Excess Extrudate (blobs) on circular perimeters

[CoffsEmma]

When printing circular perimeters, there is excess extrudate (my
technical term for a blob :-)) being deposited where the nozzle moves
to the next perimeter or layer.
There is a slight pause (fraction of a second) when the nozzle does
this move and it is during that time that the blob is deposited. It
doesn't appear to be ooze, but does seem to be extruded. The blob on
every layer causes a ridge in the finished print. The issue doesn't
seem to be related to retraction.
See http://www.datacorp.net.au/emma/3d/Cylinder_3.jpg for an example
of the issue. the image is of a single wall 30mm cylinder. The link
to the stl file is http://www.datacorp.net.au/emma/3d/Cylinder_30mm.stl.
If someone could try to print the item and lete me know if they also
experience the same issue that would be great.
I would also love to hear any suggestions on how to resolve this
issue.
I have tried every setting under the sun in sprinter, marlin, slic3r
and skeinforge...and both PLA and ABS...all to no avail.
Current config...
MG Prusa
1.75mm extruder
.35mm nozzle
Ramps 1.4
Marlin
Slic3r 7.1
Pronterface

Cheers Emma

[NCBob]

Have you calibrated the steps/mm on your extruder?

[Jay Couture]

Need to know more about the speeds and feeds in your slicer software (let's pick Slic3r). X and Y, and the Z moves.

• http://richrap.blogspot.com/2012/01/slic3r-is-nicer-part-1-settings-and.html  scroll to the  Understanding Slic3r Print Settings-  section. Z speeds are set in the retraction area. Do you have any "Retraction length" specified, and do you have any "Extra length on restart" extrusion specified?
• What material, what temperature of the hotend?
• Layer height?

-Jay

On Wed, Apr 18, 2012 at 5:14 AM, CoffsEmma <em...@mrichardson.com.au> wrote:

When printing circular perimeters, there is excess extrudate (my
technical term for a blob :-)) being deposited where the nozzle moves
to the next perimeter or layer.

 

I would also love to hear any suggestions on how to resolve this
issue.
I have tried every setting under the sun in sprinter, marlin, slic3r
and skeinforge...and both PLA and ABS...all to no avail.
Current config...

Cheers Emma

[CoffsEmma]

Hi Bob,

Thanks for your reply.

Yes, the extruder steps/mm calibrated in Marlin, and as can be seen
from the cylinder image (single wall .2mm layer), the rest of the
print (and other prints) is good with no horizontal ridges or other
issues. I have a 40mm fan on the x carriage which prevents the PLA
curl on overhangs. So all good except the excess on the layer/
perimeter change.

[NCBob]

Then Jay is on the right track in what to check. I'll try printing that same part today as well.

[CoffsEmma]

Hi Jay,

Thanks for your reply.

Have tried what seems like every possible permutaion of settings
available...
Retraction and no retraction and everything in between. As high as 3mm
at 30mm/s and as low as .5mm at 7mm/s.
I usually have 1mm retraction, .3mm lift, 15mm/s speed, 0mm Extra
length on restart, 2mm min travel after retraction. I even tried a
negative 'Extra length on restart' which only caused a poorer print.
The retraction is working as I can feel the retraction when holding
the filament near the extruder inlet during a print.
I have tried every speed for perimeter and infill from 30mm/s to 60mm/
s, with little difference in result.
Mostly use .3mm layer height but also sometimes .2mm which although
make a better print, makes no difference to the excess extrudate
issue.
With PLA I use between 175deg and 195 deg with no difference to the
excess extrudate issue.
With ABS I use 215deg to 235deg, again with no difference to the
excess extrudate issue.
I had already read the richrap.blogspot.com articles on Slic3r and
feel I was up to speed on the settings.
On closer investigation I have also found that the issue only occurs
on layer change and not perimeter change.

Cheers Emma

On Apr 19, 3:26 am, Jay Couture <jay.cout...@gmail.com> wrote:
> Need to know more about the speeds and feeds in your slicer software (let's
> pick Slic3r). X and Y, and the Z moves.
>

>    -
>    http://richrap.blogspot.com/2012/01/slic3r-is-nicer-part-1-settings-a...
>    scroll to the  *Understanding Slic3r Print Settings-*  section. Z speeds

>    are set in the retraction area. Do you have any "Retraction length"
>    specified, and do you have any "Extra length on restart" extrusion
>    specified?

>    - What material, what temperature of the hotend?
>    - Layer height?

[NCBob]

Ok, just tried to print it with almost the same settings you had, the big difference is I have a .5 nozzle and 3mm filament.

While I did get a little bit of blobbing at the transition points, it wasn't near as bad as yours.

If you don't mind my asking, how did you calibrate your extruder?  I know that when I first did it I still was getting blobs, but then Neil walked me through his method and ever since then I've had very few issues relating to my extruder.

The way Neil showed me was to take a straw and measure it exactly 100mm.  Then place it on my filament and mark the top of the straw on the filament with a nick using an exacto knife.  Then I extruded 100mm using Pronterface and measured with a caliper how far it extruded.  Then I took that and factored it against my current steps/mm and used that value.

So if it extruded only 90 mm I divided 100/90 then multiplied that times my steps/mm and that was my new steps/mm

[CoffsEmma]

Hi Bob,

Thanks for testing the cyclinder and your feedback. I follwed a
similar method to you to calibrate the extruder, but instead of a
straw, I marked the filament and measured with digital calipers. I
repeated this process a few times to am confident the extruder
calibration is very close. I also repeated this process a couple of
days ago to confirm that this wasn't an issue.

Some additonal information though...
Yesterday I removed the extruder motor and found that the filament
drive gear had an ever so slight amount of movment on the motor shaft.
I removed the drive gear and the reduction assembly from the motor. I
also found that there was a slight amount of movment between the drive
shaft and the bearings in the reduction housing. The bearing appeared
to be ok with no roughness when rotated (as I would expect considering
the kit is only a couple of months old). I applied a small amount of
Loctite 641 Retaining Compound to the shaft where it went through the
bearing and also to the bearing shaft and filament drive gear. This
removed what little movement had been present. This made only a very
small improvement to the blob issue though.

The blob is an issue whan printing single or double perimeter things
and seems to be hidden enough on the inner perimeters when using 4
perimeters. The blobbing also seems to be reduces when using slowe
speeeds 20 or 30mm/s.

I appears I will destined to continue my quest for the holy grail of
perfect prints for the time being...

Cheers from Emma

[Trevor Lewis]

I know this is probably pretty obvious, and you've likely already done it, but have you tried different filament? I've had some total crap filament before that just won't make good prints. No matter how I tweak things.

[NCBob]

Well I tried my print with some Chinese filament which is of pretty low quality, I wanted to really stack my test against it succeeding. I'll have to give it a try again with some good filament and see how it comes out as well.

By the way did you have cooling turned on in slic3r, and also you might want to try 7.2b as well to see if you get a difference.

[Jay Couture]

So I played with Slic3r a lot yesterday, and pretty much anything I did with retracts had no impact. I did modify my configuration.h to increase the Z acceleration setting from what I was using, but the biggest impact was dropping from 195F to 190F. Here is a photo http://www.flickr.com/photos/jaydmdigital/7103236101/ I think you'll see where the seam comes from. Based on this, I see no way to eliminate it.

-Jay

[CoffsEmma]

Hi Trevor,

Thanks for the suggestion. I have used both PLA and ABS from different
suppliers, and the same issue appears on both, though as I am new to
the sport of 3D printing, I am not yet sure what constitutes good
quality...only time and comparisons will tell. So you might be correct
and when I try a different supplier the issue might not occur. Or
maybe I just need to sacrifice a virgin on a full moon and sell my
soul to get the 'perfect print'...

On Apr 22, 11:29 pm, Trevor Lewis <trevorl.sa...@gmail.com> wrote:
> I know this is probably pretty obvious, and you've likely already done it,
> but have you tried different filament? I've had some total crap filament
> before that just won't make good prints. No matter how I tweak things.

[CoffsEmma]

Hi Jay,

Thanks for your testing and feedback. I agree that changes to
retraction don't seem to have any significant effect on the blobbing.
I found the slower the speed the better the outcome though. I had also
tried different Z acceleration in Marlin, but again didn't see any
significant change to the blobbing issue.

On Apr 23, 5:24 am, Jay Couture <jay.cout...@gmail.com> wrote:
> So I played with Slic3r a lot yesterday, and pretty much anything I did
> with retracts had no impact. I did modify my configuration.h to increase
> the Z acceleration setting from what I was using, but the biggest impact

> was dropping from 195F to 190F. Here is a photohttp://www.flickr.com/photos/jaydmdigital/7103236101/I think you'll see

[Triffid Hunter]

On Mon, Apr 23, 2012 at 10:18 PM, CoffsEmma <em...@mrichardson.com.au> wrote:

Hi Trevor,

Thanks for the suggestion. I have used both PLA and ABS from different
suppliers, and the same issue appears on both, though as I am new to
the sport of 3D printing, I am not yet sure what constitutes good
quality..

http://picasaweb.google.com/lh/photo/MR1TwlmRgBPcox4VThLw5NMTjNZETYmyPJy0liipFm0 

and

http://picasaweb.google.com/lh/photo/2qP3SvrwWGQ88wNhhMrmCdMTjNZETYmyPJy0liipFm0

are pretty good.. please excuse quality of photos, it's the best my crappy camera can do.

[CoffsEmma]

Hi TH,

I have been quite pleased that I have made steady progress with the
quality of my prints (although many failures along the way)...see
linked pics...but the cylinder blob is a hurdle that I would like to
overcome. Have you been able to print the 30mm cylinder as single wall
with no infill, and not get the blobbing?

Some of my latest prints...
http://www.datacorp.net.au/emma/3d/PinkPanther_1.jpg

This one has the PinkPanther in PLA on the left and in ABS on the
right... I thought I had the horizontal lines issue solved after
replacing the aluminium MG Z motor couplers with your printed block
version, but is has reappeared when I printed the pla item at .1mm
layer height.
http://www.datacorp.net.au/emma/3d/PrintQual_1.jpg

Two steps forward and one back...

Emma

On Apr 24, 12:43 pm, Triffid Hunter <triffid.hun...@gmail.com> wrote:

> On Mon, Apr 23, 2012 at 10:18 PM, CoffsEmma <e...@mrichardson.com.au> wrote:
> > Hi Trevor,
>
> > Thanks for the suggestion. I have used both PLA and ABS from different
> > suppliers, and the same issue appears on both, though as I am new to
> > the sport of 3D printing, I am not yet sure what constitutes good
> > quality..
>

> http://picasaweb.google.com/lh/photo/MR1TwlmRgBPcox4VThLw5NMTjNZETYmy...
>
> andhttp://picasaweb.google.com/lh/photo/2qP3SvrwWGQ88wNhhMrmCdMTjNZETYmy...

[NCBob]

I know when I had banding horizontally it took me a few days of experimenting to fix it, it wasn't just one thing though so I was making a change printing and seeing if it was better or worse.

Some of the things I tried:

1. Tension on the z-axis nuts, I tried no tension, fixed, and moderate tension. For me the moderate tension worked best.
2. Side play on the z-axis nuts. My nuts fit rather loose so I wrapped some electrical tape to make for a tighter fit, again I tried several amounts and ended up removing the tape and letting them slide side to side a bit.
3. Straightness of my z-rod. One of them was slightly warped and since I used the holder on the bottom with the bearings I replaced the warped rod and this helped.
4. Securing my z-motors. I did have them floating loose, but discovered when I bolted them down it removed more of the banding.
5. Trying different styles of couplers for the z-axis. I tried the aluminum ones, printed ones with tubing on the shafts, and custom printed ones with exact dimensions for my shafts. The last one is what I ended up with. Curiously on my Mendelmax where the z-motors are on the bottom I used the aluminum couples with tubing on the shaft to make it fit well and it seems to be working. I have an extra set of printed ones in case it starts to band :)

I'll do some prints tonight and post some pictures so you can compare, but judging by the other prints you have besides the cylinder your quality is very good (except for the one with the banding)