Blobs Blobs Blobs..

[Linas_capas]

Hello everyone,

I have just finished my Mini Kossel and right know i am frustrated alot, because of the blobs.. I have read almost all posts on forums, however, still no solution found for blobs.

I have tried changing retraction settings, coast distance, wipe distance, extra retraction distances etc. etc. and basicaly nothing works.
In second picture, it can be seen, what happens, when i set wipe distance to 5mm. I get tiny blob 5mm before a huge one.
Other photo, also, FFF file for last print (the stone man). Many blobs, and thicker lines (over-extrusion) before retraction?

My setup is e3d v6 bowden, 1.75mm colorfabb filament, 190 degrees temp, 0.4mm nozzle, 0.2mm layer height. Other information can be seen in FFF file.

Please help me, as I am loosing faith completely.
Thanks

[jimc]

controlling blobs is all about relieving nozzle pressure. your blob is basically at the start of your extrusion after a travel move which is pretty normal. one thing that makes this impossible to control is moisture. if your filament is damp then no matter what you do its going to be impossible to control that. you will end up with very inconsistent results. ok, as for settings, the blob at the end of the line is controlled by coasting. the blob at the beginning of the line is controlled by retraction and restart distance. try increasing your retraction just a little more and also add a little negative restart distance. maybe .05-0.1. start there as see what happens. you want the smallest amt of neg restart you can get to give you good results. in advanced tab be sure only retract when crossing open spaces is unchecked and perform retraction during wipe movement is checked. overextrusion will also cause excessive blobbing as well as extremely wide extrusion widths for the nozzle size. both of these increase pressures in the hot end.

[Linas_capas]

controlling blobs is all about relieving nozzle pressure. your blob is basically at the start of your extrusion after a travel move which is pretty normal. one thing that makes this impossible to control is moisture. if your filament is damp then no matter what you do its going to be impossible to control that. you will end up with very inconsistent results. ok, as for settings, the blob at the end of the line is controlled by coasting. the blob at the beginning of the line is controlled by retraction and restart distance. try increasing your retraction just a little more and also add a little negative restart distance. maybe .05-0.1. start there as see what happens. you want the smallest amt of neg restart you can get to give you good results. in advanced tab be sure only retract when crossing open spaces is unchecked and perform retraction during wipe movement is checked. overextrusion will also cause excessive blobbing as well as extremely wide extrusion widths for the nozzle size. both of these increase pressures in the hot end.

Thank you for your reply.

However, I have dried my filament, so moisture is not key issue here.
I have tried changing retractions from 1 mm up to 5mm with speed from 50mm/s up to 120 mm/s, extra retraction distance from 0 to -0.4mm, coasting distance from 0.2mm to 2mm, nozzle wipe from 0mm to 10mm in various increments, temperatures 170-220 degrees, NOTHING works. I am very disapointed by ongoing problems.

Maybe anyone has any other tips/solutions? Desperate cry for help here

[jimc]

i run an e3dv6 which is great but you are using a bowden setup which is much different. it requires more of everything to control the blobs. realistically by the size of your parts and the size of the blobs i personally wouldnt even call it a blob., rather a spec. they are quite tiny and its not really bad. they could be improved slightly with the right combination of ooze control settings. any way you look at it there is a start and stop to every extrusion line. i generally collect them all together so they make a seam. it always looks much better and you can put it where you want on the model. every plastic part has a seam. even injection molded parts. perhaps someone using a bowden setup could give you better starting points for settings.

[Kulturfolger]

Hi,

I found a few things in your FFF file:

1. The extrusion width is set to 0,39 which will cause issues as this is smaller than you nozzle diameter.
2. The outline overlap is way to high. With 30% you get what you hold in your hands: the infill pattern is sticking out at random places.
3. Is there any reason for infill extrusion width "200" Percent? This adds up to the outline overlap.
4. Let me guess: You changed these parameters to cover up bad layer bonding? Printer hotter and check your fan, these errors tend to occur on one side, if the cooling air from the fan is blocked on some side.

Ingo

[AK_Eric]

Not that I'm providing any solutions, but more of an observation: I have both a direct-drive bot and one with a Bowden setup: Almost never get blobs on the direct-drive, nearly always get blobs on the Bowden. I've spent months trying to minimize them, but they've never entirely go away. Both extrusion types have pros\cons, and blobbing is a known con of the Bowden :S

[Kulturfolger]

Hey AK_Eric,

This sounds like the PTFE offers to much play or is slightly twisted. While the printer head is moving the tension given to the PTFE-Tube changes the friction within the PTFE tube. These pneumatic tube connectors add to this, they move slightly als well. Weak printed extruders can bend and twist. An all metal direct geared extruder is the best to go with an bowden hotend.

Did you use the exact same hobbed Hobbed Bold on both extruder types?

Ingo

[AK_Eric]

Thanks for the thoughts on my setup Kulturfolger (as I now hijack this thread) : The hotend is (currently) a .6mm E3D-v6 Volcano nozzle, but I've also used a 1mm nozzle in the past. Where that metal hotend attaches to the X-gantry is all 3d-printed, but it's locked down pretty tight, there's no play in there. However, the PTFE tube that connects from the bowden extruder to the hotend does have some play, based on the (plastic) push-fitting into the extruder-side: I can see it hop up/down a few mm during extrusion/retraction: Are you suggesting that's contributing to the blobs in my stuff? Makes complete sense to me, but I've yet to find the "Bowden support group", so even though I've been trying to improve this for months, I'm by no means a Bowden expert
You can see a closeup of my hotend here: http://www.akeric.com/blog/?p=3374
And the Bowden extruer in this pic : http://i1.wp.com/www.akeric.com/blog/wp ... bowden.jpg

Looking through my parts-bin, I found another style push fitting (brass) that offers zero play (compared the plastic one I have in there now that provides play) : When my next print is complete I'll swap them out, see if this helps my blobbing issues any.

For the hobbed/drive gear: I'm pretty sure they're different (although look darn similar) : The one on my Rep1 is... whatever Makerbot built them with, and the one on my Bowden C-Bot is this one specifically:
http://www.ebay.com/itm/MK8-Drive-Gear- ... 1543133069
Which seems to have plenty of tooth.

[Kulturfolger]

You wrote "I can see it hop up/down a few mm during extrusion/retraction". If the E3D would work as an direct extruder, the retract would be below 1mm. I would add 2mm more retract for the bowden. You loose all the precision with moving push-fitting, thats senseless.

[AK_Eric]

New push fitting installed, seems pretty locked down (no discernible slop). Now I just need to print something else. Been so busy.... But if I notice a blobbing difference I'll post back. And agreed on the retraction : My Rep1 direct-drive has 1mm of retraction, and blobbing is nonexistent.