Any tips on Neck piston?

[and...@rekabuk.co.uk]

I'm fairly new to 3D printing ans I have most of the Torso and head printed. I started with my Arduino to move the head up and down, but the piston keeps jumping off the neck. Any advice on what to look for or how to fix it?

I'm using Bob Huston's articulated neck and I have tried sanding the ball and socket neck joint so that it is smooth. I have tired sanding the neck piston screw so that it is smooth rather than ribbed from the print.

Regards
Andrew

[Reece Isaac]

Hi Andrew,
Could you expand a little about what part of the piston is jumping off what part of the neck? 
Are you reffering to the ball and socket of the actuator or the ball and socket of the neck or something else?

Regards
Reece

[rekabuk]

Sorry, the big ball and socket for the neck is sound and I have sanded it to make it a good fit - not too tight and not to loose that it falls out.

The problem is the front neck actuator ball and socket at the top where it connects to the front of the neck. I can move the head up and down a little (don't have any figures 50-150 on MRL servo control?).

As the servo rotates to push the head up the whole actuator rotates and jumps off the top ball and socket.

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[Alan Timm]

Hey Andrew,

Bob is recommending that a small screw be used to help keep the ball joint seated for each neck "piston".

I'll be releasing an updated design this week that addresses the issue, and I think Bob is also working on something.  So if you haven't already, like and watch our thingiverse projects to keep updated on our progress:

http://www.thingiverse.com/thing:845793

http://www.thingiverse.com/thing:1243403

This is happening because the screw drive exerts a linear force (which we want) as well as a rotational force (which we don't want).  It's that rotational force that is twisting the head(s) off of the ball joints in thenect

[gael langevin]

Hi rekabuk,

Another thing you mention, is the servo control via MRL. If you use a script you can set your min and max values, to make sure the servo doesn't go further than necessary. The servo for the neck has a rotational potential of 180 degree, which if not set correctly it might overshoot the piston's length.

One more thing, the two extra back pistons are not yet implemented in MRL InMoov service.

We need to put pressure on the MRL elves, so they work on it for the next release.
:)

I really would like to add these to my build.

Gael Langevin

Creator of InMoov

InMoov Robot

@inmoov

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[rekabuk]

Thanks Alan.
Looks like very small screws with no head?
Andrew

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[rekabuk]

Hi Gary
Yes I have set min and max which give another question what kind of rotation angles should I expect to get? 30 45 60deg?
Andrew

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[Alan Timm]

Hey Andrew,

The redesign in the photo below uses 3mm x20mm Socket Head Cap Screws.

http://www.mcmaster.com/#91292a123/=114zjny

Alan

[gael langevin]

Hi Andrew,

I have designed the thread length for the servo to be able to do a full 180 degree rotation, O position being at lowest chin position and 180 at highest. If you can't achieve that, you will need to reset the piston on the servo horn with a difference angle positon.

By the way did you follow my tuto for the neck which should work even for the remix of Bob Houston.

Assuming you have already fixed your HS-805BB servo in the Torso assembly. Set your servo at 90° with arduino board. Turn “ThroatPiston” and “ThroatPistonBase” in a matter to get “NeckHinge” straight flat.

Screw “ThroatPiston” to its turntable keeping your servo at 90°.

Gael Langevin

Creator of InMoov

InMoov Robot

@inmoov

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[rekabuk]

Hi Gael
Yes I did read the tutorial.  I am also using these head modifications Modified InMoov head found on #Thingiverse http://www.thingiverse.com/thing:992918 which are based on Bob's original. I set the servo to 90 and the head straight.
Andrew

[Andrew Baker]

Part of my problem was that the NeckPistonBase was hitting the inside top of the NeckPiston before the the neck was fully pitched forward and the servo ripped the Piston off. Now I have a head and most of the torso I'll go back and try Bob's new design.
Andrew

[gael langevin]

Andrew,
make sure your servo is correctly set for the degree rotations. Other wise, even with Bob's new design you will get three broken pistons.

Gael Langevin

Creator of InMoov

InMoov Robot

@inmoov

[Andrew Baker]

Ha! thanks :)

I had already broken the top of the neck piston which came from http://www.thingiverse.com/make:198661. I didn't want to print the whole piston so I cut the top off, reprinted one of your tops and glued it on - They may not have been compatible - Needless to say I have learnt a lot!!!!

Now I have finished my torso and installed the XBOX kinect I'm going to start printing http://www.thingiverse.com/thing:1243403 by gestalt73, it looks amazing. Although I need to modify it to fit http://www.thingiverse.com/thing:992918. Nothing is ever straight forward.

Also started writing a new Inmoov head service for my modified robot - shame we have to work too :(

Andrew