Prusa MK3S Clone (FYSETC)

Hi all, I bought a FYSETC PRUSA MK3S clone and I have issues.

2 problems :

  1. Can’t use some PLA filament - won’t go thru the nozzle, jams. Using Overture PLA 1,75mm + 0,05mm and it works fine. Why ? Would changing printhead for a lager one make a difference ?

  2. Printing with Overture PLA works for small works but while printing larger item, the printer stops and display show ‘THERMAL RUNAWAY’. What should I be checking ? Why is this happening ?

Please help.

The two problems might be related. Jamming may be caused by insufficient heat on the hot end. If the hotend thermistor drops by 10 degC and not recover in time, this triggers the runaway. Perhaps the hotend thermistor cable to the Einsy board is not fully plugged in? As the extruder moves fully from left to right, it could cause the connection to break or you have a faulty thermistor. Also, but not likely, your part cooling fan shroud is not dislodged and directing air at the heat block? These are the things I would check.

I suspect @bd43 is correct. A Prusa clone will behave partially like a purse depending how good the clone is. Sadly the clone use lesser parts with worse tolerances. From Prusa:

The jam could easily be hot end issues, how ever if it is in thermal runaway (uncontrolled heating of the hot end) it will not attempt a feed. If it isn’t in a runaway and the hot end is up to temp:

Check the length and position of the guide tube in the top of the throat. Tension on the extruder gears. If the tube isn;t cut basically perfectly and shaped properly if the filament is not straight it will miss the tube and jam. I’d look there.

  1. If you have recently re-assembled your hotend, make sure everything is exactly as instructed. An incorrectly assembled hotend can also cause this error.
  2. Check the ambient temperature. The suggested ambient temperature is 16 °C or more. An unheated garage in winter might cause thermal runaway as the heater doesn’t have enough power once the print cooling fan kicks in.
  3. Visually check the thermistor if it is still securely and correctly installed in the heater block. The whole cartridge should be inside the block, with no part of it sticking out.
  4. Move the whole extruder left and right, at the full length of the X-axis, and wiggle the cable wrap behind it. Check whether there are any fluctuations in the temperature readings. This would indicate an issue with the cable.
  5. Check the thermistor cable connector on the EinsyRAMBO or miniRAMBo. Re-seat the connector so you know it is secure.
  6. Check the fan shroud for any kind of damage. In some cases, users bent the shroud during assembly or when they were removing the printed object. A damaged or tilted shroud can change the airflow and start cooling the heater block directly. For safety reasons, the heater doesn’t have enough power (by design) to compensate for that.
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