Chipmunk Physics

I use cpSliderJoints with min=max=0. but they sometimes start sliding. how can i fix it?

Why using a slider joint with min = max = 0.0f?

A couple of things to note.

If you are using a slide joint with a min/max of 0, you probably meant to use a pivot joint. It will be more stable.

If by "starts sliding" you mean that it doesn't perfectly hold the anchor points together, then you should realize that the constraints/joints/collisions are really only requests to keep certain conditions. Chipmunk will do it's best, but cannot guarantee that objects won't get pushed into each other or that joints will get stretched out.