Well, I’ve decided to start a machine build log. I’ve have already invested significant money and time on the project, so I’m committed and looking forward to beginning assembly. So far I’m still gathering parts. I have been trying to design my dream machine. But since I don’t have enough money to call the shots I pick up a good deal when/if I can find it. For better or worse this has had the result of dictating what my finished product will be like. For instance, I thought I would make a cut area of about 30 x 50. Then I ran across a really good deal on two matched ball screws with 60” of thread. So that opened up more possibilities and I have rethought the cut area, upping it to about 58” x whatever. I want to use 80/20 to frame up the table and have decided to make it about 7’ long (I want to be able to carve entry doors, among other things). And since I have both these long ball screws I can use one on each side of the gantry (I read about doing that in this forum). That means the gantry can provide for considerably more than a 30” cut. So, I figured to try for 48” there. And now it seems I have come across a deal for a ready made gantry pulled from some high tech industrial equipment. The ball screw there just happens to have 48” of threads! Previously, on EBay I won an auction for a Lintech actuator which had about 8” of travel. It seems to be in excellent condition and it will be my Z axis. I have been really fortunate in coming up with these things. Now, if I can just afford the 80/20 . . .
I bought a copy of BobCad v.22 earlier. My reasoning there was that I have 2 friends nearby who are both looking to build also. And they both have that same software. This means I will have the help learning it, which I will almost certainly need. Since they both also have Mach 3, and since there is significant approval of that program among the CNC Zone crowd, I am planning to get that, too. I went to the Hobby CNC site and ordered the 4 axis, complete kit with 4 ea 305 oz. steppers, etc.
One of my buddies, who knows about these things, watched over my shoulder as I assembled the included controller board kit. With his help it passed the test the first time. I also scavenged a 24v transformer out of some old dark room equipment to use for my power supply.
It’ll be interesting to see how this all turns out in the end. I’m excited about the whole thing and some days my mind just reels with the possibilities of what I can do with my machine when it’s ready to roll.
Things I still need to gather up are a pair of rails, 6’ or so, to go with those long ball screws; and, of course, a bunch of 80/20.
I am trying to post some pictures along with this message. I think I have that taken care of, but I don't see where I add descriptions. Sorry about that. Mostly self-explanatory, anyway.
Since this machine is still in pieces and I still have much to buy, this is a good time, too, to seek and incorporate good advice from fellow 'Zoners. Thanks in advance for any help.
Sorry this post is fairly long but now that I’ve covered all this initial stuff, my subsequent posts should be short.
Thanks,

Mike M.

Mike

PM me with your 80/20 requirements. I have made contact with a local salvage company that has a great deal of it and I may be able to meet your needs with the surplus...It is used with minor defects. Holes ect. but hey much cheaper than new.

Bob

Mike,
If you haven't already look at Joes 4 x 4 hybrid thread. Lots of good ideas and a similar size to what you are considering. http://www.cnczone.com/forums/showthread.php?t=38220
Looks like a K2 mount, but I can't tell what router its for. Likely whatever is in your router table.
You may want to consider V bearings for your axis, unless you have your heart set on linear rails. Lots of good reports on them.

Hey Blackbeard. I have a local Company here in Athens. 40 mins south of knoxville. Is it Seatons. Man they have a great deal of aluminum. All of my stuff came from there. I got everything for peanuts. Here is a link to my thread. I can help also with requirements.
http://cnczone.com/forums/showthread.php?t=50855&page=3
Planekrazie

Mike

PM me with your 80/20 requirements. I have made contact with a local salvage company that has a great deal of it and I may be able to meet your needs with the surplus...It is used with minor defects. Holes ect. but hey much cheaper than new.

Bob

This CNC bug is really taking taking it's toll on me. Yesterday I even went out and cleaned half of the garage so I would have a place for the machine!:confused:

Mike M.

Well, I haven't actually started building yet. I'm still gathering parts. I recently got some rails for the gantry. They're 48" +. Still looking for rails for the long axis. At this point I am holding out for rails and trucks. Don't see many the length I need, 6-7'. Plus, I still need a ball screw for the gantry. I will need 48" of threads there.
Where I have made progress is in my design. A 4' x 7' table seemed like it would sag beyond my self-imposed tolerance limit of .001" no matter how I looked at it. But once I got some working knowledge of ProgeCAD and started enjoying using it, ideas really started forming! I do believe I can do it by having a "floating" table. Since I will be using double ball screws for the long axis (I never know whether to call it X or Y) this would allow me to put support where it is needed without interfering in any way with gantry movement (I assume some of you would think that was a no-brainer from the start, but it actually took awhile for it to dawn on me . . . I am no machinist, or engineer). I will also include stress panels to hold the legs steady which will also be used as bracing for the table framing at a location inset a ways from the outer perimeter. This will greatly reduce the unsupported span of the framing pieces. I will try to get some JPGs of my current thoughts up soon. They are just 3-view drawings though, as I still haven't gotten anywhere with the concept of 3D drawings.
In the meantime, I still get over to the local Starbucks and mull ideas over a cup of coffee, an enjoyable thing in itself. But, these days instead of one of their napkins for inspiration, I have printouts of my drawings on which to sketch additions, changes and notes.
One thought I had, since I was able to obtain the ready-made gantry mentioned in a previous post, was to piggy-back it to the beefier gantry I plan to build as a sort of sub-gantry, facing the opposite direction, of course. This would allow me to add some versatility to my machine by mounting one of those laser heads on it that Eric from Xaser keeps promising to get to market (whenever that will be). It would also allow me to mount a dedicated sawing spindle which I also hope to make. This saw would be for small, precise cuts, such as fret slots, slices of banding, etc. The blades I plan to use are only 4 to 4 1/2" Dia. and very thin. I am envisioning a sawing spindle about 1 1/2 x 1 1/2 x 4, or so. I hope to drive it with a trim router I picked up at Harbor Freight on sale for $19 the other day. Some of you would be familiar with it already since I've seen mention of it here in the 'Zone. I would have to reduce speed by about 4 times, I think. If I can come up with the right timing belt and pulleys it seems doable. Have any of you used one for such as that?
More later.

Mike M.

Bob,

Thanks for referring me to Joe's thread. There's a lot of good ideas there worth considering, too.
BTW, yes that is a K2 mount. It will hold my Porter Cable 7518 router.

Mike M.

I took some more pics of gear I’m gathering up. Plus, I’ve converted a couple of my CAD files into JPGs which I’m posting. They show the general idea of my current thinking. The actual attachment between the ball screw and the gantry I don't have worked out in complete detail yet, although I have a general idea of one way to do it.
Photo 1: Ready -made gantry I mentioned getting which I may mount on the back side of main gantry which I will make.
Drawings: Views showing basic frame arrangement using 80/20. Notice the legs are inset from the perimeter. This will reduce the unsupported span of both the long beams and the short cross-pieces. The deflection calculator tells me this arrangement should keep deflection within .001”, if I also go ahead and use the idea of stress panels bearing against the underside of the table. I think the stress panels will be necessary since I weighed individual components of the gantry today. With the sub gantry also mounted they add up to a little over 100 lbs. And that doesn’t count the 80/20 needed yet. Drawings also show spindle in both full up and full down positions.
The DWG file I cannot seem to preview. None of my options for programs to open it seem to work. I hope you have better luck. In case you can't, the overall dimensions are 48" X 84".