Re: re gt vs htd

CB,

I just lost a long detailed response because the Yahoo "database" was
not ready.. Try in a few minutes, it says, and deletes everything I
typed (it has happened before, but in 60-80 posts, it only happens
once, so I keep getting complacent (not saving to notepad) <rant off>

So you, and the list get the short version.

1)gantry seems too light for what might be a 75# load. (I'm seeing it
as a shopbot unistrut style gantry) Do a software calc or "by eye, by
golly" mock up.

2) Don't tie two steppers to the same crosshaft! They'll
likely "fight" each other... Put one on each end of the gantry if you
must. (I don't like this approach ,but shopbot, AXYZ, Vytek, and
super tech all do it...)

3)Motors seem over sized (I haven't done the math on YOUR params) Why
does it take TWO 1200's when one w/ crosshaft was ok.

4)Try to use a 34 frame size motor if you can. Especially with the
gecko drives. 2:1 or 3:1 drive if nec.

5)Since you're just positioning to drill, try to use an s curve ramp
profile to save time and torque requirements. Works for cutting moves
also, but I'm reminding you that you don't need cutting force at
speed. Just need to take care of the inertial loads from accel/decel.

6) If you must tie motors together, or use such large motors,
consider servo drive...

Hope this (short form) helps. Guts are still here, peripheral info is
gone, for now...

Ballendo

--- In CAD_CAM_EDM_DRO@y..., carlcnc@s... wrote:
> Ballendo
> thanks for input,and to answer your questions/fill in blanks.
> 175lb is 2 ea 2x4 1/4 wall alum with 1/4 in plate both sides
> 2 12" travel Z axis with 18# 1hp DC motors,
> X Y travels 144,60.
> I do have alternate design using 2 1200ozin motors coupled to the
> cross shaft. Using two geckos driven by the same signal from CNC
Pro.
> I decided that with a max rpm of 300-350 a single larger motor
> would work and eliminates one drive,coupler etc.
>
> CB