Yet another video from Mr Imaginary CNC Man… Bit of a twist on this one though…
http://www.youtube.com/attribution_link?a=gAocr7emiZU&u=/watch?v%3D-WYsmgOC2ZA%26feature%3Dshare
Maybe use large dovetail joints on the 45° struts holding the X+Z axis gantry.
@Marcus_Wolschon
Dovetails? What’s this Chippendale furniture? How about a scab plate? Do you think that’d be OK?
With nuts and large washers on the opposite end to create compression?
Sounds like an idea.
A dovetail of cause is a no-brainer if the wooden parts are machined on another CNC anyway. If they are hand-made by someone who isn’t an experienced woodworker it’s some effort to make them fit tight.
That’s the great thing about the fixed gantry design. You could build it out of half inch steel plate if you like, except for the Z n X axis of course.
My plan is to use about I/2 inch wood bolts (w/ washers n lock washers)all around, having them as long as I can get away with. Semi pre-drilled of course, with liberal amounts of wood glue ( not liquid nails ). Bolts n nuts where I can. If this proves to be insufficient, I’ll just keep adding to it as needed.
The only real change I’ve considered was changing the vertical 2x6’s on the gantry to 2x8’s. And my only real concern is access for repair and/or adjustments…
@Marcus_Wolschon
I do not think cutting angled dovetails with a CNC machine is a no-brainer at all. I’m not even too sure it is possible without some customized tooling. At odd angles dovetail angles become odd themselves.
With weight not being an issue, nor the use of hardware (bolts n such), dovetails wouldn’t really add anything to the design or rather be the best way to go I think. They’re great on furniture and the like where tight corners and hidden hardware are a plus. Not to mention that there is essentially a dovetail where the angled 2x6’s meets the vertical by the 2x6’s added to the back of the gantry.
But I do like dovetails, and did consider them. I like the idea of a natural lock type fit where glue n hardware only serve to hold things in place. If I did add any, I think they would be at the corners of the bottom frames…
But great ideas all…
Thanks n keep em coming…
@Mat_Helm
I could see doweling and plates being good for there. Pinned and plated.
It allows for a stronger gantry without worrying about it’s weight.
The Y & Z axis. The moving table is the X axis. With one like yours ( which is very nice ) you have all 3 axis on the gantry. You have to make it lite weight but still rigid enough to not flex. With this design, the Y and Z axis are part of a frame that can be made as strong as needed without worrying about weight because the gantry doesn’t move. It takes up more room this way, but is a much more simple and stable design.
But it only takes up that room while working.
It doesn’t permanently take up twice it’s length on the hobby workshop floor.
@Marcus_Wolschon It kinda dose. At least with this design. But I guess it wouldn’t have too. Could move the rails and bearings on the X axis inward and have the table above the bottom frame. But this one is only about 800mm long I think so…
ahhh. I see says the blind man. 
They could be supported. You could use the same ones you’re using on your’s. But being that weight is no longer a factor, I thought the cheapest way would be to use large steel rods. for the Y axis…
Your machine seems to have suffered a bit of a framework failure about halfway through the video. It blew up!
@Paul_Frederick That’s a common theme it seems with most things I build… ;p
@Mat_Helm
It has been said that amateurs tend to over engineer their designs. I know I tend to err on the side of too heavy.
Nothing is too simple that you can’t overengineer it. 
That’s me in a nut shell. I can never stop tweaking a design. I have learned to stop doing so once I actually start a build. Well, I try to at any rate. If not, I’ll spend 2 days on an hours worth of work. Constant new ideas for the “as long as I’m here” or the “might as well” buckets. And when one of the vehicles breaks down, a thousand of the worst case scenarios go through my mind. Have to make myself think of the simplest things first, which is usually what it turns out to be.
@Mat_Helm
I found a solution for the design problem. Just call the first build a prototype.