I would guess the machine is around 1000 pounds. I filled all of the lower frame tubes with concrete to hopefully help(not sure what good if any this did).

The two things I'm most proud of on the machine are first the copy of the belt system I used for moving the X axis. I copied this from one of the posts here on the zone but, can't find it. Basically it was a company or person who had developed an idea to lay two timing belts on top of each other. One was epoxied or held mechanically in place on the bottom and the other belt was laid on top and clamped at each end while rolling over a timing pulley. I successfully replicated this idea on my machine and did this on both sides by running a single rod between the two timing pulleys on each side. Then I only had to use a single stepper on the end(using Nema43 by the way). Unfortunately a single revolution carried the axis around 9 inches so I have to use a pretty large chain sprocket to gear down and get it to something usable(should have used a smaller timing belt pulley).

The second thing I'm most proud of and the only thing on my machine that was an original thought, at least as far as I know, was the way I setup the ballscrews and ballnut. I actually have adjustable preload on the cheap ballnuts and ballscrews that I used(no detectable backlash that I can tell). I used two ballnuts on both the Y and Z axis. More or less what I ended up doing was machining two pieces of aluminum with three holes and a small lip that fits just over the square 1" ball nuts I used. One hole for the ball screw and two holes on each side for some 1/2" - 13 threaded rod. I put the two ballnuts on the ballscrew and then a piece of aluminum on each outer side of the ballnuts. I then put the threaded rod through the two holes in each side and use two slim 1/2" - 13 to act as a jam nut. I also used some threaded anchors that attached to the threaded rod and then drilled holes into the back of the aluminum plate for each axis to keep them held down. It is kind of difficult to explain but, if anyone shows any interest I'll see if I can draw something up and post a picture on here with better detail.

Sorry to make such a long winded post but, I figured there might be questions so I thought I would post some information up just in case.

Again, thanks to everyone who contributes to this forum as I would never have even begun to know where to start without it.

[sonicwonder2000]

Beautiful machine - must've taken some real skill to put together! Are you by chance a machinist? I notice that the frame was welded; how did you account for weld distortion? Do you mind also elaborating on the calibration equipment you own and how you used it to achieve .001 accuracy? I'm getting to the point in my build where I will have to be calibrating each axis parallel and square to the other axis. Congrats again on completion!!

[oodanner]

Thanks for the comments. Not so much skill as perseverance. No, not a machinist although I do have a mini-mill and mini-lathe. I'm a network engineer by trade. I did all of the work on the machine myself except for the ball screws which I had sent out to a local shop to have them cut to length and the ends turned down to 1/2 - 13 with a keyway.

I didn't really account for weld distortion on the lower part of the table as I ended up using bar top epoxy under the the x axis rails to get them level. As far as the weld distortion on the gantry I later wished I had bolted that part together rather than welded it. What I ended up doing to get the Z straight up and down was to put three 2 ton jacks between the front and back of the two welded 1/4'' thick wall square tube and after I got it really close to square then I welded up two 1/4" thick wall square tube pieces between them to keep it that way. Also, when I mounted the slab of aluminum that is the Y axis I used washers on the bottom row of bolts to further square it up. Using the machinist squares I couldn't see any detectable space so it appeared square but, other than the appearance of being square that is about it.

I used machinist squares to square up the X, Y, and Z axis of the machine.

As far as the cutter being level to the holding table I figured I would just cut a small pocket over the MDF(my holding table) to be sure that if the axis dips down or the table comes up at any point in the travel distance that the cutter would be level to the table. I haven't cut anything precision on the z as of yet so not sure how this will all turn out.

As far as the accuracy of the machine the only thing I have to measure with is the cheap Chinese digital calipers and when I cut a rectangular pocket say 4.000 by 8.000 then when I check with the caliper it shows 4.000 by 8.000. As far as my calculations on the machine go my X is around .0008, my Y is .0005, and my Z is .0001.

My machine is of course not perfect and I wouldn't consider myself knowledgeable enough to give proper advice on how to square up the axis. There is probably a better way than using machinist squares.

That is exciting that you are getting to that point as that sounds like you are getting close to finishing the mechanical parts of the machine. Looking forward to seeing your finished machine.

Originally Posted by sonicwonder2000 Beautiful machine - must've taken some real skill to put together! Are you by chance a machinist? I notice that the frame was welded; how did you account for weld distortion? Do you mind also elaborating on the calibration equipment you own and how you used it to achieve .001 accuracy? I'm getting to the point in my build where I will have to be calibrating each axis parallel and square to the other axis. Congrats again on completion!!

[kevin swan]

Nice build looks like it works well. what type of belts did you use grantry?

[oodanner]

I used a 2" wide rounded tooth belt for the top and the bottom belt(same belt, just laid one on top of the other). I bought it off of ebay along with the timing belt pulleys that are 3" in diameter. I can get you the exact part number if you really wanted to know but, I wouldn't recommend using such a large belt, now that I know it was extreme overkill. Plus, obviously the larger the belt and pulley, the more expensive it is. Knowing what I know now I could have used a 1" wide belt with a smaller diameter timing pulley and it would have worked just as well plus I wouldn't have had to gear it down so much to get decent accuracy on that axis.

Originally Posted by kevin swan Nice build looks like it works well. what type of belts did you use grantry?