In my machine after I change the tool start working some time the tool is falling from the spindle I checked the grriper and by marking I found that the gripper hold the pulstud only for about 0.5mm I checked everything took a part the springs and the gripper but not finding nothing that will not hold the tool like suddenly I need to change for bigger pulstud
did some one of you got this kind of problem

most probably, the drawbar cup springs are broken.

sorry but this is not the case
the gripper not closing all the way on the pullstud

dango,

Are you saying that the difference in drawbar height (when clamped) only changes .5mm when there is no tool in the spindle? The spindle drawing in the parts list should show the amount of stroke (or distance to the top of the drawnut) your drawbar should have. If the drawnut is too tight, its stroke will be too small to allow proper clamping pressure. In this case, back the nut out until you achieve the stroke listed in the parts list

Does the problem occur with only one tool or many different tools? How quickly does the tool fall out of the spindle after the tool change?

Did you count the belleville washers and make sure they're arranged properly?

Usually, they're stacked in pairs. If one pair is flipped around, it will reduce the stroke. They're usually stacked like this;
))(())(())(())(())(())(())(())((

I agree
Any problems with the curved washers affects the ability to hold the pull stud and tool firmly in the spindle taper

Your service person should have a special tool to mount in the spindle to measure the draw-bar pressure on the pull-stud , and / or set it to the correct pressure.

I think you did not understand me
I will try to explain it again
The gripper holds the tool on the pull stud by 4 fingers
The pull stud have head and then became a neck the fingers when they grub
The tool and going all the way up at this time the fingers close and holding
The pull stud and they touching or almost touching the neck of the pull stud
In my machine they are not closing enough but only 0.5mm over the head
So because of that when you cut it fall
I checked the spring and all the parts of the drawbar but
Could not find what cause the problem
It like the pull stud became suddenly too small and I need to increase the size
Of it

please refer to attached retention knob table. May be of help to resolve this fault

What about wear of the fingers? Is that possible? Are you using the exact pullstud recommended for your machine? No oddballs in the mix?

Can you measure the travel of the drawbar somehow? Compare the travel distance with no tool compared to the travel with a pullstud in the gripper.