Issues printing complex object
Hi,
I was trying to print a complex vase with Taulman T-Glase filament. First 19 hours of print were fine, until the printer reached horizontal unsupported areas. I noticed that the print head and pinda probe were hitting the printing area. Cant find a good explanation how could that happen. I would think that areas without support would just sink down instead of raising up. Also under those areas that have long span and do not have much support i noticed that the surface is bumpy. Also noticed burned spots.
The model: http://www.thingiverse.com/thing:28052
Anyways, here is the result:
Would appreciate any help to solve this.
Thanks,
Ruben
Re: Issues printing complex object
I'm going to guess you're using the standard 0.4mm nozzle and you're printing layers with a thickness of 0.25mm or less, which is normal. The material is round coming out of the nozzle, but the movement of the printer axes flattens it. When you print PLA, that's basically the end of the story: the material cools quickly right were the printer put it, flattened, ready for the next layer.
PET (T-Glase is PET), however, sticks to the nozzle a little more than PLA does, so bits of PET accumulate on the nozzle. Most of those bits fall off quickly, leading to bumps on the layers and irregularities. Some of the bits stick for a while, burn, and fall off once charred. PET also doesn't stop flowing as easily as PLA does, so it makes strings.
I have high hopes for the new E3D silicone sock:
http://e3d-online.com/Socks-Launch
They're out of stock at the moment due to unexpected demand, but I ordered some anyway. In theory, the sock should solve most of the problems I've seen with PET and other materials that tend to stick to the nozzle.
Meanwhile, I've learned to set up PET prints very carefully on my MK2:
- 235C on the first layer (a low temperature, to prevent excessive bed adhesion) and 250C on the rest of the print to promote inter-layer adhesion.
- 50% fan starting on layer 2 or 3. (The fan is required for cooling layers, but 100% is far too much.)
- Print no faster than 40 mm/s. Outer layers and top layers should print at 20mm/s for a clean surface.
- Travel moves should be at least 120 mm/s to reduce stringing (since strings are especially likely to stick to the nozzle). Be sure to switch the motors to high power mode when moving so quickly.
- Don't let the slicer generate rapid, short fills. This is a problem especially relevant to the thin walls of a vase: the slicer generates 1 or 2 perimeters, detects that the remaining part of the wall is too thin for another perimeter, and fills the interior with rapid short bursts of filament as an approximation. Slic3r and Cura both do it; Simplify3D can be told not to do it. PLA tolerates that behavior but PET just accumulates material on the nozzle when it happens. If you see this, try using no infill or changing the width of the perimeters.
Re: Issues printing complex object
Also, you should consider printing taller layers, like 0.3mm, so that the nozzle doesn't have to smash the layer very much. Less smashing could mean less contact between the layer and the nozzle for less accumulation on the nozzle. Taller layers are also faster to print, although they can hurt the quality of overhangs.
Re: Issues printing complex object
First of all thanks for detailed reply!
I'm using standard 0.4 nozzle and sliced using Slic3r with default "0.10mm DETAIL" profile. Also used "Taulman T-Glase 1.75mm" profile. I was trying to reuse existing profiles. Still not completely comfortable with messing with the configuration numbers 🙂
The settings of those profiles are:
-) perimeters: 40 mm/s; small perimeters: 20 mm/s; external perimeters: 25 mm/s
-) travel: 120 mm/s. I've been using silent mode so far. what is the difference of high power? Why is this setting available to the user?
-) "Taulman T-Glase 1.75mm" profile only cools the bridges with 40% fan speed.
-) Found another profile: "Prusa PET 1.75mm". It does cooling in some "auto" mode ranging from 30% to 50%
Also I've seen some prints with a remote square island object. By any chance is it made for a purpose of nozzle cleaning?
Re: Issues printing complex object
Yes, the remote island is called a "prime pillar" and it attempts to wipe the nozzle on every layer. I haven't tried that solution yet. It's certainly worth a try.
High power mode is useful because while moving quickly in silent mode, a stepper might fall too far behind the electromagnetic position and miss a step, ruining a long print. It's a user setting because the printer can't tell when it misses steps--there's no rotary encoder.
Every material has both a maximum and minimum extrusion rate. If you extrude some materials too slowly, they stutter and spurt. (PLA supports a wide range of extrusion rates.) With a layer height of 0.10mm, perhaps you're extruding the material too slowly. I would try 0.20mm or 0.25mm layers. When working with translucent materials, taller layers usually have better optical clarity. I've even seen a recommendation to print 1mm+ layers for maximum visual effect, but that probably wouldn't work with this model due to the overhangs.
Re: Issues printing complex object
I was able to get a pretty good print with using the "Prusa PET" profile. It uses 30%-50% fan. Also turned on high-power mode. In few spots there are burned filament areas but less than a millimeter. Overall pretty happy with the result.
Re: Issues printing complex object
That's great to hear! 3D printing can be so fun.