Prusa, please tell me you're working on this...
The process of starting prints is attrocious. I'm not going to make suggestions here because I have to believe you're already looking at improving this.
Cold nozzle, you start a print, the nozzle is set to 170, and the bed is set to print temp, while waiting to heat up the nozzle probes the bed. The nozzle still sitting at 170, the bed at print temp, the nozzle cleans itself (more on that below). The nozzle increasing to print temp, the printer self levels and starts the print. This is already a long process.
Want to make it longer?
HOT nozzle, you start a print, the nozzle is set to 170, and the bed is set to print temp, while waiting TO COOL DOWN the nozzle probes the bed. The nozzle still sitting and waiting for 170, the bed at print temp, the nozzle cleans itself. The nozzle increasing to print temp, the printer self levels and starts the print.
* The nozzle cleaning isn't great by any stretch. I just had the printer level itself with some hardened ABS ooze on the nozzle. It was literally pressing down directly onto the ooze every probe and started printing like 1-1.5mm too high. I wasn't fast enough to snap a picture but you know what I mean.
RE: Prusa, please tell me you're working on this...
Over 6 minutes from print start to actual print. Pretty sure my MK3s+ does under 3 for cold starts.
Also, why is the "cleaning nozzle" procedure done in the print area?
RE: Prusa, please tell me you're working on this...
I don't have the MK4, but may I assume that there is a means to preheat the machine to operating temperature? On the MK3S I've found that one of the factors to assure consistently good ABS prints is to preheat everything to operating temp and let it stabilize maybe 15 minutes or so before launching the print.
Nozzle cleaning? Is there a way to disable that? I agree that a blob of ooze may 'fool' the load cell sensing mechanism and give a false reading.
Another thing I regularly did with ABS prints before I got the enclosure was to use the draft shield. It's available on both PS and Cura. That used to really help with consistent ABS prints.
RE: Prusa, please tell me you're working on this...
The 170°C waiting step is standard on Mini - afaik it is to let the (oroginal) Minda probe temperature to stabilize and give stable results. One possibility is that it was left there by error, but imho more probable is that the lower temperature is used to limit any filament oozing during the "touch" calibration.
RE: Prusa, please tell me you're working on this...
To add to this, if you preheat to lets say ABS or something, when the print file is loaded, the printer will actually sit and wait for the extruder to come all the way back down to 170 from 255 before it starts doing it's thing.
RE: Prusa, please tell me you're working on this...
It can be done better and more quickly/efficiently imho. I'm amazed that Mini users have been putting up with this for so long.
Do minis also "clean nozzle" in the print area?
The 170°C waiting step is standard on Mini - afaik it is to let the (oroginal) Minda probe temperature to stabilize and give stable results. One possibility is that it was left there by error, but imho more probable is that the lower temperature is used to limit any filament oozing during the "touch" calibration.
RE: Prusa, please tell me you're working on this...
On the Mini the preheat always only goes to 170 on the nozzle no matter the material you select, only the bed is preheated fully, so at least a printer preheated this way will start the calibration immediately. Only filament change heats the nozzle fully and after a successful filament insert it automatically starts cooling down to 170. If that does not work the same way on MK4 then there are probably some bugs to catch 🙂
RE: Prusa, please tell me you're working on this...
The problem being solved on Mini was with the original Minda probe is very sensitive to temperature differences and does not have its own thermistor so it cannot compensate. So doing the MBL with different temperatures gave inconsistent results. It is not required to clean the nozzle because it does not touch the bed (well, it should not at least) and a bit of oozed filament does not mess with it (usually it is a thin line that bends out of the way, and even smaller blobs of PLA can just get squashed at 170C). There is the before-print prime line on the front of the bed but that is after MBL.
It can be done better and more quickly/efficiently imho. I'm amazed that Mini users have been putting up with this for so long.
Do minis also "clean nozzle" in the print area?
The 170°C waiting step is standard on Mini - afaik it is to let the (oroginal) Minda probe temperature to stabilize and give stable results. One possibility is that it was left there by error, but imho more probable is that the lower temperature is used to limit any filament oozing during the "touch" calibration.
RE: Prusa, please tell me you're working on this...
I meant preheat like a filament change. Yes, basic preheat mode goes to 170.
On the Mini the preheat always only goes to 170 on the nozzle no matter the material you select, only the bed is preheated fully, so at least a printer preheated this way will start the calibration immediately. Only filament change heats the nozzle fully and after a successful filament insert it automatically starts cooling down to 170. If that does not work the same way on MK4 then there are probably some bugs to catch 🙂
RE:
It can be done better and more quickly/efficiently imho. I'm amazed that Mini users have been putting up with this for so long.
Do minis also "clean nozzle" in the print area?
The 170°C waiting step is standard on Mini - afaik it is to let the (oroginal) Minda probe temperature to stabilize and give stable results. One possibility is that it was left there by error, but imho more probable is that the lower temperature is used to limit any filament oozing during the "touch" calibration.
I didn't have any reference point. 6 minutes seems like a long time, but I'm not sure I've ever timed it from a cold start before. My Mini process for printing from cold start with the latest firmware is:
- Preheat nozzle to 170 °C, bed to 1st layer temp for selected filament.
- Printer homes axis during the heating (I think).
- Usually the nozzle beats the bed to temp.
- It does not proceed until both temps are reached.
- Printer performs mesh bed leveling.
- Printer sets nozzle to print temp.
- Print begins with the purge line on the front of the plate once the nozzle reaches printing temp.
Over 6 minutes from print start to actual print. Pretty sure my MK3s+ does under 3 for cold starts.
Also, why is the "cleaning nozzle" procedure done in the print area?
I looked at your video. When you're thinking your MK3S+ does it in under three, is it for ABS? Or was that for PETG or PLA? Because I noticed your MK4 is much like my Mini. The only difference is that your printer does nozzle cleaning when the nozzle is at 170 °C, BUT, it's still waiting for the bed to finish heating, and it doesn't pause bed heating, so the nozzle cleaning isn't adding any extra time.
Homing the axis also happens when heating, so (at least from cold) that's not adding any extra time.
Your bed is going to 100 °C, and that takes a full 4:50. No matter what happens, the printer can't start printing before the bed is at temp, so this 4:50 is the fastest the MK4 could do for printing from a cold start. Any faster would require a higher wattage bed heater. As to the other 1:20, I'm not sure if they do the probing at 170 °C nozzle temp because that's what the MINI+ does (and the MINI, MK4, and XL share a lot of firmware), or because that's just best to avoid oozing during probing. I suspect they do want to wait for the bed to be at printing temp so the bed expansion stabilizes, and I also suspect they want to not do the bed probing at a hotter nozzle temp because the nozzle itself will change lengths, so having the nozzle at a consistent temp is best.
If I'm wrong, and it wouldn't change things much, then they could just probe while the bed is heating up and save time (or, probe while the nozzle is hotter if it was already hot), but in the case of your ABS, as listed, they couldn't go any faster than 4:50 for a cold start, because that's just how long your bed takes to heat.
Does the MK3 do mesh bed leveling while the nozzle and bed are still heating up? Or does it wait for specific temps? If it waits, is the MK3 faster because the bed heats faster, or because you're remembering print times for PETG or PLA with lower bed temps?
RE: Prusa, please tell me you're working on this...
It can be done better and more quickly/efficiently imho. I'm amazed that Mini users have been putting up with this for so long.
Do minis also "clean nozzle" in the print area?
The 170°C waiting step is standard on Mini - afaik it is to let the (oroginal) Minda probe temperature to stabilize and give stable results. One possibility is that it was left there by error, but imho more probable is that the lower temperature is used to limit any filament oozing during the "touch" calibration.
I didn't have any reference point. 6 minutes seems like a long time, but I'm not sure I've ever timed it from a cold start before. My Mini process for printing from cold start with the latest firmware is:
- Preheat nozzle to 170 °C, bed to 1st layer temp for selected filament.
- Printer homes axis during the heating (I think).
- Usually the nozzle beats the bed to temp.
- It does not proceed until both temps are reached.
- Printer performs mesh bed leveling.
- Printer sets nozzle to print temp.
- Print begins with the purge line on the front of the plate once the nozzle reaches printing temp.
Over 6 minutes from print start to actual print. Pretty sure my MK3s+ does under 3 for cold starts.
Also, why is the "cleaning nozzle" procedure done in the print area?
I looked at your video. When you're thinking your MK3S+ does it in under three, is it for ABS? Or was that for PETG or PLA? Because I noticed your MK4 is much like my Mini. The only difference is that your printer does nozzle cleaning when the nozzle is at 170 °C, BUT, it's still waiting for the bed to finish heating, and it doesn't pause bed heating, so the nozzle cleaning isn't adding any extra time.
Homing the axis also happens when heating, so (at least from cold) that's not adding any extra time.
Your bed is going to 100 °C, and that takes a full 4:50. No matter what happens, the printer can't start printing before the bed is at temp, so this 4:50 is the fastest the MK4 could do for printing from a cold start. Any faster would require a higher wattage bed heater. As to the other 1:20, I'm not sure if they do the probing at 170 °C nozzle temp because that's what the MINI+ does (and the MINI, MK4, and XL share a lot of firmware), or because that's just best to avoid oozing during probing. I suspect they do want to wait for the bed to be at printing temp so the bed expansion stabilizes, and I also suspect they want to not do the bed probing at a hotter nozzle temp because the nozzle itself will change lengths, so having the nozzle at a consistent temp is best.
If I'm wrong, and it wouldn't change things much, then they could just probe while the bed is heating up and save time (or, probe while the nozzle is hotter if it was already hot), but in the case of your ABS, as listed, they couldn't go any faster than 4:50 for a cold start, because that's just how long your bed takes to heat.
Does the MK3 do mesh bed leveling while the nozzle and bed are still heating up? Or does it wait for specific temps? If it waits, is the MK3 faster because the bed heats faster, or because you're remembering print times for PETG or PLA with lower bed temps?
Mk3s probes at printing temp and the bed on a mk3s takes about 1.04 to heat the there is a pause to check for stable temps that's about 10 seconds then it does mesh bed leveling then purge line from 28 degree room to abs printing is about 1.56
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RE: Prusa, please tell me you're working on this...
From a cold start my MK3S+ started in just over 3 minutes (3m 12s to be exact) including doing 9x9 mesh bed leveling. This was PETG and only 15 degrees cooler, bed was the same
RE: Prusa, please tell me you're working on this...
Speaking freely, this chatter makes me less eager to 'upgrade' the MK3S to a MK3.999999...
I admit that I am spoiled by the almost-eye-blink time of (assuming a preheated unit) pressing the button until the print cycle begins.
When I first got the Prusa, I was impressed by the warm-up and start-up time. Back before I had my own machine I printed at our local makerspace, mostly with a Taz 5, and the rule of thumb was (in timing your booking sessions on the printers) to allow 10-15 minutes from a cold machine to print start.
My other printer (Ultimaker) seems to take 3-4 minutes or so from button press to print start, which seems to vary according to the phase of the moon.
RE: Prusa, please tell me you're working on this...
From a cold start my MK3S+ started in just over 3 minutes (3m 12s to be exact) including doing 9x9 mesh bed leveling. This was PETG and only 15 degrees cooler, bed was the same
What do you mean, bed was the same? Same as in 15 degrees cooler? Because the bed going from 85 to 100 °C in your video was a full 1:30
So that would mean 6:15 your video showed would be 4:45 with PETG and a bed temp of 85 for the first layer (85 is the default for PETG on my Mini).
Then the extra 15 degrees on the nozzle took another 20 seconds.
So if I’m not wrong, based on your video, PETG should take 4:25 from a cold start?
I mean that’s still a bit more than 3:12, but not anywhere near as bad as 6:15. Need to compare apples to apples for time.
RE: Prusa, please tell me you're working on this...
I'm kind of glad the first first batch of MK4 users is working all this stuff out for me by the time my MK3S+->MK4 upgrade kits arrive... I can anticipate several firmware revisions by the time my upgrade kits arrive lol
Being the first to get most anything usually comes with the pain like this. I'm sure when my fully assembled 5 extruder XL arrives(whenever it does), I'll be finding similar things.
Thanks for finding bugs with the MK4 before the rest of us upgrade 🙂
RE: Prusa, please tell me you're working on this...
If there is not a good reason for that startup procedure it should be fairly easy to fix though. One can write basically any startup procedure into the G-code file in the slicer. Or modify the existing default commands. Of course, Prusa should optimize it by default but I would not make a decision on buying the Mk4 dependend on that.
Mk3s MMU2s, Voron 0.1, Voron 2.4
RE: Prusa, please tell me you're working on this...
To me the one glaring issue in the above discussion is that the nozzle isn't at filament melt temperature when it tries to wipe it off. No wonder there was an ABS blob still on the end of the nozzle.
RE: Prusa, please tell me you're working on this...
To me the one glaring issue in the above discussion is that the nozzle isn't at filament melt temperature when it tries to wipe it off. No wonder there was an ABS blob still on the end of the nozzle.
Wouldn't filament ooze out if the temp went to melting point defeating the purpose of cleaning the nozzle?
RE: Prusa, please tell me you're working on this...
Correct! As a long-time user of a Lulzbot mini, which has always cleaned the nozzle before leveling, the goal for cleaning is to heat the nozzle enough that the filament is “very soft” but not fully melted. It needs to be soft enough that minor pressure or abrasion will wipe it away, so that anything protruding from the nozzle is dislodged on contact, but not so hot that the filament oozes out. If too hot, then cleaning off any blob is just quickly replaced by more ooze.
To me the one glaring issue in the above discussion is that the nozzle isn't at filament melt temperature when it tries to wipe it off. No wonder there was an ABS blob still on the end of the nozzle.
Wouldn't filament ooze out if the temp went to melting point defeating the purpose of cleaning the nozzle?