Cooling of the hotend before printing  

RE: Cooling of the hotend before printing

Not sure about the Mini, but on the Mk3, the PINDA was temperature sensitive, so you'd want to have it at a consistent temperature when starting mesh bed leveling. Waiting for PINDA warmup could take a while (30 seconds to 10 minutes or more depending on ambient temps). You'd want to have the filament at a "no ooze" temp warm enough to allow it to bend if a bit had hardened on the nozzle when doing homing, but not at a temp high enough to dribble during PINDA warmup and mesh bed leveling. The "2 step warmup" is good for eliminating stringing during leveling. I assume Prusa copied the technique to the Mini startup routine for simliar reasons.

RE: Cooling of the hotend before printing

Posted by: @riho

Hi!

Is there any reason why Prusa Mini always cools down the nozzle to 170C before printing? In my opinion it is just wasting of time. If I want to print TPU I load the filament, wait before it heats to 240C, then I have to wait it to cool down to 170 and back up to 240C.

Is it intentional or just a software bug?

 

My understanding is that its to stop ozing whilst it does its mesh levelling. On the MK3 it can leave little dots all over then bed before printing because the hotend is up to temperature

RE: Cooling of the hotend before printing

I completely agree, this is a really annoying waste of time. A year later and nobody from Prusa has responded? They have still not improved the firmware? I only just started a week ago with my Mini, having been a MK3 user for several years. The MK3 does not do this silly up/down/up temp cycle and works fine, why must the Mini behave this way? It is a big time waster. At least make this "feature" optional.

RE: Cooling of the hotend before printing

From what I understand the MINDA probe is VERY sensitive to temperature (it is a cheaper variant of original PINDA) so the same temperature is always used for proper leveling to aid repeatability. I guess SuperPINDA might not need that but implementing a second process was probably not worth it.

RE: Cooling of the hotend before printing

When inserting the filament, a temperature at which the filament flows (e.g. 220 degrees Celsius) is required.

During mesh bed leveling, a temperature at which the filament does not flow (170 degrees Celsius) is suitable.

When printing, a temperature at which the filament flows(e.g. 220 degrees Celsius) is required .

RE: Cooling of the hotend before printing

Hmm, well at least that would explain things, but I'd much rather pay to upgrade the sensor and eliminate this step, it really degrades the value of the Mini in the big scheme of things, time is money...

RE: Cooling of the hotend before printing

Yes, that's a statement of what they are doing, not why. The MK3 does not require this, and "suitable" isn't an engineering word. Perhaps it's the probe as jkavalik mentioned.

Posted by: @kalimero

When inserting the filament, a temperature at which the filament flows (e.g. 220 degrees Celsius) is required.

During mesh bed leveling, a temperature at which the filament does not flow (170 degrees Celsius) is suitable.

When printing, a temperature at which the filament flows(e.g. 220 degrees Celsius) is required .

RE: Cooling of the hotend before printing

If I understand few last posts correctly, you wish that nozzle temperature wouldn't decrease to 170°C at mesh bed leveling? Because it's a "waste of time", you'd prefer oozing all over the bed during leveling?
These 2-3 minutes are negligible compared to average print time... 3D printing was never a race.

Just my opinion

RE: Cooling of the hotend before printing

You say they are not doing this on the MK3 as it doesnt 'require this', well it does.  If you don't add it to the mk3 you get little dots of filament at the sense points all over the bed.  Also Prusa would add it to the MK3 profiles if it wouldn't mess with existing operation of peoples profiles on the Mk3.  

The 2 step warm up was developed AFTER the mk3 was released, as such prusa would have people complaining if they changed the operation of existing systems.  That is standard procedure for software updates.  You always at least Try to preserve the current operation. 
A lot of us manually ADDED that process to the Mk3 (both before the mini was released and after).  This is because while you may view it as a waste of time it isn't.  It allows consistent printing, resulting is less print failures which in fact SAVES time (and filament/money).  

The Mini being a new product without an existing user base allowed them to make such improvements into the default settings of the slicer.

If you don't want it to do that step then its very simple to modify your start gcode on YOUR mini profile to remove that step.  The save the modified profile with a name of your choosing and use that to slice your files.  That's the great thing about gcode, the printers are generally dumb as a bag of rocks and its not the printer firmware doing this step, its something configured and changeable in the slicer software.  As such you can alter the operation to suit you without effecting other users.  Most of whom prefer the way it is set up.

RE: Cooling of the hotend before printing

Interesting, thanks for sharing that idea of tweaking the gcode, I have never messed with anything like that because the stock process on the MK3 works great for me, I've rarely had any dribbling of plastic on the bed during the calibration run, and I mostly print with oozy TPU. It just works great, fast and efficient. Preheat, change filament, start the print, and it just goes and works great. I want to be there to make sure the first layer is starting correctly, which is basically only the calibration delay on the MK3 (so less than a minute). On the Mini you wait for cooldown, calibration, and then the heat back up, closer to 5 minutes. Thanks for the tip.