Rough start...
Been printing 100% for a while and all of a sudden, first layers are always going down horrible after a few minutes.... On different print jobs as well.
Standard Ratos installation and doing a 20 X 20 bed mesh
62 Replies
Still cannot figure out why. New Nozzle, different print,
It is as if the mesh is not been taken into account
This is too close to the bed, if you are using Beacon Contact, follow the guide, lift the Z, and then Save_Z_Offset
I believe it's the same issue as I have (longterm, regardless of probe - inductive probe, Klicky, now Beacon). It starts OK, but after a while it's more and more "too close to bed":
If I recalibrate it, the next print starts with gaps on the beginning of first layer (and I mean really gaps between lines, basically sparse infill :-D).
Preheating bed / heatsoaking (10, 15, 30, 45 minutes, name it) doesn't help.
Another example (offset was purposely set at height when there are clearly gaps between lines. At least at start of print). When printed, the offset wasn't manually altered, it was kept as is. Bed was heatsoaked for 30 minutes:
The problem seems to be independent of bed position, it's rather ... time dependent (it shows after about 5-7 minutes from start of printing. Hotend is Rapido2 UHF)
and another example, just to show the print position on the bed doesn't affect it (since this print starts at the most "squishing" place of the previous one). Everything was the same as in the previous print (no changes were made, except the printed object):
@Raymond can you confirm the same or should I create my own post?
I don't want to hijack your post so if our issue differs in any way, please tell me and I move my issue to separate post.
Have you tried lowering accel on first layer ?
How this can relate with it?
I'm more concerned to things like thermal expansion or so.
For example, did you know the hotend itself (dunno which part, so whole from its mount to the tip of nozzle) can expand by 0.07mm in the first 12minutes from beginning of printing when it's heated to 230°C?
Which means 12 minutes from start of printing the nozzle is lower by this value than it was at the start of printing.
(I finished the measurement right now)
and 12 minutes of printing is about half of this first layer https://discord.com/channels/582187371529764864/1257286106299371621/1269287372172955658
Well... Many trials and errors... works for me on 15 printers. I set accel to 2000 on first layers, speed @60 and 180 for fissrt layer infill
That's the thing, how can accel even possibly relate to fact, that 1st layer is printed lower and lower by time since hotend is heated to final temperature? 🙂
Sometimes things don't appear to make sense, even though they do. I've discovered that a while ago while printing on glass. Try it...
With regard to expansion, I preheat my hotend to 150C prior to z tilt and bed mesh (old habit from prusa's pinda). Thermal expansion may me "pre-loaded", at least partially as well.
Pre-heat to 150°C is done by default on all contactless probes on RatOS (and on Beacon too, even if it is used for contact probing). So there's nothing different between you and me.
BTW. you print 1st layer faster than me 😄
Almost twice as fast when comes the infill (which is quite fast to me). Which also means if you have same issue, you kinda didn't notice it, because you finish 1st layer about the time when I'm at the half of it - where the issue starts to be noticeable. Which is more likely to be the reason than changing accel (although it doesn't solve the issue, more like hiding it between 1st and 2nd layer. Yet, it can be "good enough" solution).
Anyway, let say not throwing right away any advise, even when it sounds highly unlikely, this is result of your recommended speeds and accels:
(to avoid "you are too close to bed", please notice it starts so high it has gaps between lines (lower left corner on the picture is start of print)
Or if you want different light angle:
Overall, it is as I expected. Slightly better results but only because of overall print time was shorter (due to much higher infill speed than I normally use) hence it (hotend?) didn't have time to fully expand.
In theory, there's no difference between theory and practice.
In practice, I print hundreds of not thousands of hours every month without your issue. I print real parts, not theoretical 1 layer squares. Should I tune my reality to your theory then?
This is the practical print which remainded me I really have to find solution against it:
To successfuly print these, I had to raise z-offset manually several times during printing 1st layer.
👍
Try lower infil speed?
You mean back to my settings? Which is 50/80 for the first layer
Eh, sorry for the tone. It's not your fault.
It just pisses me really off and so far nothing helped (the best "improvement" so far was to wait with hotend at final temperature about 10 minutes right before start of printing. Which is not ideal and moreover the improvement wasn't so better to go this way since it has own issues).
Sign me up for the exact same issue. I have had it since day one of now going on 2 years. I basically babystep the entire first layer and then also the second and third to adjust gradually. Now, with beacon, it seems to have improved. Although I think it also shows me that there might be something mechanical going on, as after a couple of prints I have to adjust my Z again.
I only have 500's so it should theoreticaly be worth. Indeed lower your speeds ? I usually set first layers @0.24 to 0.32. maybe that could help. Also depends on material (I've stabilized my suppliers for each type of material, that helps a lot for tuning).
Also, the more "warpy" a material, the more I give it z offset
The first two, three pictures were PETG, the last one was PLA.
(not counting the bowl picture, which is PETG)
This is for example ASA (so yeah, I can agree with the higher temperatures inside, the worse result):
@NMGMarques @3DBoomer just a question, probably not related: which hotend do you have?
Orbiter or lgx, rapido UHF or copperheads, bltouch. Also works on my prusa bears with pinda and V6. All with cht nozzles.
Rapido1 or Rapido2?
Bambu Labs 0.6.
Extruder is an LGX.
OK, so not related at all 😄
I guess not. I think we may have bed or frame issues.
Is yours a 500?
no, just 300
Not so common with 300. 500... Bigger extrusion, more flex... Bigger plate and stuff... All that could allow for my issue on a 300, I wouldn't expect that.
Both
It was just a blind shot.
So it's not directly related to any specific hotend.
Here is your 300x300 square, wet Petg, on the first available 500 I had. It has 1000th of hours and the bed mesh is crappy. 0.6 nozzle @120% , first layer height 0.28, speeds at 60 and 180, accel @2000.
I'm jealous 🙂
And confused at the same time
My typical setting is: 0.4 nozzle @125%, first layer height 0.2, speeds at 50 and 80 and accel 4k (but I also tried yours speeds and accel. No change)
So the question still remains - Where could be the source of the issue 😕
Try a higher first layer. On 0.4 I usually go for 0.24 to 0.28.
Try a very low accel? Increase temp by 5 to 10°
Sometimes I even go to 180% layer width on 1st layer.
The primary question is whether it is issue or ... "feature".
If the latter one, then attempts to hide it (such as higher 1st layer or wider extrusion) makes sense.
If it is former one, it should be fixed rather than hide.
As I see it from hours of looking at first layers, the main issue is to give the material it's best chances to spread evenly.
Increase z offset so lines barely touch each other, increase temp (fluidity), increase first layer height.
Again, you're talking about general rules but not about what is the cause when the distance between bed and nozzle is shrinking/reducing during printing the 1st layer 🙂
Is it by design? Or is it flaw which should be fixed on printer itself (how)?
I'm trying to find the cause, not how to deal with consequences 🙂
(BTW you seem to have the same issue, just not so horribly pronounced as on my printer)
In terms of hiding/covering the issue, the wider line width of infill and higher layer height of the 1st layer seems to be surprisingly effective.
(it doesn't remove the issue, but it hides it enough not to be disturbing issue. Yet, the issue is still there)
I have had same issue with different printers for years. What's interesting is that I get less of it on heated chamber higher temp prints. My guess has been that it's thermal expansion in frame itself, which just happens to stabilize more when whole printer is heated
It would be real cool to find the root cause for it
Googleing for "bed mesh not compensating klipper" then you get pile of similar issues. Some people told they got theirs fixed by replacing leadscrews with ball bearing ones, coz they had less play and allowed for more precise bed movement. I haven't tried that myself
Yeah, I think the thermal expansion is root of this too. But which one?
I believe there's no much options - it's either hotend, leadscrews or X-gantry. Everything else would cause moving away from the bed when expanding rather than moving closer. Or did I missed some part?
It could be all of these together, of course (where on account of X-gantry should be only "bowl" effect, with maximum on Xmax/2)
Just throwing this in here: https://www.printables.com/de/model/230716-ratrig-v-core-3-extrusionless-x-gantry-mod
Printables.com
RatRig v-core 3 extrusionless x-gantry mod von elcojacobs | Kostenl...
V-core 3 mod to remove the aluminium extrusion from the x-gantry and run on just the rail or a top and bottom rail | Kostenlose 3D-druckbare STL-Modelle herunterladen
I had the same problems for a year, tried everything that was advised (preheat, only every 2nd or 3rd screw for the rail, lube between rail and 2020 profile, etc.).
Switched to this mod, no more problems since then. Sure, you loose some acc because of weight, but it was worth it.
Hmm, but my bed mesh doesn't change much between cold and hot. It remains moreless the same. (perhaps because it is 300 only).
Also I don't think it solves the issue when print starts in the middle of bed and end at the edge of the X axis and yet, the ending of printing is lower than the beginning.
As I wrote, the thermal warping of X-gantry keeps Xmin and Xmax at the same height and middle of X axis goes lower.
But here it gradually goes lower regardless of X (or Y) position.
Here is the example of start in the middle of the bed (the lowest possible point when X-gantry is warping) and yet, the lowest point is at the end of print, basically at Xmin and Ymin.
Hey, sorry, have been away for a while.
Yes, same as mine but I eventually figured that is has alot to do with soaking my bed on the 500 X 500 bed.
So to overcome my issues (just tested on PLA so far). I preheat the bed to 60 and the nozzle to 150.
On the bed, the variation range starts at 0.540 and then after some time (depending on the room AC as well) , settles at around 0.375 and then I can pretty much print the full bed. I think the nozzle soak also play's a role eventually in the z height (using the revo nozzle with Voron Revo heatsink).
Every 5 minutes, I run a bed level (vcore3 500), and run a new mesh (beacon probe). When I see the range is relatively the same as the previous mesh run, then only do I start the print.
Small prints I don't bother as I don't see it too much there.
I am actually putting together a Macro that runs every 5 minutes and calculate the difference in range. If less that 1%, it will then continue to start the print so that I dont have to do this manually anymore.
Just as a extra note, this did not always happen but started and got worse over the last few months. So I wonder is the bed is "getting Worse" somehow.
Also, squaring the frame again was vital after the move
Nice.
So, I should have made own post anyway since my issue is not by bed itself (heatsoaking of bed doesn't change it at all) and height difference in my case is about 0.1mm where I already measured that Rapido2 UHF hotend with diamond CHT(-ish) nozzle can easily expand by about 0.07mm in first 10-15minutes of printing. So in my case it is probably just to find how to easily deal with the fact that is happening.
I have not measured my nozzle change on heating, but I definitely see a difference if I only heat soak the bed and not the nozzle as well versus doing both and then only printing. Would be interesting to see how much the nozzle changes.
It can be quite easily measured if you have Beacon (contact) using something like this:
https://github.com/kmarty/kmarty-klipper_config_km_addons/blob/master/CHECK_THERMAL_EXPANSION.cfg
(it's based on RatOS v2.1.
BEACON_CALIBRATE_NOZZLE_TEMP_OFFSET except it doesn't make any changes, just prints results and it uses hotend temperature defined by you. Results is list of Z positions where nozzle "found" bed (so you have to subtract first measurement which is at the room temperature), each by one minute apart).I have held back on RatOS v2.1 until it becomes an official release (see it is at RC2). Not that I don't trust it, just thought I would do it later as I am trying to keep all "surprises" out of the way while completing the current client request.
But will definitely use the Beacon to do this measurement eventually.
Maybe I should rebuild Voron V0 with beacon and RatOS v2.1 just for fun...
That macro would be real interesting. I was just thinking about something similar (adjusting z offset automatically in time, if I know it's always 0.2mm over 10 minutes)
Macro would be even better tho, but I have no idea how to make it myself 😅
Ok, that's on another 500,
and... how it helps to solve the issue with gradually expanding nozzle/hotend making the 1st layer lower and lower?
Since I already found the biggest thermal expansion, the hotend (and/or its nozzle). Within first 10-15 minutes of printing it makes nozzle lower by almost 0.1mm* (at least I believe it is the main issue, 0.1mm difference is more than enough to make 1st layer ... weird).
*) 0.07mm to be precise. I didn't recheck difference between nozzles, but somehow it seems the diamond CHT-ish nozzle expands as twice as much as e.g. tungsten nozzle which I measured expansion by 0.04mm (I want to recheck again, since it seems to me too big difference for the nozzle alone. Just not soon, I have other priorities at this moment)
Well... I don't think this is an issue. That's the point. In fact I know for a fact it is not... Proof in the pudding
well, in that case you should tell it sooner :-). In that time I didn't even know whether it is issue just on my printer (and few other owners) or whether it is general issue everyone fighting against. You came just with "my printer(s) doesn't do that" (which was anything but helpful).
I mean, yeah, you sent something, but it wasn't an explanation of it, just some setting, some more, some less suspicious (i'd even call it "snake oil", but it sound too harsh since it helped, although in different way - I've never even tried to print 1st layer so fast as you before, so it wasn't completely useless. And for this suggestion, I thank you. It just wasn't solution for the issue, though).
It certainly would be good to understand where this issue comes from. I suffered from it on my vcore3 300 with eva3&volcomosq, but I upgraded to RR toolhead beta2 (with euclid) and either I have not printed large parts or the problem went away. I'm afraid to try now.. And since I am building a vcore4 400, I would like to know the cause since those seem to suffer from the same. Not all, which is interesting, but that does not make the issue go away.