[badhabit]

Just to be sure, you're using an air cylinder or a gas spring? Gas springs usually have a compressed gas eg. nitrogen inside them. I've read somewhere that counterbalance is done with gas springs? Sorry if this complicates things....

If its an air cylinder that means you have to pressurize the system prior to usage?

It's an aircylinder, this one to be exact:
https://www.ebay.com/itm/SC-125x400-...0/161235846191

125mm bore and 400mm stroke. It will pull 688kg@6bar and my Z-axis weighs ~300kg. Since i have a 1:2 ratio in the chain between the Z-axis and the cylinder i'll effectively have a 800mm stroke and 344kg@6bar, so it fits perfect(Z-axis travel is just below 700mm)...

I'll add a buffer-tank and a pressure-regulator. This way i can dial in the pulling force and the tank will help minimize the pressure fluctuation as the piston moves up and down....

And yes, i need to pressurize the system before usage... but i'll need air anyways, e.g. for toolchange etc....

[ardenum]

It's an aircylinder, this one to be exact:
https://www.ebay.com/itm/SC-125x400-...0/161235846191

125mm bore and 400mm stroke. It will pull 688kg@6bar and my Z-axis weighs ~300kg. Since i have a 1:2 ratio in the chain between the Z-axis and the cylinder i'll effectively have a 800mm stroke and 344kg@6bar, so it fits perfect(Z-axis travel is just below 700mm)...

I'll add a buffer-tank and a pressure-regulator. This way i can dial in the pulling force and the tank will help minimize the pressure fluctuation as the piston moves up and down....

And yes, i need to pressurize the system before usage... but i'll need air anyways, e.g. for toolchange etc....

That's a hefty sized cylinder.

Thanks for the link, not often do I get parts handed to me on a plate and from a german seller....