Adding Flow?

[rsterne]

In Cura, you can increase the flow without changing the layer height or the wall thickness.... I don't know how much material the "100%" setting extrudes, but the minimum would be the volume of an ellipse the layer height by the wall thickness.... A rectangle of the same dimensions would be 1.00 / (PI/4) = 127%, so I used 100% and 127% in Cura and got these Preview results.... First, the standard 100%.... 11 grams of filament used....



And next with the flow set to 127%.... 14 grams of filament used.... You can click on the images to enlarge them....



Note the slight gaps between the threads of filament at 100%, and how those gaps virtually disappear at 127%.... Now assuming that "100%" is actually a bit more than the actual volume of said ellipse (to get bonding between layers), is there not some setting, maybe between 110-120% that will increase the layer strength, because the extra filament has to go somewhere, so it should spread out to fill the gaps between the theoretical ellipse and the same size rectangle?.... Might this also increase the layer to layer bonding, and possibly improve the surface finish as well?....

Bob

[TorqueMaster]

Bob,

Somewhere in the documentation, Cura defines how each line of filament is approximated and what the cross section looks like.  I *think* they expect it to be a mostly rectangular cross section, with two semi-circles on the ends.  It ends up slightly wider than the exact rectangle would be. 

I agree your 100% flow image looks like the lines are too thin.

If you choose 100% flow, and haven't altered any other values that affect flow, you should get the exact flow that would fill your object with no voids at all.  It should track with each line exactly (or slightly wider if they display the "oval") the linewidth you chose, probably 0.40, and I'd expect the lines to be on 0.40 centers.  Assuming 0.40 nozzle.

No voids is essentially impossible, so for pla and petg, 93-98% flow is typical for proper extrusion.

The exception I've found is TPU, flexible filament -- if you are calibrated for pla or petg, TPU may need to be bumped up to 115% or so flow -- it really depends how well your extruder grips it.

If you have to bump up to 127% flow for petg, something else is set incorrectly if that's what it takes to get your lines depicted to be the width they are expected to be.  Maybe experiment with a large cube to see if the cura calculated volume of filament used is what you'd expect for the object.  At 100% flow, a 100mm cube should use...1000cc of filament, which translates to 415.75m of filament and weigh 1270 grams.

Is your materials/filament diameter set at 1.75mm?  That would cause global flow issues if it isn't.  There may be other settings that would affect similarly.  The only one I see right off is experimental/ flow rate compensation factor which should be left at 100%.

Definitely solve this one -- you've had great prints so I'm at a loss how if you are underextruding by 20%.

[rsterne]

TM, I tried 110% and 120%, and the latter was useless, the top of the print was so rough I was concerned the nozzle was getting beat up!.... At 110%, the surface was rough, but acceptable for tensile testing coupons.... However, as the flow went up, the width of the print did as well, because I was printing inside to outside.... and as a result I had to drill out the holes to fit over my pins.... Printing outside to inside fixed that, but the top was pretty rough, even at 110%....

After going down this road, I realized that the test section (5mm wide) was getting a total of 12 walls, and the thickness was set to 0.40mm (standard for that size nozzle, therefore 4.8mm total).... It should be 0.42mm to fill the space, so that may have been my problem.... In addition, although there is very little infill in the test coupons, if I set the walls to all an alternate wall, it should bond the walls better to the infill, and when the angled shoulders split, it is inevitably splitting between the innermost wall and the infill.... I'm going to go back to 100% flow and play with the other settings to try and get every coupon to break in the test section, where it should....

Bob

[TorqueMaster]

Bob,

Ok, great, you've confirmed 100% flow is the correct ballpark for a properly extruded part, not 110% or 120% which would be absurd.

I still recommend test prints to tweak your flow rate.  Print a 1cm cube at 100%, measure it, weigh it.  I bet your volume is more than 1cc.  Your weight should be spot on. (Weigh a sample length of your filament to verify 1.27 is the correct petg density.)  Tweak flowrate to get volume correct.  I expect the density of the cube to be closer to 97% of the density of the petg filament, due to unavoidable ... voids.

I'm at a loss for why the preview lines look thin.  If I saw all your settings maybe something would jump out.   If you save the project, I think it saves all settings along with it.  If you can attach one I can see if I see the same thin lines and maybe figure out why.

You are using Cura 5.x, yes?  It should sometimes slightly alter the linewidth (assuming you didn't disable that) to get you exactly the 5mm cross section you want.  If you look at color scheme and set it for line width, the preview should show you what linewidths it's using.  (It may be jacked up since your preview seems jacked up, though.) With linewidth set to .40, I see the center 2 lines (a square) are really 0.54, and the rest are 0.40.  I'm at a loss why it adds up to 5.08mm.  Guessing it must be compensating for losses in corners that aren't really square, since the nozzle is round?   Using a linewidth of 0.417 may be better for your testing ( x 12 = 5.004) 

[rsterne]

I am currently doing some testing with a line width of 0.42, but back at 100% flow.... quality is good, but one part broke adjacent to the eye.... More to come....

Bob