Flexure with 40mm Travel

Rubber band?

Living hinge?

A little more information would go a long way in this discussion.

so the thing is that this has to be vacuum compatible and has to be very stable in the full upright position. it is also in a clean room so no to very little particulate generation can be had. those are the main things but if you require more info i can do that. thanks

what do you mean by flexure? a spring? what force to move it? which is the Z direction in your 186mmx38mmx137mm space?

by flexure i mean like a 4 bar flexure or a folded flexure...i dont know many designs and wanted to use that. the z-direction is the 137mm. i am not sure what force right off hand...i will be using probably an actuator to move it...be it a linear actuator or something else.

If Z is extension, a nylon spline is my first thought. We'll see what develops.

I think I know what you are after but for the life of me I cannot remember what it is called (the flexible joints on this well-known robot).

It is also common for dangerous material handling where you put your arms through flexible arm sleeves to manipulate things in a sealed enclosure, and I am fairly sure they can be made out of single piece plastic for low pollution applications.

I don't think I can be any more vague, but someone here must know what I am on (about).

Me! Me! Let me bellow out the answer to what the joints are called: accordian [I couldn't help myself - sorry] to Wikipedia (see http://en.wikipedia.org/wiki/Metal_bellows) they're called bellows. There is information on several varieties at this site, and it has links to others.

However, I suspect that the OP is looking for something that provides better guidance, and that's a much tougher trick to perform, ESPECIALLY when (s)he needs travel that is roughly 2/7ths of the available space. Ordinary flexural linkages are limited to between 1/20th and 1/5th of the size of the flexure, and the latter are limited in precision and perhaps lifespan.

what else would u suggest that might do the trick? im kinda familiar with flexures and thats what i went to but if there is something better and would be simpler to design then that would be awesome.

Can you describe your application in more detail? A picture or diagram would really help.

Someone else already mentioned a Nylon spline. There are some dashpots which use a glass exterior tube, and have incredibly low friction forces; a pair, tied to a rigid bar to keep them in rotational position with each other, might suit. Since they're basically telescoping devices, the 40-of-137 mm travel should be doable. Since you're in a vacuum, they wouldn't provide a dashpot function, just guidance. See http://www.isotechinc.com/dash-pots.html for an idea of the type I mean.