Hey! This thing is still a Work in Progress. Files, instructions, and other stuff might change!

InMoov - Low Back Skull / Neck Joint - Modification

by dix238 May 23, 2016
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I would like to know what kind of piston I can print for this type of articulation

Hi, It was originally designed based on Bob Houstons mod https://www.thingiverse.com/thing:845793. So, the same pistons can be used. Also there is a remix with replaceable ball ends, which would allow other sizes or connectors.

Articulating Neck Joint for InMoov

Thanks for the reply
but it seems that the piston is not complete !!!
the underlying part is missing

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HI; Thanks for this modification, it looks like it will solve several problems withe the overall head space and the ability to route cables through the neck. Unfortunately, I am having some problems with getting it to fit.

First off I am using MG996R Servo. It was my understanding that it is the same size as the 15138 you call out. It fits the mount on the Back-Skull with no problem. The problem is that when I mount the servo from the top side, the gear does not make good contact to the lower gear on the neck . If I mount the servo from the bottom, the back skull will not mount to the neck holder.

I'm wondering what material you printed your parts from? I am using PETG. My thought is that if you used ABS, could the shrinkage account for the difference in size of the gears? Maybe that would make it fit? I know the shrinkage is not a lot, but the fit is only off by a little.

My second question is about the servo. The original design used an HS-805BB servo, which is a pretty hefty servo. Have you seen any issue with using the smaller servo? Is it able to hold up with continued use?

Sorry for the long post, thanks again for the work done here.


Thanks for your questions!
I have printed it using PLA as well as ABS and shrinking was no poblem. According to HobbyKing the sizes of MG996R and HK15138 differ in height. MGR996R is 2mm higher. I guess that is the issue. If so, z-scaling the NeckDriveGearV1 should help. Just for clarification, the servo should be mounted from the bottom.
Regarding your second question, I agree that the original design uses a servo that is twice as strong. So far, I didn't see any issues. According to my estimations, it should be good until the head-weight exceeds 2kg. In that case a 10kg/cm-servo reaches it's limits, if the head is in horizontal position (because it works against gravity). This estimation presupposes that the axis of rotation of the head is approx. 5cm away from the center of mass of the head.

Thanks for responding!

Yes, 2mm might help the vertical alignment, but not the horizontal spacing. Not sure what is going on there. I might just print a couple of spacers. I don't really want to print the neck piece again right now.

What eye mechanism did you use with this configuration?

I have just ordered an MG996R to check that. Maybe the position of the rotation axis differs too.

The eye mechanism is part of my current project. I am designing a face that is more "animatronic". As soon as I have a working design, I will publish it here.

I ordered the TGY S901D yesterday. Hopefully it will be in on Friday and I can try it out.

I look forward to seeing the eye mechanism. I was using the one from the InMoov sight, but with the articulated neck mod it will no longer fit. And I had spent a couple days modifying it for the camera I have too.

Trying to decide what to do next. Either way, I will have to customize it for my camera.

I was able to get the Back Skull and gears together. I reprinted the Neckdrivegear in ABS. It made it just small enough to fit. It is still a little tight, but appears to work. Not there with the eyes yet, but I think my approach will be to re-work the Neck to allow for fitting the InMoov eye mechanism. Once I got the head together, I was able to look at the space claim in that area and I believe it can be done.

Unfortunately, My printer is down for probably a couple of weeks. there is a problem with the main board and I am getting errors that kill my prints. It really sucks when a 9 hour print craps out at about 6 hours. Maybe I can take advantage of the time to get the electronics working.

Good news that it fits now!

Although I have my one eye mechanism, I am very interested in your neck modification. I already thought about rotating the mouth-servo by 90 degrees to have more space in the front. Maybe this could also be a solution for you.

Good look with your printer. I now how frustrating it can be to wait hours for a print that finally fails.

You don't happen to have a model of the neck piece do you? I would love to have a starting place for the modifications. It's kinda tough to work from the .stl file.

Unfortunately I only have it as stl. The piece is from monnerby (http://www.thingiverse.com/thing:992918). Maybe he has it in other formats. What applications do you use? For me as a software developer OpenScad is a good editor, because you "program" your objects. Usually stl files are no problem this way.

Modified InMoov head

I'm not much of a programmer, so I have never tried to tackle OpenScad. I have used several scripts that others have developed, but haven't spent much time trying to figure out how to actually program something. I started out using Google Sketchup for woodworking projects and initial 3D printer designs. I moved to 123D Design but when that was discontinued I moved to Fusion 360. Fusion 360 has a lot of good features. Some of the commands are kind of backwards from 123D Design, but after some practiceI find I get better results and can do more with Fusion 360. I have designed a number of things myself, and have made modifications to designs I downloaded, if I didn't like the way they fit, or they didn't work, sometimes I just want to add a feature. A lot of the time I use the .stl as a pattern and build a new cad file for the part and sometimes, if it is just a minor tweek, I have just modified the .stl file.

What did you use to design the lower skull back part? Would you mind sharing that file?

Actually, I try to avoid any reconstruction. For the lower skull back part, I used Netfabb and Meshlab. It was an iterative process to prepare the stl-file: remove unnecessary parts, remove holes and bulges or dents and so on. So for this part of work, I have quite a lot of stl files representing the steps I made. Nothing more. The actual OpenScad file just defines the servoholder and where to place it. I guess that doesn't help much. If you want to have a look at it anyways, I will send you the files as soon as I am back in my lab.

Thanks, wouldn't mind looking at it, but it might not be much help for what I want to do.The final .stl file will do just as well to give me what I want.

What servo are you using with this? the original large one (Hitec 31805S HS-805BB)? Also is there anyway you could update the back skull like the new one on inmoov? it now has mounting hole to connect the side ears. Thanks

I am using Hobbyking HK 15138 and/or Turnigy TGY S901D. And there are others with the same size (40x20mm).

Nice design. I updgraded to this version and it works very well.

I use the servo s3003 futaba but the head does not move help me please

Could you please provide some details? I had a quick view at the servo and it seems generally ok to use it. So, what is the exact problem? Do the gears fit or not, does the servo rotate, is something blocking? Could you post a picture?

The gears coincide, it seems as if the servant does not have the right force to rotate the whole head

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