Blobs, Extruding stops…

[polypolyp 0]

Hello, after solving some problems with the very helpful suggestions from forum members, I’ve managed to print some objects in a small scale. attached a photo of the evolution steps (from right to left). However, there are still lots of problems coming up with larger objects.

There are lots of blobs on the top surface of the layers (photo), so the layer becomes very bumpy. The Ultimaker support says this problem is related to the Cura software. I’m using standard settings, temp is 190°. Did anyone had the same problems?

Another issue is that after printing for a while, the extruding suddenly stops and it does not extrude even if I push the filament by hand. I read a lot about extruding problems on the forum, but the strange thing with my machine is, if I stop the print, the extruding stars again (Photo). Even if I start another print right after, the extrusion works well (for a certain time).

I have no idea what to do. Also, if I try to switch to another software as the support suggested, the software can’t establish a connection to the printer because the Marlin firmware for Cura uses a different baudrate.

Thanks for any help

[Daid 306]

Few things.

1) This is the first time I hear that support blames Cura for bad prints. Makes me kind of sad. I know they don't officially support it. But I didn't know they where going to play the blame game.

2) Your 2nd photos shows some signs of too little belt tension, you can see the infill is not connecting to the outline.

3) The bumps in the first layer you see in the 2nd photo are most likely caused by a bed which is set slightly to high at the start. The printer is extruding material for a 0.3mm layer (if you are using default settings), but if your bed is slightly higher then it is printing an excess amount of material. This excess material is pushed upwards.

4) 190C is very low. I almost never print below 210C. Most likely you are grinding your filament, or it's slipping because the amount of force required to print at 190C is very high. I highly recommend printing at 230C for starters.

5) Cura can run with the 115200 baudrate firmware found in RepG34, you need to change the baudrate in the preferences of Cura. And install the firmware from RepG34. You can also install custom firmware with:

http://daid.eu/~daid/marlin_build/

(The firmware in Cura is made with this builder)

[alaris2 1]

Daid's points #2 and #3 are absolutely correct from personal experience. however before adjusting bed height, consider whether you care about those bumps and how much you care..

the reason being, at the height you currently have (you probably used the tin foil levelling method?) you'll get really good first layer adhesion, actually it can be difficult to get ti off the bed when the print finishes, but change the first layer height to 0.1 or 0.2mm to reduce the 'bumps'.

if you lower the bed as I have now experimented with, you'll find getting the first layer to stick is way more difficult. in fact I've not successfully found a way to get the first layer to work unattended - it always requires me to fiddle with it a bit.

[rewolff 0]

What I've done to get the bed level is to have it print a big skirt, and then watch for consistency around the circle. If you position the skirt/object a bit smart you can even adjust the screws as it is printing the skirt.

[polypolyp 0]

Thanks very much for your suggestions!

Daid, the support didn’t blame Cura for bad prints directly. I once told them that I use Cura and in a replay they said that it seems to be a software issue. Probably they didn’t had in mind anymore what software I’m using. To me, Cura seems to be a very good software.

Printing with higher temperature solved the extrusion problem (thanks!). I lowered the temperature to stop PLA leaking from the nozzle (used ABS before filled the gaps).

Adjusting the right height for the first layer is very difficult. I also seems that sometimes the amount of filament which is extruded for the first layers is less then usual. Is there a trick to ensure that there will be enough filament extruded at the beginning of the print, so that it sticks well to the bed?

[Daid 306]

Ok. Yes, UM support does not support Cura (yet?) their support staff has to deal with a lot of issues, from hardware to software. So they only want to support one software package, one that they control. Which should be understandable.

In my own opinion, I think RepG is harder to support then Cura. But when they had to select software, Cura did not exist yet.

For these kinds of issues the forums usually get a faster response anyhow, because the community has a lot more people, and these problems are not uncommon.

PLA will always ooze a bit from the tip of the nozzle, but it shouldn't leak out of the sides. But in some cases it does leak from the connection between the heater and the PEEK or the connection between the heater and the nozzle. In that case you can use ABS to seal it, or disassemble everything and insert a tiny bit more teflon tape.

In Cura the first layer has a different thickness then the rest of the layers, in normal mode you can configure this in the advanced tab. The default is 0.3mm, which should provide a pretty thick first layer which sticks easier to the bed. (Getting a 0.1mm layer to stick properly, and come off without damaging the tape is very hard)

It should extrude enough filament at the beginning of the print. However if you let the nozzle drip empty, because you heated it up and waited a long while. Then the beginning of the print will have too little plastic. A quick remedy is to turn the big gear by hand at the start of the print if you see there is little to no plastic coming out. You won't damage the machine in any way, it can handle this.

[polypolyp 0]

Yes, I did the ABS trick to seal it, but at 220° the ABS starts to melt.

Unfortunately, the extrusion stopped again, even if I use 220°. What confuses me, as soon I cancel the print, filament suddenly comes out of the nozzle, while during running the print, even pushing by hand doesn’t help. Not sure if it’s a coincidence, but it seems that it stops while printing solid layers for a while (when parts of the 3D model merging, the slicing for this layers becomes solid). Strange, as far as I understand, there is no filament blocking mechanism in the printing head itself. How can it be that at certain moments no filament comes out of the nozzle and right after I cancel the print (just after a few seconds) filament is extruded again, even without feeding from the back?

[adhome 0]

Hallo,

I do have only 2 days experience. But perhaps your E Steps are not entered right? In the first run Wizzard you can calculate your right value.

It looks like that too mutch material will come out.

And try again lower temp. 170C° Perhaps your sensor is not working well. My was relly loose in the hole.

Your feed problem is strange. Perhaps you are touching the lower (solidified) surface and this will blockade the nozzle.

See "The extruder stops extruding"

http://wiki.ultimaker.com/Troubleshooting

 

[edgar-meyer 0]

rev.3 assembly guide says: " This becomes the adjusting screw to put the right pressure on the plastic so it will be transported by the groove in the M8 bolt. The white screw is for easy adjusting by hand, so it should be tight on the bolt."

--- How tight is "tight"???

Using the same Gcode with Cura, I have had pieces print for 7 and 3 hrs, respectively, before the PLA filament jammed, the hobbed bolt digging a groove into the filament

-or- more generally, why should the printer work perfectly for hours and then the feed mechanism jam?

[Daid 306]

It requires tweaking. And sometimes you have filament that has a different thickness throughout the roll, a sudden increase in thickness can also cause it to jam.

People are working on different ideas to fix it. For example:

https://groups.google.com/forum/?fromgr ... -BEHdvkDs8

 

[andytenbroek 0]

Hi,

I am new to 3d printing. I just have a 2 weeks experience, but I can say it's a lot of fun.

The thing I discovered with printing is that the quality of the prints always has to do with de hardware and not software. For instance belt tension, smoothness of the print head and all other moving parts (I oil it before every print with machine oil) and filament feed.

I too had the problem yesterday with the blobby ness when you have a 100% infill. You can also hear it because the print head bounces over the just hardened filament. (by the way I printed in pink PLA that I got from ultimaker)

Though the first few layers were absolutely flawless, after 20 layers the blobs came. My first thought was there is to much filament coming out of the print head. So I measured the thickness of the filament right under the extruder. There is a difference in thickness on the spool of filament, this also can cause a jam.

When you set the thickness of the filament in the beginning, the software will calculate how much filament is needed. But when the thickness changes on the spool, then you will have to much material coming out.

I thought of an idea that might prevent this problem. Is it possible to make a very accurate sensor, that measures the thickness of the filament constantly, and that the program running the gcode adjusts the material feed when the thickness changes? So therefore you will never have a difference in filament flow from the print head.

Thanks for giving it a thought.

Greetz,

Andy