Weird part failure

[rickyg32 2]

Hey all

Happy New Year.

So last night or over night I was printing an 18 hour print. Normal thing for me. However this went south in a strange way.

I had two parts on the bed. The parts filled most of the bed, two basically flat parts.

The part at the rear printed perfect.

The part at the front failed. It seem to randomly under extrude. As if there was a nozzle jam. But if there was a jam it never affected the second part in any way.

The first 12mm of the print was a disaster, the remainder seem to have a layer of serious under extrusion every 12 mm...yet the second object was fine.

I am stumped.

Cura 5.6.0

Ender 3 with direct drive sprite extruder.

 

 

[GregValiant 1,357]

That's really odd.

Set the project up again in Cura and use the "File | Save Project" command and post the 3mf project file here.  Somebody will take a look.

What material is that?

[rickyg32 2]

This is Polymaker Pre Foamed LW PLA.

Attached is the file you requested.

 

 

CE3PRO_Rhein-Flugzeugbau Fanjet 600 Canopy Base B.3mf

Edited January 13 by rickyg32

[GregValiant 1,357]

I think the failure on part #2 happened when the support failed.  You have the "hoop" of the model near the edge of the bed.  Cura noted that and sized the trunk of the tree support to fit in the room it had.

Here I've placed one model closer to the edge than the other.  You can see that the trunk of the tree on the right is much more robust and less likely to fail.

 

It looks like you had Z-hops enabled at 0.2.  Try increasing that to 0.5.  If the nozzle hits a skinny support (like the left model above) there is an excellent chance that it will knock it over and cause a failure.

 

In regards to the under-extrusion, I don't know what to make of that.

Here it looks like the supports failed because of under-extrusion.  That also seems to have been a problem lower near the build plate.  As you noted, the good part doesn't show that.

 

If it was me, I think I'd print a couple of scaled up (in the Z) calibration cubes with one in the front of the bed and one in the rear.  The point would be to try and duplicate the problem.  It isn't likely that the problem is in the gcode but rather with the printer.

 

On another topic - infill.  Everybody likes gyroid but at low densities it fails.  These extrusions are too far apart so they don't connect to the previous extrusion.  More spaghetti.  The first skin over this infill will be ugly as it will be mostly printed over air.  I understand you are weight sensitive here, but the part has to have some strength.

 

 

 

 

[rickyg32 2]

Hey there thanks for looking into this.

I confess I am stumped.

So get this I printed the same part in the same location but this time I removed the rear part and it printed just fine. 

um weird lol

I then printed a part that ran the whole length of the bed. I printed the first 10mm or so and got an under extrusion at the front end just like the photos I posted. I am running the same part on an angle and will see if it has something to do with creeping up on the edge for the bed.

I will try the scaled up cube as well.

I upped my Z hop, it shouldn't be that low as I have had print strikes in the past.

AS for Gyroid. It should be Cubic Subdivision. I had sliced a part before had that requires Gyroid and it got left behind. User error.

The tree support...ya doh that was my stupidity. I don't typically print two objects at a time and so didn't take the support into account. A learning opportunity as my boss use to say.

 

From a machine point of view I can't think of anything that would cause under extrusion only if your near the edge of the bed. It's a direct drive printer and well the print head doesn't do anything different anywhere it is unless it's commanded to do so.

Z height could affect it by perhaps binding the filament but that's in a bowden machine.

The only positional affect I can see on the machine is the slapping of the filament roll. Carboard rolls suck as they have way more drag on them. So I have ordered a bearing roll holder.

But apart from that I see nothing on the machine that would cause it and why didn't it when I printed the same part on it's own. Weird.

 

[Slashee_the_Cow 438]

59 minutes ago, rickyg32 said:

From a machine point of view I can't think of anything that would cause under extrusion only if your near the edge of the bed. It's a direct drive printer and well the print head doesn't do anything different anywhere it is unless it's commanded to do so.

Make sure your bed is properly levelled. If the nozzle is too high above the bed the filament will have to drop down, not form in position like it should.

[rickyg32 2]

I agree

I level the bed before any major printing. Which I had done in this instance.

Also if it was a level issue why would it print fine when the rear part is removed. It's strange.

 

[Slashee_the_Cow 438]

3 hours ago, rickyg32 said:

Also if it was a level issue why would it print fine when the rear part is removed. It's strange.

It's possible the springs used with the levelling screws aren't tight enough (or are just in bad shape) - the weight of the rear part could be pushing that side of the bed down and making the front go up.

[jaysenodell 18]

Dumb idea… is it possible that the filament is “under tension” when the extruder is in that location and the hot end isn’t getting fed by the system?

 

Think binding in Bowden, interference with structure/wiring in direct drive, angle between runout sensor/scrubber. 
 

it has a feeling of something related to the mechanics that aren’t normally considered. 

[GregValiant 1,357]

That's an Ender 3 of some sort, correct?

Slashee has a couple and I have an older 3 Pro.  If there was some sort of binding in the bowden I would expect it from right to left rather than fore and aft.  The bowden flexes with X movement rather with Y movement.

I think you are on the right track though.  Just because I think X movement binding problem is more likely doesn't mean your printer agrees with me.

 

 

[rickyg32 2]

So guys first thanks for jumping in on the subject I really appreciate it.

I have a theory. I am using a direct drive Sprite hot end. Love it. Works great up until now.

I sat in front of the printer and watched for a few minutes and observed something odd. You guys I think are in the right ballpark. I think lol.

Anyway the Polymaker Pre Foamed PLA comes on a cardboard spool and they have a lot higher drag on the spool holder. I suspect 2 possible problems. First that the sprite isn't pulling hard enough that the filament gets pulled back by the weight of the spool. I have noticed how it can suddenly rock backwards when the print head moves. For instance on the part I was watching. It was printing a support at the front left corner of the build plate then moved all the way to the back right to print there. The roll of filament suddenly rolled back with a bang. I imagine that bang was the filament rolling back onto the spool and reaching the end of it's freedom due to the extruder holding the filament...who knows how much filament was pulled out due to that but even a mm or 2 can screw with the print quality. IT may take some time for the machine to catch up.

 

I cranked the pressure up on the extruder to hold it tighter. So far the printing is much better.

I have also ordered a spool holder with bearings in it to help reduce the tension on the filament. But apart from those two ideas. I am not sure what other options there are. 

 

I have one other issue I can't explain. If you see the photos attached. You can clearly see that there is a line being created where the print transitions from a flat surface to something else. I am at a lose to know what causes this or what setting needs to be changed. 

Anyway thanks everyone I will let you know how the test goes.

 

 

[Slashee_the_Cow 438]

11 hours ago, rickyg32 said:

Anyway the Polymaker Pre Foamed PLA comes on a cardboard spool and they have a lot higher drag on the spool holder. I suspect 2 possible problems.

The biggest problem I've had has actually been with a plastic spool - instead of being a ring on each side it had a hollow tube connecting the two halves. Some really nice, smooth plastic. So smooth it vibrated right off the end of the filament holder and hit the bed with a decent bang. Not sure if it caused permanent damage, to be honest, because that carp managed to clog my hot end so bad I got a refund on the printer and bought a new one.

 

11 hours ago, rickyg32 said:

I have one other issue I can't explain. If you see the photos attached. You can clearly see that there is a line being created where the print transitions from a flat surface to something else. I am at a lose to know what causes this or what setting needs to be changed. 

Are they the same material? Different materials often don't bond well. That or I'm completely missing the actual problem because I'm not always great at figuring things out based on photos.

[rickyg32 2]

wow bang that doesn't sound good. Never seen the spool move like you describe. wow.

 

A for the photo yes its the same pla. Something in the transition from the flat to the other surface causes the line.

No idea what it is.