Hi all, new to the forum and the 3D-printing. We recieved the Velleman K8200 for a course in school. We have had some problems along the way with a wallowing z-axis and a broken contoller board but now it’s printing. Things was fine for a while but now I’m stuck and can’t seem to find any existing answers.
So, what happens is that the extrusion is not consistent and sometimes mostly air comes out or it comes out in small blobs, held together by small plastic strings. When extruding air bubbles are visible in the melted plastic and sometimes it sound like someone is popping bubblegum bubbles to find any likness, however the sound is not as loud. The perimiters i have adjusted to 200% in Slic3r.
Repitier-Host v0.90C, Slic3r Version 0.9.10b
My thought is that the extruder is not pushing out material fast enough and would thus like to adjust the e motor steps. I have googled how to do this but can’t find any guide. I remember seeing something written by Kuraasu here on the Forum but can’t seem to find it agian.
If anyone has experienced the same problem or know what it could be a result of I would be really happy for some help!
Hi, yes I do. 3 mm Velleman PLA coloured green (actual diameter 2.91 mm)
About the temperature, I have not verified the temperature readings. Any tips on how to meassure this in a decent way? Will it be enough with a cooking thermometer?
I’m not sure whether that’s a good idea. If your extruder does not transport the correct amount (i.e. length) of filament, then a calibration of the E steps is of course necessary. However, if the E steps were ok before, you shouldn’t have to change them now.
Adding to VEL417’s questions, is the thermistor mounted correctly, inside the hole in the heater block? Which temperature did you set for the extruder?
Iirc that was one of the more troublesome versions of Slic3r. 0.9.9 is often used as an “old” version, and the current one, 1.0.1, is also quite ok. However, the extrusion problem is not caused by this.
Thanks for your replies! I will try to look at the temperature, the thermistor is however mounted inside the designated hole in the heater block. I will also test a newer version of Slic3r.
Any other ideas to what could cause it? And does it sound like it’s too hot or too cold?
I’d say it’s rather too hot, but you can check it yourself: start low, say at 160 or even 150 °C, and increase the temperature stepwise. Test whether you can extrude a bit of filament by hand. Below 170 °C, the PLA should be quite viscous, and extrude only with high force in small amounts. Above 170 °C that should change into low viscosity and low force. Plus / minus five degrees won’t matter, but if the PLA is fluid below 160 °C or only above 180 or even 190 °C, something’s wrong.
Do you have a second type of PLA available for testing and cross-checking?
Another possibility is water: PLA absorbs moisture. Unfortunately, the effect differs a lot depending on the additives (coloring agents etc.), so there is no one-fits-all solution. But you can try to dry some of your filament and see whether it prints better. A usual oven should do, just don’t apply too much heat, since PLA starts to soften at ca. 60 °C. After one or two hours, the moisture in the plastic should be reduced to a minimum.
If you want to make it a double test, you can also store another length of filament in a plastic bag with some wet cloth or paper and test that, too.
You also need to check the extruder gear to make sure it turns freely and consistently, and also check the pressure roller tension. Your problem does sound to me to be more like a lack of feed to the filament rather than a temperature issue.
there are several possible reasons for your problem:
The extruder gear slips on the extruder motor shaft. Make sure, the screw holds the gear tight on the shaft without any slip. You can set a mark with a felt pen and check this out when the extruder runs.
As steve_b said, the spring of the pression roller has not enough tension. Every printer and filament has it own needs there, but you should not let the tension screw full out. A good starting point is to set it somewhere in the middle, not fully in, perhaps two or three rounds in.
The pression roller can not move properly because the two screws are not properly filed down as described in the manual.
kuraasu said it, the temperatur eventually is not measured correct. You have checked the position of the thermistor already, but there could also be a problem with the electrical insulation of the thermistor’s wires. Have you checked the temperature curve for irregularities?
You can check if you have to change your E-steps following this procedure:
Mark your filament at e.g. 150 mm above the extruder hole, perhaps with a felt pen.
In the “Manual” tab of repetier let 100 mm extrude at a common printing speed, perhaps 30 mm/min.
After the extruding has stopped, again measure the distance between the hole and your mark. The distance should now be around 50 mm (150 - 100 = 50).
That are all ideas for the moment, hope you get your printer running properly soon,
I’m also having this issue. I’m using the sample PLA that came with the printer so I assume it’s Velleman brand (it was just loose in the box, no spool or branding).
Even forcing it through by hand I get the bubbles, does that mean it’s too hot and possibly letting air mix before it can be extruded? Or maybe the feed rate too slow? I’ve only printed a couple of things and all of them have been lumpy so it’s not an issue that has cropped up over time, but one that’s been there since the start. My IR non contact thermometer doesn’t seem to be reading properly and the only other one I have only goes up to 110 degrees celsius so I can’t use that.
When pushing it through by hand, should it be really easy to push, almost like toothpaste? Or should it require quite a bit of force? Do you recommend heating manually and pushing it through, and the temperature at which it only just starts to flow is the temperature I should use?
first thing to check is the correct position of the extruder thermistor. Is it sitting in its hole?
The filament itself can be a problem too, PLA can adsorb moisture if stored in a place with high humidity.
Yeah, the thermistor is in the right spot, there’s only one place it can be. I managed to find a higher temp thermometer and when set to 170 degrees, the head is actually at 190+ so at 190 degrees it was way over temperature.
Also the e-steps were too low so I raised them up, lowered the extruder temperature.
IMHO it was a stupid move of whoever wrote the firmware to comment out the eeprom chit chat variable. It should have been left enabled to see what the e-steps were and to easily correct issues. Bad form.