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Thread: How to shop for a 3-D printer

  1. #1
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    How to shop for a 3-D printer

    How many different basic types of 3-D printers are out there now, and where do you find them to compare & decide which to buy?

    What materials can you print with them, and what are the physical characteristics of the resulting objects?

    Do some manufacturers have better options than others for designing the shapes to print?

    Do they come in different resolutions so some would make rough surfaces and some would make smooth surfaces?

  2. #2
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    Hello Delvo,

    You could inform yourself at Reprap.org.

    You can build your own with much their help. They also have user forums discussing most of the commercial machines.

    Cheers,

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    Going to assume you are talking about a home printer on a budget of order hundreds rather than thousands of dollars. Because there are more options once you get to a budget of tens of thousands!

    Basically the home market is dominated by two technologies at the moment. FDM, which is the classic moving print head laying down molten plastic, and SLA which is UV cured resin. I've run both for a few years and there are pros and cons for each. It's very much about level of effort and your goal.

    FDM printers are much easier to use and can print a range of materials. PLA is the workhorse which makes reasonably tough plastic objects cheaply. There are loads of alternatives if you need certain properties though. All of them, however, are thermoplastics so don't have good heat resistance. The new printers are pretty good but all FDM outputs I've seen do have a slightly rough, layered look to them. A bit of post processing (sandpaper and paint, basically) can reduce that, though. When picking one do look at the advertised resolution. It varies a lot on these. There are lots of 3D print sites out there that offer reviews too. Strongly advise browsing them, I found them really useful (especially all3dp which has regular wrap ups of the current best printers for different budgets).

    SLA is a different beast. These are temperamental, use some smelly and irritant chemicals - generally much harder to use. And I love them. Mainly because they make incredible, high resolution outputs that are smooth and tough (although they get brittle with exposure to the sun for too long, paint is your friend). Getting them to work reliably is an art form. Can't stress that enough. With these things I've found it's a rollercoaster of amazing results followed by disappointment. The material is a resin, there isn't much choice about it's properties. Again, review sites are your friend.

    Slicing software does vary by manufacturer but most people I know use a third party app anyway so I wouldn't worry too much about that. Ultimate Cura (FDM) and Chitubox (SLA) are common tools, if your printer is supported by them then you don't have to worry about the default software.

    I've not made much practical with the printers but in general I've found FDM rules for larger objects (>10cm) and bulky things. Because it is cheap and tough I've used it for things like boxes, war game terrain, replacement bits for plastic things I broke. SLA rules for small, detailed things. I've made board game pieces, war game miniatures and stuff like that with it. A word on models. It's not hard to make your own, but quite time consuming. But there are loads online you can get free or buy. Modifying them is often much faster.

    Happy to discuss any specific uses you are thinking about. I'm no expert though, just an enthusiastic amateur. Which probably comes across in this wall of text...

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    Quote Originally Posted by Shaula View Post
    ...war game terrain...
    War game terrain? Why didn't I know about you doing this? Do you have website or images? Please?
    Solfe

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    Quote Originally Posted by Solfe View Post
    War game terrain? Why didn't I know about you doing this? Do you have website or images? Please?
    This is going to sound like a terrible series of excuses but I just checked my phone and I don't have any pictures to hand. And I'm moving, so all my stuff has just been sent to storage! If this had come up a month ago I'd have been able to post something. Sorry about that... I'll try to remember this when I get myself set back up but it might be a few months now.

    And to temper expectations all I've done is a few buildings (adobe village style and corrugated iron sheds) plus some scatter terrain (crates, storage units). I had grand plans for some gothic sci fi stuff I bought on Kickstarter but ran out of time. My biggest problem is I'm stuck on what game system I want to make it for. My favourites are currently a 28mm and a 6mm scale and I've not had time to support both. Which has meant I've not really done either!

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    Quote Originally Posted by Delvo View Post
    How many different basic types of 3-D printers are out there now, and where do you find them to compare & decide which to buy?
    As Shaula said, there's basically filament deposition printers that lay down layer after layer of molten plastic, with several different mechanisms for moving the print head, delivering plastic, etc, and a few different variations of printers that selectively cure UV-sensitive resin.


    Quote Originally Posted by Delvo View Post
    What materials can you print with them, and what are the physical characteristics of the resulting objects?
    The FDM machines take spools of plastic filament as an input material. There's some gotchas, like problems that can arise if the filament absorbs moisture (which can be remedied by baking the moisture out, preferably in something like a food dehydrator that isn't used for food). Some materials take particular care to get to adhere to the bed, or require a heated enclosure to print well. If a print fails you can end up with a pile of spaghetti, or a blob of death encasing your hot end. If it goes well, depending on the material you can pop a usable print off the bed.

    The SLA machines take some expensive and noxious resins, and more solvents for cleaning the prints afterward. You may also need to expose them to more UV in a postprocessing step to fully harden them. The resin obviously can't be UV-stable, so it'll degrade if not protected. Material selection is limited by the fact that it has to start out liquid and harden when exposed to moderate levels of UV.

    Some FDM machines can use multiple materials, for example using soluble support material, or mixing colors. SLA machines are pretty much limited to a single material at a time, at most you might change the resin mid-print.

    FDM materials include PLA (a biodegradable, temperature-sensitive plastic that's somewhat brittle but rigid and cheap), PETG (tough but a bit less rigid), nylon (tough and self lubricating), polycarbonate (very strong and temperature resistant, but hard to work with and requires high printing temperatures), PEEK (an aerospace engineering plastic that is very strong, tough, and stable, but requires even higher printing temperatures and is very expensive), flexible thermoplastic polyurethane, PVA (water soluble, a removable support material), and many others. There's also versions of the above that are strengthened with glass or carbon fiber, versions that are somewhat electrically conductive for ESD suppression, etc. Some incorporate wood fibers or metal powders.

    FDM prints generally have an interior fill pattern that is mostly empty space. Physically, they're a bit like a hard shell around a regular geometric foam. The layered structure shows in the surface finish, but can be smoothed out by sanding, tumbling with abrasives, applying coatings, and with some materials by using solvents.


    Quote Originally Posted by Delvo View Post
    Do some manufacturers have better options than others for designing the shapes to print?
    Technically, but I wouldn't use any manufacturer-provided software for designing shapes, there's going to be better-developed alternatives like Blender, FreeCAD, OpenSCAD, etc. Prusa maintains their own fork of the slicer software for generating the actual control files for the printer, but you could use something else (or use theirs with a different printer, or modify their version and build your own).


    Quote Originally Posted by Delvo View Post
    Do they come in different resolutions so some would make rough surfaces and some would make smooth surfaces?
    Different printers will achieve different resolutions. SLA printers are better at fine details. FDM printers can use nozzles of different sizes, so you can use a small nozzle for extra detail or a large one for extra print speed (or for printing some materials that don't work well with small nozzles, like the wood-filled filaments). I upgraded mine to a Mosquito hot end largely to make nozzle swapping easier. (...and have not changed the nozzle since.)

    Some example FDM prints:
    Gale Crater in PLA (Martian cacti sprouted all over it for some reason, need to tune some print settings):
    https://i.imgur.com/LT6haWq.jpg
    https://i.imgur.com/VGBrxlr.jpg

    A treefrog (a standard benchmark model) in black and marble PETG:
    https://i.imgur.com/fNHQBdL.jpg
    https://i.imgur.com/JEN8ctV.jpg

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    Quote Originally Posted by Shaula View Post
    This is going to sound like a terrible series of excuses but I just checked my phone and I don't have any pictures to hand. And I'm moving, so all my stuff has just been sent to storage! If this had come up a month ago I'd have been able to post something. Sorry about that... I'll try to remember this when I get myself set back up but it might be a few months now.

    And to temper expectations all I've done is a few buildings (adobe village style and corrugated iron sheds) plus some scatter terrain (crates, storage units). I had grand plans for some gothic sci fi stuff I bought on Kickstarter but ran out of time. My biggest problem is I'm stuck on what game system I want to make it for. My favourites are currently a 28mm and a 6mm scale and I've not had time to support both. Which has meant I've not really done either!
    Aw!

    But I have a question about this. A few years back, I set up a couple of 3D printers (Cubify machines, they wanted several of them and that's what the budget said) for the local science museum. In doing a couple of test prints, I noticed that a model tended to "drift" in scale. I printed a 500mm tall pawn on three identical printers using PLA and they all came out 3 differents sizes. It was odd, because when we did it again, the same thing happened but the differences didn't correspond to specific machines. One day, we'd get a 499mm print and on the next day the same product was 502mm. I was a volunteer so I didn't stick around to troubleshoot such a small variance but I still wonder about it.

    More recently, I ordered some 25mm printed figures and they seemed to be about 35mm. Is 25 or 28 mm too small for most machines?
    Solfe

  8. #8
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    Quote Originally Posted by Solfe View Post
    Aw!

    But I have a question about this. A few years back, I set up a couple of 3D printers (Cubify machines, they wanted several of them and that's what the budget said) for the local science museum. In doing a couple of test prints, I noticed that a model tended to "drift" in scale. I printed a 500mm tall pawn on three identical printers using PLA and they all came out 3 differents sizes. It was odd, because when we did it again, the same thing happened but the differences didn't correspond to specific machines. One day, we'd get a 499mm print and on the next day the same product was 502mm. I was a volunteer so I didn't stick around to troubleshoot such a small variance but I still wonder about it.

    More recently, I ordered some 25mm printed figures and they seemed to be about 35mm. Is 25 or 28 mm too small for most machines?
    For the pawn, the "bead" of plastic gets squashed flat as it is deposited, and there's residual stresses after it solidifies. There might have been some rebound afterward as the plastic relaxed into a final shape. It could possibly depend on bed heating, fan cooling, drafts, etc.

    A 25 mm part coming out 35 mm is something else entirely though. That's not warping plastic, and if the machine was that far off dimensionally, it wouldn't be laying down enough plastic to successfully print. It sounds like it was scaled up at some point in the printing process. And no, 25 mm is not too small.

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    Quote Originally Posted by Shaula View Post
    FDM printers are much easier to use and can print a range of materials. PLA is the workhorse which makes reasonably tough plastic objects cheaply. There are loads of alternatives if you need certain properties though. All of them, however, are thermoplastics so don't have good heat resistance. The new printers are pretty good but all FDM outputs I've seen do have a slightly rough, layered look to them. A bit of post processing (sandpaper and paint, basically) can reduce that, though. When picking one do look at the advertised resolution. It varies a lot on these.
    How much heat is a problem for them? One of the projects I've imagined making would be the things that go around the light bulb in a small light fixture like a wall sconce or pendant light or some kinds of vanity lights, about 15cm wide and usually 12-20cm tall, usually made of glass. The bulbs are LED, not incandescent, so they're safe to touch even after being on for a while, but they do still feel warm.

    I've seen pictures of things being printed in various colors of plastic, but it always looks like it's one color per project. So you can't print something with different parts already in different colors? And what form is the stock material in before you use it? A big solid block? Beads? Liquid? And how tough is "tough"?

    Quote Originally Posted by Shaula View Post
    There are lots of 3D print sites out there that offer reviews too... Again, review sites are your friend.
    Where?

    Quote Originally Posted by Shaula View Post
    SLA... I love them. Mainly because they make incredible, high resolution outputs that are smooth and tough (although they get brittle with exposure to the sun for too long, paint is your friend).
    If sunlight is bad for the products, doesn't that mean they'll suffer anywhere that isn't completely windowless, just over different lengths of time? (For example, some rooms in my home have shades/blinds on the windows so nothing is ever directly sunlit in there, but enough light does come through the shades/blinds to light up everything in the room just as much as artificial lights would at night. And that would presumably still include UV coming through the shades/blinds along with the visible.)

    Also, although this might not matter if the plan is always to paint the anyway: does this stuff come in different colors? Do people who use this kind just not care what color it is because they'll paint it anyway? Can it be transparent/translucent? (Aside from the light fixture things, another thing I've imagined printing is transparent or translucent items of various shapes to be lit up with LEDs. The need for transparency/translucency alone could force me into one printer type if the other can't do that.)

    Quote Originally Posted by Shaula View Post
    SLA is a different beast. These are temperamental, use some smelly and irritant chemicals - generally much harder to use... Getting them to work reliably is an art form. Can't stress that enough. With these things I've found it's a rollercoaster of amazing results followed by disappointment.
    What kinds of things go wrong with them when you try? I'm interested mainly in the results I can get, not starting a new hobby of lots of work just for the sake of working on it, but the smoother surfaces (and maybe greater toughness, until the UV gets to them?) might compel me to go this route anyway if the struggle isn't too horrible.

    Quote Originally Posted by Shaula View Post
    I've not made much practical with the printers but in general I've found FDM rules for larger objects (>10cm) and bulky things... SLA rules for small, detailed things.
    That reminds me of another problem I'm likely to run into. Another project I've imagined would be a set of skinny pedestal-like tables, about the same height as most other tables & desks but less than 30cm across for the top surface and footprint. From what I've seen in pictures of these things mid-job, there's got to be a maximum height, either because it's the depth of the pool of starting material, or the distance from the bottom of the work area to a working part of the machine above, or because adding more height would mean adding more weight and it can't hold up too much weight while it's still fresh & hot. So would the tables be something I need to just give up on or find a way to separate into smaller pieces to be combined later?

    * * *

    No metal options, apparently

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    Quote Originally Posted by cjameshuff View Post
    For the pawn, the "bead" of plastic gets squashed flat as it is deposited, and there's residual stresses after it solidifies. There might have been some rebound afterward as the plastic relaxed into a final shape. It could possibly depend on bed heating, fan cooling, drafts, etc.
    Indeed - I don't have much to add except that if there is a critical dimension re-orienting the print can help. I've printed boxes with very tight sliding draws without an issue - that can't have had more than a couple of mm tolerance.

    Quote Originally Posted by cjameshuff View Post
    A 25 mm part coming out 35 mm is something else entirely though. That's not warping plastic, and if the machine was that far off dimensionally, it wouldn't be laying down enough plastic to successfully print. It sounds like it was scaled up at some point in the printing process. And no, 25 mm is not too small.
    Agree again - I've printed stuff at much smaller scales than that. SLAs are generally better at the smaller scale stuff, I've printed chess-like game piece sets with 10mm pieces using them. I've also printed bases for 6mm infantry models which fitted them perfectly with an FDM. This is a scaling issue in the print chain, as cjameshuff says.

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    Quote Originally Posted by Delvo View Post
    How much heat is a problem for them? One of the projects I've imagined making would be the things that go around the light bulb in a small light fixture like a wall sconce or pendant light or some kinds of vanity lights, about 15cm wide and usually 12-20cm tall, usually made of glass. The bulbs are LED, not incandescent, so they're safe to touch even after being on for a while, but they do still feel warm.
    Guideline I have seen is >60C and you start to weaken it (PLA has a phase transition around there). I have made lithophanes for use around LEDs and they didn't have issues. Cjameshuff has mentioned some other materials - I don't have experience with them, so I will leave it to them to talk about.

    Quote Originally Posted by Delvo View Post
    I've seen pictures of things being printed in various colors of plastic, but it always looks like it's one color per project. So you can't print something with different parts already in different colors? And what form is the stock material in before you use it? A big solid block? Beads? Liquid? And how tough is "tough"?
    Cjameshuff mentioned that for FDMs the stock is a spool of filament. For SLAs it is a bottle of gloop. You can get dual extruder machines (FDM) that let you print two materials (and hence colours) at once, not sure if there are more than that. SLA it is really one material only. If you need many colours it is easier to print the parts seperately and join them later. Lots of colours is getting into industrial machines which are expensive and I don't have any experience of.

    Quote Originally Posted by Delvo View Post
    Where?
    https://all3dp.com/
    https://reprap.org/wiki/RepRap
    https://www.techradar.com/uk/best/best-3d-printers
    If you search for "best 3d printer 2020" you will find llists

    Quote Originally Posted by Delvo View Post
    If sunlight is bad for the products, doesn't that mean they'll suffer anywhere that isn't completely windowless, just over different lengths of time? (For example, some rooms in my home have shades/blinds on the windows so nothing is ever directly sunlit in there, but enough light does come through the shades/blinds to light up everything in the room just as much as artificial lights would at night. And that would presumably still include UV coming through the shades/blinds along with the visible.)
    Yep, although it is a slow process. And all that happens is that the reson becomes more glass like and less flexible which means that small pieces/details are easier to break off. It takes days in full sun to really see this though (at least at 50N). For your goals I don't think it is an issue. Plus you can use something like polyurethane varish (clear) to help with this problem and protect the piece.

    Quote Originally Posted by Delvo View Post
    Also, although this might not matter if the plan is always to paint the anyway: does this stuff come in different colors? Do people who use this kind just not care what color it is because they'll paint it anyway? Can it be transparent/translucent? (Aside from the light fixture things, another thing I've imagined printing is transparent or translucent items of various shapes to be lit up with LEDs. The need for transparency/translucency alone could force me into one printer type if the other can't do that.)
    The resins and filaments are interoperable so manufacturer doesn't matter and there are a lot to choose from. For example:
    https://www.amazon.co.uk/AmazonBasic...t-1-75mm-Spool - Amazon own brand (I am not recommending this one, by the way, it is just an example) with 20 colours including glowing and translucent.
    https://www.amazon.co.uk/ELEGOO-405n...r-Photopolymer - Elego resins, 18 colours including transparent.
    My experience is that (especially with SLA) anything is translucent if printed thinly enough. FDMs can struggle with that thought (very thin films distort and show up structure). I'd prefer SLA for translucent stuff as it doesn't show the print structure. Look up lithphanes - there is a community out there that does this who can probably get around some of these issues.

    Quote Originally Posted by Delvo View Post
    What kinds of things go wrong with them when you try? I'm interested mainly in the results I can get, not starting a new hobby of lots of work just for the sake of working on it, but the smoother surfaces (and maybe greater toughness, until the UV gets to them?) might compel me to go this route anyway if the struggle isn't too horrible.
    I will caveat this with the fact that I had very little trouble out of the box - my issues came later after the machine got worn. Other people have had more problems.

    Basically it is down to plate adhesion. The way an SLA works is usually a build plate is dipped into a tray of liquid and the UV light is shone upwards. So the object has to stick to the plate really well throughout the process to print properly. The issue is that every time the build plate moves up there is strong suction from the layer sticking to the bottom of the tank. So often you have to tweak the build or alignment to avoid this and have a model that is cleanly built and not warped by this force. I think that it is mostly about experience. That said when my build plate got old I hit a wall and nothing I did worked. I've replaced it and hopefully this will fix it.

    The other issue is (and I'm probably a bit cavalier about this) that the resins are irritants and quite unpleasant. Gloves, ventilation and washing the object are vital. You also have to cure it in the sun for enough but too much time (1-2 hours on a sunny day is fine, its not a precise thing). I didn't find any of this particularly an issue, but compared to the very safe and simple FDM it can put some people off. Oh. And thanks to people stockpiling Isopropanol washing them is more expensive than it should be...

    FDMs are much easier in that they are not fighting gravity and suction. I found them easier to troubleshoot and work out.

    Quote Originally Posted by Delvo View Post
    That reminds me of another problem I'm likely to run into. Another project I've imagined would be a set of skinny pedestal-like tables, about the same height as most other tables & desks but less than 30cm across for the top surface and footprint. From what I've seen in pictures of these things mid-job, there's got to be a maximum height, either because it's the depth of the pool of starting material, or the distance from the bottom of the work area to a working part of the machine above, or because adding more height would mean adding more weight and it can't hold up too much weight while it's still fresh & hot. So would the tables be something I need to just give up on or find a way to separate into smaller pieces to be combined later?
    Max build height for most printers is 20-50cm, so you would have to do them in pieces. It is not hard - Blender or other tools lets you chop stuff up. I will say that larger projects take a long time to print. I would not be shocked if you were looking at 18-24hr per print (and 4-6 prints) for something that big. Home 3D printers are optimised for smaller things. And you would never do this with an SLA. Not only would it be prohibitively expensive but it would take forever. Big projects are FDM all the way. Nice thing with that is that you can get very strong plastic glues that cold weld the pieces together.

    Biggest things I've printed are game box organisers at 40x40x15cm or so and they took an age and had to be done in bits.

    Quote Originally Posted by Delvo View Post
    No metal options, apparently
    I focused on home machines from 100s to 1000s of dollars.
    https://m.all3dp.com/1/3d-metal-3d-p...l-3d-printing/

    If you have $50,000 - $250,000 to spare there are solutions. Most cheap ones are not great resolution and the one cheap option requries you to pay for every piece you make (it is an FDM printer that prints metal rich plastic, they they debind and sinter it for you). You also may need inert gas supplies.

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    Quote Originally Posted by Delvo View Post
    How much heat is a problem for them? One of the projects I've imagined making would be the things that go around the light bulb in a small light fixture like a wall sconce or pendant light or some kinds of vanity lights, about 15cm wide and usually 12-20cm tall, usually made of glass. The bulbs are LED, not incandescent, so they're safe to touch even after being on for a while, but they do still feel warm.
    That would probably be fine. It's more of an issue for things that might get left in the car, for example. I've printed a lid for an electric kettle that softens when it's been heated and has severely warped, but still fits. (Actually, I haven't yet gotten around to modeling the actual lid, this was just run off as a fit check to make sure the dimensions were right...but it works.)


    Quote Originally Posted by Delvo View Post
    I've seen pictures of things being printed in various colors of plastic, but it always looks like it's one color per project. So you can't print something with different parts already in different colors? And what form is the stock material in before you use it? A big solid block? Beads? Liquid? And how tough is "tough"?
    The FDM machines take plastic filament. Some have multiple heads, some can change the filament on the fly to do multiple colors/materials, but multi-material printing is generally more complex and finicky. FDM machines can do translucent parts, but they can't do high optical quality, parts look a bit like they were formed out of ice.

    Toughness depends on material (and even on the particular blend produced by a given manufacturer). PETG can be extremely tough, bending and stretching quite a bit without breaking. Same goes for nylon and various other materials.

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    Quote Originally Posted by cjameshuff View Post
    For the pawn, the "bead" of plastic gets squashed flat as it is deposited, and there's residual stresses after it solidifies. There might have been some rebound afterward as the plastic relaxed into a final shape. It could possibly depend on bed heating, fan cooling, drafts, etc.

    A 25 mm part coming out 35 mm is something else entirely though. That's not warping plastic, and if the machine was that far off dimensionally, it wouldn't be laying down enough plastic to successfully print. It sounds like it was scaled up at some point in the printing process. And no, 25 mm is not too small.
    Ok, that makes perfect sense. I was messing with "leveling the bed" throughout the whole process of printing pieces. I was the only person troubled by this small change.
    Solfe

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    Quote Originally Posted by Delvo View Post
    How much heat is a problem for them?

    If sunlight is bad for the products, doesn't that mean they'll suffer anywhere that isn't completely windowless, just over different lengths of time? (For example, some rooms in my home have shades/blinds on the windows so nothing is ever directly sunlit in there, but enough light does come through the shades/blinds to light up everything in the room just as much as artificial lights would at night. And that would presumably still include UV coming through the shades/blinds along with the visible.

    No metal options, apparently
    I don’t have the wealth of experience of other posters here but a few pointers:
    Normal window glass will shut out the UV so your plastic should be perfectly safe indoors.
    The toughness of those fibre printed models can be greatly increased by using Super glues which wick into the porous nature.
    The metal 3-D printers are in a different price class.
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
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    Quote Originally Posted by profloater View Post
    I don’t have the wealth of experience of other posters here but a few pointers:
    Normal window glass will shut out the UV so your plastic should be perfectly safe indoors.
    The toughness of those fibre printed models can be greatly increased by using Super glues which wick into the porous nature.
    The metal 3-D printers are in a different price class.
    Glass greatly reduces UV, but enough still gets through to fade pigments and dyes and make plastics go brittle. And even if they were total protection, it'd only work if you never opened a window.

    The prints are not particularly porous, they just have rough surfaces. And I think even PLA is less brittle than cyanoacrylate glue.

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    Once you buy your 3-D printer, make a copy of this miniature "Mars rover" which uses robotics to drive over rough terrain.

    https://phys.org/news/2020-12-d-mars-rover-exomy.html
    Do good work. —Virgil Ivan "Gus" Grissom

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    Quote Originally Posted by Roger E. Moore View Post
    Once you buy your 3-D printer, make a copy of this miniature "Mars rover" which uses robotics to drive over rough terrain.

    https://phys.org/news/2020-12-d-mars-rover-exomy.html
    That's over a hundred dollars in servos alone. Why do people keep using expensive servos modified for continuous rotation when cheap gearmotors are widely available? I mean, here's a pack of 6 for $12: https://www.amazon.com/Antrader-Moto...dp/B07DDC3ZBK/

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    Quote Originally Posted by cjameshuff View Post
    Glass greatly reduces UV, but enough still gets through to fade pigments and dyes and make plastics go brittle. And even if they were total protection, it'd only work if you never opened a window.

    The prints are not particularly porous, they just have rough surfaces. And I think even PLA is less brittle than cyanoacrylate glue.
    Thanks for that, the pieces I made were used in water and it got through, superglue solved that and made it a composite material. But it would depend on the print parameters. I have also made custom fine porosity filters, rather like sintered material, but in useful shapes. But i did not have my own printer, I had access to one. So I escaped much of the trial and error. I think there are more factors in post moulding changes than a little UV. I imagine the process leaves a matrix of build in stresses and all unreinforced plastics creep. It is not something I considered for 3D printing but it is a big factor in other processes. I hope to experiment with a 3D printer of my own next year.
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

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    Quote Originally Posted by profloater View Post
    Thanks for that, the pieces I made were used in water and it got through, superglue solved that and made it a composite material. But it would depend on the print parameters. I have also made custom fine porosity filters, rather like sintered material, but in useful shapes. But i did not have my own printer, I had access to one. So I escaped much of the trial and error. I think there are more factors in post moulding changes than a little UV. I imagine the process leaves a matrix of build in stresses and all unreinforced plastics creep. It is not something I considered for 3D printing but it is a big factor in other processes. I hope to experiment with a 3D printer of my own next year.
    I would suggest acrylic instead of cyanoacrylate. Less brittle, easier to get a good finish, and you're less likely to end up semi-permanently bonded to the print.

    UV wasn't being suggested as a cause for the dimensional issues, it causes embrittlement of resin prints. FDM materials can be UV-resistant, they just need to be thermoplastic.

  20. #20
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    Quote Originally Posted by cjameshuff View Post
    Some FDM machines can use multiple materials, for example using soluble support material
    Do you mean multiple materials in one job, or different materials in separate jobs? If some machines can handle one per job but multiple materials in separate jobs, that means some can't do that... so I'm likely to get a machine that can handle some plastics on the list but not others? I saw that some FDM plastics are said to need higher temperatures than others; is a machine's maximum temperature the only limiting factor in choosing a material, or are there more?

    (Yes, if the question sounds like I'm already pretty settled on FDM and not SLA, that's because I am.)

    Quote Originally Posted by cjameshuff View Post
    There's also versions of the above that are strengthened with glass or carbon fiber, versions that are somewhat electrically conductive for ESD suppression, etc. Some incorporate wood fibers or metal powders.
    What effects do the wood and metal have, and how is the electrical conductivity achieved? And are these additives a matter of choosing which spool to buy, not something I need to get separately and know how to combine with the plastics?

    Quote Originally Posted by cjameshuff View Post
    FDM prints generally have an interior fill pattern that is mostly empty space. Physically, they're a bit like a hard shell around a regular geometric foam.
    That sounds like they not only wouldn't like having anything on top of them but also wouldn't like nails or screws. So the only way to attach them to each other or something else is glue?

    Quote Originally Posted by cjameshuff View Post
    A treefrog (a standard benchmark model) in black and marble PETG:
    https://i.imgur.com/fNHQBdL.jpg
    https://i.imgur.com/JEN8ctV.jpg
    What's the size? It's coming up about 8" wide on my screen, but I'm guessing it's really under 4" and maybe closer to 2". At anywhere around those sizes, the tiered structure is just fine to me, somewhere between unnoticible and just giving it a bit of character. I actually think the excess loose fibers would be more annoying.

    I love the fact that the white one is speckled. I was wondering whether it would be possible to print a speckled object, since a spool of fiber doesn't sound like something that could easily have specks in it. Also, I notice that the tiering is far milder on the white one. I suppose part of that could be the orientation relative to the light source and the camera, but it also seems as if different colors exaggerate or diminish the effect. (The black is not a flat black but a shiny one, almost like a pewter sculpture, so there's more contrast between some surfaces and others.)

    Quote Originally Posted by profloater View Post
    The toughness of those fibre printed models can be greatly increased by using Super glues which wick into the porous nature.
    How on Earth would you combine the glue with a project in progress?

    Quote Originally Posted by cjameshuff View Post
    There's some gotchas, like problems that can arise if the filament absorbs moisture (which can be remedied by baking the moisture out...)
    Once an object has been made, does water harm it, or is this only about spools waiting to be used?

    Quote Originally Posted by cjameshuff View Post
    Glass greatly reduces UV, but enough still gets through to fade pigments and dyes and make plastics go brittle.
    Quote Originally Posted by profloater View Post
    the pieces I made were used in water and it got through, superglue solved that and made it a composite material.
    What got through where: water through the printed object or UV radiation through the water? I'm guessing you mean these things can soak up water unless something is done, such as a glue infusion, to prevent that. (It sounds at first like you might be talking about UV radiation going througrh water, but I fail to see how glue in the printed object would prevent that.)

    Another one of the concepts I've had for a thing to print would be taking the place of wood in a situation where it would get rained on. But I can easily go back to what I thought of in the first place for that one: just wood with lots of protective stuff applied.

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    Quote Originally Posted by Delvo View Post
    Do you mean multiple materials in one job, or different materials in separate jobs? If some machines can handle one per job but multiple materials in separate jobs, that means some can't do that... so I'm likely to get a machine that can handle some plastics on the list but not others? I saw that some FDM plastics are said to need higher temperatures than others; is a machine's maximum temperature the only limiting factor in choosing a material, or are there more?
    I think he means different materials in one job - most machines can print in most of the materials listed. I haven't seen one on the market that can't do all of the basic materials for some time. As you say it is just about nozzle temperature. Worst comes to the worst you may have to buy a specialist nozzle for outre materials (such as chocolate).

    A comparison of the materials. https://www.3dhubs.com/knowledge-bas...ials-compared/

    Quote Originally Posted by Delvo View Post
    What effects do the wood and metal have, and how is the electrical conductivity achieved? And are these additives a matter of choosing which spool to buy, not something I need to get separately and know how to combine with the plastics?
    You buy pre-blended spools - you don't try to mix them yourself. Not sure what the actual effects on the print are - I only know from articles so I will leave that question to someone with more experience.

    Quote Originally Posted by Delvo View Post
    That sounds like they not only wouldn't like having anything on top of them but also wouldn't like nails or screws. So the only way to attach them to each other or something else is glue?
    Yes. Screws are bad news - the interior is generally a light matrix. The screw just destroys it without getting much grip. You could print with a very high fill ratio (which you can set in the slicer) but you will end up with prints that take a lot of time and material.

    Quote Originally Posted by Delvo View Post
    I love the fact that the white one is speckled. I was wondering whether it would be possible to print a speckled object, since a spool of fiber doesn't sound like something that could easily have specks in it.
    You can buy speckled and marble effect filaments. The specks tend to be small and shiny. Have a look on Amazon - you will find all kinds of filaments (including rainbow, glittery, marbled etc)

    Quote Originally Posted by Delvo View Post
    Once an object has been made, does water harm it, or is this only about spools waiting to be used?
    If you finish it with varnish its generally fine. Otherwise PLA and Nylon tend to swell and absorb water (other materials are more resistant). For prints the biggest issue is with PLA - it is biodegradable and will gradually break down unless properly finished. Water makes the process much faster. For filaments it makes them harder to print with. You get more breakage, less adhesion and generally a poor experience. Just give it a few coats of polyurethane varnish and it is fine. A friend actually has a PLA thing in their pond and its been fine. It was very, very varnished though!

    Quote Originally Posted by Delvo View Post
    Another one of the concepts I've had for a thing to print would be taking the place of wood in a situation where it would get rained on. But I can easily go back to what I thought of in the first place for that one: just wood with lots of protective stuff applied.
    It should be fine - just pick the right material or treat the final piece properly.

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    Quote Originally Posted by Shaula View Post
    I think he means different materials in one job - most machines can print in most of the materials listed. I haven't seen one on the market that can't do all of the basic materials for some time. As you say it is just about nozzle temperature. Worst comes to the worst you may have to buy a specialist nozzle for outre materials (such as chocolate).
    Multiple materials in one job, yes. There are some that are effectively limited to PLA's temperature range, or which take special cartridges so you only get what the manufacturer makes. I would recommend against those, fortunately they're a very small minority.


    Quote Originally Posted by Shaula View Post
    Yes. Screws are bad news - the interior is generally a light matrix. The screw just destroys it without getting much grip. You could print with a very high fill ratio (which you can set in the slicer) but you will end up with prints that take a lot of time and material.
    If you include a screw hole in the design, normal machine screws perform quite well. Nuts can be used for more strength.

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    Quote Originally Posted by Delvo View Post
    What effects do the wood and metal have, and how is the electrical conductivity achieved? And are these additives a matter of choosing which spool to buy, not something I need to get separately and know how to combine with the plastics?
    The wood and metal are just cosmetic, the only other effects are that wood-filled filament can tend to clog nozzles and seems less dimensionally accurate, metal-filled filament can abrade nozzles and is expensive. There are iron filled filaments which are somewhat magnetic.
    The electrical conductivity is achieved with carbon fiber and/or conductive carbon powder.


    Quote Originally Posted by Delvo View Post
    That sounds like they not only wouldn't like having anything on top of them but also wouldn't like nails or screws. So the only way to attach them to each other or something else is glue?
    You can make hollow structures that are extremely strong in compression. If the fill doesn't provide the rigidity you need, adding some holes can help.
    I mostly bolt things together.


    Quote Originally Posted by Delvo View Post
    What's the size? It's coming up about 8" wide on my screen, but I'm guessing it's really under 4" and maybe closer to 2". At anywhere around those sizes, the tiered structure is just fine to me, somewhere between unnoticible and just giving it a bit of character. I actually think the excess loose fibers would be more annoying.
    Those were printed with a 0.1mm layer height, IIRC. The toe-span of the treefrog is 2".


    Quote Originally Posted by Delvo View Post
    I love the fact that the white one is speckled. I was wondering whether it would be possible to print a speckled object, since a spool of fiber doesn't sound like something that could easily have specks in it. Also, I notice that the tiering is far milder on the white one. I suppose part of that could be the orientation relative to the light source and the camera, but it also seems as if different colors exaggerate or diminish the effect. (The black is not a flat black but a shiny one, almost like a pewter sculpture, so there's more contrast between some surfaces and others.)
    The layers are just more obvious due to the contrast of the gloss on the black one. PETG is notably shiny, PLA tends to be more matte finish.

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    Quote Originally Posted by Shaula View Post
    I copied & pasted the list from earlier in this thread into my own file and have added comments people posted about each material along the way since then so I'd have it all in one place. That list and the one at this link both include PLA and nylon, but after that, they diverge. I'm inferring that PET and PC are abbreviations of PETG and polycarbonate. If so, that just leaves:
    mentioned earlier in this thread: PEEK, polyurethane, PVA
    described at the link: ABS, TPU

    Are any of those alternative names for each other?

    And now, in this thread, there's also a mention of wacky alternatives like chocolate, which made me wonder how many other wacky alternatives I'll never use are out there.

    Polycarbonate... isn't that the stuff they're making lightsaber blades out of these days?... although I'd expect the printed stuff to be weaker than the same stuff made by processes that don't come in layers.

    I notice that polyurethane was mentioned earlier in the thread but given no particular description, and now I see the same substance mentioned again for what I've previously known it for: something you brush onto something else for waterproofing:

    Quote Originally Posted by Shaula View Post
    If you finish it with varnish its generally fine. Otherwise PLA and Nylon tend to swell and absorb water... Just give it a few coats of polyurethane varnish and it is fine...

    ...It should be fine - just pick the right material or treat the final piece properly.
    So, on the "pick the right material" thing to avoid letting water ruin an object, polyurethane is the most naturally waterproof material to print? Or just "anything but PLA/nylon" is about the same?

    Quote Originally Posted by Shaula View Post
    Screws are bad news - the interior is generally a light matrix. The screw just destroys it without getting much grip. You could print with a very high fill ratio (which you can set in the slicer) but you will end up with prints that take a lot of time and material.
    What would that do to the object's traits other than the obvious weight increase and apparently more compression resistance? Lower flexibility? Worse crack propagation?

    And another thing about this spongey inside, aside from various concepts of "strength": if you print a clear plastic do you still get a foggy look from all those interior surfaces? Does setting it to print solid all the way through make it clearer by eliminating interior surfaces?

    How thick is the outer shell? Is that another decision at the slicing stage? Some of the projects I'm thinking of would be so thin they might end up being nothing but shell.

    Quote Originally Posted by cjameshuff View Post
    The wood and metal are just cosmetic
    What are the cosmetic effects? I'm sure throwing a few lignin/cellulose fibers into mostly plastic doesn't create the look of wood, and I'm sure throwing some metal powder into mostly plastic doesn't make the object look like it's made of metal, but I'm having trouble picturing what else either would do instead. (Then again, that black PETG frog already did look almost like metal, so maybe metal powder is specific to PETG, to exaggerate that aspect of PETG in particular...)

    Quote Originally Posted by cjameshuff View Post
    If the fill doesn't provide the rigidity you need, adding some holes can help.
    I mostly bolt things together.
    So you design a shape with a tunnel through it for the bolt so the bolt has the solid "outer shell" version of the substance all around it? When I'm pre-drilling a hole in wood to put a screw in, I pick a size slightly narrower than the outer edges of the screw threads, and let the screw threads dig in a bit to create their own spiral groove to fit into. Would that work with plastic?
    Last edited by Delvo; 2020-Dec-13 at 08:52 PM.

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    Quote Originally Posted by Delvo View Post
    I copied & pasted the list from earlier in this thread into my own file and have added comments people posted about each material along the way since then so I'd have it all in one place. That list and the one at this link both include PLA and nylon, but after that, they diverge. I'm inferring that PET and PC are abbreviations of PETG and polycarbonate. If so, that just leaves:
    mentioned earlier in this thread: PEEK, polyurethane, PVA
    described at the link: ABS, TPU

    Are any of those alternative names for each other?
    PETG: Polyethylene terephthalate glycol-modified, a modified version of polyethylene with properties that make it better for printing. Plain PET has been used, but "PET" is generally PETG.
    TPU is Thermoplastic PolyUrethane. Most flexible filaments are these.
    PVA is PolyVinyl Alcohol. If you've seen PVA wood glue, this is the same stuff in filament form. It's water-soluble, and used as a support material in multi-material printing.
    PEEK: PolyEther Ether Ketone. Printing temperature ~400°C. You'd probably need hot end upgrades to print it. Very strong, very heat and chemical resistant, very expensive. MatterHackers has it for $345.00/500 g: https://www.matterhackers.com/store/...mm/sk/MQKH3YHL


    Quote Originally Posted by Delvo View Post
    Polycarbonate... isn't that the stuff they're making lightsaber blades out of these days?... although I'd expect the printed stuff to be weaker than the same stuff made by processes that don't come in layers.
    It's the same stuff, often with some additives to reduce the melting point. It's very strong and tough.


    Quote Originally Posted by Delvo View Post
    So, on the "pick the right material" thing to avoid letting water ruin an object, polyurethane is the most naturally waterproof material to print? Or just "anything but PLA/nylon" is about the same?
    Nylon might have issues if you're depending on it staying rigid or having precise dimensions. The main things you'd want to avoid are PLA (which is biodegradeable) and PVA (unless you want it to dissolve).

    All the polyurethane filaments I know of are flexible. They're kind of a slick-surfaced, stiff rubbery material.


    Quote Originally Posted by Delvo View Post
    And another thing about this spongey inside, aside from various concepts of "strength": if you print a clear plastic do you still get a foggy look from all those interior surfaces? Does setting it to print solid all the way through make it clearer by eliminating interior surfaces?
    Printing solid makes it clearer, but you're not going to get great optical quality. You're better off printing a mold and casting resin if you want crystal clear objects.


    Quote Originally Posted by Delvo View Post
    How thick is the outer shell? Is that another decision at the slicing stage? Some of the projects I'm thinking of would be so thin they might end up being nothing but shell.
    It's something you set up in slicing, yes. Thin enough portions will merge the surface shells together without any infill. Some objects can be printed as a single pass that just spirals up from the base around the perimeter.


    Quote Originally Posted by Delvo View Post
    What are the cosmetic effects? I'm sure throwing a few lignin/cellulose fibers into mostly plastic doesn't create the look of wood, and I'm sure throwing some metal powder into mostly plastic doesn't make the object look like it's made of metal, but I'm having trouble picturing what else either would do instead. (Then again, that black PETG frog already did look almost like metal, so maybe metal powder is specific to PETG, to exaggerate that aspect of PETG in particular...)
    My "wood" filament looks more like cardboard, honestly. Some other kinds darken a bit with the heat of printing, and variations in that effect give it a somewhat more realistic grain appearance. The metals will give you a dull metal look (the treefrog was just black PETG). Iron-containing filaments can rust for a weathered appearance.


    Quote Originally Posted by Delvo View Post
    So you design a shape with a tunnel through it for the bolt so the bolt has the solid "outer shell" version of the substance all around it? When I'm pre-drilling a hole in wood to put a screw in, I pick a size slightly narrower than the outer edges of the screw threads, and let the screw threads dig in a bit to create their own spiral hole to fit into. Would that work with plastic?
    Yeah, that's what I do. It works well with PETG, but may take some experimentation with more brittle plastics.

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    What does "support material" mean?

    Did the description of nylon as "self-lubricating" mean "very low friction"? I can't believe any of these things actually ooze liquid.
    Last edited by Delvo; 2020-Dec-14 at 12:06 AM.

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    Quote Originally Posted by Delvo View Post
    What odes "support material" mean?

    Did the description of nylon as "self-lubricating" mean "very low friction"? I can't believe any of these things actually ooze liquid.
    Support material is temporary material laid down to support parts of the print when they aren't self-supporting. It can be the same material as the print, printed so it (hopefully) doesn't adhere very well, or it can be a different material, like water-soluble PVA.

    Some nylon blends actually do, others incorporate dry lubricants, and you can find self-lubricating plastic filament for printing (https://www.igus.com/info/3d-printing-materials has some, but I'm not sure if they specifically have nylon), but you'll have to hunt them down and pay extra. I wouldn't expect it of normal nylon filament.

    I've seen the "nylon is self-lubricating" claim but nothing to support it as a general trait of nylon, I suspect it's confusion about nylon's low-friction nature or not understanding that it was a feature of a specific blend. A lot of materials experience high friction when you have surfaces of the same material rubbing against each other, sometimes making squeaking and creaking noises, while nylon slides with relatively low friction and wear.

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    Quote Originally Posted by Roger E. Moore View Post
    Once you buy your 3-D printer, make a copy of this miniature "Mars rover" which uses robotics to drive over rough terrain.

    https://phys.org/news/2020-12-d-mars-rover-exomy.html
    I see the Borg got Gumby

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    Quote Originally Posted by Delvo View Post
    What would that do to the object's traits other than the obvious weight increase and apparently more compression resistance? Lower flexibility? Worse crack propagation?
    My experience with high density infill is that it makes the object heavier and more impact resistant (once you damage the outer shell of a print the inside is prone to take even more damage from accidental impacts). I'd guess it would affect flexibility too. But the big one is cost and the need to change the filament mid print. I normally run at 15-20% infill (from memory) so a 1kg reel of PLA filament (£15-£30 in the UK) would be expected to make a single solid cube 10x10x30cm in size. At 100% infill you'd get something 10x10x7cm. These are rough estimates.

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