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.

Bob La Londe writes:

Is there any reason why the gantry has to move on a CNC router?

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.

Bob La Londe wrote:
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.
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

On Feb 9, 8:38*pm, "Bob La Londe" wrote:
Is there any reason why the gantry has to move on a CNC router? *
Just thinking out loud.

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

"Bob La Londe" wrote:

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.




We had a Asi Accucell that worked that way. It was a waterjet cutting system (non
abrasive).

http://archive.dovebid.com/brochure/bro998.pdf


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

Bob La Londe wrote:

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 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.