why doesn't this print now? It has before  

RE: why doesn't this print now? It has before

Posted by: @paul-beard

This has printed perfectly before. This week, before and after a new print bed and a couple of complete re-calibrations, it won't. The workpieces consistently show those gaps you can see in one of the toroid "blades." That was not the case a couple of weeks ago. Same filament, same machine. Seems almost if if the bed is not level but how did that come to be and why isn't it being picked up in the calibration process? 

First off how's your first layer looking there is a chance the new printbed isn't level my favorite way to test that is print a 1 layer thick square the size of the bed that will Also insure the first layer is dialed in correctly 

Your first layer looks OK.  If it has printed well before it's likely to be a filament issue; have you kept it dry?  Have you  printed a different type of filament in the interim?

What is the filament?

Cheerio,

RE:

it's Prusament. It was bagged up before this job. Lots of other colors and filaments have been run through it. I just ran a much more involved job overnight and those pieces look OK, no thin layers or sections like this though. 

If it hadn't printed OK before I'd have asked to see the project file.  As it's been out at this time of year it's worth drying the filament - then print a little slower to aid interlayer adhesion.

If you have used any higher temperature filaments purging by manually pushing some PLA through at the higher melt temperature should shift anything left behind.

Cheerio,

RE: why doesn't this print now? It has before

I am not that sophisticated as to run different temperatures for different flavors of PLA. I know the various slicers can manage all that. If I can tame some of these issues, I can drill down into the specifics of that. But I'm not investing the time in that just yet. I have this filament in a sealed bag with large dessicant pack, I'll see about running it again a day or two. The fact that the artifacts show in the same places on every print are curious, as if the bed is out of compliance. I'd expect more randomness, maybe a chunky first layer, but I am not seeing that. It's always the same…what look like inter-layer gaps in the same places. 

RE: why doesn't this print now? It has before

With the curved perimeters and the slope the ga-a you see are caused when the layer being laid down does not adhere to the previous layer. It’s probably not related to bed level at that point, it’s far more likely to be environmental factors or the filament taking on moisture. Colder ambient temperatures for example. Which is why Diem suggested slowing the print down. This gives more time for the layer to adhere. Printing hotter can do the same thing. 
Also just because it’s stored with desiccant does not mean it’s has not taken on moisture. 

OK, I wondered if you'd been printing PETG or similar and left residues.  Dessicant doesn't dry filament, it does slow down the rate of water absorption but don't rely on it for long periods.

Go back and check the same places in parts you printed before - perhaps there was an issue that went unnoticed.  If so: save your project as a .3mf file

Files > Save Project as

Zip the .3mf and post it here. It will contain both your part and your settings for us to diagnose.

Cheerio,

RE: why doesn't this print now? It has before

enjoy 

RE: why doesn't this print now? It has before

Posted by: @paul-beard

This has printed perfectly before. This week, before and after a new print bed and a couple of complete re-calibrations, it won't. The workpieces consistently show those gaps you can see in one of the toroid "blades." That was not the case a couple of weeks ago. Same filament, same machine. Seems almost if if the bed is not level but how did that come to be and why isn't it being picked up in the calibration process? 

It looks like some of the print isint touching the bed and some is am I right

RE: why doesn't this print now? It has before

That's top and bottom of one piece so no, it's not all in contact with the print bed. I removed it to inspect it, then thought maybe someone here could add some clarity. 

RE: why doesn't this print now? It has before

Same design/STL printed on an AnyCubic mega S. Looks good. No gaps between layers or any of that. 

I printed it with your settings and freshly dried Prusa PLA - it came out perfectly so you probably have a filament issue.

Having said that - the part is very light, too light in my opinion as it is likely to distort in operation.  The thickness allows for just two strands of filament to be laid down in each layer, I would thicken it to allow for some semblance of an aerofoil profile incidentally increasing the stiffness.

Do you gain much thrust to power ratio advantage with this part?

Cheerio,

RE: why doesn't this print now? It has before

Based on my using the same filament on a different machine and your print on whatever you used with good results, I suggest it's not the filament that's at issue, but the machine setup. As noted, it has been printed correctly in the past, same machine and filament. It's worth noting that the failures occur in the same places on subsequent prints, not in random locations. I may try again with two different filaments on it later today, just as a reference test. It may be too delicate to scale down or I might try copying it to test multiple prints: the print bed can only hold one of these at a time. 

I ran a couple of larger jobs yesterday on it (12 hours for one) and they came out very well but did not have any parts as delicate as this piece. 

As to performance, I didn't design the piece, but it does offer good results. 

I also have a hygrometer arriving today to get some data on humidity, both ambient and in the sealed bags I use. 

Sorry, I should have said, I printed on Mk3. 

Filament is very sensitive to atmospheric moisture.  Dry it.

Cheerio,

RE: why doesn't this print now? It has before

¯\\_(ツ)_/¯ 

The same filament on two different machines with different outcomes seems to remove filament from the equation. Resolution/print quality might be an issue, I have yet to dig into that. Maybe the Prusa is set to a higher resolution (.15mm vs .2mm, for example). 

My hygrometer is out for delivery so perhaps will give me some more data around humidity/moisture. 

RE: why doesn't this print now? It has before

While waiting for the hygrometer and after a couple of unsuccessful print jobs, I decided to run another Live Z box check — 12 boxes, .2mm in thickness. I quit after 10 squares, I had seen enough. It looks like -1.825  is the sweet spot but -1.85 will work as well. This is after a  7 x 7 calibration and PINDA calibration. Whether or not you can write on your first layer is a good test: the -1.7 layer was too ragged as were -1.9x. 

This is what I am seeing for ambient humidity. Marginal, from what I can determine. 

That toroid rotor still prints fine on the other machine, running right now. 

Far too humid. Print quality drops with only a couple of days at 50%.

Thomas Sanladerer tests filament drying:

After a week exposed in a room with a dehumidifier running there was noticeable deterioration of PLA finish...

CNC Kitchen - skip to 7.40 for time to fully hydrate results.

( 5 days )

Cheerio,

RE: why doesn't this print now? It has before

Well, in that case this hobby will never work here. Are there classified ads here where people in non-desert climates sell their kit? 

RE:

Just buy a cheap food dehydrator and dry your filaments. 

We see a seasonal pattern of humidity problems in the forum.  In winter when central heating is on and to a lesser extent in summer there are relatively few such problems with the common filaments.  In spring and autumn when neither is in use the issues spike.  Unfortunately whilst aircon and heating reduce problems they don't eliminate them so experienced users routinely dry their materials.

Cheerio,