Hurco BMC 30 won't unclamp and stay open

[gmachine84]

I have a Hurco BMC 30 and am having a problem when attempting to change my tools either automatically or manually. When using the manual switch I can sometimes get the tool in the proper position. However this doesn't fix my problem. I opened up the spindle door exposing the pneumatic power cylinder and was trying to see if I could find any problems. Nothing was obvious. I replaced the manifold but the same problem occurred. I could now see more what was going on at least.... SO HERE IS WHERE I NEED HELP.... When pushing the button to release the tool I can see the cylinder push down the drawbar briefly and then it retracts slowly to the clamped position. (even with out letting go of the button) I feel as though it's an air leak but cannot find anything. I'm not sure where to go from here. Please respond as I need to get my machine back up and running asap!

Thanks.

[bloke]

Sounds like the seal in the main unclamp cylinder or the solenoid. Unclamp it and then quickly remove the bottom pipe from the cylinder. If air escapes from the pipe, the solenoid is suspect if it escapes from the cylinder, then that is suspect.

[gmachine84]

Bloke, I've have attempted to do what you had said... however with out an extra hand it was somewhat difficult and I am also not even sure if I was removing the correct pipe. So I have not real good results from that test. I've uploaded some photos. Would you mind pointing me in the correct direction? I've also uploaded a video to show exactly what it's doing. The photos are on my tumblr account located here.....

3 pictures and video click here

Please let me know what you think. I need to have my machine fixed badly.

Thank you.

[bloke]

Looking at the video, what seems to be happening is the air is entering the top pipe to the unclamp booster and is pushing the cylinder down as normal.
Once unclamped though, it seems there is a leak between the top half of the booster and the bottom so that eventually, the air leaks to the bottom side and equalises the pressure. With the springs in the drawbar pushing against the cylinder, it returns to it's clamped position.

Mark up the pipes to the top, middle and bottom position of the cylinder and remove them. Then apply air to the top fitting and see whether it unclamps properly with no air escaping from the lower two fittings.