wirlybird
Posts: 1238
Joined: Sun Jul 17, 2016 1:32 pm

Outer shell no adhesion and final layer gaps

Mon Aug 08, 2016 6:50 pm

Hi all,

I am calibrating new extruders, Flexion, on my QIDI using S3D.

Everything is going good except if I set the extrusion multiplier per various instructions on printing a calibration cube (1 perimeter, 0 top, 0 bottom, 0 infill)
Running the first test at defaults gave walls that were about .45 so that gave 40/45*.9 = .8 this gives a wall about .39-.41. That seems good but when I print a solid cube ( 2 shells, 3 top, 3 bottom, 100% infill) the outer most perimeter only adheres at the corners and the top layer is not filled completely. This would all seem to point toward under extrusion.

I was told by Flexion that my extrusion multiplier would be about 5% less than with the original extruders.

Thanks for any thoughts.

P.S. The torn away sides was my doing testing the adhesion, not the machine while printing!!!



Image

CompoundCarl
Posts: 2005
Joined: Wed Aug 05, 2015 7:23 am

Re: Outer shell no adhesion and final layer gaps

Tue Aug 09, 2016 6:49 am

Yup, looks like under-extrusion to me too. Increase your extrusion multiplier a bit more and try again

wirlybird
Posts: 1238
Joined: Sun Jul 17, 2016 1:32 pm

Re: Outer shell no adhesion and final layer gaps

Tue Aug 09, 2016 7:45 am

CompoundCarl wrote:Yup, looks like under-extrusion to me too. Increase your extrusion multiplier a bit more and try again
Is this where it becomes a bit of a trade off? Walls a bit thicker for good adhesion?

I did ramp the extrusion multiplier back up (.88-.9) and the outer shell got better but the final solid layer still seems a little sparse.

We are gaining on it!!

Thanks so much for the help.

Derrick
Posts: 31
Joined: Wed Jun 15, 2016 10:15 am

Re: Outer shell no adhesion and final layer gaps

Tue Aug 09, 2016 10:42 am

wirlybird wrote:
CompoundCarl wrote:Yup, looks like under-extrusion to me too. Increase your extrusion multiplier a bit more and try again
Is this where it becomes a bit of a trade off? Walls a bit thicker for good adhesion?

I did ramp the extrusion multiplier back up (.88-.9) and the outer shell got better but the final solid layer still seems a little sparse.

We are gaining on it!!

Thanks so much for the help.
I have a Qidi at home too, and I had the same problem with a few different filaments I've used.

Some materials do not have a high die swell, which COULD be your issue. The automatic ~20% die swell works well for PLA and ABS, but not all materials. If you cannot get the extrusion multiplier to fix your issue (which you should definitely try first), then try this. Uncheck "automatic extrusion width" right under the flow rate multiplier. I found that for some filaments, I needed to go down to 0% die swell (so for a 0.4 mm nozzle, extrusion width is 0.4 mm), and then set the flow rate to 60%. This will make each tool path closer together, so if you "under extrude" the layers are now closer to each other and can still bond. You will have to play around with it to find a good setting. For quickest troubleshooting, I would use that cube but cut off the bottom in CAD and print with 2-layer perimeters, since the vertical walls will give you the clearest indication if your parameters are good.

wirlybird
Posts: 1238
Joined: Sun Jul 17, 2016 1:32 pm

Re: Outer shell no adhesion and final layer gaps

Tue Aug 09, 2016 12:02 pm

[quote="Derrick

I have a Qidi at home too, and I had the same problem with a few different filaments I've used.

Some materials do not have a high die swell, which COULD be your issue. The automatic ~20% die swell works well for PLA and ABS, but not all materials. If you cannot get the extrusion multiplier to fix your issue (which you should definitely try first), then try this. Uncheck "automatic extrusion width" right under the flow rate multiplier. I found that for some filaments, I needed to go down to 0% die swell (so for a 0.4 mm nozzle, extrusion width is 0.4 mm), and then set the flow rate to 60%. This will make each tool path closer together, so if you "under extrude" the layers are now closer to each other and can still bond. You will have to play around with it to find a good setting. For quickest troubleshooting, I would use that cube but cut off the bottom in CAD and print with 2-layer perimeters, since the vertical walls will give you the clearest indication if your parameters are good.[/quote]


Ok, so I am not using automatic extrusion width and have manual set to .4 same as the nozzle and the multiplier back up to about 90%. This is how I ran the original extruders and it was good.

I started the test with the above settings and the walls were a bit over (about .43-.45) when I got down to 80%, which is what the calculation suggested, the walls became more .39-.41but then I got the adhesion issue.

As a side note and may be relevant, when I print a solid cube the top layer has small gapping and looking under the magnifying glass you can see the extrusions are not touching giving the appearance of under extrusion.


Thanks for the input, had everything going good until I upgraded extruders!! Now we start all over again.

I put it back up to around 90% and that seems to fix that issue but on a separate issue I am still getting gaps in the final top layer.

Derrick
Posts: 31
Joined: Wed Jun 15, 2016 10:15 am

Re: Outer shell no adhesion and final layer gaps

Tue Aug 09, 2016 12:57 pm

It might be good also to get your calipers out and measure the extrudate, if you haven't already. It would be weird though if you have proper adhesion on the walls and gaps on the top of your part. That would indicate that the extrusion rate is different for the top vs. sides. If you only have 3 top layers and a poor support structure for the roof, the bottom 1-2 layers of extrudate for the roof may sag down a bit, meaning your effective volume to print is higher, because you're printing more in the Z direction (down). After a few (4-5) layers, this should even out though, even with a lot of sagging from a poor support. Also, if you're not already, I'd suggest printing slow (20-30mm/s) till you get a feel for your extruder. If you're using a flexible material, I'd say half that.

wirlybird
Posts: 1238
Joined: Sun Jul 17, 2016 1:32 pm

Re: Outer shell no adhesion and final layer gaps

Tue Aug 09, 2016 1:45 pm

Derrick wrote:It might be good also to get your calipers out and measure the extrudate, if you haven't already. It would be weird though if you have proper adhesion on the walls and gaps on the top of your part. That would indicate that the extrusion rate is different for the top vs. sides. If you only have 3 top layers and a poor support structure for the roof, the bottom 1-2 layers of extrudate for the roof may sag down a bit, meaning your effective volume to print is higher, because you're printing more in the Z direction (down). After a few (4-5) layers, this should even out though, even with a lot of sagging from a poor support. Also, if you're not already, I'd suggest printing slow (20-30mm/s) till you get a feel for your extruder. If you're using a flexible material, I'd say half that.
I am reading that slowing down could be good, maybe the gantry is just outrunning the extruder. The print with the tiny gaps in the top layer is the one pictured above (hard to see) and is at 2 shells, 3 top & bottom with 100% infill.

It is doing the perimeter much slower that the rest so maybe that is a factor. I had the print speed set at the default 3600mm/m. I'll try running the speed way down and see how the same print comes out.

All testing is being done with Makergeeks PLA. Also trying to dial temp in. Flexion says to reduce the temp by 10-15 because the thermistor is in a different place so the reading is off but it is pretty close to the original location. I printed ok as far down as 175 indicated, was printing the same stuff at 190. I think my temp test will be a part that can string easily and back the temp off until that stops but also I have not gotten into the retraction yet.

I think once this is dialed in and I understand what it needs it is going to rock out the prints on the QIDI!

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