geert_2

I also have this on small parts, for example on fine text of a few mm height. It indeed seems to be caused by the head stopping for a fraction of a second while retracting, and then moving on. I can reduce it but not eliminate it by reducing temperature and printing slower, for PLA down to 180°C or 190°C, and 20mm/s, for small parts.

The idea is not to reduce warping while printing, but to reduce internal stresses that would cause problems later on during the part's service life. A bit more about the background: when any parts are moulded in metal, glass or plastic (for example via injection moulding), they have huge amounts of internal stress moulded in due to the force of the flow that was used, and due to the always uneven cooling that follows. Edges and thin areas cool faster than the inner parts and big volumes. If you watch transparant parts of glass or plastic under polarised light, you will see al those nice color changes due to these internal stresses. If you bend the part, you see the colors changing in the areas of stress. (I 'll see if I can find a few pictures I made years ago.) These stresses will later on cause fatigue effects such as cracks or deformation of the part, although it may take months to show up. I have seen polycarbonate parts with fine details starting to totally crack after a year. If you leave such a part in a hot car, it is likely to deform due to the part getting closer to its melting temperature, and those stresses acting up. To relieve these stresses, after production the parts are subjected to an elevated temperature for several hours, or sometimes even for days (especially for glass lenses). This elevated temperature is around the glass transition temperature, so that the molecules have a little bit of freedom to move, but not too much. Then they will slowly "relax" and remove stress. When I do that with 3D-printed parts in a normal oven (I have a lab oven adjustable from room temp to +100°C), the parts will warp during the relaxation of the stress. So I need to put a weight on it, or clamp them while annealing. However, when printed freshly, the parts are still firmly "glued" to the glass plate of the printer. So there is no need to clamp them to avoid deformation, as they can't move anyway if the bonding was good. That is the beauty of Artiz' idea to move the whole glass plate into an oven *immediately*, before it cools down and the part falls off. So he can anneal it without corners lifting. We could use this same idea, but do the annealing in Ultimaker by using its heated build plate as an oven. To reduce heat loss, and to get an even heating, the model has to be covered. That could easily be achieved by putting a box over it, or isomo, or something similar, if the model is not too big. I would recommend only covering the model on the glass plate with a box that is a little bit bigger than the model. Not the whole printer, so that the electronics do not get subjected to the heat longer than necessary. In case of printing with PLA, annealing the parts may increase temperature resistance with 10 to 15°C, which may be enough for some applications. So they experience less warping when you use them in your car, for example. I have tried that: it did not eliminate warping in the sun, but it reduced it by at least 70% for my parts, which was enough. And we had a couple of very hot days this summer. Practically, I think a good starting point to test this concept would be to use the same bed temperature for the annealing, as used for printing that part. And then see if it sags or not, and adjust temperature accordingly for the next parts. If I have time next week or the week after, I will try. And yes, you are right that a huge drawback is that this method occupies the printer for a couple of hours. So it will not be suitable for people who are doing 24h serial production on their printers. But for others who don't print at night, they could use that time to leave the print stuck to the glass bed in the printer, and keep the heated bed on. I hope this clarifies the idea a bit more? I am not sure it will work, but it might be worth trying. Then the Ultimaker would double its function as both a printer and an annealing oven.

In another post user Artiz mentions as a side note that he anneals his polycarbonate prints by moving the glass plate directly from the printer into an oven, and let it sit there at elevated temperature for a couple of hours, to relieve the stress due to uneven cooling caused by the printing process. This seems like a very good idea. The advantage of doing this on the glass plate, immediately after printing (thus without the glass cooling down) is that the models do not warp as long as they sticks well to the glass. I have done annealing in an oven too, but only after removing the parts. In which case they tend to warp in the oven indeed. I did not do this to relieve stress, but rather to increase temperature resistance a bit (which seems to help indeed, although it does no miracles). But not everyone has a suitable oven, and not everyone likes to remove the glass plate from the printer every time. So I just got this idea: why not anneal the parts directly in the Ultimaker itself? After the print finishes, as soon as the build plate has lowered, immediately set the build plate temperature to the desired level (depending on the material). And keep it there for a few hours. Also immediately put a little plastic box, or cardboard or isomo box, on top of the model, so the heat is contained well. This should be easy to do, should increase temperature resistance of the parts, and should avoid or at least reduce warping. Might be worth experimenting with? I haven't tried it myself yet, but I thought I would let you know the idea already. Otherwise I might forget.

If you *tune* the speed up to 150%, then you not only increase printing speed, but also traveling speed (which is usually much higher than printing speed). If traveling speed would for example have been set to 200mm/s, then that would become 300mm/s after tuning, which might be higher than the maximum the stepper motors can handle without skipping. Could that be the cause? When playing around with tuning speed up very high, just to see what would happen to my extrusion, I experienced something similar. I would suggest you try setting the printing speed at a desired high value in Cura (or whatever slicer you use), but without increasing traveling speed above a safe maximum. See if that works?

Since about 10 days I wipe the nozzle with non-stick silicon oil prior to printing, and then again after each print. I use the sort of silicon oil that is also used for easier release of castings from a mould. Since then I have no more build-up of molten material under the nozzle. Maybe you could try that? First clean the nozzle's outside thoroughly: warm it up a bit (to 120°C or 150°C or so) and wipe it clean with a tissue. Then spray silicone oil on a small paper tissue (but do this far away from the printer, so that you get no oil on the build platform, which would destroy sticking). And wipe the nozzle with that tissue. After a print, immediately clean the nozzle and wipe it again with oil. Apart from the brown spots I think your models come out quite nice, regarding those small details. Reducing temperature might also reduce the amount of brown goo, but that could also reduce layer bonding, so that might not be a good idea.

Do you make them on a vacuum thermoforming machine where the model and the plate to thermoform are both placed under a heater, and the hot molten plate is then pulled over the dental model, and sucked vacuum? (Such as the Erkodent thermoforming machines?) In that case, probably the heat is the main problem. PLA starts getting soft from around 50°C, and your thermoforming plate is heaten to maybe 120 or 150°C or so. So I would suggest that you try printing the teethmodel with 100% infill, just for testing, and that you put that model in the freezer prior to thermoforming. Do not yet insert the model in the machine while this is heating up, but only insert it at the very last moment when the heating is finished, and when the molten plate is ready to be pulled over the teeth model. So that the model is still ice-cold when the hot plate is pulled over it. (But only if your machine allows this manual handling, of course; since this may not be possible on fully automatic machines.) Then try to cool the whole thing as fast as possible, with a cold fan blowing over it, or so. Try if that works, or do you still get deformation? Otherwise, try printing in a material that can withstand much higher temperatures.

I see that you print with 2mm filament? I guess by that you mean: "2.00mm", is that correct? could you check that again? Normally, the filament should be 2.85mm (which is sometimes referred to as "3mm filament"). So, if you use 2.00mm filament indeed, you will sure get underextrusion, since the printer expects a much thicker filament. The surface area of 2.85mm filament is about twice that of 2.00mm filament. So you need to accurately measure the filament diameter and set this correctly in the settings (but I don't know where to find that setting), or you need to adjust flow rate accordingly manually. If this is the cause indeed, then increasing temperature will make the layers bond better, even with underextrusion, but it will not cure the real cause: not enough material. A too hot temperature might even burn the PLA in the nozzle, or make it decompose chemically and reduce strenght. Using filament that is too thin will also cause other issues, such as back flow in the nozzle, and twisting in the bowden tube.

I never use the official method to change filament. It goes much easier in this way: - Remove the horseshoe clip on the head, and remove the bowden tube from the head, with the filament still in it. Since the Ultimaker2 does a large retract after each print, this goes easy. - Move the material 1 cm forward, and cut off that irregular molten end. This eliminates the risk of getting that irregular blob stuck in the feeder, or getting the thin string in the feeder. - Do an atomic pull to remove the remains of old material from the nozzle, and to clean it at the same time. Do more atomic pulls as needed until the nozzle is clean. - Pull the old filament manually out of the feeder from the back. (You may need to switch off the printer first, if it can not be moved.) - Replace bowden tube and clip. Switch the printer on again. - Change material settings to the new material. This will give the new material the correct temp. - Insert the new material and use "Move material" to forward it to the nozzle. This requires quite some rotating of the knob. - Manually try extruding a little bit, using the "Move material" function. - Exit the "Move material" function, so the material does not get burned in the nozzle. And that's it. In this way you have no risk of incompatible temperatures, no incompatible materials in the nozzle, no risk of a deformed material end or a thin string getting stuck in the feeder.

The software seems to be their own development. The basic idea is brilliant, definitely worth remembering. But at this moment the distortion seems to be too much concentrated in a few small areas. If the distortion was more equally distributed over a much larger area, this would greatly improve component life, I think.

I used to say that 3D-printing was not accurate enough to create smooth dolls like barby dolls or so. But obviously I need to revise that statement. Then a question: instead of using a brush, have you ever tried using a spray bottle? The sort of bottle with a hand pump, and adjustable spray nozzle, which people also use to spray plants? If the spray could be adjusted fine enough in a fine mist, without big drops and pooling, then you wouldn't need to touch the model while spraying. So you have less risk of getting marks on the model. Or would that have other side-effects?

As Didier says. I also had this once when the 230V power cable came loose from the power supply. After that I made a clamp from steel wire, so that the power cable can never detach by itself. Never happened again. Also, on the Ultimaker2 (I don't know about the plus), the little power connector at the back of the printer needs to *click* into place. Otherwise it is not inserted deep enough. I would check these first.

If you would ever have an issue with PLA not sticking well to the glass plate, try my "salt method" first: dissolve some table salt (NaCl) in water, and use that to wipe the glass plate. Let it dry into a thin mist of salt stuck to the glass. This gives an excellent bonding when hot (60°C), and no bonding at all when cold (20°C). Salt and water cost you nothing. - For Ultimaker and colorFabb PLA: excellent bonding, no corners lifting at all, no need to use brims or whatever. - For ICE-PLA: still good bonding, but not perfect: occasionally corners of difficult objects (big, 100% filled) do lift a bit. But it only works for PLA, not for ABS. I have not tried any other materials. See the PDF manual and pictures also: https://www.uantwerpen.be/nl/personeel/geert-keteleer/manuals/

Does it need to be 3D-printed? Another option might be to print a negative in 3D, thus a mould, carefully sand that so it has a perfect shape, and then use that to cast the models in any appropriate material? For example polyurethane? This comes in a lot of different qualities, from hard, to tough but still hard, to very flexible. If it needs to be stiffer, or reflective, you could add in filler particles, such as metal. If you need a lot of copies, this might be the fastest way? In Youtube, search for: mould making and casting, to get an idea.

My printers were too busy to print a FilCatch thing. So I decided to model one out of steel wire (chromium steel, inox, very hard and with spring-effect; the same steel as used for dental retainers on kid's teeth). But apart from that it is the exact same concept as yours. I placed it on a height where the nozzle just touches it when moving across. When the buildplate rises, it also touches the steel wire, but due to the spring steel, it bends upwards and then bends down again without damage. This works well too, and it should live longer than a plastic one. So, thanks for that great idea. This might be a solution for those cases where 3D-printed ones wear out too fast? See the photos:

Hello Sander, Did one side of the glass plate get a special surface treatment to get different specs? And if so, which one, and why exactly (in chemical/physical properties)? Having a better understanding could help in case of other adhesion problems too.

I would suggest you handle all sensitive equipment yourself: cameras, computers, 3D-printers... Or let it do by reliable family or friend. Some transport companies will do a good job and be very careful. But I have also seen postmen unloading a train by just throwing the boxes out onto the concrete floor, which was a two meter drop. Even boxes labeled with the "fragile - glass" symbol. To survive that, you would need 0.5m of shock absorbing material around anything.

My two UM2 printers were delivered with 4GB Sandisk SD cards. Obviously they work. I don't know if it are SD or SDHC (I can't pull them out now since the printers are busy).

What I would certainly do, is have a small object printed in front of my eyes. Then it is obvious if it works well or not. Maybe also print a big low object (e.g. 200mm x 200mm x 0.5mm) that almost fills the build plate, then you see if all axes move fine. Carefully watch and listen. Also ask about the PTFE couplers in the nozzle (the white cylinders): have they been replaced recently? If not, they will be worn out and you will need to replace them.

I am not sure if PLA is the best choice for this. There do exist special filaments for casting. I haven't used them, and don't remember the names, but I saw a thread a few months ago. Maybe you could find that? There were waxes and other materials. If you print in wax, attaching other wax parts should be less of a problem. PLA might leave black ashes when it is burned away beforehand. And if you pour hot metal directly onto it (without burning it away prior to casting), it might catch fire and explode in your face.

Even if you would succeed in printing this in one shot, it is likely to break when removing the supports, due to the very thin items, and since they are printed in the "wrong" direction, not along the layers (like wood cut in the wrong direction, instead of along the direction of the fibers, is also very brittle). If you can edit the model, it might be worth trying to split it up in several parts: railings apart, stairs apart, etc... And then print each part flat on the bed, without supports, and glue them together. Like the model railroad houses we built as kids. This would cost you less material, less printing time, and probably look better and be stronger.

That FilCatch is a nice idea: I use to do the same manually with a pincette, but this would automate the process. But for sharpening the filament tip, cutting it off in an angle of 45° to 60° (thus in a sharp point) with an electronics cutter seems way faster and easier. Then it can easily be inserted in the feeder too.

Apart from all other solutions above, what about rotating that model 45°? Almost all skulls are way narrower than long (and I have seen quite a few in our dissection rooms). Then it might fit on the platform? But whatever orientation you print it in, any round object is always going to require a lot of support structures which need to be removed and which will leave marks. FDM-printers may not be the best option for printing skulls, balls, skelets, or similar things; and nor may lithography printers (laser in liquid bath). For this sort of model, in real size, I would rather recommend using a powder or sintering-based printer (such as Onshape's nylon printers). Some of our surgeons use nylon sintered models for replicating human bones and parts of skulls, and they look fine. You need to carefully study specs and use the right tool for the right job. Preferably before buying anything. If you want to print it with good quality on any FDM-printer, it might be a good idea to cut the model in smaller parts, make sure that each part has a nice flat side on which to print it (to eliminate the use of support-structures), and glue those parts together afterwards.

Just to make sure: it's not about layer thickness, but about layer surface. (I use Cura 14.09, where all layers have the same thickness, except the first one.) If I have a model which has - at a given point during printing - a surface area of 10cm2 on let's say layer nr. 86, and then that surface area suddenly changes to only 1cm2 on layer 87, then that big change in surface area will be visible on the side walls. It causes a "thick line" on the side. On models where this is an issue, I usually print multiple parts at the same time (so each layer gets enough cooling time to almost environment temperature), or I print a dummy block next to it. I have also tried designing a small "complementary dummy model" to print together with the real model. This complementary model would have the opposite shape, a sort of negative, so that each layer would get exactly the same surface area. But that was way too much work and wasted too much material. So that was a once-only thing, without conclusive results.

I have tried it a couple of times now: I sprayed silicone oil on a tissue and wiped the nozzle with it, prior to starting each print. Results: on the white PLA filament there is still a little bit of build-up of molten filament on the nozzle, but less than before. And it is way easier to remove afterwards than before. On the orange PLA filament there is none. (Both filaments: ICE brand.) Further, the extruded sausages do no longer curl up and stick to the nozzle when starting a print: an unexpected result, but of course good. So it is definitely worth trying. I think I am gonna make it a standard of my preparation too. Thanks for that tip.

Yes, this is even more simple, definitely worth trying. I just hadn't thought of it... Why make things simple, if we can also make them complex?