mitchfx
Posts: 184
Joined: Fri Feb 27, 2015 6:01 pm

Re: Reducing gaps between outline shells and top surface fil

Wed Mar 18, 2015 11:37 am

Test results so far using Dremel (stock) PLA, which seems to conform closely to 1.75mm so I left the Filament Diameter setting alone...

Mult=1.00, Width=0.40 - Resulting walls measure average 0.38mm thick. Surface looks good with an every so slight line texture when scraped with fingernail.

Mult=1.00, Width=0.45 - **Resulting walls measure average 0.45mm thick. Surface looks even smoother with hardly any line texture when scraped with fingernail.

Mult=1.02, Width=0.40 - Resulting walls measure average 0.48mm thick. Surface has noticeable blobs and over oozing pattern.

Mult=1.00, Width=0.41 - Resulting walls measure average 0.42mm thick. Surface very smooth like test #2 with hardly any line texture.

**I'd have to judge #2 (1.00/0.45) as the best surface overall.

So, if I wanted to try to hit 0.40 mm wall thickness on the money I could try either a 0.405 width or 1.005 multiplier but not sure if that many decimal points over to the right would be diminishing returns as far as accuracy goes.

Here is what I find most interesting...most of my full prints have been on the HIGHER end of this spectrum in terms of extrusion width (usually 0.45 to 0.48mm) but I STILL get fairly open gaps between outline shells as well as top surface fill! This leads me to believe there may be something to the claims and complaints about something defective in S3D's slicing algorithms when it comes to these areas. I can even see these gaps in the build preview and predict exactly where they will occur. I need to do some comparisons with the included Dremel slicer to see if there is a difference.

Interesting indeed.

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jimc
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Re: Reducing gaps between outline shells and top surface fil

Wed Mar 18, 2015 12:58 pm

ok mitch, is should not matter where you have the width. once the multiplier is set correctly and assuming the filament dia. stays dead on accurate then you can make the width whatever you want and the slicer will create wall that width. so a breakdown here is if with a 1.00 multiplier and a width of .45 you got .45 then at .50 your wall with should be .50. the only variable there that would affect that is how accurate the extrusion of your filament is. if the filament varies dia just a little it throws that off.

jimmybuckets
Posts: 68
Joined: Thu Sep 11, 2014 7:42 am

Re: Reducing gaps between outline shells and top surface fil

Wed Mar 18, 2015 2:02 pm

Changing your extrusion width prob won't fix your problem...like others have said you need to figure out what you actual extrusion width is. I didn't have good luck with downloaded "thin wall tests" since they are designed by one person with a specific set up that usually doesn't match mine. The easiest and most effective thing I have found is similar to what others are doing with a thin wall test...but instead of making it all complicated this is what I do...
1. draw a cube...size is up to you...but not too small...I used 50mm
2. change your settings in S3D to a single loop, no top layers and bottom layers are optional...I did no top and no bottom.
3. set your extrusion width to what you want...
4. print...I usually stop the print after it reaches about 25mm
5. measure the top 1 or 2 layers thickness in several places on every side of what should be your single wall topless cube. Be careful not to take too much of a bit with calipers since you want to be measuring the thickness of the extrusion with out any variation in layer stacking. Take an average of all measurments.
6. divide to figure out the % diff between what your actual average extrusion width is and the specified extrusion width in S3d.
7. Adjust your extrusion multiplier up or down by the % diff.
8. repeat, remeasure...should put you pretty close to specified extrusion width...I did it twice to get extra dialed in.

mitchfx
Posts: 184
Joined: Fri Feb 27, 2015 6:01 pm

Re: Reducing gaps between outline shells and top surface fil

Wed Mar 18, 2015 2:38 pm

jimc wrote:ok mitch, is should not matter where you have the width. once the multiplier is set correctly and assuming the filament dia. stays dead on accurate then you can make the width whatever you want and the slicer will create wall that width. so a breakdown here is if with a 1.00 multiplier and a width of .45 you got .45 then at .50 your wall with should be .50. the only variable there that would affect that is how accurate the extrusion of your filament is. if the filament varies dia just a little it throws that off.
This totally makes sense, and something that I already understood. I guess the disconnect was going back to earlier recommendations to INCREASE the width setting to compensate for really crappy top fill areas. Doing this eventually led to chronic clogging of my nozzle during large prints, presumably because of over extrusion. Up until doing this wall tests I've never changed the extrusion multiplier from the default 1.0 value, but I have gone from 0.40 to 0.45 then to 0.48 width setting progressively to try and get a solid top fill. The top fill never really got much better but I did end up with failed prints due to a backed up nozzle at 0.48.

Running further tests using my favorite filament (gray PLA from Push Plastic) this morning, it appears that everything default across the board is the most accurate. 1.00 mult, 0.40 width and 1.75 filament setting. Surface of walls is smooth as butter, thickness is dead on at 0.4mm.

If I understand what you are saying, I should be able to change the width value and simply make thicker walls but keep the quality of the surface the same. In turn, that should reduce the gaps in top areas. However, how do I compensate for potential clogging issues once I start pushing the width beyond 0.45mm?

Thanks,
Mitch

mitchfx
Posts: 184
Joined: Fri Feb 27, 2015 6:01 pm

Re: Reducing gaps between outline shells and top surface fil

Wed Mar 18, 2015 2:44 pm

jimmybuckets wrote:Changing your extrusion width prob won't fix your problem...like others have said you need to figure out what you actual extrusion width is. I didn't have good luck with downloaded "thin wall tests" since they are designed by one person with a specific set up that usually doesn't match mine. The easiest and most effective thing I have found is similar to what others are doing with a thin wall test...but instead of making it all complicated this is what I do...
1. draw a cube...size is up to you...but not too small...I used 50mm
2. change your settings in S3D to a single loop, no top layers and bottom layers are optional...I did no top and no bottom.
3. set your extrusion width to what you want...
4. print...I usually stop the print after it reaches about 25mm
5. measure the top 1 or 2 layers thickness in several places on every side of what should be your single wall topless cube. Be careful not to take too much of a bit with calipers since you want to be measuring the thickness of the extrusion with out any variation in layer stacking. Take an average of all measurments.
6. divide to figure out the % diff between what your actual average extrusion width is and the specified extrusion width in S3d.
7. Adjust your extrusion multiplier up or down by the % diff.
8. repeat, remeasure...should put you pretty close to specified extrusion width...I did it twice to get extra dialed in.

Ok, this is pretty much were I am now and the settings that ended up being most accurate for the current filament (Push Plastic PLA) are actually defaults...1.00 mult and 1.75 filament diameter. With my extrusion width set to 0.40mm I get EXACTLY a 0.40mm wall in the print. Now the problem I'm dealing with is that cranking up the extrusion width to 0.45 and beyond appears to be causing backflow issues and clogged nozzle during printing. Do I need to now adjust my retraction settings to compensate?

Thanks,
M

jimmybuckets
Posts: 68
Joined: Thu Sep 11, 2014 7:42 am

Re: Reducing gaps between outline shells and top surface fil

Wed Mar 18, 2015 3:09 pm

clogging could be too much retraction. I only use about 1.5mm...also you may need more temp.

mitchfx
Posts: 184
Joined: Fri Feb 27, 2015 6:01 pm

Re: Reducing gaps between outline shells and top surface fil

Wed Mar 18, 2015 3:39 pm

jimmybuckets wrote:clogging could be too much retraction. I only use about 1.5mm...also you may need more temp.
I will check my retraction setting tonight. I've never fiddled with those.

For the Push Plastic PLA I'm running at 200c temp since their recommended range is 190-200. I could go hotter but would prefer not to since I detest shiny plastic :)

jimmybuckets
Posts: 68
Joined: Thu Sep 11, 2014 7:42 am

Re: Reducing gaps between outline shells and top surface fil

Wed Mar 18, 2015 9:50 pm

not sure then. Too much retraction can cause plug. I thought I had a plug increase but just had my extruded too tight and it was actually grinding away the filament and eventually just spinning g in a groove it ate in the filamen.

rebible
Posts: 2
Joined: Tue Mar 17, 2015 7:08 pm

Re: Reducing gaps between outline shells and top surface fil

Wed Mar 18, 2015 11:50 pm

I have the same problem on a davinci duo 2.0.

I have the extrusion at 1.0 extrusion width at 0.4 and I am measuring .6 on the thin wall test.. this is not consistent with this causing the gaps...

any comments.

thanks
robert

JoeJ
Posts: 1436
Joined: Sun Feb 16, 2014 10:52 am

Re: Reducing gaps between outline shells and top surface fil

Thu Mar 19, 2015 6:12 am

If your extrusion width is set to 0.4mm, but you measure it at 0.6mm, then your extrusion multiplier is not correct. You need to calibrate it so that the measured width is the same as the extrusion width you put in the software.

The software uses the extrusion width that you specify as the spacing between all of the lines. So if you tell it you have a width of 0.5mm, but in reality it's only 0.4mm, then there will be gaps. If you tell it the width is 0.5mm, but it's actually 0.6mm, then you will get over-extrusion.

So calibrate your extrusion multipliers!

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