How can I improve blobbing on holes?

[truenorthtrader]

Hello

I may have posted this before but with no result

Prints where I have holes always leave blobs on the inside of the holes and I have to do judicious sanding though I've seen rostock prints that are clean.
If holes are square doesn't seem to do it very much but mostly on anything roundish.

I already installed a new 4mm J-Head hot end with quite a bit of improvement but still have blobbing so must be something else.
Tried different travel speeds from 100-250 and no improvement

Any insight?
thank you all again

[bubbasnow]

throw up a pic lets see what u got

[truenorthtrader]

Yes was late last night when I posted, here are a few
Note I've had my Rostock since the Kickstarter and have calibrated it over and over trying to find the problem, bearings checked, filament measured with digital caliper, belt tightness, arms, bed calibration, extruder flow calibration everything seems good can't figure it out.

As you can see the picture of the Vase I made with square holes is much cleaner although I used a mouse sander to smooth the outer surface which was fine but wanted it smoother. On Solid models perimeters look good.
Thank you!

[Glacian22]

What slicer are you using?

[truenorthtrader]

I use the newest version if Cura that came out recently.
Slicer is never as good
I also upgraded the firmware this week and repeteir is up to date
Thanks!

[Polygonhell]

Blobs are usually one of a few things, insufficient retraction speed, insufficient travel speed, or if it's the temperature might be a bit high.

In the first case you get the blob at the point where the move starts, in the latter two cases, it's at the end of the move.

Basically the head sits still while retracting, and can leave a blob if that takes too long, and if it takes too long to get to the end of the move, or the temperature is too high, the nozzle dribbles during the move.

[bubbasnow]

i also get blobs if the nozzle has picked up some material from earlier in the print, and deposits it elsewhere.

I would try to make it blob with a test print, watch if its because of material coming out of the nozzle, or if its because the nozzle had picked up some from elsewhere.

I haven't used cura so, I'm not sure about retraction/wipe/fill density/prime stuff but if you can give us more details about where in the tool path this is happening it would help.

if solid models are coming out good, but its really an issue of blobbing where the nozzle picks up and puts down it would be nice to know. i would like a wipe/prime setting or min distance to wipe/suck/prime might be the trick.

[truenorthtrader]

Thank you sir! Messing with those settings now for a good combination

[626Pilot]

The annoying thing with Bowden systems is that there's significant hysteresis between what the extruder motor is doing and what's coming out of the nozzle. The higher your average volume over the last few seconds, the more of it is going to ooze. Some things to try would be thinner layers, slower print speeds, or more conservative jerk/accel settings to let the filament "slow down" before it hits a retraction point.

[truenorthtrader]

626Pilot where do I adjust jerk settings? That sounds like it could be it. I checked Arduino saw under Configuration.h
#define MAX_JERK 20.0
#define MAX_ZJERK 20.0

Is this it? If so how much to increase?

I had this problem with the stock Hot End, not as bad with the J-Head but it can't be the nozzle as I tried 2 already.

The Bracelet was .2 or o.18 already thin layers. The Octagon thing was .22 or .24 no difference really except it's much bigger.

The Blobbing appears right after retraction when it's leaving the print area, then even as it hits the new area.

I have travel speed of 280 and it's still the same as when it was slower.
I tried lowering the temp 5 degree's to 218 for ABS, upped retraction from 55 to 70 and from 4.5mm to 7mm haven't noticed any change.
Not sure how much I can increase retraction speed

Will try more difference in temp and such on next print tonight
thank you all!

[626Pilot]

I would not be messing around with these things by editing defines and recompiling. Repetier will let you modify this directly from EEPROM in real time and observe the results. Try setting the jerk to 6 instead of 20 and your acceleration to 1000 if it isn't close to that already.

[truenorthtrader]

Yes thank you so much! I adjusted settings but looks like it's still doing it.
Here's my Eeprom settings just incase I screwed something up there

I'm really surprised that after changing the temps, retraction speed and amount, travel speed and now the Jerk and Acceleration there is absolutely no change.
I hit M500 in Repetier and changes were sent. I even restarted Repetier and rechecked and settings are updated.

The new print was stopped as there was no point continuing it.

[Eaglezsoar]

Are you using the Steves extruder?

[truenorthtrader]

Yes Steves Extruder only changed to a J-Head Hot End, everything else stock

[Eaglezsoar]

Yes Steves Extruder only changed to a J-Head Hot End, everything else stock

Have you calibrated the Steves Extruder lately? This is an area that could cause some of the problems you are seeing.

[truenorthtrader]

Thanks for the suggestion, I just recalibrated, chose 30mm and pushed exactly 30mm. at 560.00 setting

I actually lowered it to 540 because the nozzle kept touching the print after about the 20th layer but now that I'm using glass and Kapton tape with ABS juice it might not knock prints off.
I also had to adjust the flow of 75 in Cura but I'll put it to normal and see what happens now.

I'll try the bracelet again
thanks much!

[ccavanaugh]

I had a similar issue with my H1-1. It turned out to be a consistently slipping Steve's extruder that would grab and over extrude at all the wrong times. Once I sorted out the slipping, most of the issues went away.

The new SeeMeCNC extruder nozzle vs. the original design helped significantly also.

[626Pilot]

I don't think filament flow rate is what knocks prints off. I had to change my delta arm length to get my printer to stop doing that. (Trick Laser arms)

Your EEPROM settings look OK. I would say, try messing with retract settings and upgrade to the EZ-Struder. The reason for this is that you have a shorter Bowden tube, and that's a win all around.

[lordbinky]

Try increasing your jerk and accel: Mine are Accel:2000 and Jerk: 80 (I suggest starting at 40-60 though), do that for your Z height jerk as well.

What's the motor current in your firmware. I think steve's extruder doesn't need as high a current as the ezstruder but when hunting down problems it's best just to eliminate potential sources. Also, I don't know what to suggest for steve's extruder's upper limit for retract speed, but increasing that helps with blobbing as well.

Try slicing with kisslicer and see if it's the overlapping in G-code that might be an issue as well.

What is your print speed? Higher print speeds should make blobbing less likely because you're stretching the filament more than at slower speeds, so it would be less likely to creep over the edge of the previous layer as it settles.

[truenorthtrader]

Hey I tried all the suggestions and ever recalibrated the Extruder, machine and did PID as well.
Extruder doesn't seem to be slipping everything probably as set as is possible, not even any ABS dust on the rollers, tight so can't move it, but not too tight

The result is still pretty bad. I printed a model while I was away and it turned out with broken parts, the nozzle is still hitting the piece or the blobbing is curling up and hitting the nozzle.

I just increased all the access to 2000 and 80 for both Jerk settings in the EEPROM and try again

I tried low temps and higher temps for ABS. This last pic was at 220. lower than 214 and things stop sticking, higher seems to get more blobs.
thank you all so much!

[truenorthtrader]

Took Extruder apart again and it's working perfectly but same blobbing problems.
My Jerk is 60, Accel settings are at 2000 and extruder acceleration at 3900 ( tried from 200 to 4500 )

Here's a slow motion video of printing of a holed part. Seems like some retractions like the last one are way before they should be.
https://www.youtube.com/watch?v=W2Sn5fqdsY4

Tried temps from 217 to 230 no change.
Could the temp of the hot end be way off what it's showing?

Solid objects come out gorgeous, calibration items are perfect, but holes are always a problem.

Am I expecting too much? Are other printing like items experiencing this?

Upgraded extruder looks like the only option?

very puzzled

[truenorthtrader]

Hey folks I may have solved it ( if anyone else has the problem )

I increased the Jerk to 80 from 60 and lowered the extruder accel to 3000 and set the layer height at .3 ( J-head nozzle is .4 ).
That's all I changed and as you can see it's not blobbing even at .3!!!

MERRY CHRISTMAS EVERYONE!
You're all a fine bunch of people, hope you all have a great time.

[Nylocke]

Ive gone as low as .1mm with a .4mm nozzle, .24 is nothing. I never print above .2mm, even with a .5mm nozzle.

[truenorthtrader]

That's good to know! Austin been the jerk settings then.

[Flateric]

I personally do not use cura, but had a similar problem recently with blobbing and solved it by lowering my extrusion width value.

I have a theory that I was trying to push too more than appropriate through for the nozzle size I was using.

Try this after you are fairly certain you have explored and gotten your retracts and temps correct.