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If there's one thing I have learnt over the years, it is that if you
want to tell people that doing a certain thing is not necessary, and you
do not say this in exactly the perfect wording, then this imperfect text
will actually incite more people to do the unnecessary thing.
In this case, people keep asking me for explicit permission to sell this
model. You DO NOT need explicit permission, it's the whole point of the
CC-BY-SA license. I hope the new formulation makes this truly obvious.
8f112c3

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Flexi Rex with stronger links

3D printable print-in-place flexible T-rex, with strong links to be more kid-proof (formerly thing:2738211)

License

Creative Commons - Attribution - Share Alike

Attribution

This is another remix of Kirbs' Flexi Rex (Thingiverse thing:1759297), based on airfish's remix (Thingiverse thing:2189652). That model in turn was most likely inspired by the ‘Flexy Rex’ by zheng3 (Thingiverse thing:929413).

Gallery

Photo 1🔎 Comparison🔎 Photo 2🔎 Photo 3🔎

Description and Instructions

This is the Flexi Rex, which now seems to have joined the club of things anyone having bought a 3D printer ought to print at least once. This is not the first version of this dinosaur. All credit for the original design and appearance goes to Kirbs. My print of Kirbs' model was not very kid-proof however: one of the links broke after some rough handling. Hence in this updated version I made all links more robust. This means this model can probably be printed even smaller than the original ones before the links become too weak. Of course you can also scale it up at will.

‘Dual’ files are also available if you have a multi-material printer and want to do a dual material print with alternating colors.

If you want to make a really huge print, there is an alternative version where you can print each segment separately and then assemble it. This also allows to print the model in multiple colors on single-material printers, but you do lose the magic of a fully assembled model coming straight out of the printer.

If you want to create your own flexible model, make sure to check the Hinge Design section below.

License clarification: read this before contacting me

Read this, and you'll see that you probably have no need to contact me at all.

  • Q: “I want to sell prints of this model, do I need your explicit permission?”
    A: No, but you must provide attribution, which means put a clearly visible link to this GitHub page on both your web store page and on a piece of paper included with printed objects. See below for instructions.

  • Q: “Do I need to share profits if I sell this?”
    A: No. All you need to do is provide the attribution as explained below. You're free to donate to show gratitude, but it is not required.

  • Q: “I want to sell this but I don't want to do the attribution thing, can I bypass it by offering to share profits after all?”
    A: No. Just provide the attribution, there is nothing difficult about it.

  • Q: “Can I give away prints of this model?”
    A: Yes, but you also need to provide attribution on a piece of paper included with each printed object.

  • Q: “Can I use this model in a video or photo on a website for demonstration purposes?”
    A: Yes, if you provide attribution, by linking to this GitHub page on the webpage where the video or photo is hosted.

  • Q: “Can I modify this model and sell the modified model or prints of it?”
    A: Yes, but you must provide (guess what) attribution, and also make your modified model available under the same Creative Commons license, or a stricter license.

  • Q: “So, I can start selling prints of this model without even having to spend time on figuring out how to contact the author?”
    A: Yes indeed, thanks to the CC-BY-SA license under which it is released, at the condition that you comply with the conditions explained below.

What does “attribution” mean?

This model is released under a Creative Commons - Attribution - Share Alike license. The details can be found on the CC website but in a nutshell, my interpretation of this license is that you are pretty much free to do anything with this model including selling prints if you comply with the following conditions:

  • ‘Attribution’ means you must always provide a clearly visible reference to the source of the model, both on the webpage where you sell or display the model, and inside the packaging of the actual physical product. This is a very easy requirement that does not incur any extra cost except a few minutes of your time.
    In the most minimal form, it suffices to make a hyperlink “print3D-FlexiRex by DrLex0 on GitHub” that leads to this GitHub repository. You should also, and perhaps in the first place, refer to the original model from Kirbs (thing:1759297).
    The attribution message must not be hidden by silly tricks such as an unreadable font or putting a lot of whitespace before it.
    As for paper print-outs, simplest is to use the ready-to-print attribution cards in PDF format that can be found in this repository.
  • ‘Share Alike’ means that if you make modifications to the 3D model and sell or give away prints based on that modified model, you must publish this modified 3D model and it must be licensed under either the same CC BY-SA license, or a more restrictive license. Of course wherever you publish your modified model, the webpage must also link back to the origin (i.e., this page). Again, this costs you nothing except a few minutes of your time.

As you can see:

  1. There is no requirement to ask and obtain my explicit approval if you simply follow the conditions of the license. Feel free to drop me a message to notify me that you'll be selling or displaying this model somewhere, but it is not required.
  2. There is no need to share profits. Of course you can always tip me if you insist on sharing some profits or just want to show some appreciation.

Notice to anyone buying prints of this model: it contains about 70 cents worth of material when printed in a premium filament. Add to this the costs of electricity and perhaps depreciation of printing infrastructure, and a bit of profit margin, and you might end up with about $2. Anyone who pays much more than that for a print is being ripped off.

I found someone violating the license, now what?

If you see this model or prints of it being sold somewhere without the required attribution, don't try to contact me right away. I do not have the time or means to hunt down all the unscrupulous people who want to make it seem as if they created this model and sell it at an exaggerated price. Also don't try to report it as a copyright violation yourself, this usually has to be done by the author of the work themself. It would be most helpful if you would first notify the author of the sales page and point them to this GitHub page. Ask them to add the required attribution. If they do not seem to care, you can go a step further and tell them you will contact the author. If that still doesn't help, then you may actually start contacting me (create an issue on GitHub, or use the contact page on my site).

Also note that selling the STL file for money is perfectly legal. It would be kind of dumb, but is allowed if proper attribution is provided on the page where the model is sold. The attribution would of course require to provide a clearly visible link to this page which provides the same download for free, and makes it obvious that the seller is a prick, but being a prick is not prohibited by the license.

Print Settings I've used

0.2 mm layers, 15% infill, no supports and no raft, rigid.ink silver ABS

Pretty much any material should work. You could print it in a flexible filament to make it even more flexible and pretty much impossible to destroy, but plain PLA is probably easiest.

No supports needed. I used 3 perimeters to ensure the hinges are strong, this is much preferred over trying to obtain strength through infill. If you use too high infill, the model may become poorly balanced due to the head being too heavy. If you want to improve stability, use a higher infill for the piece with the legs if you can.

If you have problems with parts curling up and the print head knocking them over, try to apply more cooling (but don't exaggerate, because too much cooling will result in a weaker print).

This should move freely right after you take it off the build plate. If you print ABS with hairspray on a glass bed, the Rex will likely spontaneously jump into a random pose all by itself when it pops off the plate after cooling down. If you need to use force to free the hinges, you still have some optimization work to do on your printing technique.

This is not a demanding print. If this is one of the first things you're printing and it fails, expect other things to fail as well.

Remarks

  • This model was designed using Blender, which is a mesh-based program. Mesh-based models cannot be generally converted into a volume-based representation as used by technical CAD programs, so please don't ask me for a STEP file or whatever other CAD format of this model, because there is none. If you want to modify the model, the most sensible approach is to use a mesh-based editor.
  • The Blender source file is available (requires 2.92 or newer). The model is constructed using Boolean operators and will not be entirely clean when merely applying the operations. (This is because some of the surfaces in union operations are coplanar, which is generally a bad idea but difficult to avoid in this case.) Especially if you plan to further edit the mesh after applying the Booleans, I recommend to clean it up first.

History

This is what I could find by tracing back remix sources and searching models on Thingiverse. There might be older history, or things that I missed. (I will not list the countless further remixes that have been made from the model that is hosted in this repository.)

  1. On January 06, 2015, zheng3 published the Robber Rex, intended as a replacement for the ‘robber’ player piece in the Settlers of Catan game. Although it was a single solid piece and much wider than the Flexi Rex, it already had the general shape.
  2. On July 17, 2015, zheng3 published the Flexy Rex, a remix of his Robber Rex made flexible by means of a thin spine connecting the model sliced into thin plates.
  3. On September 08, 2016, Kirbs published the original Flexi Rex, because zheng3's Flexy Rex proved too fragile for being handled by kids. It was redesigned from scratch albeit still with the same overall looks, but narrower and with a shackle construction instead of the flexible spine.
  4. On March 20, 2017, airfish published a remix of Kirbs' Flexi Rex, replacing the inset eyes with a through hole.
  5. On December 30, 2017, DrLex published the Flexi Rex with stronger links based on airfish's remix, with improved shackles (and a minor tweak to the spines on the back), because his print of the Flexi Rex still broke too easily when handled by kids. This version of the model became hugely popular, maybe thanks to its increased robustness.
    On March 21, 2020, this model was migrated to GitHub because Thingiverse has become too much of a pain to work with. The Thingiverse page still exists but will not be updated anymore.

Hinge Design

If you want to create your own flexible model, by all means copy the hinge design from this one, or at least use the hinge dimensions image as a guideline. I see way too many ‘flexi’ models that still use the weak hinge design from the original model, or other shapes that have way too little material in the most crucial locations, often the end of the shackle or ‘ring’ is too thin. Make sure to provide as much material around the axle hole as possible, instead of cutting away as much as possible as some designers tend to do. You won't gain any flexibility by providing more clearance than needed, the model will only become weaker.

Hinge dimensions
Hinge dimensions (🔎 view larger image)

TAGS

dinosaur, flexible, print_in_place, t-rex, toy, Tyrannosaurus_Rex

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