What causes this? Too hot?  

RE: What causes this? Too hot?

Links to larger images:

https://imgur.com/hLgQu64

https://imgur.com/PmrRGFq

RE: What causes this? Too hot?

Bad adhesion and the part is warping.

Soap and water are your friends; and finger prints are your enemy.

Alcohol rinse: every few prints

• Gloves recommended.
• Once in a while, an alcohol rinse is helpful to remove PLA residue. It does not remove finger oils well.
• Pour a 5 cm puddle of 91%+ alcohol in the middle of the bed, with clean hands use a fresh paper towel to scrub the bed. Wipe up all the alcohol.

Acetone wash: infrequent

• Pour a 2 cm puddle of acetone on the bed, scrub it around with a fresh paper towel. It will evaporate fast as you clean. This step removes PEI oxides that form over time and with heat, and improves PLA adhesion to a like new state.

Hot Water wash: often, as needed, and after any of the above

• Handle the bed only by the edges.
• Wash the bed in hot water, use a fresh paper towel as a wash cloth, with a few drops of plain dish soap (Dawn, unscented, no anti-bacterial, etc.).
• Rinse well in hot water - if you have very soft water, rinse a bit longer.
• Dry the bed with a fresh paper towel.
• Handle the bed only by the edges.
• Place bed on printer.

Streak test: when contamination is suspected

• With a fresh piece of paper towel, and very clean fingers, dampen the towel with 91%+ alcohol, and wipe the bed side to side moving back to front, like you're painting it with alcohol. The alcohol should be thin enough on the towel it quickly evaporates. If you see any streaks, the bed is dirty and needs a wash.

RE: What causes this? Too hot?

Thanks for responding. So are you also saying that the part is warping because of the lack of adhesion? Or is that another issue?

RE: What causes this? Too hot?

Warping will happen with any plastic, PLA on.  It happens at large scale (warp) and at small scale (curl).  Some warping can be "minimized" by maintaining good adhesion. 

Larger parts can lift, and when the edge lifts it compresses the printed layers and the perimeters squeeze out like toothpaste. It also can lead to nozzle jams.  And it the part lifts it can wobble causing upper layers to have similar effects.  Hard to say exactly, but it looks like your part has some of this going on.

RE: What causes this? Too hot?

Check your first layer this should be perfect, this very important, also for sticking to the bed.

Sticking to the bed,

first layer make it very good,

hotter fist layer(normally not)

slower first layer(normally not)

Clean, very important,

Set the auto bed level before printing on 7 points, so the bed is more level.

Then your print, on your whole print there are holes, maybe print slower, hotter or colder settings, extrusion multiplier, do a test print on a small cube, or a big flat square, to see if you can make a smooth flat surface.

Big flat objects, make a big brim attached to the object,

also for small objects with little contact to the bed, make a big brim,

And glue stick can help, if needed.

RE: What causes this? Too hot?

Oh - and one "trick" to help large PLA parts stick and warp less is to raise the bed temperature from 60 to 70C once the first layer is down.  The higher temp helps the plastic adhere and helps upper layers cool more slowly.  You can also slow down the print fan.

People serious about controlling warp - especially printing ABS and other high temp materials - resort to enclosures.

RE: What causes this? Too hot?

My guess here: Contaminated PEI bed, improperly tightened pulleys, at least on the Y axis and the extruder. I see poor retract behavior on the wide part of the object as well as partial layer shifts where the purple arrow points. I also wonder whether I'm seeing underextrusion on the wide part of the object.

The tightening procedure is to 

1. Loosen both set screws, possibly put a drop of blue Loctite on them
2. Align one of them with the flat part of the motor shaft
3. Tighten this one, making sure it self-aligns on the flat
4. Only tighten the other one once the first is fully tight

The order is important to make sure the self-alignment is proper. Without it, the pulley will move back and forth a little on the shaft.

Regarding the contamination, others have already answered that. If no washing helps, think whether you may have contaminated the bed with silicone grease or silicone oil, possibly from a cosmetic product. Those are truly hard to remove. For an experiment, you can try the other side of the sheet. A localized 'low' like that is uncommon and would likely be noticeable to the naked eye under right lighting.

Also, when you ask whether it's 'too hot', it'd be nice to mention what material are you using (Prusa PLA?) and what temperature and what cooling.

RE: What causes this? Too hot?

Posted by: Vojtěch

My guess here: Contaminated PEI bed, improperly tightened pulleys, at least on the Y axis and the extruder. I see poor retract behavior on the wide part of the object as well as partial layer shifts where the purple arrow points. I also wonder whether I'm seeing underextrusion on the wide part of the object.

The tightening procedure is to 

1. Loosen both set screws, possibly put a drop of blue Loctite on them
2. Align one of them with the flat part of the motor shaft
3. Tighten this one, making sure it self-aligns on the flat
4. Only tighten the other one once the first is fully tight

The order is important to make sure the self-alignment is proper. Without it, the pulley will move back and forth a little on the shaft.

Regarding the contamination, others have already answered that. If no washing helps, think whether you may have contaminated the bed with silicone grease or silicone oil, possibly from a cosmetic product. Those are truly hard to remove. For an experiment, you can try the other side of the sheet. A localized 'low' like that is uncommon and would likely be noticeable to the naked eye under right lighting.

Also, when you ask whether it's 'too hot', it'd be nice to mention what material are you using (Prusa PLA?) and what temperature and what cooling.

Thanks for the tips @vojtech-p6 the steps you provided, are they for tightening the Y-Axis since you mentioned it may be improperly tightened? I am new to this so I didn't think to include my details of the material. I'm using PLA, all standard settings, 60 bed 215 extruder. I'm posting another picture that may help shed more light on the issue. I printed a small part, about 3/4" diameter that's threaded. The first thing I noticed is that the top and bottom had flat sides and were not truly rounded like the sides. I used a red to point out the sides that were more 'flat'. Does this provide more evidence to your Y-Axis theory?

RE: What causes this? Too hot?

If you post a picture, via media  i think, then to the right side you can choose the size of the picture, then the picture will be bigger to see, know i cannot see enough in your pictures.

RE: What causes this? Too hot?

Telly - is that part supposed to be round?

It looks like the belts are very very loose. And quite possible the gears are not properly attached and are spinning on the shafts.

You should be able to hold the motor gear with pliers (gently) and NOT be able to move the bed or extruder.  If you can see any movement, there is a tension problem.

You can also measure belt tension using a small fish scale - bed back, and extruder to the left, lift the lower of the belts at the mid point until you see 8 ounces on the scale. The belts should deflect about 15/64" - if 8 ounces cause the lower belt to touch the upper belt, you have some adjusting to do - and need to take the belts in at least one tooth. 

RE: What causes this? Too hot?

Posted by: tellyname

Thanks for the tips @vojtech-p6 the steps you provided, are they for tightening the Y-Axis since you mentioned it may be improperly tightened? I am new to this so I didn't think to include my details of the material. I'm using PLA, all standard settings, 60 bed 215 extruder. I'm posting another picture that may help shed more light on the issue. I printed a small part, about 3/4" diameter that's threaded. The first thing I noticed is that the top and bottom had flat sides and were not truly rounded like the sides. I used a red to point out the sides that were more 'flat'. Does this provide more evidence to your Y-Axis theory?

Yes, it does. The way the object is flattened shows slop in the Y axis. I'm sticking with the guess that the problem is with the pulley, but as @tim-m30 says, it could be a loose belt too.

RE: What causes this? Too hot?

The more I look at the image to more a sloppy loose belt fits the problem.  Hysteresis diagrams come to mind when looking at the part.  We're talking millimeters of slop: several teeth of looseness.

Telly - post a photo of the printer - extruder pushed to the left and bed full back.

RE: What causes this? Too hot?

Posted by: ...

The more I look at the image to more a sloppy loose belt fits the problem.  Hysteresis diagrams come to mind when looking at the part.  We're talking millimeters of slop: several teeth of looseness.

Telly - post a photo of the printer - extruder pushed to the left and bed full back.

The belts would be visibly drooping if loose by a few teeth.

RE: What causes this? Too hot?

Yep - and why I want a photo of the printer ...

RE: What causes this? Too hot?

Well guys, this simplest explanation does it - the Y-axis pulley was loose. The pulley was mounted and tightened properly on the flat but for some reason the tension loosened up on the belt. I took it apart and tightened it, the last print is now round like it should be and the threads look great. I haven't tried a larger part yet to see if I have the original issues again.

Thanks @tim-m30, @vojtech-p6 and @peter-m26 for offering up suggestions to help me troubleshoot this issue; albeit a simple one that I now know what to look for and how to resolve. I've also started to use warm water and alcohol cleaning more often.

Thanks!

RE: What causes this? Too hot?

Flat First: Drive gears must be tightened flat-first.

1)   Start with both set screws fully loosened so the pulley is free to spin on the motor shaft.

2)   Align one set screw dead center with the flat on the motor shaft, slowly tighten the screw until it fully contacts the flat surface.

3)   Torque the flat set screw to spec.

4)   Now tighten the jam set screw, and torque it to spec.

Once tightened, never touch the flat set screw unless the jam screw is first fully loosened.

Why Flat First? Set screws have flat ends. If you tighten the jam screw first the set screw on the shaft flat doesn't fully contact the shaft, only one small edge of the screw surface is biting. Reversing torques can easily shift the shaft to a position the flat screw no longer contacts the shaft. This lets the jam screw wriggle loose. And after a while, vibration loosens the screws until the gear is free to rotate.

And you don't need LocTite when using this method. The second set screw jams the assembly so nothing can move.  

RE: What causes this? Too hot?

And you don't need LocTite when using this method. The second set screw jams the assembly so nothing can move.  

Interesting. How would that work? What forces would make sure vibrations don't loosen the screws eventually?

RE: What causes this? Too hot?

Well - if you understood mechanical things I could explain. But friction and torsion are involved.  Dig up a good ME curriculum and study.