Sieg X2 head weight

[pequod]

Hi,
I've converted a Seig X2 mill to CNC (CNC Fusion), and removed the torque bar.
I wish to fit a counter weight over a pulley to take the load off the ball screw/ball nut.
Does anyone know the weight of the spindle head, so I can balance it reasonably evenly:question:
Thanks in anticipation.
Ed

[Jonathan]

I've no idea what the mass is. I bet John S knows...

I would make the counterweight a bit lighter than the head as that will ensure you still have force downwards on the Z-ballnut. This will eliminate backlash, except where you have a force parallel to the Z-axis which is greater than the imbalance (e.g. drilling).

[i2i]

just a guess, 830 kilos...ish

[John S]

Sorry, can't help. I have an 'X2' head here but it's one of the new SX2L heads with the brushless motor and no gearbox so the weights will be all different.

[tumutbound]

I have the LMS airspring which is rated at 35lbs and Daniel over at Hossmachine built his counter weight at 38lbs.
I did weigh the bits off my X2 mill at one stage and the figure 18Kgs seems to ring a bell.

[russell]

Can anyone explain what the problem is with the supplied counterbalance system?

Russell

[ecat]

I've no idea what the mass is. I bet John S knows...

I would make the counterweight a bit lighter than the head as that will ensure you still have force downwards on the Z-ballnut. This will eliminate backlash, except where you have a force parallel to the Z-axis which is greater than the imbalance (e.g. drilling).

I'm sure this applies when dealing with low friction linear rail but does it apply when dealing with the dove tail and gib set up used on these Siegs?

As a quick test, when the gib is snug is the head free to fall under its own weight? If the answer is yes then the above does apply, if no, then the weight of the head is insufficient to overcome the friction in the ways so there is no downward force available to eliminate the backlash.

From my experience with the X1, and possibly the X2 and X3 from what I've read, the head is far more likely to rotate about the lowest corner of the head dove tail than it is to fall smoothly down the column. And a gib tight enough to minimise this rotation results in more friction than the weight of the head can overcome.

Edit:
It was bugging me that I didn't specifically mention the 'quick test' should be done with the head free from screw! Just make sure to support the head on a wooden block or such in case it is free to fall!