Re: Hexapod question

Hello,

For those who would like to know, but don't want to take the time to
search:

Hexapods in general offer basic advantages in stiffness, accuracy,
speed, dexterity, and scaling.

Stiffness.
When the hexapod is loaded, strut forces act only longitudinally
either in tension or under compression. These can be accommodated
more robustly and with a lighter structure than the bending moments
experienced by conventional orthogonal beam machines. A conventional
multiaxis machine has a series of connected movable linkages that
each contribute some slack; on a five-axis machine there will be a
minimum of six. In the hexapod, the links act in parallel, leaving
two in the chain.

Accuracy.
Manufacturing errors in parallel structures are subject to
averaging; whereas errors in serial structures are additive. The
lightweight and low friction hexapod is less prone to hysteresis on
movement reversal and can follow a tighter machining path. Most
errors in conventional multiaxis machines originate at the rotary
stages because of the complication of the gearbox. A hexapod platform
can effectively rotate simply by altering strut lengths.

Speed.
A hexapod can be designed such that none of the heavy motors and
servos need do more than gently oscillate. The moving mass is
therefore comparatively small, minimizing inertia and machine power
needed to overcome it. Also because all the necessary freedom of
movement is enabled by the mechanism, the workpiece and its generally
heavy bed can be stationary.

Dexterity.
A good hexapod with well-designed linkages can articulate farther
than the usual tilt stages. The mechanism can also reach over a
larger area than its own framework and is therefore very compact for
its working volume. Multiaxis stages are available to increase the
dexterity even further.

Scaling.
Struts, which carry only axial loads, can be scaled up economically.
Doubling their diameter allows a fourfold increase in length with a
sixty-fourfold increase in working volume, or a sixteenfold increase
in maximum loading. This can be achieved with only a modest increase
in weight and cost.

This info was taken from:

http://www.manufacturingcenter.com/tooling/archives/0996/article026.ht
ml

Ballendo

> OK gang, I have been following this thread for some time now, and I

am still at

> a loss as to what the possible practicable use a Hexapod would be

in a

> machining environment.