geert_2

You missed stone-fills. I found that plain white (colorFabb) is also slightly abrasive. On one of my printers I only printed colors (mainly orange, red, natural, blue, pearl, from both Ultimaker and colorFabb), and on one I printed almost only white. After about 800 hours of printing on both, the "white" nozzle is clearly worn: the flat area at the bottom of the nozzle is larger than that of the "color" nozzle, which is still fairly original. The inner diameter of both nozzles has increased from 0.39mm to about 0.41 or 0.42mm. I haven't counted the amount of white spools I printed: maybe 6? I guess this is due to the filler particles used in the white, to get a thick opaque color. But I have no idea which particles they use: talcum? Titanium dioxide? Other? So, nothing to worry about if you print only a few spools of white. But if you print white for 24h/day, you should keep an eye on this.

The scale of 1:72 is way too small. You are likely to get the following problem due to insufficient cooling, because the nozzle is hanging around too long on the same spot: Further, due to the large nozzle size, compared to the details in the models, any fine details will be lost anyway: noses, lips, eyes, hair style, fingers,... The face will be just an unrecognisable blob. As a kid, I have painted lots of figures that small for my HO-trains. I had to "paint" the eyes and mouths with a sharp needle, because even the smallest brushes (size 000) were way too big. There is no way to get a decent print quality (=recognisable face) with an FDM printer at 1:72. I recommend making them 10cm high, at least, but preferably more: 15cm or 20cm. And print slow and cool (try 180 to 190°C for PLA, at 20mm/s). Give them a big baseplate around their feet for good adhesion to the glass (and cut that off later if necessary). A size of 10cm will be much more pleasant and recognisable. Maybe print multiple at once: this gives more cooling, but it also gives more strings and hairs due to the traveling from one object to another. If you absolutely have to print them at 2cm high, use another printer, with a laser in liquid bath, or have it done by a print service company, but that is less fun. There do exist printers that can print microtext: legible text of 0.1mm high, so they should be able to make such small figures too.

I use this on an UM2: - PLA: always on. Bed at 60°C. - PET and NGEN: off when the model allows it (e.g. a thin flat model without overhangs), then it can be printed on bare glass. On at 40...50% if required to prevent overhangs from sagging, but then it requires bonding aids (dilluted wood glue or so) to prevent warping. Bed at 80°C.

Just out of curiosity: I always thought that you needed a primer color that was identical or very close to the final color, so that defects or scratches would be almost invisible. Then why would you use black as background for gold? Or does that give any special effect? Similar to the "red wine metallic on gold" that is sometimes used in special car paintings for a deeper gloss in the red metallic?

You could manually file it, but anything mechanically that works at higher speeds (like grinding disks), or with more force, is likely to melt it. Even gentle drilling, or thread-making by hand, or cleaning edges with a dental drill (similar to a Dremel, but can work at lower speeds), do melt it. I have a big water-cooled grinding disk: this produces some particles (together with dust and debris from the disk itself), but it also melts the grinded part to some degree, thus creating fibrous blobs instead of powder. So the resulting powder is not usable as a product.

There is also a risk of bending the rods by atomic pulls, if you do them too brutally, or by lifting the printer by pulling on the rods. I am not saying that has happened to your printer, it's just as precaution. If you want to use a more gentle atomic pull, try this method: https://www.uantwerpen.be/nl/personeel/geert-keteleer/manuals/ Instead of pulling brutally, this method uses gentle wiggling and twisting instead, plus much deeper cooling to room temp, before reheating. But no brute force at all. Cleaning results are similar to the standard atomic pull. I should update that manual a bit, but meanwhile you can still use it.

It could be a visual photo-effect, but there appear to be other deformations too: the shape being oval instead of round, different ring thicknesses... I have no idea what a Prusa printer looks like, but I would guess this is caused by too much play in the mechanics? So, when changing direction, you get a sort of hysteresis effect?

Depends on the printer brand and type. FDM-printers and most laser-cured liquids use the same material as the print itself, in fine support structures. Powder based printers don't use any support: the powder supports the model. Some expensive industrial printers (50.000...100.000 euro) that I have seen, sometimes used a support material that dissolved in caustic (I don't know what material exactly). And the Objet-printers which have a system that looks like an inkjet printer (=ejecting liquid drops, which are cured by UV-light) also uses some sort of gummy washable material: it is washed off with a high pressure water jet. Could be PVA-based, could be something else?

Do the missing layers show up in other views, or when you travel down layer by layer? Very occasionally in a few models I also had similar gaps in the layer-view, in an old Cura version. But this was just a rendering issue in Cura. In other views (normal, transparant, x-ray) everything showed up okay, and when viewing the missing parts layer by layer, they also showed up correctly; and most important: they printed fine. If they are also missing in all other views, or shown in red in x-ray view, then obviously it is a model-issue.

If that is printed upside down (thus as shown in the Cura-view above), then the overhangs are probably too big: then the printer always has to print the outer layer half in the air without anything supporting it, so it deforms: it sags or curls up. Try printing this as slow and as cool as possible, and maybe try placing a fan in front of the printer. I would try 190°C and 25mm/s, with a desktop fan in front at low speed, and see what that gives.

What about printing only the frame of the sails, and filling in the sail with real tissue? If you use modern tissue like used in sports shirts (thin and a bit shiny), this would probably look the most realistic. If you want it to get a fixed shape, you could wet it with dilluted wood glue or so, set a powerfull fan to it, and let that dry. Then you could redo it if required by wetting again.

As far as I can see, no FDM 3D-printed model is food-safe: they all contain little holes where food rests can accumulate, and bacteria can get a good grip, so you can't wash them out. I think the printer nozzles are not going to be the problem: they operate at +200°C: not much bacteria are going to survive that. And the wear is very low, otherwise there would not be a nozzle at all anymore after a few meters of printing filament... Wood-filled material is even going to be much worse than unfilled plain PLA, obviously, due to its porosity and natural materials which can be eaten by bacteria and fungi. There is a reason why people do not recommend cutting meat on a wood plate, or why doctors discard the wood spatulas after they used it in a patient's mouth. If you want to use food-safe materials for printing toys, just to make sure the kids won't get poisoned by ingesting cadmium or poisonous plastics, when they accidentally bite in it, then PLA and PET would be "safe enough", I guess. If you want to make drinking cups, spoons, forks, dish plates, and similar stuff for repeated use in the mouth, nothing is going to be safe.

I believe 230°C is too high for PLA, at least at normal default speeds. Then it would soon burn inside the nozzle and get brown. Try 210°C first. Also, did you check if the little fan at the back of the nozzle does work well? If it does not, heat will travel upwards into the filament, and soften it way up there. This could cause blocking due to "swelling" (actually the half molten filament is squeezed together). This is for an UM2, I don't know how it looks in an UMO or UM3.

What happens when you sink most of the model into the build plate, so only the offending top parts are visible and printed?

Slowing down will probably not be enough: if the nozzle stays too long in the neighbourhood of the already printed areas, the radiated heat will still prevent the part from cooling down. Since I often have small models, I tried all sorts of different solutions. For such small objects, now I always design and print a dummy model next to it. The dummy needs to have a sort of "inverse" or negative shape of the real model, so the total printing time per layer is equal: this is important for good quality. Sudden differences in layer printing time (and thus in cooling time) do show up as horizontal lines in the print. One way you could do this, is make a cube that is slightly bigger than your model, move a copy of the real model into the cube, and subtract it. So the dummy cube now has a hollow of the same size as the real model. Then create a bottom layer of 0.5 mm under the hollow part in the cube, to get good adhesion to the build plate. And make sure that the dummy is at least one layer higher than the real model (typically 0.1mm or 0.2mm). When printing this dummy, sausages of filament will sag down into the hollow part, but this does not cause problems in my experience, as long as there is a solid bottom layer under the void. Printing this at the lower edge of the temp and speed range of the material, also helps. For PLA you could get down to around 190°C and 20mm/s. Putting a desktop fan in front of the printer also helps for PLA, but is likely to cause warping for other materials. Yes, a dummy wastes some material. But less than you would waste when you don't get any usable models. You could also recycle the dummy cubes and use them as "houses or hotels" in Monopoly, or as pawns in other games...

I once read about people drilling a small hole from an opposite side into the nozzle, or in an angle, so that the sensor could be pushed out from the back? I never had to remove a sensor yet, so I am not sure if this would work? Anyway, you would need to take great care that you don't drill through the filament feeding channel, nor come too close to it (could hurt heat distribution). Using dislodging oil, and very gently tapping (not hammering!) on stuck parts to make them loose, might also help: this is commonly done in old cars, to dislodge corroded screws. The very light tapping for some time breaks the bonding due to oxidation. So I would try this first.

I have had that with PET and using dilluted wood glue as bonding. During cooling down I already heard weird cracking sounds. When I took off the model, it required very little force, but the glass was chipped. So it probably chipped already during the cooling cycle. Anyway, even with full cooling, I had absolutely no warping during printing. Now, if the model allows, I try to print PET without any bonding aid, and use less cooling (to prevent warping). Never had that sort of thing with PLA, using the "salt method" as bonding aid (=wipe the glass plate with a tissue moistened with salt water, leaving an almost invisible mist of salt). If for a particular model and material, I would ever have to use any bonding aids like dilluted wood glue or hair spray, I would probably try neotko's release method: this releases the model when still warm, thus should give less risk of chipping due to different shrinking of glass and model.

In injection moulding, all manuals clearly state that you carefully have to dry the materials (usually ABS, nylon, PC,...) before starting to mould. Otherwise your models will be ruined. There is no reason why this should be different for 3D-printing with the same materials. But you really should try it: cut off 50cm of nylon filament, leave that out in the open air for a day, or let it sit in water for an hour, and then feed that manually into the nozzle after removing the bowden tube. And compare that with a dry piece of filament fed through. You will clearly see the steaming, and hear and see the bubbling of the moist filament. Then inspect the extruded sausages under a microscope or under a big magnifying lense.

If you are not allowed to operate the printer yourself (like in schools where students have to submit their designs to an operator), your best bet would be to kindly educate the operator. He may not be aware of bed leveling methods or bonding methods. Don't blame him or her, but offer help and give facts: that is easier accepted.

If your cables are damages, maybe you could use some silicone as insulator? Normally, silicone is heat resistant up to 220°C ... 250°C; but there may also be high-temp versions. Or use shrink wrapping for cables (not sure if that is the correct English term): the sort of black tubing that you put around cables and then shrink with heat from a heat gun or soldering iron.

Just out of curiosity: while printing with the old nozzle, did you closely watch what happened exactly, so why the hairs occured in your case? I am trying to understand, if an worn out nozzle would cause this, then why? Is it also the same filament as before?

Depending on the amound of identical masks you need, another option might be to print one mask, glue that together, adapt it, and sand and post process as required for good surface quality and fit. And then make a silicone mould for casting additional masks in any material (except silicone). Or make a plaster mask, seal that, and use that for casting in silicone. Or use the 3D-printed model to vacuum thermoform additional masks, if you have a vacuum thermoforming machine at your school. Once you have a good mould, casting usually goes faster than printing for big parts. All these methods could be very educational, so you could do it in class, or on a free afternoon, with some of the kids.

I guess by "fluffy" you mean: sort of hairy, but not with thick strings, but rather very thin hairs? As far as I have seen on my printers, there are two main causes for strings and hairs: - Strings (=rather thick wires) come about when the nozzle leaks while traveling over a gap, and it leaves a string behind, or the leaking drop gets deposited on the side of the next object upon reaching that. - Hairs (=very thin) come about when there is a bit of overextrusion, or when molten material accumulates on the outside of the nozzle. And then, as the nozzle passes along the model, this molten material sags down, touches the already printed parts, gets very lightly attached and leaves a hair behind when it is pulled away by the nozzle. Both happen more when the printing temp is rather high. So printing cooler and slower (=less pressure in the print head) usually helps. Some colors and materials have this more than others. This is what I have seen, but of course there may still be other causes too.

You can find the full manual on the "salt method" here, with a lot of photos of the results and limitations: https://www.uantwerpen.be/nl/personeel/geert-keteleer/manuals I should update it, but meanwhile it is still useful.

If you print 4 or 5 "skirt" lines around the object, this also allows you to verify and if necessary fine-tune the distance between nozzle and print bed (at least on UM2 printers, I don't know if this still applies to UM3).