Z-scars? Or something else?

[swbluto]

The only thing that solved the z-scar for me was a coast distance between 1.8 - 3mm, depending on the filament in question.

Matching your outline speed to the coast value is important, too. I keep my outlines at 20mm/s to keep things looking nice (And to control that variable for standardization facilitating ease of finding the optimal combination of values.)

[thegammaray]

Alright, here's my current (final?) situation: I've found a combination of settings (including print & travel acceleration, coast, extrusion multiplier, print speed, and x/y movement speed) that eliminates blobs at the layer change points. But I'm still left with these tiny divots that seem to result from the printer not quite completing the layer. In other words, the ends of each layer ring don't quite meet. I don't know whether the layer is begun too late or abandoned prematurely.

In any case, the divots are insignificant. I just figured I'd let people know where I ended up, and maybe learn something about the various print settings in the process. Thanks for all your help! Stay tuned for my inevitable next forum thread.

[3dPrintingMD]

You would have to post the profile in order to know. Sounds like your coast is too much.

I would honestly like to see the settings and give it a try.

[thegammaray]

You would have to post the profile in order to know. Sounds like your coast is too much.

I would honestly like to see the settings and give it a try.

My coast might be too much, but I don't think that's the cause of the divots. They seem to happen even without the coast. Reducing the coast value seems to increase the lumps before the divots. But I dunno.

I've attached the FFF profile. Just to make sure we're performing the same experiments: I've been printing that owl at 25% of original size.

NOTE: I use a Zebra plate, so adjust the profile accordingly for other surfaces.

[3dPrintingMD]

While I've seen it recommended a bunch of times, I have not had good results with a 5mm wipe. I'm at work, but I believe I found that something small, like 0.20mm is a good wipe and 0.05 coast.

I would back down your wipe to say 0.05, leave coast where it is, and see if you have any different results.

[Jules]

Looked at your profile and saw a couple of things:

1. You were still using multiple outlines. That's what's causing those "backing up" divots to form.
2. Your infill is too low. Upped that to about 25% or so, because deep divots will form over low infill, especially on curved surfaces.
Increased your number of top solid layers.
3. You don't need to coast at all with PLA. Coasting causes the extruder to stop extruding for however many mm you have it set for before the end of the row. That causes a thin spot in the print. (PLA does not require coast. Other filaments sometimes do.) Since you are having divots form, the coast is making the situation worse.
4. The owl does not require support to print, so i turned that off.
5. I upped your speeds in a couple of places, and lowered the cooling speed threshold. It's a very small print and requires a bit more cooling time on the tiny top layers.
6. I increased the first layer height to 100%. You generally don't go lower than 100% with a first layer height, although you can go higher if you need help getting the thread to stick in a low spot on your plate.
7. Your Z-Offset value is on the high side at -0.27 mm. I left that alone, because it might be giving you perfect first layer adhesion, but if you have to move the bed that close to the nozzle with the offset, it would be a good idea to look into re-setting your Z-Stop one of these days. (Not now....try the attached FFF profile first.)

Try the profile below and see if it works any better for the little owl before messing with re-setting the Z-stop.

mine 2 PLA.zip

(2.92 KiB) Downloaded 496 times

[thegammaray]

Sorry for the delay. Real life keeps interfering with my hobbies. >:[

1. You were still using multiple outlines. That's what's causing those "backing up" divots to form.
2. Your infill is too low. Upped that to about 25% or so, because deep divots will form over low infill, especially on curved surfaces.
Increased your number of top solid layers.
3. You don't need to coast at all with PLA. Coasting causes the extruder to stop extruding for however many mm you have it set for before the end of the row. That causes a thin spot in the print. (PLA does not require coast. Other filaments sometimes do.) Since you are having divots form, the coast is making the situation worse.
4. The owl does not require support to print, so i turned that off.
5. I upped your speeds in a couple of places, and lowered the cooling speed threshold. It's a very small print and requires a bit more cooling time on the tiny top layers.
6. I increased the first layer height to 100%. You generally don't go lower than 100% with a first layer height, although you can go higher if you need help getting the thread to stick in a low spot on your plate.
7. Your Z-Offset value is on the high side at -0.27 mm. I left that alone, because it might be giving you perfect first layer adhesion, but if you have to move the bed that close to the nozzle with the offset, it would be a good idea to look into re-setting your Z-Stop one of these days. (Not now....try the attached FFF profile first.)

1. A couple weeks ago, I tried a few prints using single outlines, but I couldn't tell the difference in divots. I reverted to multiple outlines because I kept snapping the prints in half trying to get them off my built plate.
2. I couldn't tell the difference with infill percentage either, so I lowered it to save plastic.
3. I tried two owl prints using the profile I posted earlier, one with coast and one without. I can't tell the difference in a blind test. I guess I may as well disable coast to keep things simple.
4. I must have left it on by accident. I haven't been using support for the owls, but I've been intermittently trying to print Donkey Kong. He's..... difficult.

6. Why would we raise the first layer height to accommodate a low spot on a build plate? I thought first layer height was a percentage of the distance between the nozzle and the nominal bed location, making a lower number appropriate for a low spot on the plate.
7. I've found that my manual Z-stop adjustments are much less precise than changing the offset value. I have several craters in my Zebra plate from inept manual adjustments. :S

Thanks for the attached profile. I printed an owl using it, and it turned out relatively well. I don't think I could tell the difference in a blind test with that one either, though. I was planning to post pictures, but I accidentally broke the owl in half. See point 1.

What's the logic behind raising the temperature of the nozzle? I've been told to print at the lowest temperature the material will tolerate, but obviously there's wiggle room given that MakerGear recommends 220.

[Jules]

Sorry for the delay. Real life keeps interfering with my hobbies. >:[

.....I kept snapping the prints in half trying to get them off my built plate.

2. I couldn't tell the difference with infill percentage either, so I lowered it to save plastic.

If you are snapping your owl print in half, you are not removing it correctly from the bed. If it's stuck that hard, you'll want to freeze it off. Put the whole plate into the freezer for about 10 minutes - the owl will pop right off into your hand. (And it's always best to use a thin spatula to just pry up from one corner on your prints - it breaks the seal.)

Ed just did a nice little write-up on another thread discussing the differences between number of perimeters and infill amount. Might want to take a look at that. viewtopic.php?f=2&t=3132#p20313

In this case, you are printing that owl at one quarter size and the details are incredibly tiny. The reversals show more on that small of a shape, and a single perimeter gives a better result. So you would want to increase your infill to compensate for the single perimeter and build strength into your model.

And for organic shapes (rounded on the top) you want to increase your infill a bit, and the number of top solid layers. It makes for a nicer top surface finish.

6. Why would we raise the first layer height to accommodate a low spot on a build plate? I thought first layer height was a percentage of the distance between the nozzle and the nominal bed location, making a lower number appropriate for a low spot on the plate.

From the Tips section on the S3D forum:

"If your First Layer Height is below 100%, the extrusion amount will remain the same, only the Z-will change, but if you increase above 100%, the extrusion amount will scale accordingly."

That means that using a first layer height under 100% only moves the nozzle closer to the bed, and you can do that more effectively with the global Z-Offset. In addition, lowering the first layer height under 100% is actually interfering with whatever you have set up as your Z-Offset value.

If you have a single low spot somewhere on the plate though (glass is rarely perfectly flat, and neither are Zebra plates), over-extruding a little bit by raising your first layer height gives you a better chance of filling the low spot and getting good adhesion there.

While it's okay to keep adjusting your first layer height to compensate for a bad gap (which you have - it's too large) you are working a lot harder than you have to.
(If you set that Z-stop correctly, (you just have to do it once) and then you can fine tune with the Z-Offset, and that shouldn't change until you change filament type. It will make the rest of your prints go a lot quicker/smoother.)

7. I've found that my manual Z-stop adjustments are much less precise than changing the offset value. I have several craters in my Zebra plate from inept manual adjustments. :S

Yeah, with a Zebra plate you absolutely have to use a metric feeler gauge to set the Z-stop. Hitting the plate with a hot nozzle does cause divots. (Sorry to hear that - totally sux!)

If you're happy with the prints, keep on doing what you're doing. You're getting very good prints. There's more than one way to cook a goose, and there is no "one right answer" for everyone. But if you want to try the other method, make sure you use a gauge to set that gap. (I use a 0.15mm gauge (0.006 in) to set the gap while the bed and nozzle are hot.) Just make sure to not hit the bed with the hot nozzle. (But you know that part! )

If you've got a V4, it's very easy to set the gap correctly by adjusting how the nozzle is seated. (Instead of futzing with the Z-stop screw.) Steve's got a great write-up here:

viewtopic.php?f=3&t=2783

And after that, a quick calibration to fine tune with the Z-offset, and you'll be good to go with all your future prints:

viewtopic.php?f=3&t=3124&p=20258#p20258

I know it's a bit of a pain to think about re-setting that gap - the payoff is much easier prints in the future. Your prints are already good.

[Pekish79]

my Zebra look like a piece of swiss cheese but it's still working yesterday i tried PEI (i have 2 pei plate as well one on the back of my most tortured zebra and one on a glass) and nothing was sticking till the day after when i noticed i was using the glass side thinking was the PEI side.... no comment

I still think i like Zebra the most but pei if you actually use the pei side is good and slightly cheaper true is the office pay my part/material/plate so i tend to judge without keeping cost in account

anyway last but not least my Mic6 plate arrived and is too big i said 8x10 but i guess they chopped it slightly too big and hit the screw not sure if i want to go to the trouble to send it back maybe is the fate that tell me to dont bother with it i will try to use it once with just rubber and clamps no screw (or only some screw and not all) but i am not in a rush to try it.

so far i will keep my wavy zebra in which some corner stuck too much some other too little but at the end we find always the way to print something