Tips for printing at 295°C with max bed temperature  

RE: Tips for printing at 295°C with max bed temperature

I have recently been printing Rigid.Ink polycarbonate at 295 Deg C and bed temperature of 110.

295 is the highest the Prusa can go in stock form and getting the bed temperature above 115 took forever. This is without an enclosure.

At 295 Deg I got Maxtemp errors if I tried to set this temperature from cold, so had to set to 292 then 295 once it had stabilised, I tried a PID tune but this did not help, I have a silicone sock on the hot end as well.

If you wan't to go higher for the hot end you will need to replace the thermistor with a PT100 sensor and amplifier board and modify the firmware, also I would recommend a nickel plated copper heat block and maybe a titanium heat break, there is no reason to replace the heater element but if you are planning say 350 Deg C and upwards, then maybe a better heater.

The heated bed, you could try to insulate the underside and or replace the stock prusa power supply with a meanwell LRS-350-24 unit and slightly over volt it to 26v output, the EINSY will handle this without an issue as will the hot end and heated bed. The stock PSU barely manages to achieve 24v at full load.

The stepper drivers can handle up to 46v input and the 5v regulator will handle up to 42v input.

Oh, you may... no , you will have to replace some of the parts close to the hot end with polycarbonate parts as the PETG parts will melt.

And sooner than later as printing the polycarbonate parts, you kinda can melt your extruder. I built a skelestruder then had to reprint parts and used the Rigid.Ink clear polycarbonate, this particular PC is quite pure so requires the full 295 Deg to print, but due to this it also has the best glass transition temperature of many polycarbonate filaments which are doped with other polymers to bring their printing temperatures down.

Hope this helps, there are web pages detailing the PT100 upgrade and firmware modifications, but I'm at work at the moment and don't have access to my favourites on my home machine.

I am toying with a hot end upgrade like this as well as a volcano hot end, but can't really justify the spending yet as I'm still learning about 3d printing. Only got my first 3d printer last October, and so far have nearly replaced / upgraded every part so soon will be able to build another with all the original parts.

RE: Tips for printing at 295°C with max bed temperature

Also don't go higher than 26.0v MAX as the volt sense divider will end up shoving more than 5v into the ATMEGA 2560

There are voltage dividers consisting of a 10k and 2k37 resistor which at 26v will give a 4.981 voltage output which is used to sense the incoming voltages on pins A9 and A4 of the ATMEGA.

RE: Tips for printing at 295°C with max bed temperature

Posted by: chocki

Hope this helps, there are web pages detailing the PT100 upgrade and firmware modifications, but I'm at work at the moment and don't have access to my favourites on my home machine.

Thanks for your thorough answer @chocki! 

So today, after having printed for the first time a really flawless Benchy (!), I was really happy and went on to test the nozzle for 295°C after having cleaned it out of the silver PLA. I also installed an e3D sock. I also haven't set any enclosure yet. I have installed latest firmware, V.3.7.0 as well.

The nozzle went up to 295°C without any problem, sticking rather closely to it +/- 1°C. I am still interested for your links @chocki though, since I don't want to be that limited to 295 tops.

I want to stay more or less below 310°C since I won't be printing polycarbonate but a polymer that really has been printed once or twice on a FDM machine before (this is a university research project).  In the end I want to print at enclosures temperatures of up to 50°C. 

Considering this, is it really needed to change to a nickel plated copper heat block and a titanium heat break, and to change the parts close to the extruder to PC as you were saying?  PETG has a glass transition at 80°C, would that be far away enough? And if not, what parts need to be reprinted more specifically? 

Then, after checking on the nozzle, I went on to check for the bed temperature. Getting the bed to temperatures of 100°C was rather fast, I could even achieve 110°C easily and then I pushed things to 118°C, still no problem, and finally at 120°C I got a bed preheat error. Then, in order to check whether I was really achieving these temps, I used a thermometer with a Type K thermocouple and taped it with Kapton tape to the print bed, and heated the bed at various temperatures. I found that my readings were off compared to what the printer was sensing, by a large amount, like from 10 to 25°C. So I guess this is not even a problem of power supply from the PSU but really a some glitch in the sensor. I'll expose this issue in another topic since this one is more on the modifications needed.

RE: Tips for printing at 295°C with max bed temperature

It's not the ambient temperature you need to worry about, it's the radiant heat from the hot end onto the extruder plastic. I have had parts  of it soften and warp at PETG printing temperatures, so I guarantee you will need to replace the extruder body with something else if you intend to print with your hotend at 295.

RE: Tips for printing at 295°C with max bed temperature

Posted by: vintagepc

It's not the ambient temperature you need to worry about, [...]

Well... you do need pay attention to ambient temps if you're still using an air-cooled setup. The E3D v6 is rated to 40C ambient. But yes, the  inability to cool and the *resulting* radiant heat is what causes problems.

RE: Tips for printing at 295°C with max bed temperature

Posted by: bobstro

Posted by: vintagepc

It's not the ambient temperature you need to worry about, [...]

Well... you do need pay attention to ambient temps if you're still using an air-cooled setup. The E3D v6 is rated to 40C ambient. But yes, the  inability to cool and the *resulting* radiant heat is what causes problems.

Heh, oops. I accidentally a word, "primarily" 😀

RE: Tips for printing at 295°C with max bed temperature

So what you are saying is that I absolutely need to replace some parts of the extruder. Does this mean all of the extruder printed parts, or just part of it?  No matter what I do, I guess I need to start working on the enclosure now, either to print ABS or PC.

Would you still recommend changing the parts to PC  (a filament like PC-max) even though from I've understood it's much more difficult to print than ABS? I have had a look at Metacollin's settings from here where people say it's easy, but since I'm new to 3DP, I'm a bit cautious about this. 

I'm also interested for anybody's experience with replacing the thermistor to a PT100+Amplifier. This post is all I could find for the MK3(S) and it's not really helpful/confusing...

RE: Tips for printing at 295°C with max bed temperature

Posted by: vintagepc

Heh, oops. I accidentally a word, "primarily" 😀

Good thing you can just edit... never mind.

RE: Tips for printing at 295°C with max bed temperature

The stock thermistor is at risk at temps higher than 280c; continuous 295c might be pushing it.   In any case, it wouldn't hurt to also run a PID at the planned temp so the controller can better control temp excursions.

RE: Tips for printing at 295°C with max bed temperature

I'm going to have to find a lot of my links again since the old links pointed to the old forum! 😐 

Ah here's one that does not point to prusa.

https://www.rocketryforum.com/threads/prusa-mods.150336/#post-1853767

RE: Tips for printing at 295°C with max bed temperature

Checked my bed temperatures and at 90 Deg Setting, mine varies between 76 and 81 over the bed, but not one spot ever reaches 90.

I had to reprint my cooling nozzle as this softened and drooped when printed from PETG. then the thin section at the front to the right of the e3d heatbreak near the PINDA softened, drooped then finally touched the heater block which was running at 295 Deg C, lots of acrid plastic smell and me coughing and opening windows.

I had by this time already printed everything I needed for a skelestruder so rebuilt as this extruder, which also melted!, luckily the bottom part nearest the heater block is a seperate part on this design, so I reprinted it as 100% polycarbonate as well as the cooling nozzle and have not had any further issues.

RE: Tips for printing at 295°C with max bed temperature

Posted by: Caroline

Hi all,

I'm relatively new to 3D printing and I have just mounted my first MK3S which so far prints like a charm. For my MSc project I will eventually need to print a polymer (Vectra) that has been printed before on an Ultimaker with some modifications at 295°C. So my question is simple:

What modifications should I do on the stock MK3S to be able to reach this extruding temperature safely?

The datasheet says you can print at temperatures up to 300°C, but I've also read that the stock thermistor doesn't perform well at these temps - and at the same time I've read that the PT100 thermocouple wasn't supported by Prusa (not much more info: https://www.reddit.com/r/prusa3d/comments/9infon/how_to_set_up_pt100_on_a_mk3/?depth=2 ). So is the stock thermistor really to be changed, and if yes, what alternatives are there?

I also foresee that even in the case that I wouldn't need to change any hardware (that would be cool but I doubt it),  the fact that I'll be printing close to the limit temperatures would provoke a lot of Overheating warnings. Should I change something in the firmware to avoid this?

Another question that I have is the maximum bed temperature. Is the 120°C max. in the data sheet a reliable value to reach and maintain without damaging anything? 

Thanks for your tips and thoughts! 

I've printed at those temps. IIRC, it will hit 295/120 no problems. However, you will need to reprint the extruder body in something with a higher glass transition temp. Mine is printed out of polycarbonate. 

RE: Tips for printing at 295°C with max bed temperature

OK! I've ordered some black PC-Max to start reprinting the extruder parts once I get the enclosure set up. Thanks to all of you for your answers and thumbs up to @chocki for the link, which led me to another link (Here for the record) where all my questions got answered, at least until I get the PT100 and Amp and have to install them 😉