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Robotic Arm Questions

Hello, I am reporting an issue that I have come across with the claw on the robotic arm. The claw seems to have stopped working. The gear on the back of the robot is starting to open exposing some of the internal parts of that gear. whenever we try to manually close the claw it springs back open. If someone could reply asap it would be much appreciated.


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A photo or two would help in determining a solution to your issue.
What sort of robot claw do you have? It almost sounds like the toy claw arm (the sort that looks like the B9 Lost In Space robot claw (*even though that claw was a little different)) and has a handle on it. If it is like that the spring inside the claw forces the claw open. Pulling the handle pulls a metal bar attached to the middle part of the claws forcing it to close. If this bar has come lose or snapped nothing is available pull the claws shut internally.

Please explain which claw you have and post pictures.
United Kingdom
Is this the same claw you have already asked about previously?
Rich- Yes it is the same arm I have talked about previously. Hopefully these photos I attached can better explain what I am experiencing. I have added a material called polymorph to help with the closing of the claw but just today, the claw stopped working. It used to be able to open and close but not fully.
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These videos were taken after we programmed the robot and that was when my team and I encountered that the robot won't fully open and close. Now it wont even function.
OH, OK. Not the claw I was picturing. I believe your servo can not move any further. Consider the server has a limited range of motion, probably 180 degrees. If you have been experimenting and took the servo off the gripper you likely repositioned the servo so it can not open all the way. When this happens to me, I take the servo off, manually adjust it (or via script :D ) to the center position, then reattach it. You should see a full range of motion again, based on what I am seeing in your video.
@Matrin13 thanks for the photos and the videos. As @JustinRatiff mentioned it may be your servo has shifted out of its normal area of control. It would be best to disconnect the servo from the claw mechanics and then make sure there is no mechanical reason for the claw not fully closing or opening. Once that is verified then you can re-center the servo position with the claw.
The servo that works for the claw can't be removed. I have tried but it looks welded on to a piece of metal from the gear. Plus the other servos I have are to big. The claw servo is 2x smaller than the normal ones that come along with the kit. I have no idea what to do now *confused*.
It would seem that either the servo is defective or there are mechanical issues with the claw and its gear mechanism. You might consider taking pictures of both sides of the claw then disassemble the individual parts to free the servo and it gear then test it for proper movement.

Is this the claw from sparkfun.com that has a built in clutch ?
@Robot-Doc yes it is the arm from sparkfun.com that has the spring loaded clutch built in.
Your screws might be too tight and that SUGRU stuff on there may be preventing your mechanism from turning.

Hope this helped.
United Kingdom
Remove the servo and reset the position of it so that it can close all the way, currently the servo doesn't look like it can move far enough to close the claw.

The servo will come out, it is designed so the servo can be removed. If you cannot see how it comes off there are youtube videos of how to assemble this claw which should give an indication in how to disassemble it.
Here is a LINK that should help you with repair of your claw.

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Thanks so much to everyone that helped! This really did help my team and i a lot. I think that now we will be able to fix the problem we had with the claw. Again, thanks to everyone that helped! I really appreciate it!