Is there any reason why the gantry has to move on a CNC router? Seems to me you could get a lot more rigidity by moving the table along one horizontal axis instead. Then just move your Z axis assembly along the gantry for the other horizontal axis, but have the gantry solidly bolted to your table base. I realize it will take up more room when working this way, but that's no different than a mill.
Just thinking out loud.
No, it is just less expensive to cover a given envelope that way, at the cost of less rigidity. But for routing you typically don't need rigidity like a milling machine.
If the gantry moves, the machine only has to take up slightly more floor space than the length of that axis. If the table moves, the machine occupies TWICE the floor space for the same travel. That IS the difference. No question whatsoever that a moving table and rigid gantry is stiffer unless you go to insane extremes on the gantry.
Jon
I bought a book at a garage sale or thrift store entitled "Three Dimensional Trimming and Machining " Subtitle is " The Five Axis CNC Router." You might be able to find a copy at ABE or Amazon. It might stimulate more thoughts.
Dan
We had a Asi Accucell that worked that way. It was a waterjet cutting system (non abrasive).
I'm shocked that dovebid has this auction pdf still up.
Page 3 shows a 2 axis motion system that drove an injection head between both presses. I built that many years ago in house.
Page 5 shows a Accucell with two y,z,a,b heads. They should not have put them on the same framework. I always wanted to cut it in half to keep motion from one side affecting the other side. Accell/decell effects tended to show up randomly in each sides work.
The Fanuc robot based assembly and waterjeting systems I built are not shown. GM managed to buy them for a price less than the cost of the light curtains on them before the auction.
Wes
No reason at all, heck, you can move the table in two axes and have a nice rigid Z axis only gantry.
It all depends on what you want to build, both work envelope and physical envelope, as well as the parts you can find on ebay or the cnczone classifieds, of you want to spend new $$$ on.
They type of work you plan to do also significantly affects the design requirements, i.e. routing commercial grade wooden signs requires a more rigid machine than routing foam for lost foam casting.
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