1.0mm nozzle odd top/bottom shrinking

[jaysenodell 18]

Setting up for "bulk printing" with 1.0mm nozzle. Bulk in this case is large objects not so much large quantity. I have things generally working ok until I try to optimize for "print big faster". But that I mean upping the layer thickness to 0.6mm which should be well within the scope of a 1.0mm noz. The problem that I'm seeing is that as I increase the layer thickness the "top/bottom" layer shinks in the XY by about the thickness of the Z change from default 0.32mm layer thickness. 

 

I've attached a 3mf from a run of a 20mm cal cube with layer at 0.6mm. Pictures of cube. The wall, top, and bottom quality are fine with the exception of the shinkage that should obvious. Any suggestions? 

 

10mm Calibration Cube - 1.0mm PLA.3mf

Edited February 11 by jaysenodell

[gr5 2,265]

I think you need more cooling on your printer.  If you are going to 4X the volume you need to at least double the amount of fan.  You need each layer to cool completely before you start the next layer

 

Or since you say you will be printing large objects, try printing something much larger in X and Y just to see if that gives each layer more time to cool before the next layer is placed down.

[jaysenodell 18]

Let me making that a 50mm cube and see if it is better. Please hold. 

 

Likely need to do the same with the temp tower too. this little one is unhappy. 

[jaysenodell 18]

Well this is fun..  I can’t get past layer 8 before the infill is torn apart by the nozzle. You can hear it snaking the hardened previously laid infill as it lays a new line in the same layer. 

 

that said, you can still see the shrunken bottom layers. 

 

I did slow the head down as well. It’s interesting that the shape is so convex. You can see it was stuck to the bed like the government is to my paycheck. This is creality pla that I’ve been using since day one. Only real change is big nozzle. 
 

Is it unrealistic to expect the ability to print and 0.6mm layer with a 1.0mm noz?

[Slashee_the_Cow 480]

4 hours ago, jaysenodell said:

Is it unrealistic to expect the ability to print and 0.6mm layer with a 1.0mm noz?

Not completely unrealistic, at least when it comes to the nozzle size : layer height guideline ratio, although you are sitting on the borderline, and obviously it varies printer to printer.

 

You're just asking a lot of the printer - depending on the line width, it's at least 3x the flow rate of a 0.2mm layer height on a 0.4mm nozzle (which isn't a problem, a 0.4mm nozzle can push more than 0.2mm). But you have to consider the following:

• Can the extruder keep up the flow rate required?
• Can the hot end get hot enough to heat the filament all the way through? You need to run hotter than normal for that material because you have more filament going through the hot end at once (like how a microwave will get the outside of something burning hot while it's still freezing in the middle, although maybe not that extreme a difference).
• Slowing down the print head is a good idea - it reduces your flow rate and gives the material more time under the fan to cool.
• Can the fan cool your filament quickly enough? You have a lot more to cool and again, it has to cool all the way through. A second fan is not an uncommon printer mod.

Another important thing: you have to get your bed dead flat, or at least as close as possible, and make sure your Z offset is perfectly tuned. If it's even a smidge too low then the nozzle could be smooshing the first layer down and spreading it out a little a bit.

 

One experiment that may be worth trying: try printing without heating the bed. PLA doesn't need a heated bed, although without it you might sometimes need some hairspray or something to make sure it sticks. Like almost everything, plastic contracts as it gets cooler, so if your bed is heated then the bottom layer will never contract.

 

With the calibration cube in the first post, I suspect the problem is something to do with how the parts with the letters (and any skin that generates above and beneath them) are printing more slowly and have more material (thanks to the walls and such) than the empty layers - more material reduces the effects of expansion/contraction because it has to fight itself for the space, and because they take longer to print they're cooling at a different rate.

 

Cura does have a feature built in to handle this, although it sort of defeats the purpose of printing bigger to be quicker. In Cooling > Minimum Layer Time you can set the... well the minimum time it will take to print each layer, by slowing down the print head to as low as Cooling > Minimum Speed. If it can do the whole layer in less than the minimum time even at the minimum speed, it'll just wait at the end until the time is up. If you make sure your empty layers take as long to print as the ones with stuff in them, the cooling effect shouldn't be nearly as prominent. But as I said, defeats the purpose of "bigger nozzle = faster prints". Try different layer heights, changing it a bit each time, and see how high you can go without having issues like this (and remember, small scale testing is your friend).

[gr5 2,265]

I agree with messing with the "minimum layer time" feature.  I still think it's a cooling issue.

 

It's possible the print head isn't keeping up but it's usually obvious if you look at the temperature of the nozzle - it will be dipping below the desired temp.  So if your print temp is 200C then you will see it dip down to 195C or lower.  But I don't think this is your issue.

 

That curve you see near the bottom is quite common.  Some people call it "elephants foot" but that's a bad name as it often doesn't look quite like an elephants foot most of the time (including your example).  But you can google "elephants foot 3d printing" or something and see what other people say.

 

Elephants foot only happens on heated beds.  I'm not saying you shouldn't use a heated bed.  And if you are printing PLA you want the bed well above 52C but as cold as possible to reduce "elephants foot".  60C is the recommended temp.  70C will definitely give you some "elephants foot".

 

There is a setting to help a bit with "elephants foot" called something like "initial layer horizontal expanstion".  Set that to about negative half the nozzle width so something around -0.5mm.

 

So that curve is related to how hot PLA acts when still in liquid form.  Imagine the 3rd layer up is being printed.  The molten platic comes out and within milliseconds it is cooling which means it is shrinking.  And molten PLA sticks to itself like snot.  LIke mucus.  So it is like a liquid rubber band.  As you go around the outer corners of a cube it is pulled inward like a rubber band but the layer below is holding it from shrinking too much.  But if the layer below is still not completely solid you get that "elephants foot" shape.  As you get farther from the heated bed, things recover.

 

So...  add more fan.

[jaysenodell 18]

Hmm.. fan at 100% already. With 0.4 and 0.6 Was runing 210/200 and 65/60 initial/subsequent with good results. Since I can't "up the fan" would lowering the initial temps be viable. 

 

The extruder show no flucturations on temp with the 1.0 when priting. I have the "upgraded" sprite direct drive on this (ender 3 s1 pro). Even when I was trying to increase the print speed to 100mm/s the temp was rock solid. I think the largest fluctuation I noted was 0.5°. 

 

I do think I have my Z too low for this noz. The initial layer is super squished. I have to pry the PLA off even after the bed has readeched room temp. As far as flatness.. it's an ender. I have the "it's withing acceptable limits" warp. I've been avoiding "fixing it" because the ABL mesh has worked around it well enough so far. 

[gr5 2,265]

Squishing is good as it keeps the part from warping off the bed.  Especially as you get parts that extend all across the print bed.

 

I don't think lower printing temps will help much.  You want to cool the layer being printed onto.  Down to maybe 70C?  60C?  not sure.  When you print a much larger part - it will have much more time to cool down.

 

When I said "add more fan" I basically mean: modify the printer.  Crossflow fans are a good option.  Or a desk fan.  But if this is just a test and you will be printing parts that cover the whole print bed, then no fan should be needed.

 

But if you are going to be printing 20mm cubes with this volume of plastic then you need more cooling.  Much more cooling.  Like maybe 4X as much cooling.  Or you can switch to a higher temp material like PETG which only needs to cool down to maybe 80C before putting the next layer on top.

[jaysenodell 18]

The end prints are large oval tubes in the 200x180x1200 range (some shorter). Tube being key. They are hollow inerior. I'm using the cubes in an effort to ensure I have the printer dialed in before I start blowing through media (each tube set is about one spool). With the 0.6 it was 24hr per section (three sections), I need to try to get it down closer to 24hr for the whole thing. 

 

I have moved my test cube up to 50mm to be more real. maybe move it to 100mm...

 

Lowering temps is resulting in some bed adhesion issues (as predicted). Ran some "bottoms only" tests for Z offset. My personal opinion is that strict measurements are great in a lab, but sometimes you have to look that the results. Added 0.06mm more space between snoz and bed to get less "push" on the edges but still have 100% closure between lines.  

[jaysenodell 18]

So I'm thinking (which is dangerous) why do I need 4 top/bottom layers when each layer 0.6mm thick. Same with wall layers. Do I have room for speed  optimization here by reducing wall/bottom/top?

[Slashee_the_Cow 480]

9 hours ago, jaysenodell said:

The end prints are large oval tubes in the 200x180x1200 range (some shorter). Tube being key. They are hollow inerior.

9 hours ago, jaysenodell said:

I have moved my test cube up to 50mm to be more real. maybe move it to 100mm...

Don't print cubes, print tubes! Cubes and tubes behave differently mechanically, for starters because one has corners and one doesn't. Calibration cubes are sort of like benchmarks for computers: it doesn't matter what the hell your computer scores as long as it works like you want it to. If you can print tubes fine but your calibration cubes are off, who cares?

 

6 hours ago, jaysenodell said:

So I'm thinking (which is dangerous) why do I need 4 top/bottom layers when each layer 0.6mm thick. Same with wall layers. Do I have room for speed  optimization here by reducing wall/bottom/top?

If you're testing with hollow tubes, you don't need any skin 😄. I'd never go for a single wall, even if it's thick, it has no way to spread stress and walls adhere great to other walls, so you could probably get away with 2 walls, but I would use as many as you intend to use in the finished product to best replicate the conditions.

 

10 hours ago, jaysenodell said:

Lowering temps is resulting in some bed adhesion issues (as predicted). Ran some "bottoms only" tests for Z offset. My personal opinion is that strict measurements are great in a lab, but sometimes you have to look that the results.

We call this the "trial and error" approach. Since I've yet to see a printer made to the tolerance standards Lego uses (seriously, everything has to be exactly perfect and they randomly test batches) there's no perfect setting that will work for every printer of a particular model, and in this case, the bigger you go, the more room for error... literally.

 

10 hours ago, gr5 said:

When I said "add more fan" I basically mean: modify the printer.  Crossflow fans are a good option.  Or a desk fan.  But if this is just a test and you will be printing parts that cover the whole print bed, then no fan should be needed.

 

But if you are going to be printing 20mm cubes with this volume of plastic then you need more cooling.  Much more cooling.  Like maybe 4X as much cooling.  Or you can switch to a higher temp material like PETG which only needs to cool down to maybe 80C before putting the next layer on top.

I have one of these. It's designed to circulate the air in a large room without having a regular fan blow all your stuff around. But this thing BLOWS. I haven't needed it for printing... yet.

[gr5 2,265]

34 minutes ago, Slashee_the_Cow said:

Don't print cubes, print tubes! 

 

Agreed.  Maybe make a test one only 2cm tall.

 

[jaysenodell 18]

Well fine. I shall simply chop a tube at 2cm and see how it explodes.

 

I'm also thinking I need to increase my "hop" distance to reduce the snoz smack on infill. The Z hop at 0.2mm is no prevening the snoz from removing the top layer of infill. 

[jaysenodell 18]

Ironically the cap is exactly 20mm high so there's a perfect test. 

 

I definately need to reduce the wall count as I'm basically printing a solid infill at this point. Also need to use way less wipe distance; there are some underextrudes on z starts (I see them on layer start but not really visiable since I'm using radom z seam). 

 

I am seeing a bit of temp wobble on long wall runs (199.1). 

 

I this will work fine given the 3hr reduction on this part. I need to run a few more test prints on this though. I'll keep you updated.

 

Cap_10_PLA.3mf

Edited February 13 by jaysenodell

[Slashee_the_Cow 480]

3 hours ago, jaysenodell said:

Also need to use way less wipe distance; there are some underextrudes on z starts (I see them on layer start but not really visiable since I'm using radom z seam). 

If you're having specific problems like that, put the Z seam in the same place every layer so you can see if any changes have an effect.

 

Wipe distance (unless it's huge, but you shouldn't need huge since it really only needs to cover the Z seam) shouldn't make too much of a difference. If you think it's causing a problem you can turn up Travel > Retraction Extra Prime Amount. This will technically cause overextrusion but if you're underextruding then it can help even it out. Basically it makes it push a bit more filament into the nozzle than it retracted to make sure there's enough pressure in there to start extruding as soon as it starts trying to extrude. Can make a difference on Bowden extruders because they're slower to react to changes than direct drive extruders.

 

*loads project* Okay yeah that's definitely waaaaaaaaaaaaaay too much. Shouldn't need to be more than 1-2mm. Whenever the input field in Cura turns yellow that's basically saying "this is technically possible, but you should double check just to make sure".

 

3 hours ago, jaysenodell said:

I am seeing a bit of temp wobble on long wall runs (199.1). 

Technically will make a difference, practically shouldn't make enough of one to notice, unless you need to print parts with the precision required for a rocket used for a moon launch.

 

7 hours ago, jaysenodell said:

I'm also thinking I need to increase my "hop" distance to reduce the snoz smack on infill. The Z hop at 0.2mm is no prevening the snoz from removing the top layer of infill. 

Well you are printing 0.6mm layers. You want to be double sure it won't hit anything, make your hop height taller than that.

[jaysenodell 18]

This is not “the best print” but most recent…

 

wipe 0

coast false

2mm walls

0.6mm height

retraction false

 

those voids align with layer starts/stops. All I can think of is that I need “prime” in the snoz for a few seconds before the start. I see the SAME thing on layer 0 as well.
 

 

[jaysenodell 18]

3 minutes ago, Slashee_the_Cow said:

put the Z seam in the same place every layer so you can see if any changes have an effect.

Sure… make a suggestion that would simplify my troubleshooting. Bah!

 

4 minutes ago, Slashee_the_Cow said:

Travel > Retraction Extra Prime Amount. 

once again, I need to ask, is that in expert/all settings? I’ve looked for that and couldn’t find anything resembling prime other than “flow for prime towers” 

[Slashee_the_Cow 480]

1 minute ago, jaysenodell said:

once again, I need to ask, is that in expert/all settings? I’ve looked for that and couldn’t find anything resembling prime other than “flow for prime towers” 

Sorry, I keep forgetting that I always have all settings shown so I don't know what's not in the other modes. Although if you search (as in, using the search tool which I'm pretty sure is at the top of the settings but I can't be 100% sure because I use a plugin which changes the settings interface so each category is its own tab) the settings for something it should show up regardless of whether it's normally shown or not.

 

But as a general rule I don't make up settings*, so assume it's shown in expert/all if I mention it.

*Except for people who act like self-entitled <censored> and deserve to be messed with

[jaysenodell 18]

Fun nugget, the UI says “yep, this section would have something but you don’t trust yourself to see it”.

 

although… maybe that’s not an options for “draft” mode? Or because I have retraction off. That’s it. Retraction is off. Have it now. What a moron. 

[Slashee_the_Cow 480]

2 hours ago, jaysenodell said:

What a moron.

We all have our moments. The "moron" part really depends on their frequency.