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03-20-2017, 08:14 AM
It's been a frustrating few weeks. I've been working on my enclosure and fighting with the printer to get it to work reliably again. (I took the opportunity to cut the Z brace threaded rods to the length they originally should've been, and removing the braces mucked with the printer's squareness more than expected, causing a large increase in print failures.) Stuff is getting somewhat back to normal, apart from some of my filament not seeming to like the PTFE tube I'm using to guide it into the enclosure, so I'm back to working on Treadwell.
In my last post, I mentioned I'd started to work on revising the eyeboxes as prep for fleshing out my eye mechanisms, so that's where I'm picking things back up. Why revising? Well, I've noticed a couple of oddities in the plans here on the site...
* Firstly, the aspect ratio of the rear face of the eyebox (1.3571) does not match the aspect ratio of the front face (0.9821). In other words, the front face is slightly taller than it is wide, but the rear face is much wider than it is tall. That's rather peculiar, given the simple design of the part. It's hard to be sure from eyeballing it, due to the perspective, but I don't think that that's accurate. From having a look at the deleted vaparator scene, it seems to me that the rear faces of Treadwell's eyeboxes are relatively square, just like the front faces. For example:
The change I'm making here is to normalize both faces to exact squares. The front face is presently 88 mm on each side, and the rear face is 52 mm on each side. These numbers represent a compromise between the width and height I originally had for each face.
* Secondly, the original prop does not have the features that I called the "eyebrows" earlier in the thread. I knew all along that those came entirely from the plans here. It's not a bad look, but I've decided to remove it in the interests of helping others be more accurate. As alluded to in the thread on the Paterson projector, the lens holder simply appears to screw to the front face of the eyebox. See here:
The lens and its retainer must protrude slightly inside the eyebox, so the front face currently has a 66 mm hole to accommodate them. I may need to tweak this opening since I believe the lens is not perfectly vertically centered in the Paterson holder (it's a little closer to the bottom edge than the top edge; the flange on the bottom makes this less obvious than it would otherwise be). Haven't looked into it yet.
* Thirdly, as I hinted in my previous post, the truncated pyramid that forms the eyebox is skewed in the plans. If you look back at the very first eyebox schematic that I posted, you'll see four angles that give the slope of the long faces of the eyebox relative to the rear face. All four angles are different from one another. This essentially moves the rear face of each eyebox closer toward the horizontal centerline of Treadwell's head, and upward from the vertical center. My change here is to center the front and rear faces with each other. Since both faces are also square, that means all of the slopes will be identical.
So those are a few things I'm fixing. Here's a cross section of what I have rebuilt so far.
This is arranged in the orientation that it would be printed in. The two holes at top are for the lens holders. As you can see, I've now added the vertical split (so it'll fit on my printer). Each eyebox would be held together with three screws shown, and/or glue. I might also work some captive nuts into those screw holes.
What you can't see in that pic is how the parts join together away from the centerline. There is a little ridge that goes around the inner edge, except where the screws are. Here's a closeup of just the rear half.
This ridge was originally just a straightforward rectangular extrusion and helped hold the halves together, but then I realized that the other half of the eyebox would need support for the matching surface. So it is now chamfered instead and just helps center the parts. I'm not sure that I like this setup (among other things, it removes a good chunk of the plastic that'd be attaching the front section to the print bed). Since I plan to use the screws regardless, and those are perfectly capable of aligning the parts, I might abandon it.
Printing in this orientation does mean that the layer lines won't be optimal if the printer doesn't produce a good bond, but I don't think the eyeboxes are going to weigh enough to cause delamination issues, even with my eye mechanisms. Maybe they would if you used actual glass lenses, but I don't have those.
The alternative is printing with the eyebox lying flat -- which would require even more support -- or printing the faces flat, individually. Or a compromise ... lie the part down, but leave off the topmost face to be printed separately. The latter idea might be the most practical from the standpoint of putting in an eye mechanism, but my print bed is too small to print the eyebox length as one part, no matter which way it's turned, so I think it'd make the split I have now even worse. I'm sticking with the design above for now.
In my last post, I mentioned I'd started to work on revising the eyeboxes as prep for fleshing out my eye mechanisms, so that's where I'm picking things back up. Why revising? Well, I've noticed a couple of oddities in the plans here on the site...
* Firstly, the aspect ratio of the rear face of the eyebox (1.3571) does not match the aspect ratio of the front face (0.9821). In other words, the front face is slightly taller than it is wide, but the rear face is much wider than it is tall. That's rather peculiar, given the simple design of the part. It's hard to be sure from eyeballing it, due to the perspective, but I don't think that that's accurate. From having a look at the deleted vaparator scene, it seems to me that the rear faces of Treadwell's eyeboxes are relatively square, just like the front faces. For example:
![[Image: normal_treadwell_tatooine_08.png]](http://www.rebeldroids.net/gallery/albums/userpics/10002/normal_treadwell_tatooine_08.png)
The change I'm making here is to normalize both faces to exact squares. The front face is presently 88 mm on each side, and the rear face is 52 mm on each side. These numbers represent a compromise between the width and height I originally had for each face.
* Secondly, the original prop does not have the features that I called the "eyebrows" earlier in the thread. I knew all along that those came entirely from the plans here. It's not a bad look, but I've decided to remove it in the interests of helping others be more accurate. As alluded to in the thread on the Paterson projector, the lens holder simply appears to screw to the front face of the eyebox. See here:
![[Image: normal_treadwell_tatooine_06.png]](http://www.rebeldroids.net/gallery/albums/userpics/10002/normal_treadwell_tatooine_06.png)
The lens and its retainer must protrude slightly inside the eyebox, so the front face currently has a 66 mm hole to accommodate them. I may need to tweak this opening since I believe the lens is not perfectly vertically centered in the Paterson holder (it's a little closer to the bottom edge than the top edge; the flange on the bottom makes this less obvious than it would otherwise be). Haven't looked into it yet.
* Thirdly, as I hinted in my previous post, the truncated pyramid that forms the eyebox is skewed in the plans. If you look back at the very first eyebox schematic that I posted, you'll see four angles that give the slope of the long faces of the eyebox relative to the rear face. All four angles are different from one another. This essentially moves the rear face of each eyebox closer toward the horizontal centerline of Treadwell's head, and upward from the vertical center. My change here is to center the front and rear faces with each other. Since both faces are also square, that means all of the slopes will be identical.
So those are a few things I'm fixing. Here's a cross section of what I have rebuilt so far.
![[Image: normal_20170320-NewEyebox.jpg]](http://www.rebeldroids.net/gallery/albums/userpics/10380/normal_20170320-NewEyebox.jpg)
This is arranged in the orientation that it would be printed in. The two holes at top are for the lens holders. As you can see, I've now added the vertical split (so it'll fit on my printer). Each eyebox would be held together with three screws shown, and/or glue. I might also work some captive nuts into those screw holes.
What you can't see in that pic is how the parts join together away from the centerline. There is a little ridge that goes around the inner edge, except where the screws are. Here's a closeup of just the rear half.
![[Image: normal_20170320-NewEyebox-joint.jpg]](http://www.rebeldroids.net/gallery/albums/userpics/10380/normal_20170320-NewEyebox-joint.jpg)
This ridge was originally just a straightforward rectangular extrusion and helped hold the halves together, but then I realized that the other half of the eyebox would need support for the matching surface. So it is now chamfered instead and just helps center the parts. I'm not sure that I like this setup (among other things, it removes a good chunk of the plastic that'd be attaching the front section to the print bed). Since I plan to use the screws regardless, and those are perfectly capable of aligning the parts, I might abandon it.
Printing in this orientation does mean that the layer lines won't be optimal if the printer doesn't produce a good bond, but I don't think the eyeboxes are going to weigh enough to cause delamination issues, even with my eye mechanisms. Maybe they would if you used actual glass lenses, but I don't have those.
The alternative is printing with the eyebox lying flat -- which would require even more support -- or printing the faces flat, individually. Or a compromise ... lie the part down, but leave off the topmost face to be printed separately. The latter idea might be the most practical from the standpoint of putting in an eye mechanism, but my print bed is too small to print the eyebox length as one part, no matter which way it's turned, so I think it'd make the split I have now even worse. I'm sticking with the design above for now.