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  1. #121
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    I think the reason for that would be cost (and a bit of ease of use/ weight saving too). Feeding a filament into a hot end is easy - all it needs is a motor to push on the filament and you are done. However, if you look at an injection moulding machine the extruder is quite long. For those who aren't familiar, it is a screw (bit like the old mincers) that takes beads from a hopper and while the barrel is heated, pushes the beads together until they are molten and combined. Without that screw section you would not get a continuous flow of material. For a 3d printer that would probably mean an extra say kg of weight having to be moved back and forth, several hundred dollars of screw, a (relatively large and powerful) motor, barrel and heaters and even more opportunities for heat related injuries.
    Buying/ getting a small extruder and making your own would be possible but the filament cross section would need to be very carefully controlled (too big and it won't fit the hot end, too small and molten plastic will extrude back in the wrong direction)

    To make matters worse I was reading about one brand of printer where you must buy filament from them - the reels have a chip in them that keeps track of use (and colour and probably other things), which of course means unless you can reset the chip, the printer will not function with 3rd party filament in it. Buying 'official' HP ink is annoying but does not happen often; with a 3D printer I would imagine that a 600g roll of filament would go quickly, so you would be paying that premium quite often.

    Michael

  2. #122
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    Quote Originally Posted by Michael G View Post
    To make matters worse I was reading about one brand of printer where you must buy filament from them - the reels have a chip in them that keeps track of use (and colour and probably other things), which of course means unless you can reset the chip, the printer will not function with 3rd party filament in it. Buying 'official' HP ink is annoying but does not happen often; with a 3D printer I would imagine that a 600g roll of filament would go quickly, so you would be paying that premium quite often.

    Michael
    Screw that, imagine buying a CNC mill that'd only use end mills with an RFID code from the mill manufacturer.

    I actually think it's probably illegal under Australian consumer law anyway - something about 3rd line forcing comes to mind, but I might be full of it here. Just there's something ringing a faint bell in the back of my mind about companies being prohibited from tying customers to suppliers of consumables.

    PDW

  3. #123
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    In regard using beads, that would be ideal, but for all the reasons Michael said, it's likely not practical. The filament diameter is actually quite critical, and you should always measure it and input the exact dimension into the slicer. These days they're normally quite good, but in the earlier days they were all over the shop. Consistency in filament diameter is one of the differences between quality and cheap filament. The extruder will just push out xx millimetres of filament, and it doesn't know the precise thickness. It can have a large effect on print quality, and as Michael said, at an extreme cause the extruder to mis-step. It can also vary as the spool is consumed, so it's something to check from time to time.

    As I mentioned earlier, I would personally strongly suggest an open source printer if anyone chooses to buy one, and that goes for filament too. However as always there's no right and wrong here, and that suggestion needs to be tempered in light of the intended use. Not everyone wants to fiddle with these things, and one of the ideals of the manufacturers in the sector is to get something as close to an "appliance" as they can. By controlling as many inputs into the whole chain as they can, they can provide for a more predictable outcome. It's the model Apple also use, and love it or loathe it, it works for that intended purpose. For example, imagine you're running a design company or similar, you don't want your staff dicking around with a printer for hours each week at zero billable hours, instead the additional cost of buying filament cartridges is fairly small in the grand scheme of things, and will be part of the whole chain of making a very predictable end product they can pass on to the customer. I've seen some of these printers running, and one in particular was producing a very good result, with cartridges that weren't outrageously expensive. The same technique is used by all the big commercial printers, at least all I've ever seen or heard of, and nobody throws there arms up in the air about having to buy supplies (and servicing incidentally) from the manufacturer. Their supplies aren't cheap either incidentally! Again it comes back to what I've been trying to emphasise to people who are thinking of getting into this area, do your research before buying, and try to get an understanding of why a printer costs what is being asked (and whether that cost is justified or just a try-on). I'd really like to see more people here buying 3D printers, because once you have one it's remarkable how useful it is as a workshop tool. However it's a real minefield of information surrounding them and it would be a shame to see somebody buying a cheap printer thinking they'll just plug it in and start printing, conversely somebody else thinking they have to spend multiple thousands in order to achieve what they want and either paying more than they needed to or not buying one at all. In fact often neither case is true, and how much you pay basically comes down to how much work you're prepared to put in to finessing the printer you buy.

    A spool lasts quite a long time in most applications. Remember these models aren't normally printed as solid and instead just a hollow honeycomb shell, so while they may look plastic hungry, often they're not. IIRC most slicers will give you the weight of the plastic used on the print after slicing the model, and it's typically just in the grams range. Obviously if you print very large models or need solid models the weight will go up.

    I was ordering some more Arduino gear yesterday and decided to throw in a spool of PETG while I was at it. I haven't yet printed in it and it could be a good compromise to polycarbonate. PC is excellent and I initially ordered it, but the print and bed temperatures are right up there, up around the 275-300 degrees mark, so I decided to take it out of the order for now. Here's some brief details from the E3D site which tends to be quite reliable. Polycarbonate

    Again, they emphasis the need for an all-metal hotend, and at those temperatures it should be easy to understand why. I have that on my printer, but being an acrylic frame on the printer I would be concerned about the heat from the heated bed distorting the acrylic table it rides on. While it stands off from it and I insulated under the heated bed when I replaced it, nevertheless there could be enough heat there to distort the acrylic. I want to replace that with a piece of aluminium plate, not a big job if I use the existing bed as a template, but just another job on the list. The other thing to consider is the heat around the hotend support. My E3D hotend has quite a good cooling fan and duct (I've also printed an additional cooling duct with centrifugal fan for plastics that need cooling when printed), but not all hotends are as good in that regard, so something to watch out for if you want to print high temp plastics.

  4. #124
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    The one that looked to me the most likely to work is/was the sculptify Sculptify the extruder head stays stationary and the platform moves, which sort of makes sense mechanically, however they appeared to have vanished from the face of the earth since reaching their $100,000 kickstarter goal. They either took the money and ran, or couldn't get it working, probably for all the reasons already mentioned.

    Anyway here is the video for a non-existant 3D pellet printer.



    Ray

    PS. Sculptify made the list of 3D printer kickstarter disasters, some of which appear to be just out and out scams.

    https://callmevice.com/2016/05/20/an...the-disasters/

  5. #125
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    First reason is that an extruder head will be heavy, and there's no real way of 'piping' the hot plastic to the nozzle for a remote installation. Having a heavy extruder attached to the nozzle will limit the maximum speed the nozzle can travel, limiting printing speed and requiring a much stronger frame and motion parts.

    Secondly, building a consistent extruder is no simple feat, and simply adds to the cost of the printer, as well as the maintenance nightmare that would be changing over materials. Many people have tried to build filament extruders for exactly the reason you state, however I believe the current state of the art is that there are very few successful attempts, and it has proven difficult to achieve the consistency of diameter required of filament to work effectively.

    By contrast, filament can be routed through PTFE tube with ease for flexible connection to a remote spool from the print head. That, and they now have a 'consumable' they can sell to you.

    Regardless, I believe FDM will be the 'dot matrix' of the 3D printing world, to give way to inkjet and stereolithographic technologies in the future.

  6. #126
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    Quote Originally Posted by Pete F View Post
    By controlling as many inputs into the whole chain as they can, they can provide for a more predictable outcome. It's the model Apple also use, and love it or loathe it, it works for that intended purpose.
    That's true for IOS as used in the Apple phones and tablets. Not so on Apple computers running OS X - there, open source software works just fine (or not, with all the possible hassles that free open source software is prone to). In fact the only non-open source software I have is MS Office because I needed it for one development contract.

    PDW

  7. #127
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    Quote Originally Posted by PDW View Post
    That's true for IOS as used in the Apple phones and tablets. Not so on Apple computers running OS X - there, open source software works just fine (or not, with all the possible hassles that free open source software is prone to). In fact the only non-open source software I have is MS Office because I needed it for one development contract.

    PDW
    Ok Peter. It's the model Apple IOS uses. It was simply an example some people may have been familiar and able to associate with.

    That's a shame that printer didn't work out Ray, but apart from the reasons mentioned earlier, another good point noted above is the change over from one plastic to another would be tricky. With conventional filament you typically heat the hotend to around the glass transition temperature, so the plastic is pliable but not melted, and pull it back out. With most plastics it will pull the whole lot out in one go, right down to the nozzle. Indeed you can do that with some of the flexible plastics to try to clear a blocked nozzle. I don't know how they would do that with pellets.

    A lot of the claims made in the video seem dated (in terms of limited filaments available), or technically true but a bit of a stretch in reality. It's true pellets are very cheap and readily available, what they don't say is they're normally sold in bulk to industry. Forget the crap that are sold for stuffing dolls etc, 3D printers can be a bit fussy with what they're fed, and recycled plastic or plastic with crap in it won't fly. Keeping the rubbish out of pellets would be an issue, as would storing it without wading around in a sea of rogue runaway beads. So it goes on.

    One of the main issue in my mind however is accurate control of the extruder. The plastic doesn't just come out at a constant rate as some people may assume, instead the extruder will vary the speed to suit the requirement of the print. So for example approaching a corner the head may slow down to turn the corner, hence the extruder will feed less filament. Often the hotend will move from a printed area to another printed area and no plastic at all is required, if even a small amount comes out you'll get stringing. Getting an accurate extrusion from pellets would be a tough gig I'd think as you don't have that filament to push on.

    Regardless, I believe FDM will be the 'dot matrix' of the 3D printing world, to give way to inkjet and stereolithographic technologies in the future.
    I agree wholeheartedly. The current FFF printers are now quite a mature technology and have basically just adapted common injection moulding thermoplastics to suit their use. It's why I don't believe we'll see any great advances in this area. Gradual improvement, sure, but the great leaps some seem to be waiting for? Unlikely in my opinion. I've seen some of the "ink jet" style printers run and they're amazing, however suffer some of the same issues as FFF in terms of being slow. Personally I think the future is with SLA technology and their derivatives. As far as I'm aware those resins weren't used in large production environments, hence there probably hasn't been a lot of R&D put in to developing different resins with different properties. Maybe there has been, but not as far as I'm aware. However if resins could be developed with similar properties to some of the engineering plastics we're talking an absolute game changing situation. Something that would change society I would think. BUT we're not there yet, and there's been no real evidence it's even possible beyond the hype. Likely? Yes I think so.

    FWIW this is probably the state of the art in 3D printing now.

    Newpro3D Super Fast 3D Printer, World's Fastest 3D Printer of the Day



    I'm a bit sceptical about the claims of printing wind turbine blades etc, because in those applications the resin doesn't really provide the strength per se and I believe that will come from the composite fibres they're using, just the same it's still quite amazing technology. The company boasts it's been working on this technology for a whopping ... 2 years. It goes to show the pace of change!

    Having said all that, it doesn't mean the current FFF printers won't have a place or use for now and the immediate future. If you're the type of person who is always holding out for the cutting edge to become available cheaply in the general market, just accept the fact you will never own a 3D printer and move on. There is always a cutting edge, and there always be something much better just around the corner. That doesn't mean that you won't get plenty of utility out of a current generation of printer even when some of these other technologies become more mainstream. That's just the state of the world now.

  8. #128
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    Quote Originally Posted by Pete F View Post
    ... another good point noted above is the change over from one plastic to another would be tricky. With conventional filament you typically heat the hotend to around the glass transition temperature, so the plastic is pliable but not melted, and pull it back out. With most plastics it will pull the whole lot out in one go, right down to the nozzle. Indeed you can do that with some of the flexible plastics to try to clear a blocked nozzle. I don't know how they would do that with pellets.
    Typically with an injection moulding machine you finish the run you are doing, empty the hopper and fill with something a different colour and then just purge the machine - the resultant plastic purge material looks like something a really big dog would leave. If you are just changing colour then that's all that needs to be done but if you are stopping for the night or changing to a different material of around the same colour then you might have to do that twice - purge with something like polyprop (cheap and remelts easily) and then put your new material in and purge that through.

    The other problem with pellets is keeping them dry - they can be hydroscopic so when heating them up to over 100 degrees you start getting steam produced = poor finish/ lack of bond and so on. Much less surface area with filament and easier to arrange a low humidity environment.

    While the idea of printing turbine blades captures the imagination, like Pete I'm not so sure how that would work in practice. One of the nice things about filaments is that they can have things in them - like wood or CF. In industry filled plastics are used to bulk out materials, add strength or other enhance other properties (temperature tolerance for example). Resins are 100% resin - I can't see how you would have a CF resin for example, so in terms of resin SLA, the properties are going to be the properties of the bulk cured resin. My experience with resins is not large but the few that I've used tend towards the brittle side of things. They can still be tough but fracture in a brittle sort of way. I suspect that FDM/FFF will be around for a while just because of the way the materials behave and fail.

    Michael

  9. #129
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    Quote Originally Posted by Pete F View Post
    FWIW this is probably the state of the art in 3D printing now.

    Newpro3D Super Fast 3D Printer, World's Fastest 3D Printer of the Day
    https://3dprint.com/108599/patent-nexa3d-newpro3d/

    What are the odds two companies come up with same technology at the same time?

  10. #130
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    Quote Originally Posted by RayG View Post
    https://3dprint.com/108599/patent-nexa3d-newpro3d/

    What are the odds two companies come up with same technology at the same time?
    Cripes, what a cluster!!! It's a shame when some seriously good technology gets derailed by bickering, but I guess each company think they're right.

    The other problem with pellets is keeping them dry - they can be hydroscopic so when heating them up to over 100 degrees you start getting steam produced = poor finish/ lack of bond and so on. Much less surface area with filament and easier to arrange a low humidity environment.
    That's also something to consider with filament too Michael, though the extent will depend on the plastic. Nylon for example is seriously hydroscopic, and even though I keep mine sealed with desiccant it still absorbs moisture. It's not like I'm using it every day, so I normally pop it in the oven (on lowest setting) for a couple of hours to dry before I'm going to use it. Even then it will still hiss and spit while printing (the steam coming out). It's dry enough that it doesn't affect the print, but I've heard if it's not properly dry (say you just left it out unsealed without any precautions) it will cause all manner of grief. It's a great plastic to use for many applications though; almost indestructible.

  11. #131
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    Gold, the colour of choice for the discerning person.

  12. #132
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    Default Right angle castings

    Bit of an update - the castings finally came back from the foundry. They look really nice, I'm very happy with them.

    I hear from a reliable source that one local recipient couldn't help himself and has already machined one up.......

    PDW
    Attached Images Attached Images

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    Looks good. Nice smooth edges as well.

    I finally have a 3D printer now as well. Got the build finished this morning.

    Currently testing it by printing a whistle to give to the nephews to annoy their parents. bwa ha ha.
    Gold, the colour of choice for the discerning person.

  14. #134
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    Quote Originally Posted by PDW View Post
    Bit of an update - the castings finally came back from the foundry. They look really nice, I'm very happy with them.

    I hear from a reliable source that one local recipient couldn't help himself and has already machined one up.......

    PDW
    They certainly look the goods. Do they come stress relieved? Or do you have to do that yourself?

    What's the thing in the middle between the angles?

  15. #135
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    Quote Originally Posted by RayG View Post
    They certainly look the goods. Do they come stress relieved? Or do you have to do that yourself?

    What's the thing in the middle between the angles?
    More angle squares, just end-on. I got 6 of each size cast up.

    Stress relief - they're left to cool in the mould so they're pretty well relieved. I've never done anything to the straight edge castings and I've not had any problems with movement. In fact when I re-spotted one of mine after trading up to a bigger plate I was pretty happy with how it spotted on the new plate. Indicated that the plate was also good as it'd be really unlikely a plate would have worn to be a perfect match with a straight edge. Anyway the 2nd SE I checked, a 1m long I beam type, spotted well also.

    Now if only I had time to move some of the machining projects along a step or 2..... At least the bronze port hole castings are now fully machined & installed on the boat. Pity I need 2 more trim rings and getting anyone to do a simple bronze casting is damn near impossible. Doesn't get much simpler - a 3mm to 3.5mm thick ring of bronze, approx 250 OD and 170 ID. All I need is 2 of them and I *really* don't want to have a go at it myself at this point in time.

    PDW

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