Problems with Top Layer

Hi everybody.

I build a Prusa i3 Hephestos about three weeks ago. With the help of this forum I managed to get some decent prints up to now. Had some issues with z-axis calibration and such, but that's solved.
But now I have an issue that I can't seem to solve.

I've been calibrating the printer now for three days. Printing One-Layer cubes without top or bottom layers with different temps and speeds. All works fine. But wenn I try to print something with a top-layer all seems to go wrong. (See foto)

I'm printing PLA with temps from 200 to 220 C. I'm using slic3r and repetier host. I've even set the speeds to low values around 30 mm/sec. The bottom layer prints good and slow. The sides and the infill are good and slow too. But wenn it comes to the top layers, the machine goes crazy. It suddenly speeds up and does the top-side boundary really fast. It then tries the top layesrs with the same fast speed.
I can't seem to find the right adjustment to slow that down.

I'm assuming that the fast speed is the cause for the problems with the top layer, because everything else works fine. The extrusion seems fine. The widths of the one-layer boxes are around 0.4 mm, just what the should be.

Data:
prusa i3 Hephestos
Extruder: witbox extruder
Nozzle: 0.4
filament: 1.75 mm
extrusion multiplier: 1
layer height: 0.2 mm
first layer height: 0.35 mm
perimeters: 3
horizontal shells: top 3 and bottom 3
infill set to 30% honeycomb
speeds set to 30mm


Can anybody point me in the right direction?

Karl Dabsch

I use simplify3d so I can't help you much with other slicers, but 3 top layers isn't enough for a 30% infill to close all the gaps, I usually set anywhere from 4 to 6 top layers (most of the time 6).

On the slicer look for infill speed and reduced some, usually 80% is standard.

Also make sure you measure the filament and use that exact measurement in slic3r. It's very common for filament to be a bit undersized and that will affect the coverage. If you don't already have one, invest in a digital caliper as it's a much used tool in 3D printing.

Hello everybody.

After a five hour session after work yesterday I'm getting good prints again. I had a fresh install of Slic3r at work. Send the virgin "simple mode" config back home and installed it after work. Also increased the temps to 230/first layer and 225/other layers.

Seems to work. Still don't know what I did wrong. Is it normal to print with pla at 225 C?

But one thing I've learned in the last few days. When a 1 kg roll of filament falls on your printplate, you have to recalibrate. You just have to.

+ggherbaz: That's a good point. Didn't need to do that with the other colors but I'll try that after work.

+tmorris9: I tried that. I got an averige of 1.69 for the white filament. But when I put that into Slic3r, the machine seemed to underextrude a little. After I set Slic3r back to 1.75 mm it was fine again. (At least for the bottom and sides).

Peace.
Karl Dabsch

225 is hot for PLA, but not unusual for certain colors and speeds. I print between 190 and 220 depending on color and speed. But be aware that high temperatures might have undesirable efects, the lower the speed the lower the temperature needs to be.

Hi.
+ggherbaz I printed some small drawers last weekend with the white pla Filament. I did the first one at 220C.
The edges warped up a few milimeters. So i decreased the temp on the second drawer to 200. The warping
did get better. So for the third drawer i decreased again to 195C.

That's when the prusa went ape shit. I guessed the temp was too low. Then i started to mess with all the
speed settings and the conundrum started.

To check the temps, I made a one layer cube without tops or bottoms. It was 30 mm high. I started with 220C
and weht down with the temp every 5mm. The Video where i got this from said that you will notice when the temps
are too low by how the outer layer looks. I went from 220 down to 195C, but didn't see any difference. That's wenn i concluded that the temps can't be all that important and my previous problems must have had another reason. Boy was i wrong.

But I'm learning.

Karl Dabsch

Edited 2 time(s). Last edit at 02/21/2015 03:31AM by Dabsch.

I know you are using slic3r, but try curaengine. After starting with slic3r and then going to curaengine, my prints are considerably better and slicing takes like half the time of slic3r. I will admit that I liked slic3r's arsenal of settings, and that cura lacks quite a bit that slic3r does, but cura seems to be better overall. I originally switched because slic3rs raft is broken.

half your infill speed for top layers. the current speed may be pushing the flow limit of your extruder design, and decrease pla temp. higher pla temp may make it flow faster because it reaches melting temp equilibrium faster, but it also will not cool fast enough for the bridging to not sag on its own weight. if possible turn up cooling fan, lower temp to 190c, and see your results. if at 190 your flow rate significantly drops, then you are already exceeding normal performance of your machine. it could also be that the layer heights are thick enough that flow rate can not keep up. can you verify that temp is actually 190c, or simply check room temp of extruder and verify it is 17-30 deg c?

also it is important to have several top layers to allow for an even top surface to form because you need filament to be able to squish down, I would have at least 1mm top layer height. so if doing 0.25mm, then do at least 4 top layers. have at least 3 top layers.

also the space gaps between the perimeter shells and the top infill layer suggest that your flow rate should be increased. there are also a lot of 0.4mm nozzles that are actually 0.45mm. get detailed specs, or measure diameter with a micrometer.


experimenting with different slicers as well may be beneficial.

let us all know the settings you use in slic3r

as a side note higher print speeds are with really good extruders, and extremely powerful cooling.

Edited 4 time(s). Last edit at 02/22/2015 08:33AM by jamesdanielv.

I would say : underextrusion + pillowing + number of top layers too low. See : Ultimaker troobleshooting guide.

---

Collective intelligence emerges when a group of people work together effectively. Prusa i3 Folger (A lot of the parts are wrong, boring !)

Hi everybody.

As I've discovered on the weekend, I have some serious underextrustion. But just intermittent. For every 100 mm filament I try to extrude, only about halt of that ist pulled into the extruder. The first thing i checked was the nozzle. With the kit i had gotten two 0.29 mm needles. I inserted one into the nozzle, an it moved freely. So i don't think i have a blocked nozzle.

Next i took the extruder apart and put it back together. Right after that the full 100 mm were pulled in. Then I startet a print. Everything went ok for the first oh, 20 minutes. Then it went bad again. I stopped the print and checked the extrusion again. Again only about half was beeing pulled in?!? Wenn i pulled the filament out, there were some scratches on it, as if the extruderpulley had slipped.

As far as i have read, that could have several causes:

1.) the pulley that pulls the filament into the extruder is worn. I have held that thing in my hand, but it was the first time i saw something like that, so i couldn't really tell. There was some filamentdust in there which i cleaned out. Also a filament splitter was in there, about 4 mm long. I will get another one today at lunch. Come to think of it, there was one thing. A few days after i finished my build, and after a few smaller successful prints, i tried printing something bigger. The problem was that i had apparently crossed the filament on my roll and when i wasn' looking it had snapped. Can that damage the pulley?

2.) the stepper motor doesn't get enough current. Will try that if the pulley wasn't it. But since the printer did do relatively normal prints from the start, i'm unsure here.

3.) the tension on the extruder pulley is to low. I have a Witbox extruder. It's all metal. Didn't find anywhere to adjust that.

4.) filament diameter is too low. I am using the bq-filament. As far as i have measured, it's pretty close to 1.75. As an average I got around 1.72. Don't think that small a difference can cause 50% underextrusion.


+iamdarkyoshi
I have cura installed. Have used it only to load the Marlin 1.4 hex onto my printer. As soon as i get the other problems licked, i'll give it a try.

+jamesdanielv
The highest speed i have set is 50mm for the perimeters, everything else is lower, exept the travelspeed which is set at 130mm. The info on the prusa i3 hephestos says that 50mm are recommended.
The temp is probalby too high. I guess i was trying to compensate for the underextrusion. Will lower that.
Haven't touched the layers. On slic3r they are preset to 3 layers top and bottom.

+Zavashier
You are right. Underextrusion is my main problem. The pillowing is probably a result of my increasing the extrusionspeed in repetier host. Won't be doing that again. The interesing thing is that increasing the extrusionspeed compensated for the underextrusion. At least for a little while. I have absorbed the link you provided. Some good info. Didn't find that on my google searches.

Another thing that may (on not) be relevant. A few days after I build my printer, i ruined the small 40mm fan that cools the extruder. I replaced it with a 40mm noiseblocker i had laying around. But the noiseblocker only turns with ca. 1000 rpm. Is it possible that because of that the extruder istn't beeing cooled enough? Have read something about heat creaping up the extruder. Didn't have any blocking though.

So, totally confused, i'll try again this evening after work. This machine can make some good prints. Maybe one day i know how to, too.
Karl Dabsch

Hi.

Got some work done on my machine yesterday. Tried to exchange the extruder motor with a stronger version. The one build in was a 1.7 Ah Nema 17. Yesterday i bought a 2.4 Ah Motor with a new Extruderpulley. Was very surprised that i didn't have the tools for it. The pulley has a maggot screw that needs a hex screwdriver with a size between 1.9 and 1.3 mm. Of course, i didn't have the one i needed. Back to Amazon on this one.

Anyway, while putting it back together i looked at the old and the new pulley. They seemed the same. No wear on the old one. Next i played with the pot on the driver for the extruder. Turned it back and immediately got some strange motor noise. So i turned the pot to the right a little bit more that it was.

Most of the underextrusion is now gone. It went from about +50% underextrusion to about 10%. It gave me that amount consistently yesterday, not like the days before where the underextrusion varied from 80% down to 30%. The surfaces of objects are still being filled badly, but it's better than before.

Guess now is the time to look at the e-steps. The store i bought the set from said you shouldn't have to mess with those setting because the software was preset from BQ. Don't know what to think about that.

Also played with the temps. But is still don't really see any difference between 220C and around 200C. Will try a lower temp in the evening.

Here i have to bitch a litte about my extruder. The prusa i3 hephestos used to come with an extruder where you can change the nozzle. It costs about 10€. Now they switched to an all aluminum extruder where the nozzle and extruder are in one. Now if the nozzle cloggs, you have to change the whole thing and that costs 70€. Don't know if that's so smart.

Priorities for today: Get that hex screwdriver i need. Put that new motor in. Maybe work some more on my prusa i3 hephestos voodoo doll. Already have some nice big pins to put in that.

And the big question: Am i having fun? Oh yeah!

Peace
Karl Dabsch

Hi people,

my frustration level is on the rise. Yesterday evening i replaced the extruder pulley and the extruder motor. The motor was only a 1.7Ah so i thought maybe it is to weak.

Didn't change anything. Now the stronger motor starts clicking. I played with the current -screw on the driver but to no change. I have the current set to max now but the pulley still slips. The extrusion i'm getting varies 50% and 90% of the 100mm it should push through the extruder. I took away the fan and heatsink from the extruder to watch the pulley. It is slipping and making those clicking noises. Also, when this happens, i can't push the filament through with my hand either.

It almost seems like the plastic doesn't want to go through the hotend. It seems to start of ok. Then the motor starts clicking and the extrusion stops or slows down to a crawl. When that happens the plastic curls up right under the nozzle and bunches up until plastic starts to come out again and the stream of filament resumes. The diameter of the filament that is extruded is what it should be, 0.4mm.

Then i played with the steps per mm setting. the eeprom reads 100.45 for the extruder. (Its a Witbox all-metal extruder where the entire hotend is in one piece) According to the formula i put in 300. Didn't change anything. the extrudermotor tried to turn faster but didn't change the extrusionrate. I put that back the way it was.

I'm starting to think that the hotend ist somehow partially blocked. I bought some 0.4mm drillbits yesterday and insertet one into the hotend from the bottom. It went in without problems. The thin needle that came with the kit (0.29mm) goes through to the top. I don't understand that. What kind of hotend blockage can cause the extrusion to vary by that much and still lets the needle go completely through the hotend? I've only put about 1/4 of a filament roll through that hotend so it can't be wear and tear.

Can anybody point me in the right direction? I've been all over the forum here and can't seem to find anything.

Yesterday i was so close to throwing that thing out the window. The little store i bought the kit from is no real help either. When i tould the guy there about my extrusion problem a couple of days ago, the guy looked at me as if i were talking in spanish.

Karl Dabsch

increase your top layer into 5. i am using slicer.and set your temperature to 190 if you are using PLA.set your speed into 40 for the top solid layer..

Hi people,

+ignacio_3D
Thanks for the answer. I too, am using slic3er. I have alle speeds set to 30mm/sec right now. The coldest i've tried to print is 195C. Will try going lower later. I planned to increasing the number of top layers. But have to wait until the machine works again.

A few minutes ago i took the hotend back to the store. They will test it in another machine. On first glance the man said that the hotend is clean. Lets see what happens.

Karl Dabsch

Edited 1 time(s). Last edit at 02/25/2015 09:50AM by Dabsch.

Hi,

Just got news from the store. The hotend ist clogged. They testet it and it showed the same symptoms. There is something wrong wirh or stuck in the hotend. Will go back tomorrow and get a loaned one while they look at it. I don't think i dropped anything in there?!

By the way, i'm impressed with the service. The guy there immediately offerd to test it. Take back all criticism from yesterday. Great service. That's why i bought at a local store instead of the internet. There are some things you can buy from the internet, and some things you shouldn't.

Peace
Karl Dabsch

Nice that they offered to fix it, my anubis got clogged to the point where it couldnt be fixed, so i got an E3D V6, and I love it. I am rebuilding the printer, and every time i try to print something huge (I always need to be near it incase something stupid happens) it skipps steps whe I am not looking. Every time I turn the current up, it fixes it, and a week later it misbehaves again...

Good evening from Vienna and from a "happy pappy"

Got the loaned hotend from the store and installed it. Everything works! I'm printing some letters in different temps and speeds. The hotend nozzle is a bit bigger than the one i have, but i will adjust that with slic3r.

+jamdarkjoshi
I looked up the e3d v6. Looks like a serious piece of kit. I like that they kept the replaceable nozzle. If my hotend had that, i would have spend the 10€ a week ago. Live and learn.

It will be a busy weekend.

Karl Dabsch