Looking good so far. Any tips on articulation? Such as the math/engineering behind it and tolerances I should be aware about? I 3D printed a glue gun casing for a school with some articulation and sadly it didn't revolve as much as I wanted to so I had to sand my model a little bit in order for it to work properly. I'm trying to avoid any issues with my semester project.

 

I haven't 3D printed anything yet so I dunno much about tolerances. I figure I'll probably have to print some from Shapeways, test them, tweak the design, and have them printed again and I'm sure I'll be doing some sanding (have to sand anyway to get rid of the ridges from the print). The nice thing about doing it from Shapeways, though, is they're using high end printers that also print out a support material so the prints should be pretty accurate. The other nice thing about Shapeways is they have some sort of deal with Hasbro for some of their toylines including Transformers where you can sell Transformers toys and Hasbro gets a cut. And they've got different materials with different strengths and weaknesses so, for example, the more detailed pieces can be printed in frosted ultra detail while the parts that need to be more durable can be printed in strong and flexible (or whatever they call it).

As far as the math, I put the piece where I want it in bot mode and then put it where I want it in vehicle mode and then calculate where the joint needs to be based on the coordinates. So her leg transforms pretty much like all of the Arcee toys out there with a joint mid-thigh so that the entire leg can move out to the side. So I've got two sets of coordinates: where the hip started in bot mode and where it ended in vehicle mode (the point I'm using is the point where the hip rotates in bot mode). What I need is essentially a circle that intersects those two points with its center somewhere mid-thigh. The center will be the joint. The formula for a circle is (x-h)^2+(y-k)^2=r^2 so I set up a system of equations plugging one set of coordinates in for x,y in one equation and the other set into the other equation. Since both equations =r^2, I can set them equal to each other: (x1-h)^2+(y1-k)^2=(x2-h)^2+(y2-k)^2. I know how deep into the side of the thigh I want the joint so I place a point at that depth and use its x value and plug it into the equation as h and then solve for k to get the y value for the joint. Then I stick a pin at those coordinates (the pins are just visual guides while I'm building) and set the thigh piece to rotate at that point (in Blender, this is called setting its origin).

Then when I want to figure out the angle to rotate the thigh, I calculated the angle from those two points. I can remember how to get slope and distance from two points but I can't remember how to do degrees so I just used an online calculator. For some reason that didn't work at all (probably has something to do with the fact that the thigh also had to be rotated 180 degrees around the x axis to get it lined up along the car body) so I just used trial and error until I found the right angle. So far that's the only joint I've needed math for: everything else has just been done by sight; but I'll need to do a lot more math when I start putting in the joints to move the car parts around.

 

Yeah, that's what I thought I would have to do: basic circle equation. Seems simple enough. For my glue gun model, I was using Solidworks and kept drawing construction circles as a guide to see where my part would ultimately end up at. It worked, but my dumbass forgot to simulate the process before I printed at Shapeways so I could meet deadline. It was colliding with the main casing.

Regarding tolerances at Shapeways, I would definitely have my pins at least a -0.001" tolerance. The pin had an identical radius as the hole it was going into. It's not perfectly identical to the CAD model; I had trouble even slotting in my pins. Sanding helped, but then the pin sat a smudge too loose.

 

I'm not worrying too much about tolerances just yet. The pins you see in my screenshots are just visual representations of where the joints will be: they don't necessarily denote actual pins. As for leaving -0.001" tolerance, is that even possible? I didn't think 3D printing was that precise. At any rate, I'd rather the joints be too tight and I can sand them down instead of having them too loose.

Here's the face sculpt:



The ball is just a place holder until I build the real head: I just needed a rough idea of how her face would look in her head. There are some artifacts where the nose joins the face but those won't be present when it's finalized: it's a result of the polygons being in nearly the same place overlapping.

I just learned about these tritium vials you can get: radioactive light sources; and I'm thinking about using a blue one for her eyes so they're always glowing. It's not a super bright glow (would only really be visible in low light). I dunno'. What do you guys think? I may have an exaggerated idea of their brightness: has anybody messed with them?

 

Arcee came out in the 80's, not the 70's. Adjust her hair according.

J/k.

Shame on me for not saying this earlier, but I complement your modeling in Blender- especially being new to it. You have some good skills on display.

 

Thanks. I try my best and I'm really hoping I can pull this off. I think I've '80s'd up her hair a bit: what do you think?

Here are some more pics showing the head and with the parts I've built arranged how I think they'll be in robot mode. I haven't built the dashboard yet and the seats are just a couple of blocks that will need... well seats molded onto them. I also haven't built the panels that will form the read of the car (like the trunk is there, but not the back end/bumper). Putting in all of that along with the parts needed to move everything around will add some bulk to the backpack but I'm still cautiously optimistic about the possibility of having it reasonably compact.

 

So back to the pins. Is there really no way to get the kind of pins that are used in the real toys? I mean I guess nails are ok, but I'm surprised you can't just get real pins.

[edit] Ok, I found something: Amazon.com: uxcell® 100 Pcs Stainless Steel 1mm x 15.8mm Dowel Pins Fasten Elements: Industrial & Scientific

They're not perfect but it shouldn't be too hard to cut them to length and I can dab a tiny bit of super glue on the end when inserting them, since they're not knurled. I suppose I also might try scratching in my own knurling and heating the tip just before inserting. Either way, I can start planning on 1mm and/or 1.5mm pin hole sizes which is right around where I was aiming. I'll probably get a set of the 1mm to use in smaller joints (the toe joint for example) and a set of 2mm dowels for heavier joints like the hips.

 

Quick update. I modeled the feet and went ahead and sent them to Shapeways for printing. I'll post back with the results once I've got them in hand and I've had a chance to sand and primer them. I had to use sprues to put all of the pieces into one part which brought the price from $13 down to $3something, and I went ahead and ordered two sets since shipping was going to cost more than the actual part. That way I can experiment with sanding or using acetone to smooth them.