Re: Z axis on the knee, how practical????

On industrial machines I have seen At least four methods.
first is chain/cable and a counterweight.
Second is a hydraulic cylinder and counterbalance valve (nachi or
daikin)used with a hydraulic pump.
a variation on this is the bizarre european practice of a hydraulic
cylinder and gas charged accumulator. It does not give constant
counterbalance.
Third is springs and levers in an arrangement to give a constant
spring rate. no added inertia compared to a counterweight and no
hydraulics needed.
Last is to use a very large motor.

Gas struts would fall into the cylinder/accumulator category of non-
constant counterbalance.

--- In CAD_CAM_EDM_DRO@y..., "Ian W. Wright" <Ian@i...> wrote:
> Air assist has been mentioned a couple of times but how practical
are other
> methods of knee counterbalancing? I'm thinking of gas struts
(because I saw
> a guy selling some new ones at a boot sale for 25 pence each - how
do you
> determine the working strength of such things?) or weights and
lines over a
> pulley.
>
> Best wishes,
> Ian
> --
>
> Ian W. Wright
> Sheffield, UK
> ----- Original Message -----
> From: "Keith Rumley" <DSCadCam@y...>
> To: <CAD_CAM_EDM_DRO@y...>
> > A driven quill won't drop on you in an e-stop situation. Most
knee drives
> > won't, but some Series II will if the air assist is
inadvertently removed.