Sintron Prusa I3 under extruding badly but strangely..

Hello, i have a Sintron prusa i3 which i have been using for the last couple months,
Over the last weeks it has given me headaches with the extruder which i cant pinpoint the failure.

in the pics you can see the first layer which almost doesn't print, but if i let it run the print ends up decent....only fails a bit when head moves to new position to extrude.


Been trying different temps, from 190 to 230 for PLA, calibrated the stepper driver, checked my extruder and cant find whats wrong.
have freed the extruder and pushed the filament trough the hotend by hand, and it extrudes well while trying to run a print.
Switched stepper drivers, still the same.

my last attempt will be checking ptfe tube , but since it was change not even 2 months ago, and i print normally around 190 degrees, should be good.
After that i can only change the extruder stepper for a new one more powerful since its a 2.7kg/cm and i could buy a 5kg/cm...
my extruder is an mk8 direct drive, also my first layer is super slow(15mm/s).
Any comments? thanks.

Typical problems with the MK8 extruder are:
Drive gear got loose on the stepper shaft. Especially on cylindric shafts without a flat spot.
The lever that holds the idler gear got loose. Remove the fan/heatsink and check the screw in the elbow of the lever.
The grooved bearing of the idler gear is not aligned with the throat of the hotend. I had to shim it with a thin washer.

Your print looks underextruded to me. Maybe you could clean/replace the nozzle, it might be partly clogged.

Ok...
changed ptfe and nozzle (although nozzle is a cheap ebay chinese), checked drive gear good, idler good. still crappy extrusion

Now i increased extrusion multiplier to 1.4 and its much better, not good but decent ...

So, i got 2 last things, nozzle which i ordered one new, and a motor, also....could be filament, gonna order a roll from my original seller.

one thing i also don't know its that i hear lots of bubbling in first layer...maybe its nothing, but when filament touches the glass with hair lacquer it bubbles a lot, next layers doesn't happen.

Also my new filament comparing to old one is 1.70mm versus almost 1.8mm so less filament being pushed, dont know if it makes such a difference

Edited 1 time(s). Last edit at 07/23/2017 06:57PM by oinquer.

If the extrusion multiplayer is set to 1.4 then your steps/mm might be wrong. The multiplayer should be set to 1.0 =- 0.1

Are you printing with a skirt to prime the nozzle or do you have a nozzle prime in the g code? Sometimes it takes time to get the plastic flowing, adding a skirt will give the plastic time to start flowing. This will also explain the bubbles as there will still be air in the melt zone. If you get the bubbles any higher or hear a poping sound then there might be moisture in your filament.

As for the print failing a bit when it changes a bit, look at your retraction settings and make sure that enough plastic is being extruded after a tool movement.

If you have not done so before, have a quick read through of the calibration guide on the wiki [reprap.org] lots of good information on getting the right print settings

i always have a 2 loop skirt around my piece, and its more than enough since the last loop is always perfect.

my steps are well calibrated, did the math and got a few confirmations around the webs, after printing at 1.4 i seen too much overextrusion, now will try at 1.25, im pending back to the filament maybe being the culprit, look at this:

in the photo its all bent instead of round, and the reel is all like this. seems BQ filament has this problem...an youtuber already pointed it out...

already ordering a good reel of filament to test.

Looking at the pictures you posted I could not see the skirt, why i suggested it, so we can rule out priming.

When you say you did the math for the steps I'm guessing you mean XYZ and thats fine, but the E steps still need a bit of fine tuning to make sure if you say to extrunder 50mm of filament it feeds 50mm of filament into the extruder.

Back to this after a couple weeks, i'm gonna let this end and blame filament.

After all tests and stuff verified from our talks, i tried to print some stuff with a bit filament i had from other good vendor and its printing much better, with this filament (BQ filament) although its a bit better than initially its still bad., already ordered new reel for my original vendor and will try again to verify!

THANK YOU GUYS!