geert_2

Maybe you could print some sort of dampened zigzag line for testing? Thus a sort of dampened triangle wave? Let's say the zigzag amplitude is 10mm at the start, and then very gradually reduces 0.1mm or so? If there would be resonance effects, they might show up?

I took a quick look, and in the models I have laying around here, a simple plain cube or rectangular bar shows ringing best (thus worst, with the most defects): 10mm x 10mm x 10mm, printed 100% filled. Or 15mm x 15mm. See the white dummy bar in the image below. This is where cooling is on the edge of being sufficient (and clearly insufficient in the cones). Things that suffer from slowing down in corners are mainly tiny text: caps height 3.5mm, line-width 0.5mm, character-width ca. 2mm. Text raised 0.2 to 0.5mm above the surface. Here the ends and corners of the characters get visibly thicker. You can find test character sets on my page: https://www.uantwerpen.be/nl/personeel/geert-keteleer/manuals/ The zip-file includes the design files (RSDOC, DesignSpark Mechanical), and STL-files with raised, recessed, and hollowed-out test texts. The hollowed-out are for transparant materials only, of course. All printed on an UM2 (non plus) in PLA, 0.1mm layers. So I don't know if this applies to an UM3 too,but you could try.

This company in the Netherlands has it. They are the official distributor in the Benelux. I don't know if they ship to outside the Benelux, but you could ask. https://www.jwb3dprinting.nl/

Several months ago there was a survey on which materials people used most. If I remember well, empty spool weight was one of the many items in the list? Other items were spool dimensions, etc. Maybe you could find additional info there, if you can find it back? Concerning estimations of remaning material: I use the Cura-estimation as guide, and then just add some spare. Usually I manually unwind and straighten a bit of filament (the UM2 is sensitive to too much friction in the feeder traject), and since my prints rarely use more than 3 meters per print, this gives a good idea if I have enough.

Yes, but both inside the nozzle and at the bottom outside of the nozzle you will get accumulation of material that will get burned. Also, ABS starts giving off nasty fumes as soon as it melts, long before it burns. So I thought this could be the same with PVC? Burning appears to be a gradual decomposition and oxydation process. But of course, if you are familiar with PVC production and the risks, don't let this stop you. Feedback would be very welcome on how well it melts, sticking to the glass, layer bonding, toxic smells, side effects,... I wasn't even aware of the corrosion risks.

I have never heard of PVC filament? Wouldn't that give off nasty chlorine fumes when heated? PVC is said to do so when being burned, and 3D-printing temperature is close to burning temperature, usually.

Just an idea concerning painting instead of plating. Here in Antwerp every summer we see "living statues": people mimicking bronze or stone statues. Often they are students from art schools. The most impressive are usually the dark bronze ones with copper green oxydation, as they look the most realistic. Sometimes the only way to distinguish the fake statues from the real ones is by counting. If you know there are four real bronze figures in a scene, and one day suddenly there are five, then one of them has to be a fake. :-) Or sometimes the living statues can be recognised because they have lined their hats and clothes with a thin gold line as finishing touch. So they are even more beautiful than the real bronze ones. Maybe this is something you could try too, instead of plating and chemically aging? It might be equally beautiful but with much less hassle and chemicals?

And how does it handle cutting and sanding? Does this leave dirty marks, or is it smooth? Like some PLA gets ugly white marks or becomes terribly fibrous, when cutting or sanding it, while on some others it is barely visible? I haven't seen it in reality, but on photos I like the satin-metalic shine.

Are these drawings, or 3D-scans from real people? If real, it could be kind of fun mounting them on animal bodies, like mermaids, horses, dragons,... (I don't know the correct names for all these mythological inbetween human and animal forms).

Yes, somewhat comparable with a desktop fan in summer. Although with less electric motor buzz, and more neutral air noise. Not exactly silent, but a laboratory can have that.

I have no experience with woodfilled filament. But if it is the matte finish of the models you are looking for, maybe you could find unfilled PLA that produces such a matte surface texture, instead of glossy? That would be much easier to print than any filled filaments, print faster, and probably be cheaper too. Some time ago I saw promo for a new matte filament, unfilled, but I don't remember the brand. Also, colorFabb can now deliver custom colors, and it already has a lot of soft sand and stone colors available from previous custom orders and formulations. Spray painting with a rough texture also could be an option. This might go faster than printing with filled filament. If you have lots of identical models, like the tiny houses, then you could also design and print one mould in PLA, and then pour the models in gypsum. Make sure the mould can be opened, thus no undercuts. This would automatically give you the desired natural sandstone look. And it would go a lot faster, since it only takes a few minutes for gypsum to cure, instead of hours to print. Colors can be mixed into the gypsum powder, or be painted on. The disadvantage of gypsum is that it is a dirty mess, and you should *never* pour water with dissolved gypsum down the drain. Never. Even not if there is only a thin mist of gypsum in the water. This will very soon clog your whole drain. You can pour water with gypsum in the garden however, it is innocent and even quite fertile. If I had to do it, for these particular models, I would probably go the gypsum road. Maybe these alternatives might be worth looking into? That said, I do like the rough texture and dull colors of the models in the photos. It adds to the medieval look.

The above is just from experience via trial and error. I am not a specialist in air flows. When I needed extra cooling, like in the hot summer we had (>30°C), the desktop fan at lowest speed, and from some distance, worked very well. This gently cools the whole model, but not too much the nozzle itself. It just removes excess heat in a gentle way. I also tried blowing compressed air directly on the model, just below the nozzle, but this would cool the nozzle too suddenly, and cause temp fluctuations, and errors if done excessively. So the airflow has to cool the model, but not the nozzle. It should solidify the printed lines immediately so they are stable, but not too much, so the next layer still bonds well. And the glass should stay hot enough to preserve a good bonding (especially with my "salt method" for bonding, without any glue). All this is not an easy balance. This is why I would not exagerate in adding fans. Just my personal view, but of course you are free to see things differently, and your models and circumstances may differ from mine. I have never had any problems with PLA with the standard nozzle fans, although cooling runs at 100%. Bed temp then is set to 60°C, which might locally cool down a bit to 50 or 55°C. This is not too far away from room temp, 20...25°C, so cooling is not excessive. But I did have issues when printing PET, where the glass temp is much higher and thus the local cooling effect seems a lot bigger. Glass is an insulator, so I guess it can't keep up with the local heat loss. I had to increase the set glass temp from 80°C to 90 or 95°C to get good bonding. So that after cooling locally, it would still be around the desired 80°C for this sort of PET.

For comparison, my printers are sitting in the fume extraction cabinet in my laboratory. This extraction cabinet has an exhaust pipe diameter of 200mm. And the rectangular front opening is ca. 1100mm x 50mm. All this to get a smooth equal air flow. Although this is designed for extraction of chemical fumes, it is just standard lab equipment, I guess the concept can be ported to extraction of heat too, since both are about getting enough air flow, and good equal distritbution. I have no idea what fan is in there, since it is a huge central fan on the roof for all cabinets. But you can really hear and feel the airflow. Yes, you could disassemble a mini-fridge (like those in hotel rooms), put the cooling radiator inside and the heat radiator outside. But then you are going to have that constant compressor rattle. Or you could disassemble a cooling box based on peltier-elements and use these. But I doubt if this has enough capacity? It has to remove 100 up to 200 Watt of heat. And you may get condensation and corrosion. Probably a big fan is still easier...

They resemble steppers from old floppy drives? They had one to move the heads. For a direct drive of the filament, it would need a huge reduction gear to get enough torque, I think. But I like the idea.

A problem with a strong and very local airflow is that it cools the glass too much in some areas, especially when printing small objects. Even with the standard fans on my UM2, I have measured temp differences up to 15°C when printing tiny models in PET: in these areas the bed was cooled to ca. 75°C instead of the set 90°C. This might affect bonding of the model. Personally I feel rather like putting a 250mm desktop fan (like used in summer) in front of the printer, at a distance of 1 or 2m, set at slowest speed. This provides lots of airflow to evacuate excessive heat, but it is nicely distributed over the whole printer.

Personally, I have the feeling that those little holes are not enough, and neither are the small fans. I would rather go for 2 silent 120mm fans, or one 200mm fan, or so. But it could also be that the extracted air volume would be enough, but that the airflow does not reach the parts to cool? For best results, you would need a diagonal flow. Maybe try inserting a few cardboard pieces to guide the flow? What you could also try: temporarily replace the front door with a piece of cardboard, in which you mount the fans. Fold and glue it in place with removable tape. So you can try the effect of different types of fans, and locations, without drilling holes everywhere and ruining the cabinets. And of course, the cabinets above and below also need big enough openings on their other sides, and between walls and cabinet. You have to add all these resistances in series. So total resistance is probably 4x higher than that of the one of the printer alone. Concerning current, I have set mine to 900mA, if I remember well (UM2 non-plus). But that was to prevent the X-, Y- and Z-steppers to skip steps when too hot. Not the feeder.

Could you post images (screendumps) of the design in Cura, and photos of the results? The photos with ruler, so we can see the dimensions. I haven't printed with nylon yet, but there could be other things involved, such as insufficient cooling in a tiny model, so the model can't solidify. Or overextrusion due to slowing down in corners, when the internal pressure can't immediately be released, etc. For PLA, printing slow and cool usually helps. And printing a dummy tower next to very small prints, so the nozzle is away from the model, allowing it to cool, and so that printing-time per layer is equal for all layers. As said, this works for PLA and PET. But I don't know if it also applies to nylon (if too cool, you get poor layer bonding). But of course, it could be something else too. Below: a few images of the dummies: the basic concept, and a real model.

This are 3 separate rings. Probably you would need to "union" them in your CAD program, so it becomes one single object. Edit: while I was still typing, ahoeben already answered. Speed is everything. :-) But he is right: it is best to design the wall thickness in your CAD-program too. Don't leave such things to the guessing of automatic tools which don't know the meaning or purpose of your model, nor your wishes. So they have to make generalised guesses.

I have no experience with tough PLA, but from standard PLA (Ultimaker blue) and PLA/PHA (colorFabb) I have made sifts which are sitting in the drain of my laboratory tables. In one year they got a little bit duller, but they did not decompose (what I originally expected) and did not crumble apart (what I also expected). So if only for a short time, I wouldn't expect any problems. If you have sea water available, just make a couple of test prints and let them sit in it. And give feedback, so we also know. :)

PLA? Are you sure? Could it be PVA? That one dissolves in water and is quite bio-compatible (but not for all people - some show an allergic reaction). No I think it is PLA indeed, or some sort of. I have also heard that it is used for wires to sew body parts back together, and for some inserts and splints (not sure if that is the correct medical term) around which tissue is supposed to grow. These wires and supports should gradually dissolve in the body, but only very slowly, after the bone or tissue has cured. So it would be rather in weeks or so, depending on size and composition, not in just half an hour. :-) PLA slowly dissolves in lactic acid, its basic monomer, and then further into H2O and CO2, if I remember well. It seems that it is decomposed by the enzymes in the body, similar to the way they also help decomposing food already in the mouth.

Thanks. I'll try to get skull or bone data from the veterinary faculty here, and try it out. This could be usefull for lessons and research.

I like the black painted too. It adds some darkness to the theme of the scene. :-)

The plated of course looks best. But I think the unplated also looks cool. Maybe if you would use this smoothing method on Polyalchemy Elixir filament, or other copper/bronze colors (=not metal filled, but just with glitter particles in it like mica), it might also give an old worn or oxydated look? Without having to plate it?

Question: in what fileformat were the original scan data, and how did you get this into STL or another printable format?

Yes, I can see the use of a separate print stand for printers with swappable nozzles. But it would require temperature control: heat on/off, plus adjusting the temperature. And it would need a powerfull blower or cooler, to cool down the nozzle fast again. So you don't have to wait for ages. Thus this would almost require the electronics of a printer: CPU-board, nozzle holder, rotating knob, display. On my UM2 (non-plus) I use a much more gentle style of atomic pulls (thus the cold pull, or better luke-warm pull), to avoid damaging the rods or head. I use it always when changing colors and materials. For long runs with one color, I use it occasionally to remove accumulation of burnt residu. In short it goes like this: - Via the Maintenace-menu, heat up the nozzle to melting temp (210°C for PLA). - Then manually push through some filament until you have a nice steady flow (unless totally blocked of course). Push gently!!! - Dial the temp to zero. - Stop pushing filament through when the temp reaches 200°C. Do not keep pushing. This avoids getting a big blob in the teflon coupler that might get stuck when doing the pull. - For a worn-out teflon coupler, even do a slight "manual retraction" of a few mm, when the nozzle is still around 200°C. This makes removing easier later on. - Then let the filament alone. - Cool down the nozzle with compressed air, if you have an oil-free compressor. Or blow onto the nozzle. This greatly reduces cooling time. If you don't have a compressor, and don't want to blow, just wait. Never use spray cans with compressed air: these contain flammable or explosive gasses, and you don't want that on a hot nozzle. - After the nozzle is cold (=room temp, 25°C), wait for another few minutes. This gives the filament time to solidify totally internally, and in the teflon coupler too. Otherwise it might still be liquid in these insulated areas. - Once cold, gently try to rotate the filament. But gently!!! - Then heat up the filament again to 70°C (for PLA, other materials require different temps, e.g. PET may require 110°C). - While heating, gently, very gently pull and rotate the filament. - As soon as it reaches about 60°C, you will feel that the filament comes loose. - Gently keep pulling and rotating: now the filament will come out and take the dirt with it. Then restart the cycle. Do this a few times untill the dirt is removed. The key is to pull and rotate very gently, with only two fingers. No brutal pulling. In this way, you never exert high forces on the rods, nor on the nozzle and spring. No risk of bending the rods or displacing the nozzle. But due to the rotating and pulling action, it still removes the dirt very well. The deeper cooling to room temp allows the inner core of the filament to totally solidify. When reheating, this adds strength to the filament. Only the outer edge is then softened. If the nozzle is totally blocked, you could push from below through it with a soft steel needle. I use a medical needle from which I cut off the sharp cutting edge, and then rounded the end. I also grinded it down from 0.41mm to 0.39mm diameter. Here too: push very gently, and only use a rounded needle, no sharp one, which would damage the nozzle. Another thing that works: once the filament is removed, I sometimes gently clean the inside of the nozzle and teflon coupler with a brass M3 thread. Gently, always gently, grind the M3-thread up and down the teflon couper and nozzle. This works as a very soft file. Use brass, no steel which is too hard. I have rounded the M3-thread at the bottom, so it does not damage the nozzle internally. I have been using this for a couple of years now, without any problems.