1 Topic by sayluv

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Topic: Need help finding appropriate plastic

Hi.

I make artificial limbs and braces for pets. I have started experimenting with 3D printing to make prosthetic feet for small animals. My first stab at it went fairly well, however, I am not sure about the long term durability of the foot I created and wanted some feedback on what people think would be the best plastic to use.

Ideally the plastic is resistant to cold, cracking, and can flex over and over without reducing the rigidity.

Attached is a picture of a 3D printed foot I made for the hind leg of a 45 lb dog. It flexes/compresses about .5" vertically when loaded with weight and returns nicely. I control the amount of flexion by changing the thickness of the foot and/or by adding some struts.

I am currently using Shapeways to print my feet so I am limited to what they have, but I am open to changing providers if there is a better one out there. The plastic in the photo is there Strong & Flexible. They also have an HP plastic which is twice the price but I wasn't able to find any info on why it would be better. I think the tensile strength is about the same but I am not sure what other characteristics I should be looking at.


Thanks, jeremy

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2 Reply by Tin Falcon

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Re: Need help finding appropriate plastic

Research Ninja flex products also TPE and TPU

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3 Reply by sayluv (edited by sayluv 2018-02-13 16:51:15)

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Re: Need help finding appropriate plastic

ty, cheetah stuff looks great.

4 Reply by AZERATE

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Re: Need help finding appropriate plastic

For what you are trying to achieve, I don't think one singular material is the answer.
There is a massive difference for manufacturing style. As an example, a PETG water bottle is fairly flexible but does't break (typically) even in thin designs. A printed PETG bottle, though strong, is too rigid and therefore breaks at the layer lines. If you go to a MakerFaire and talk to people who compare molded vs printed with different resins, they will tell you the same thing.

I would say a E3D Chimera (two in/one out hotend) to customize your ratio of rigid and semi flex materials to simulate a molded design. That is, if you plan for production and quality. And Like Tin said, and as I've tested, TPU would be the best option for a flexible liner.

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5 Reply by carl_m1968

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Re: Need help finding appropriate plastic

You might find printing to be viable as simply a mold for a design that uses a liquid polymer of some kind that is cured by UV or heat. You might not find a material suitable to print a finished product.

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6 Reply by yizhou.he (edited by yizhou.he 2018-02-13 19:50:43)

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Re: Need help finding appropriate plastic

AZERATE wrote:

For what you are trying to achieve, I don't think one singular material is the answer.
There is a massive difference for manufacturing style. As an example, a PETG water bottle is fairly flexible but does't break (typically) even in thin designs. A printed PETG bottle, though strong, is too rigid and therefore breaks at the layer lines. If you go to a MakerFaire and talk to people who compare molded vs printed with different resins, they will tell you the same thing.

I would say a E3D Chimera (two in/one out hotend) to customize your ratio of rigid and semi flex materials to simulate a molded design. That is, if you plan for production and quality. And Like Tin said, and as I've tested, TPU would be the best option for a flexible liner.

I have no experience working with PETG, but I observe similar thing with PLA and ABS easy to break at the layer lines. This can be overcome by increase printing temperature at cost of slightly lowered overall print quality and often require fine tune the balance of nozzle temperature and layer cooling fan (in the case of PLA). Also where the layer cooling fan blow at also make huge difference.

Another tools I use to enhance the strength of my print is draw lines across layer line with 3D printing pen with exact same filament I used to print the part. I then smooth the patched area with sanding in area where strength is more important than details. You can even rescue parts that already broken and achieve better strength after patched with 3D printing pen.

I have not test this method with PETG or TPU. I'm not sure if it also work for PETG and TPU but it worth a try. 3D printing pen that can achieve PETG temperature will be needed.

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7 Reply by AZERATE

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Re: Need help finding appropriate plastic

yizhou.he wrote:

I have no experience working with PETG, but I observe similar thing with PLA and ABS easy to break at the layer lines. This can be overcome by increase printing temperature at cost of slightly lowered overall print quality and often require fine tune the balance of nozzle temperature and layer cooling fan (in the case of PLA). Also where the layer cooling fan blow at also make huge difference.

Another tools I use to enhance the strength of my print is draw lines across layer line with 3D printing pen with exact same filament I used to print the part. I then smooth the patched area with sanding in area where strength is more important than details. You can even rescue parts that already broken and achieve better strength after patched with 3D printing pen.

I have not test this method with PETG or TPU. I'm not sure if it also work for PETG and TPU but it worth a try. 3D printing pen that can achieve PETG temperature will be needed.

I was mainly pointing out the differences in rigidity and flex between 3D printing and molded parts. The Chimera would be the best for this 3DP option as I explained above; as it is the only way to achieve flexibility AND rigidity. If the OP were to pull the trigger on this route, multiple materials become an option and not just one so long as the is a TPU/TPV/TPE blend in the part along with a durable material like ABS/PETG/CF/Nylon.

One thing to consider here, however, is that a Chimera only has one thermistor. So for best results, one would need to use materials that share a similar melting point.
e.g. Nylon Bridge + ABS
       TPU + PLA

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8 Reply by Kronikabuse

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Re: Need help finding appropriate plastic

AZERATE wrote:
yizhou.he wrote:

I have no experience working with PETG, but I observe similar thing with PLA and ABS easy to break at the layer lines. This can be overcome by increase printing temperature at cost of slightly lowered overall print quality and often require fine tune the balance of nozzle temperature and layer cooling fan (in the case of PLA). Also where the layer cooling fan blow at also make huge difference.

Another tools I use to enhance the strength of my print is draw lines across layer line with 3D printing pen with exact same filament I used to print the part. I then smooth the patched area with sanding in area where strength is more important than details. You can even rescue parts that already broken and achieve better strength after patched with 3D printing pen.

I have not test this method with PETG or TPU. I'm not sure if it also work for PETG and TPU but it worth a try. 3D printing pen that can achieve PETG temperature will be needed.

I was mainly pointing out the differences in rigidity and flex between 3D printing and molded parts. The Chimera would be the best for this 3DP option as I explained above; as it is the only way to achieve flexibility AND rigidity. If the OP were to pull the trigger on this route, multiple materials become an option and not just one so long as the is a TPU/TPV/TPE blend in the part along with a durable material like ABS/PETG/CF/Nylon.

One thing to consider here, however, is that a Chimera only has one thermistor. So for best results, one would need to use materials that share a similar melting point.
e.g. Nylon Bridge + ABS
       TPU + PLA

Edit: The chimera has 2 thermisistors. one for each hot end. Azerate is thinking of the cyclops which only has one therisistor.

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9 Reply by AZERATE

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Re: Need help finding appropriate plastic

D-oh!
Yes I meant the Cyclops. My daughter turned 5 yesterday so my mind was elsewhere

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10 Reply by Barret Zhang (edited by Barret Zhang 2018-05-15 02:04:36)

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Re: Need help finding appropriate plastic

We suggest you could have a trial with tpu material or tpe Plus material. Both are flexible material. tpe plus is tpee, has good flexible and strength. This main used in earphone wire and there are many type hardness for option

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