Nozzle clogges during print and bed seems to grow after heating

Basic Information:

Printer Model: Wanhao i3 Plus (Micro Swiss all metal hotend)
MCU / Printerboard: ATMega 2560
Host / SBC: Raspberry Pi 3B
klippy.log
klippy.zip (336.5 KB)

Good afternoon,
I made my Wanhao i3 Plus printing, but I’m facing 2 issues, as the object:

  1. after leveling the bed (manually) I start printing the benchy, but the filament seems not to flow and the nozzle scratches the bed (magnetic, flexible). After troubleshooting, it seems that the problem is that, after heating up, the bed is thicker, so I adapted the leveling and now I can print
  2. The first part of the benchy is printed ok, I have to tune the parameters in Cura, but for now is enough. At a random point the nozzle clogges, the filament stops flowing and the printer continues, just like everything is going fine, except that nothing is printed and the extruder keeps moving without extruding material, so I stopped the job.

While the extruder was still hot I pushed a couple of times my pla in and the extrusion started again.
It happened 2 times from this morning.

Does anyone have (or had…) the same problem(s)?
Maybe changing the bed to place a glass type can help the leveling, but the clogging nozzle is more annoying…

Thank you in advance, obviously

Hi,

Not really a klipper problem so perhaps you should also try some discord group on your type of printer or the microswiss extruder you have.

The bed will always expand as it heats up, this is normal of course. This is why you should do the bed level and offset calibration when the bed is at print temperature temperature. If it still does it you might nead to heat soak your bed for a while until it is stable.

As for the extruder clogging there can be a hundred reasons, so without knowing exactly what your setup is I will only tell you a few of the times I experienced the same and hope you will find what is your issue.

First: Quality of materials. The microswiss system is very popular and due to this the market has many (cheaper) copies for you to choose from. The biggest problems with this are that not every producer makes their products to the exact standard that the originals are made to. Little differences in tolerances or unfinishes sharp edges are a nightmare inside your heater block.
Imagine your heatbreak having a slightly larger hole for the filament then the nozzle. Immediately you have an edge where molten filament will experience pressure differences and eddy currents. This means that some plastic will stay there getting heated up all the rime and carbonise. Eventually it lost all its plasticisers and becomes rock hard but brittle. Pieces will break off and clog your nozzle.
Also imagine the heatbreak not having a flat and straightedged end so it only touches your nozzle with a small area opposed to everywhere on the end flat.
Again this might work for a short time but eventually carbonised plastic will ruin your day.

Secondly, partly also due to the manufacturing, the nozzles or heatbreaks may have different thread lengths from original, which means they will not lock up against each other. Some sellers will offer thin copper washers to build up your nozzle seating but these should be avoided as if they are the plague for the above mentioned reason.

Third: wrong temperature. Too high for your plastic and it will carbonise too fast. Too low and you may experience backflow and this way block your nozzle or heatbreak. Do a temperature tower as test.

Fourth: bad tolerances of the filament. Much less an issue these days but if you purchased some filament simply because it was cheap it could be a bad batch. Stay with a known brand you have researched and experience with.

Fifth: filament gets stuck somewhere before the extruder. Not really clogging but can create similar symptoms. If the reverse bowden tube is too small or has some other restriction. If the filament is tangled on the roll and seizes up. It could be that the extruder looses grip on the filament and starts chewing and slipping. Also you should check the strength of the gripper arm. Hard to find clear instructions on how tight it should be but generally the teeth from the extruder gear should be visible but the filament should not be deformed too much or flattened by them.

These few reasons all happened to me in my first year and I learned the hardway how to avoid them. Now I only buy my known brands of filament, nozzles or heatbreaks and also no aftermarket heat blocks. I once had a V6 heatblock that was more then 1 mm bigger which meant the nozzles could not reach the heatbreak.
Keep it all clean and lastly, make sure the heater cartridge is powerfull enough and is properly fitted so it can heat the heatblock evenly without variations during print. A PID test will also help with this.

I hope some of these will help you and I wish you happy printing.

Yes, I know it’s normal, but about 0,5mm seems too much to me…
Anyway, the problem can be addressed easily, by setting the height after warmup or estimating a delta between heights and setting the height in cold condition as normal+delta. Maybe I’ll switch from magnetic bed to micropores glass bed and ease the problem a little…
For the second issue, the throat was original, the nozzle not and, despite being a high quality part, when I dismantled the extruder assembly I discovered the problem: the two parts didn’t make full contact, so the filament (Sunlu, it seems good, the temperature declared was from 215°C to 235°C and I set 220°C) clogged the thread and all the hotend. It was so stuck that, rotating the throat, it broke apart and now I have to buy a new MK10 extruder. Maybe I’ll be able to save the heater/resistor…
I saw Prusa printers use a long nozzle, which passes through the throat, any experience with that? It seems to me a very good solution to avoid this kind of troubles…

It is not Prusa that is the inventor or manufacturer I think, the all in one nozzle with incorporated heatbreak is from E3D and called the REVO.

I have used a REVO Micro for as long as they have existed and everytime when I have a problem with another system, when I change it for the REVO it seems to solve all the trouble so, yes I like it and it is my goto type of hotend system.

My biggest reason for using it is indeed the heatbreak and nozzle are one piece but more important for me is that I change nozzles really often from print to print, and with the REVO ecosystem the differences are so minute that a simple babystepping routine on the first few lines of the new print sets the z-offset quickly and reliably. I even found that the different nozzles in the same range do not need any offset change.

I am glad you found your problem and that I could be of help.
Happy printing from now on!