almost there (I think)! pointers?

So, after messing around with the skeinforge settings for a few days (and starting over thanks to a freshly printed Greg's Accessible Wade) - I have finally been able to print the elusive hollow pyramid (20x20mm version)



It's not by any means perfect, but I've never gotten past the second layer of pillars before extrusions start flowing into open space... also had a ton of trouble with any sort of overhangs. That seems to have gotten better as well.

I also was able to finally get a semblance of a roof on a 20x20mm hollow cube, but the first of three "roof" layers started sagging about 1.5mm (in previous attempts the strands just fell to the bottom). The final couple layers didn't sag as much, thanks to *some* support from that first fill layer, but its still far from where I think I'd like to be.

I'd mainly like to avoid the overhang drooping. So far I think I stumbled on a lucky combination - and would like some advice before I start taking myself off course...

So, if anyone has some insight on what parameters I should tweak in a certain direction, I'm all ears. I'll list what I think are the important bits of my config here below (if I am missing anything, please let me know). Thanks in advance for sharing your experience and knowledge with this beginner.

Extruder: Greg's Accessable Wade's (that actually calibrated right at 700 steps/unit!)

.5mm nozzle
1.75mm PLA @ 175C 

Dimension:
   Extraction Speed           15 mm/s
   Filament Diameter          1.75 (measured)
   Filment Density Ratio      .97 

Carve:
   Layer Thickness            0.3mm
   Perimeter over Thickness   1.5 

Speed:
   Feed Rate                  50 mm/s
   Flow Rate                  50 mm/s
   Bridge Feed/Flow ratios    1.0/1.0
   Feed/Operating ratio       .5  
   Flow/Operating ratio       .5  

Cool:
   Bridge Cool                1.0 
   Max Cool                   9.5 
   Min Layer Time             10  

Stretch is disabled

Without know much about your machine, my recommendations would be to lower the temperature in 5 degree increments, keep the speed constant for now, and compare to the current results. With PLA, it's good to have a gentle breeze blowing nearby too. If you are getting sagging on overhangs, what I have mentioned should help.

I'm a bit hesitant to go any lower on temperature. Seems that the other part of the sagging issue is that the thread is not always attaching to the perimeter wall and falls off.

Speaking of speed - what's the fastest (reasonable) feed rate you should expect from a Prusa?

Edited 2 time(s). Last edit at 08/12/2011 11:50AM by TheCase.

Falling off is most likely due to backlash in one or both of your belts. Make sure you are suing the right pulley with your belt type.

I am sure I have the proper T5 belt/pulley/gear combo. Perhaps I need to tighten the belts a bit more...

Yup - starting doing some stuff with circles- way off! The X was lashing in a big way.

Long story short (had to fix about five other problems), I'm back to what looks more concentric prints.

I'll report back - not sure if I can get to a hollow/roof tonight...

TheCase Wrote:
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> I'll report back - not sure if I can get to a
> hollow/roof tonight...

To get good bridges you want your deposited plastic cross-sectional area to be smaller than your nozzle. That way you are more or less stretching the filament. I am able to do bridges in PLA of over 20mm with virtually no droop.

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Ok - so I found a (working) solution.

I started fiddling with the feed/flow rates, but even got sag up to the point where the bridges were breaking because the were too thin.

Went back to a 1.0 feed/flow rate (50mm/s) with a layer of .4mm and a w/t ratio of 1.5 - this time I'm using a cooling fan that blows just around the nozzle. The bridges are holding as expected and I even made a 30x30x5 hollow cube with a straight and flat roof (three layer) roof! No sagging!

It's a shame I had to resort to the fan - I'm sure it can be done without - but for now, I'll settle on nice, flat and straight bridges...

My Miss's Says she loves the light in your photo

Mine printing to a similar level, no stings though and squarer corners

Im running at 190 deg'c with my filiment retract set at 1mm and 2.5mm/s in SF41

if that helps

Rob

ijmok Wrote:
-------------------------------------------------------
> My Miss's Says she loves the light in your photo
>
>

Hah! Nothing but an Ott Light overhead and a bounced flash against a sheet of copier paper. Have to log that one

> Mine printing to a similar level, no stings though
> and squarer corners
>
> Im running at 190 deg'c with my filiment retract
> set at 1mm and 2.5mm/s in SF41
>
> if that helps

That does help - always good to know what settings folks are using and having success with. Was your pyramid scaled down to 20x20mm as well? (the original is 38mm sq and much easier to get square corners).

>
> Rob

Aha nope mine wasent

heres a photo of my first one to help you gauge what im getting

[www.flickr.com]

since ive fiddled lots and its getting better slowly,

im on hol in bulgaria atm but home tomoro so might be printing this weekend to see if i can get something tangible,

any success ill post my settings up

Rob