The first test print revealed that the inside of the bones needs additional clearance for the brazed joints. I’ve modified just one of the joints so that it can be test printed to test the clearance. This is the right knee joint on the femur, intended for a 90 degree T-connection.
Additional bones and angles will follow once we get the connection portion sized correctly.
- I’ve added clearance in the areas that @rlisbona recommended.
EDIT: Drawing previously said 3mm radial clearance. That is incorrect. It is 3mm diameter clearance.
- There are two versions of the file available on the committee drive (rev A folder). Since we’re only testing the fit and not the appearance, I thought it might make printing easier to have a temporary version that’s flat on the back, but that’s up to whoever prints it to choose (sorry - I’m not a filament printer person). @CaryF300 - are you the person who printed the first tests?
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Yes, I printed it. The flat back one will make printing faster. I’ll get it printed tomorrow.
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@rlisbona had a vision that he’d like an immobile knee “joint” that slides over the vertical tubing somewhere between the brazed joints (so it looks like a knee in the middle). I’ve modeled such a thing but Randy needs to decide if it should be printed.
I modeled the complete joint and then split it. If we were to print both sides of it they could be assembled over the tubing and then cable-tied together. Might need to epoxy or cable tie the frame to keep it from slipping up/down. IMO the back side is more interesting than the front - and it’s also a little thicker.
(EDIT: For truth in advertising, I started with stl models of the independent bones, converted them to solid models, and then made modifications).
Models are in the committee drive: DMS Special Interest Projects / Coffin Racing / Consol knee joint. I’ve only uploaded the right knee but can add left knee if desired.
Yes, I know there is no patella. I’m not sure if the patella would be realistic - it might fall off the skeleton when the cartilage disintegrates. There’s not likely to be a patella unless someone models a patella and sends me the solid model. If you’re motivated to model a patella … please add a three-dimensional DMS logo to it!
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Awesome, @CaryF300 can you also print a knee bone?
I love art where you see something that gets your attention and then when you look closer you see more and more details, so I kinda think we are going to need to embed some jewels in the knees or etch something like a Best Before date or a Wham-O logo.
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@rlisbona, yes, I’l print a knee today, too.
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Got over here a lot later than intended. All three bones are starting on Hyneman now. Should be complete about 10pm tonight. All I had with me was purple filament, so that is what this round is printed with. lol
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Cary – there’s a report that the Hyneham is spitting spaghetti…
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The knee printed great! It is too tight on the frame. I’ll try a 1% increase overnight and see how it fits tomorrow.
Latest printed pieces are with the frame.
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101% is better, but still not quite there. I’ll try 102% today. It’ll probably be Monday before I can get back to the Space.
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Do you think that with a cable tie on it, it would be cinched down enough to work?
I figured out the support problem on the femur with the flat back. One of the sides is not even with the rest of the flat part.
@John_Marlow can you take a look at your model and see if that can be fixed easily?
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I think you printed femur-knee, didn’t you?
Let me check. I might have grabbed the wrong file off the jump server.
That is right_femur knee_revA_flat_back.stl.
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OK, here’s what I think I’ve agreed to do - with one question.
As we agreed, once we know the correct scale I’m going to scale the model so it will print repeatably without relying on individual slicing adjustments. I need to know what scale for the femur-knee joint - 102%??
- Consolidated Knee joint. (the 2-part knee that cable ties to both sides of a vertical pipe).
- Scale the model to 102% and we are going to consider it “final” (at least until further notice
.
- I will make the left consolidated knee and it will also be considered “final”.
- Femur-knee joint. This is the joint you’ve been working on because it’s the only one where I hacked the back flat.
- First I’m going to see if I can find the interference/anomaly you identified above.
- Scale the model to (102%??) - you need to let me know what percent you’re ready to test next.
- All joints that cable to the front of the pipes without a separate back piece (femur-knee, and femur-hip at this point):
- Cut the major “nub” off the back so it will print flat on the build plate. Put two alignment holes in each for 1/4" dowels.
Item 1 completed. Files are in “committee” drive.
Item 2 is completed. Scaled to 102%. Files are in “committee” drive.
Item 3 is completed on Femur-knee and incorporated into item 2 files listed above.
Please let me know if 102% was the right scaling. Thx.
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Yes, 102% is the right number. I’ll pull them and get started printing.
EDIT: Printing of the left side has started. When it finishes I will print the right side and take them to the 'Space tomorrow.
The 102% femur knee prints fit well. A couple of zip ties to hold them on and a couple of pins and glue to hold the backs on and I would call them done. The flat backs cut the print time almost in half, and really reduced the filament usage.
There is one white and one purple, again. I forgot to pick the correct filament when I did the left one. 
EDIT: I took all of the versions that were too small. The only ones left with the frame are the 102% ones.
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I’ve added the femur-hip to the committee drive. It’s 102%, should be flat on the back, and is split into two pieces. Right and left hips. These are all the pieces for the four orthogonal joints … now I have to make some measurements of the 13 odd angle joints - or figure out a way to hollow out the backs of some of the joints.
Do you want me to add some 1/4" pegs to print so we don’t have to look for dowels? They would only be half inch tall so I think they could easily be printed on the same plate.
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Looks great. I’ll get them printing over the weekend.
I don’t think we need to print pegs. 1/4" dowels will be easy to source and size approriately.
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