Nic 77
Thank you for all your calculations/information. I am indeed familiar with rodless cylinders, as I had said in an earlier post. They have some cons, one of which is cost. You should not discount pulley systems so readily as 'DIY', they are a cornerstone of mechanics. This whole build could be regarded as 'DIY' as we are doing it ourselves, but, as we are reasonably competent mechanical engineers building a commercial use machine I would argue that nothing on the build could be considered as 'DIY' in the context that you have used the term. Another poster said "I have had good luck with gas struts..." well, we do not rely on luck, rather good engineering and intelligent thought.
Air over hydraulic - I do not believe that a hydraulic ram is a good solution for a high speed system (1.0 m/s).
As you have gone to the trouble to provide all that information, I propose that we fully indulge your fetish for counterbalances by giving you correct parameters to work with. I suggest that we should consider the following configurations:
1) Single acting pneumatic cylinder 400mm stroke / 4:1 pulley system.
2) Single acting pneumatic cylinder 500mm stroke / 3:1 pulley system.
3) Single acting pneumatic cylinder 750mm stroke / 2:1 pulley system.
4) Rodless pneumatic cylinder 1500mm stroke.
Parameters:
Z-Axis mass = 120kg.
Z-Axis travel, use 1500mm.
Z-Axis travel velocity: 1.0 m/s.
Available factory air: 80cfm / 100 psi.
Factory air receiver capacity: 0.5m3 + 100m of 1.5"NB Schedule pipe reticulation system.
Additional air (spindle tool change, etc): 2nd stage compression - 175 psi / 5 cfm / 50L air receiver.
Note #1: We can fit an appropriate additional air receiver / accumulator dedicated for the counterbalance system, or,
Note #2: We can consider using the factory air system as the accumulator, or,
Note #3: We can consider using the main frames as the dedicated air receiver / accumulator, capacity = 22 meters of 200x200 RHS.
Note #4: I would suggest a safety factor of 1.5 should be applied to the ram size calculations.
Have I forgotten anything?
Regards
Jono
Ps: merry xmas all