Photogrammetry, 3D modeling, and design (building a custom case)

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29 Jul 2018, 01:56

I was talking to green-squid about the possibilities of building a keyboard from the guts of an IBM Wheelwriter. It would be ideal if someone had already designed a case that could be 3d printed or cut from layers of acrylic. But alas, it seems no one had done such a(n) (obscure) thing (yet).

My next thought was designing one myself. I have very limited experience doing something similar for a Macintosh Portable keyboard assembly; building a case from layers of acrylic. That took a lot of precise measuring and guesswork on my part.

That got me thinking: I have the Wheelwriter assembly already... can't I just take photos and create a 3D model that would be easier to work with? Which then got me googling for photogrammetry software that might work for this task.

I've been playing around with Agisoft PhotoScan software and it seems pretty powerful. I took a bunch of photos of the keyboard guts and loaded them into the software which processed them and spit out a 3D mesh that (I guess?) can be loaded into some 3D modeling software. I don't need anything photorealistic, just the basic shape and dimensions around which a case could be designed.

I guess I have a couple of questions at this point:
  • Is there any more appropriate software for this task? (preferably something affordable/inexpensive from a hobbyist perspective)
  • Similarly, is there any good 3D modeling software that might be a good fit for designing a keyboard case?
  • What are some tips on manually measuring the keyboard guts then translating those measurements into a design?
  • What are the pros and cons of 3d printing vs building from layers of acrylic?
  • Based on what I'm trying to do, are there any methods I should check out?
BTW: Once I figure out how to share the output of this little PhotoScan experiment I'll upload what it produced for me. It's pretty cool but again, seems more aimed at producing photorealistic 3D models for films/games.

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29 Jul 2018, 04:10

I thought this message was funny


And this question form my girlfriend killed me :lol:
Why does it look like pudding and mold???

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29 Jul 2018, 04:12

Photo scanning is something I have been discussing due to my line of work with my mentor. It's really a good way of capturing shapes of objects but has its limitations to for an example 3D scanning objects. But due to the availability with photo scanning and free software that works for your phone it could be used as an early prototype that you work from.

I'm primarily using Autodesk Maya. It could technically be used for creating and designing keyboard cases but that is not the intended use due to the core principal of the software. I do know that Blender which is free can also be used and can make the appropriate file for 3D printing.

I would concentrate on other CAD programs if your main mission is to design keyboard cases like Fusion 360. Sketchup would also work.

I would revise over your thoughts of stacking layers that could potentially cause more work than to use something like 3D printing or outsourcing CNC operations.

If the purpose is to do a 1:1 scale of the IBM case I would make an exploded view and take measurements and establish as many details as you can. From my experience I would read up on how people go about making replicas. Mainly over at therpf. And using the endless amount of tutorials online on the proper way of utilizing the tool you choose to go with.

If you want to divulge yourself with design in mind I would suggest you to use the many resources online that is free.


01 Aug 2018, 19:14

show some photos so that we can have an idea what the thing looks like.

if you just need some basic shapes and measurements, you are often better off with calipers, rulers and tape measures.

to design a case takes some kind of engineering sense and planning and precision anyway, and studying the existing assembly/mechanism with these tools while also studying its shape with an engineering mindset will help you understand deeper how you should approach the task. e.g. unless you want renderings for aesthetics, you won't need to model individual keys, you can simplify to model the field(s) of keys; you also don't need to model/care for the electronic components on the PCBs, etc. with a few simplifications like that you might find all that you need is on the order of 15-20 basic shapes.

you absolutely should look for a modern 3D CAD software for mechanical engineering/product design, instead of 2D CAD or generic "3D modeling" software. SolidWorks is one popular one, although it is not cheap; you could look for alternatives however, e.g. ... ernatives/ or

do you have a concept of what you are trying to build and what its features should be? think about that first and come up with a list, while also studying your preexisting assembly, and you'll be surprised how much that will help.

also, cardboard, X-Acto knife and cellotape are your friends.

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03 Aug 2018, 19:36

Thanks for the info guys.

Here is the result of my experiments with photogrammetry

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12 Aug 2018, 16:38

If this is going to be a one-and-done then don't tie yourself into that layout unless you can't imagine a better layout. Replacing the membrane with custom capacitive PCB is cheap relative to the cost of a custom case.

My first custom case was done with layered acrylic sheets and cost about $50. I discovered that my design was off by just one mm, so another $50 later i had a new acrylic case. I was happy with the fit and shape, but decided the mechanical properties of acrylic were less than ideal, so i am now spending about $300 getting it CNC machined from aluminum. Cost comes down as the quantity increases.

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