Spindle inside the gantry?

[cvriv.charles]

Anyone ever kick around the idea of having the spindle inside the gantry instead of hanging off the side?

I've been thinking long and hard about building a machine. I am very stuck on building thee most rigid machine possible. I need cutting speed. I seen some high end machine cut pretty quick. I would like to try and match that at a fraction of the cost

I am thinking I want the spindle inside the gantry instead of hanging off the side. If your having trouble picturing this,... just imagine the spindle being snadwiched between two gantry's.

There would be a mother gantry and a daughter gantry. The mother gantry having the same characteristics as a normal gantry. The daughter gantry being a simplified gantry. That basically meaning it has nothing to do with lead screws, only rails. That meaning it's not driven by the x axis lead screw and it does not have a z axis lead screw. The mother gantry has all that. The daughter gantry kind of just holds on and follows the mother. you know what I mean?

The two gantry's would be bolted at their very ende. Also, the y and z axis platforms would be bolted to each other too. the spindle brackets would be secured to the spindle alone. Then both z axis platforms would be bolted the the brackets on both sides.

Can you picture that? Do you think it would be beneficial? I think so. Two gantry's holding the spindle from both sides,... I think so.

But I want to hear what your pro's think first. Im going to create a model of this machine soon.

Thanks.

[nikodell]

This one has that

http://www.mechmate.com/

[multiplex]

i thought about this for my current rebuild, and had some issues working out the details without over complicating things. One benefit i saw was an easy way to square up the spindle using 4 jack screws on top of the carriage.

I eventually 'split' my gantry, and put the bearing rails on the back and have the spindle on the front - not sure if there is a benefit, but it kept things from hanging 100% off the front

[planebuilder]

It’s personal preference but I would not want the spindle “between” two gantries. IMHO If you want more
rigidity use a larger beam for the gantry, one large box beam weighs about the same as two smaller
ones. You want precision AND speed, each is easy, together they are more difficult, but can be done,
more $$. I have found rigidity is more important than speed, but that depends on specific use. Don’t
forget the value of MASS in the rigidity (anti chatter) equation. You don’t see good,
LIGHTWEIGHT, heavy duty mills. The cost is speed.
The reason I don’t like the spindle between beams is versatility. I have a 4'x8' table with a steel tool plate about 12"x12"x1/2" on the Z. It is drilled and tapped with a grid pattern. I can bolt a number of things to it
because it is exposed, not hidden between beams.
I use:
A big milling spindle taken from an old Moog Mill for milling steel.
A router for aluminum, plastic, wood .....
A pen for drawing.
A homemade vinyl cutting head for vinyl signs and masking.
Most recently I built a 4'x4' plasma table on wheels. It rolls up against the end of the main table and
I bolt a 5 foot outrigger arm to the tool plate that holds the plasma torch so I can plasma cut on the
accessory table.

[cvriv.charles]

But thats the only reason you wouldnt want to do it?!?! Because you cant easily access the plate? I thought about that and it does bother me because this machine once built is what it is. I will build other specific machines for other tasks.

Other than having to unscrew a few bolts,... thats all that would be need to get the spindle out. My machine is going to be uber heavy and big. I want a 4' x 8' but that foot print is going to be a lot bigger. I also want it so that the spindle hangs off the table in 0,0,0 position.

I want wider and heavier. I will have to get larger steppers to get and keep this beast rolling.

The two gantry halves are going to be steel boxes using square tubes. This mahine like I said it going to be heavy. Or maybe just two very thick square tubes on each side but very wide apart both horz and vert?!?!

A lot to think about. But seriously,... you dont think its any more rigd than a regular gantry? I guess it just depends on the design?!?!? A regular ganrty could be more rigid than a double and vise versa?!?!

[neo dilbert]

Originally Posted by planebuilder It’s personal preference but I would not want the spindle “between” two gantries. IMHO If you want more rigidity use a larger beam for the gantry, one large box beam weighs about the same as two smaller ones. You want precision AND speed, each is easy, together they are more difficult, but can be done, more $$. I have found rigidity is more important than speed, but that depends on specific use. Don’t forget the value of MASS in the rigidity (anti chatter) equation. You don’t see good, LIGHTWEIGHT, heavy duty mills. The cost is speed. The reason I don’t like the spindle between beams is versatility. I have a 4'x8' table with a steel tool plate about 12"x12"x1/2" on the Z. It is drilled and tapped with a grid pattern. I can bolt a number of things to it because it is exposed, not hidden between beams. I use: A big milling spindle taken from an old Moog Mill for milling steel. A router for aluminum, plastic, wood ..... A pen for drawing. A homemade vinyl cutting head for vinyl signs and masking. Most recently I built a 4'x4' plasma table on wheels. It rolls up against the end of the main table and I bolt a 5 foot outrigger arm to the tool plate that holds the plasma torch so I can plasma cut on the accessory table.

Super idea for the outrigger.
I will have to remember this.
Thanks!

[Gerald_D]

An advantage of having the spindle between "gantries" is the fact that you can get a good distance between the rails and keep the rails low down. This gives the car a wider and lower "footprint".

A disadvantage is reaching below a gantry to change cutters.

And a couple more points on both sides of the pro/con arguments . . . . .

[cvriv.charles]

Originally Posted by Gerald_D An advantage of having the spindle between "gantries" is the fact that you can get a good distance between the rails and keep the rails low down. This gives the car a wider and lower "footprint". A disadvantage is reaching below a gantry to change cutters. And a couple more points on both sides of the pro/con arguments . . . . .

Well,... I thought about the changing cutters things and decided that when the gantry returns to its 0,0,0 position that it would be off the table completely. So I dont have to squeeze my hands between the gantry and the table.