Dome and Circular objects 'stinging'

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Chip Luck
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Dome and Circular objects 'stinging'

Post by Chip Luck »

Gang,

Progression on the HIC i3 is getting better every day, however I still have issues with 'stringing' on dome or circular shaped objects. This image is of a BB-8 top dome piece, left to right: original printer settings, some calibration, then on right with a center support that broke off and left stings of fiament in the top:
BB-8 dome bottom views
BB-8 dome bottom views
Here is the tops of the center and right dome parts:
BB-8 dome top views
BB-8 dome top views
Then today, a Star Wars Thermal 'Detonator' thing from the movie, well here is the lower part, outside and inside view. You can once again see stringing near the top in the inside view, outside looks good enough and is usable I figure:

(Object located here: http://www.thingiverse.com/thing:185165)
Det' Bottom Outside
Det' Bottom Outside
Det' Bottom Inside
Det' Bottom Inside
And just started printing the Thermal's top part and it started stringing on just a few layers after the start of the print:
Det' Top print just started
Det' Top print just started
Very interesting. A 20x20 solid calibration cube looks great. I have always had this problem with these types of prints from the beginning and now as more calibrations have been performed. Any idea's for a quick check or what I should do? Thinking of trying some round calibration objects instead of 'real' parts to save time an filament. Looks like more research to do, not quite there yet! Got to love it..

Thanks in advance.
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Re: Dome and Circular objects 'stinging'

Post by Chip Luck »

Guess eveyone is MIA...
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Re: Dome and Circular objects 'stinging'

Post by Neotko »

I think that, I don't know this machine btw, you should print cooler and make your travel moves as fast as the machine allows. Also, options like coasting on cura beta or coast/wipe on s3d can help you remove that filament excess before the hotend moves. Also, combing (so the hotend travels inside the print area, helps to reduce that travel moves.

Anyhow, that interior overhangs looks quite nice. You could add a simple inner tower designing your own supports so the top prints cleaner.
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Re: Dome and Circular objects 'stinging'

Post by Chip Luck »

Neotko wrote:I think that, I don't know this machine btw, you should print cooler and make your travel moves as fast as the machine allows. Also, options like coasting on cura beta or coast/wipe on s3d can help you remove that filament excess before the hotend moves. Also, combing (so the hotend travels inside the print area, helps to reduce that travel moves.

Anyhow, that interior overhangs looks quite nice. You could add a simple inner tower designing your own supports so the top prints cleaner.
First thanks. The filament inside the object is actually the inner perimeter separating from other internal perimeters only on the top or angled parts. Straight walled objects print fine, even a bridging calibration or other cal object. This only happens on circular objects as the angle goes from horizontal to the more 'angled' or closing off the top of the sphere.

Printed: PLA, 205c, 6 sides, 6 bottom/top, 20% infill/pattern=line, print speed 80mm/sec max, perimeter speed 40, infill speed 60, solid infill 30, top infill 30mm/sec, max travel speed 150.
Slicer: Slic3r v1.2.9
HICTOP Reprap Prusa i3 printer: cooling=yes after 5 layers, bed 60c start, 50c afterwards

I'm pretty new at this stuff < 2 months and finishing calibrations.
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Re: Dome and Circular objects 'stinging'

Post by Neotko »

Indeed it happens because it doesn't have enough angle to print. Filament drops because it can't print on the air, then that filament moves with the hotend and makes a visual mess. You need supports for that area.

Ofc, if you print slower they will print better.

It's been a long time since I touched slic3r but I think last versions have an option to change the speed at certain points. Check that and if so adjust it near the problematic area.
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Re: Dome and Circular objects 'stinging'

Post by Amedee »

I am not 100% sure, but from the pictures I see, this is not stringing, this is bad layer adhesion. So if this is the case printing colder will make it worse...

Your model has steep vertical angles, so there is little overlap between layers (check the 45° rule)...

A couple of tips that might help, depending on the situation:
  • Print hotter to get better adhesion
  • You have not mentioned your layer height, but if possible you can use thinner layers, so you get more overlap on layer by layer basis
  • A tiny bit of over extrusion
  • Ensure you print the inner walls first; use 3 walls instead of 2.
    ('Inner walls' in 3d solid printing terms, not in the inner part of your object ;) )
  • Don't print too fast -- if your 'perimeter speed' of 40mm/s applies to all perimeters then it is OK (it is not clear from your post if it is for all perimeters or not)
If these quick/simple tips aren't helping: use supports ;)
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Re: Dome and Circular objects - adhesion issues?

Post by Chip Luck »

First, thank you very much for your responses.

A few additions and corrections. Agreed, it is not 'stringing' as in such as from point to point during a move, only while actually extruding/printing.
// Layer height was set at 0.2mm
// Slic3r was set to print external perimeter first for some reason. Will be unchecking that option to print inner perimeters (walls) first.
// Nozzle was set 205c. PLA print rated at 190-220c. Will up temp to 210c, however extruder/flow will need calibration

I would assume inner walls means inner perimeters? Slicers use different terminology, I would assume with Slic3r with inner perimeters set at 3 it will print one outer and 2 inner perimeters or walls.

Printed a just a few layers of the object shown below and is not a angled part. Yet after a few layers it appears to have adhesion issues, again a circular object which seems to be the problem (along with angles show in previous post). View 1a and 1b show inner adhesion issues and also look closely at the holes inside the ring, has same issue. However some of the holes printed fine, makes no sense to me. Same print setting as before.

View 1a : Ring with inner adhesion issues:
0420161327a_1024.jpg
View 1b : Ring with inner adhesion issues:
0420161329_1024.jpg
View 2 : Ring re-printed this time with print speeds lowered a little and only 3 perimeters (my default setting). Things improved quite a bit:
0420162003_1024.jpg
View 3: For reference, Host screen shot of ring object:
Host
Host
View 4 : And again, the object without angles, only circular (after just a few layers printed, bottom layers adhere?):
0419162127_1024.jpg
Looks like a combination of speed and temperatures. I cannot see lowering the speed a whole lot, it will take forever to print parts and this printer should run at least 50mm/sec max print speed (for a 'slow' setting) and up to 80mm/sec for draft or fast speed. Default still to 120mm/sec max travel speed.

If you have any suggestions for a circular calibration object let me know. I'm going to make those changes, inner before outer and increase temp.

Thanks again for all you help. Cheers..
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Re: Dome and Circular objects - adhesion issues?

Post by Amedee »

Chip Luck wrote: I would assume inner walls means inner perimeters? Slicers use different terminology, I would assume with Slic3r with inner perimeters set at 3 it will print one outer and 2 inner perimeters or walls.
Yes, walls and perimeters are the same things
Chip Luck wrote: // Layer height was set at 0.2mm
I would go to 0.15 (or 0.1, but that will take a very long time...)
Chip Luck wrote: // Slic3r was set to print external perimeter first for some reason. Will be unchecking that option to print inner perimeters (walls) first.
Yes, that will offer a bit more material to rest on when you print the outer perimeter
Chip Luck wrote: // Nozzle was set 205c. PLA print rated at 190-220c. Will up temp to 210c, however extruder/flow will need calibration
I am not sure why you would want to recalibrate after changing temperature. It is very common to tweak temperature for prints.
Chip Luck wrote: this printer should run at least 50mm/sec max print speed (for a 'slow' setting) and up to 80mm/sec for draft or fast speed.
You probably need to review your expectations here. On the Ultimaker my default speed is 40mm/s and I play in the 30-50mm/s range. I don't think a Prusa i3 can go much faster than that... I worked with a Mendel 90 (which is a more stable version of Prusa I3) at the FabLab, and the speeds were very similar.
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Re: Dome and Circular objects 'stringing'

Post by Chip Luck »

FYI or reference here is a worksheet that has all My HIC i3 Slic3r settings and on a separate tab on the bottom of the worksheet a list of EEPROM settings. I use this as to track changes to the slicer settings and any EEPROM updates, make notes, etc. It maybe could be of use to others.
Cheers

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Re: Dome and Circular objects 'stinging'

Post by Chip Luck »

Wish I change the default topic... however I have updated a few things, and I'm learning that in engineering, and a golf swing you only change 1 thing at a time.

Thanks again to everyone that has chimed in. Learn more each day and getting there with a lot of research and help from you folks.

1. Slic3r now set to print exterior first as suggested
2. Travel (non-print speeds feedrate) changed from 150mm/sec to 120mm/sec
3. MAX print speed changed from 80mm/sec to 50mm/sec (now as suggested going to default to 40mm/sec)

Everything else stayed the same, layers, temp's, etc.

I looked more closely to the the print and now appears the reason is due to large gaps/bridging on the lower layers. If you look at the object now, it has quite a span to accomplish after the scattered bottom pillars are printed, we have not even gotten to the dome yet. I'm surprised the machine even pulled off attempting to bridge a gap that large. Second object printed post above changes follows, and did not go high enough this time to show there is an inside flat/flange that was causing all the other adhesion issues on the previous print.
Object View 1
Object View 1
Object View 2
Object View 2
View from host, what it should look like
View from host, what it should look like
So the question now is, how to print this thing? I assume supports will be required for bottom and possible the top dome area, going to give that a try.

Cheers,

Chip

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Re: Dome and Circular objects 'stinging'

Post by Neotko »

Indeed you need supports. One think it's to print a linear bridge, but a curve one, that's just black magic. Supports, don't be afraid to use them, they are to support you... Worse pun ever...
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Re: Dome and Circular objects 'stinging'

Post by Amedee »

Alternatively, cut it in 2, print separately and glue...
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Re: Dome and Circular objects 'stinging'

Post by Chip Luck »

Got the point folks, my overthinking mind = well never mind. And, the journey into 3D printing has just begun, news on at 6...

Chip
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Re: Dome and Circular objects 'stinging'

Post by Chip Luck »

Neotko wrote:Indeed you need supports. One think it's to print a linear bridge, but a curve one, that's just black magic. Supports, don't be afraid to use them, they are to support you... Worse pun ever...
Actually no worst pun = good stuff, can I quote that! <G>
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Re: Dome and Circular objects 'stinging'

Post by Amedee »

Chip Luck wrote:And, the journey into 3D printing has just begun
That's learning on the job ;)

It won't take long before you quickly spot what's printable and what's not (or at least not easily), and think about printing during the design stage to get printable parts.

The Designing for 3D printing guide is a nice start for that.

When you need to print replicates from existing parts you don't always have many choices, but model orientation and assembling are always an option...
Supports will always be my last resort as they often require a lot of post-processing for a nice finsih.
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