Following error and contact

I am currently using a motion system which has been neglected for a while due to some shortcomings for the original application.
I'm trying to revive it by making use of the following error to detect when contact is made between two objects. The main Problem I have is reducing the contact pressure in such an arrangement. I have implemented a basic version where the axis moves until the following error goes above a certain value (say 30 = 30um) upon which the axis then stops.
The problem is that I'd like to choose a much smaller value, but the jitter is too large to allow this. I get values anywhere between 0 and 20 while the axis is moving. Of course the following error increases dramatically once contact is made, but the problem is detecting this contact point quickly enough so that the pressure created is as low as possible.
I've tried limiting the torque of the servo motors, but I'm not sure this has had an effect.
Does anyone have an idea what I can change to improve this apart from using a different algorithm to detect smaller changes of the following error (slope over the last 10 measurements or something)? Do I need to modify the coupling between the motor and the axis?
Thanks
Shane.
PS, I have already got some micrometer switches hooked up to the hardware, and they work nicely, but the ACTUAL contact points between two non-micrometer switches is what I'm after.
Using LV 6.1 and 8.2.1 on W2k (SP4) and WXP (SP2)

Jochen,
Thanks for the answer.
I've tried testing it with a 1mm glass substrate between the axis head (flat steel surface) and the stage (also flat steel surface) so that the two steel surfaces are slightly tilted to each other (representing what I hope is a real-world scenario).
I can drive the axis with 5 RPM (enough for my application) and a permitted following error of up to 2000 without breaking the glass. I think this already gives me enough information to continue. Incidentally, the rising flank of the following error curve versus position allows me to work out the exact point of contact afterwards, thus giving me the required accuracy.
I think the clue to all this is the way the axis is coupled to the motor. I reckon this is absorbing a certain amount of tracking error and as long as I don't drive the axes together with great speed os allow a huge following error, things should be fine. I think I'll use 60 or 100 as my limit, then things should be OK.
A lot depends also on HOW the surfaces come into contact. Edge on edge will break most things, but as long as they're more or less parallel to each other, the tolerance seems to be quite a bit higher than I originally thought.
Thanks again.
Shane.
Using LV 6.1 and 8.2.1 on W2k (SP4) and WXP (SP2)

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