[jm51]

The machine is a Zenbot 1216 but I guess the question applies to all lightweight gantry machines.

The Zenbot is currently fitted with a Dremel but I have an unused 800w wc Chinese spindle that seems to me to be too heavy to use on such a small machine.

I'm thinking of fitting a pulley on a shelf high above and having a counterweight take the load off the Z axis. Would this work or are there problems with doing this?

[awerby]

You could do that, but it would also put a strain on the gantry as it tried to move around. It might be better to use a gas spring, like the struts that hold a hatchback open.