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3D printing....do we not have hands any more ??
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raygreenwood
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PostPosted: Tue Sep 21, 2021 10:06 am    Post subject: Re: 3D printing....do we not have hands any more ?? Reply with quote

Ian wrote:
Here's a radio bezel for padded dash Type 1 I designed and printed in Hatchbox PLA. I use FreeCAD and Cura.

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Check out Fosscad on Reddit if you get bored.



Nice!

PLA = Polylactone plastic? correct?

Not ideal for an application in open air that sees some heat and sun...but nice job...and if it craps out over time....just whip out another one!

The issue with PLA...is that it technically was designed wit ha range of biodegradability. In absolutely "pure" water....it does not degrade. But in dirty water with oxygen..... moisture, mineral salts and bio-activity....meaning people touching it with our filthy skin Laughing ....along with heat and UV.....it can start to break down very fast when it gets to a certain point.

It will look a bit like corrosion. The plastic starts getting chalky and crumbly. In damp environments this is mostly from a specific form of protozoa that can be common. This was also a common problem back in the the 50's through 80's with molded nylon 6 components in suspension components.

Once items like ball joints and tie rod ends got small leaks in their boots....small amounts of dirty street water get in. Protozoa grow and EAT the nylon and turn it into crusty much. I have some photos of this in my centerlink rebuild thread in the 411/412 forum. Ray
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theastronaut
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PostPosted: Tue Sep 21, 2021 12:27 pm    Post subject: Re: 3D printing....do we not have hands any more ?? Reply with quote

I can see both sides of it. I see people making ridiculously simple pieces that would've been easier to make with 'traditional" methods/materials and the part would've turned out more durable as well. Although many of the people making said part don't have the tools or skills for that, but they can model and print a part. I saw a post about 3D printed shift linkage bushings in a FB group and the guy was sad that they didn't hold up more than a week. New oem bushings for that car are $3 a pair. Laughing

I think the most ridiculous use of 3D printing I've seen is a guy in the 'DIY Miata" facebook group that is printing and assembling a ton of small sections to build a hard top mold because hard top prices have skyrocketed. The amount of print time was crazy, plus he has to assemble all of the sections accurately, hope the print was dimensionally accurate, then smooth the surface to make a usable mold out of it, then do all of the fiberglass work, then bodywork/paint, then figure out weatherstripping and latches and glass and mounting it, and... Rolling Eyes

I have a friend who developed an intake manifold to adapt Yamaha RX1 carbs to a Mazda B3 engine. He printed a test manifold, made a few revisions, then printed patterns to cast them from aluminum. He sent me the patterns to smooth up and paint since the surface finish was pretty rough as-printed. Once I got them the pieces were warped so I had to heat and reshape them so the flanges were flat and the runner halves were aligned. With a non-warped print I can see the advantage of 3D printing for developing and manufacturing patterns for something obscure and complex like an intake manifold, but the simple "trinket" parts so many people are making still makes me scratch my head.

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raygreenwood
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PostPosted: Tue Sep 21, 2021 7:08 pm    Post subject: Re: 3D printing....do we not have hands any more ?? Reply with quote

theastronaut wrote:
I can see both sides of it. I see people making ridiculously simple pieces that would've been easier to make with 'traditional" methods/materials and the part would've turned out more durable as well. Although many of the people making said part don't have the tools or skills for that, but they can model and print a part. I saw a post about 3D printed shift linkage bushings in a FB group and the guy was sad that they didn't hold up more than a week. New oem bushings for that car are $3 a pair. Laughing

I think the most ridiculous use of 3D printing I've seen is a guy in the 'DIY Miata" facebook group that is printing and assembling a ton of small sections to build a hard top mold because hard top prices have skyrocketed. The amount of print time was crazy, plus he has to assemble all of the sections accurately, hope the print was dimensionally accurate, then smooth the surface to make a usable mold out of it, then do all of the fiberglass work, then bodywork/paint, then figure out weatherstripping and latches and glass and mounting it, and... Rolling Eyes

I have a friend who developed an intake manifold to adapt Yamaha RX1 carbs to a Mazda B3 engine. He printed a test manifold, made a few revisions, then printed patterns to cast them from aluminum. He sent me the patterns to smooth up and paint since the surface finish was pretty rough as-printed. Once I got them the pieces were warped so I had to heat and reshape them so the flanges were flat and the runner halves were aligned. With a non-warped print I can see the advantage of 3D printing for developing and manufacturing patterns for something obscure and complex like an intake manifold, but the simple "trinket" parts so many people are making still makes me scratch my head.



the problems you quote....warping...cracking....and others...crazing, spalling and weak tensile/impact strength....are a big part of what I was getting at.

Mostly incorrect material selection combined partly with incorrect processing.

To be fair, some of this IS within control of those 3D printing...but some...up until recently has not been.

1. New people...and DIY'ers....who buy either "affordable" and even sometimes expensive 3D printers...and whether they have engineering/design knowledge or not and whether they are good at CAD or not...have up until recently been limited greatly by lack of knowledge of plastics and processing for specific plastics.

This is partly because it was not so readily available (unless you knew what to look for). And too many people ....and I see this in these forums quite a bit.....think plastic is plastic. I see too many people look at a part being made and think that if its not metal...its weak. They have no idea that there are plastics that will resist galling, corrosion and deformation that many metals cannot.

Its NOT just all about tensile strength or compressive load or impact strength...depending on the part in question.

Getting to the point....a lot of what until recently has been limiting people...besides knowledge of plastics.....is the range of AVAILABILITY of filament types that they could easily use in their home or even light industrial 3D printers. And....what readily available filaments there have been....if they are of engineering quality....were EXPENSIVE.

And they should be expensive. Thats another myth that plastic is cheap. High end materials like alloyed nylons with heat capability, PEEK, poly amide-imide and others.....are expensive in any form.

So up until recently....partly because they did not know any better and partly because they could not get anything else.....you see people using what's common...what's cheap......basic nylons, basic polypropylenes, basic polyethylene's and polylactones.

Unless you choose the RIGHT nylon.....it can suck for what you use it for. The moisture absorption of nylon 6 (even though it melts the best).....has been known to suck for about 45 years for critical components. Use nylon 6.6 or nylon 11 or nylon 12 or even blends.

There are numerous grades of polypropylene and polyesthylene as well. You need to use what the use conditions of the part requires.

2. The processing knowledge....and choosing equipment based on what you are doing. Having a heated base board to work on its critical. Having the ability to pre-bake layers to de-stress or post bake whole parts to "anneal" is REQUIRED......even in normal plastics work not using 3D technology.

Knowing how to design and program your machine to deposit layers at specific bias to each other ....to PREVENT warpage....and to increase strength....is required and only gained by experience.

Lots of tutorials and libraries of knowledge are appearing by machine and material manufacturers now.

3D is coming of age. Ray
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Ian
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PostPosted: Wed Sep 22, 2021 7:15 am    Post subject: Re: 3D printing....do we not have hands any more ?? Reply with quote

Check out Hoffman Tactical on Youtube. Tim has put together some great videos testing various filaments.
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Ian
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PostPosted: Sat Sep 25, 2021 7:16 pm    Post subject: Re: 3D printing....do we not have hands any more ?? Reply with quote

Here is my final version of the stereo kit for padded dash bug. In some of the pics it looks bowed but it's not, it's actually the dash pad that has a slight bow.

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Without trim insert:

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With trim insert:

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