In contrary to the trend to switch to the E3D hotend I elaborated some modifiations to improve the available hardware of the K8400 by maintaining most of the parts.
So in order to overcome the weakness of temperature control I build the following heater block:
The design uses an axial thermistor (Epcos, 100k, Marlin ID “1”), which is hidden in the heater block and thermally coupled by thermal grease. So far this approach is similar to the E3D-V6 design.
The rest remains the same. This hotend can be put on the K8400 nozzles and uses the heater from the original part.
Having this hotend the lower side of the heater block is flat except the nozzle tip itself. The thermal sensing is minimally affected by mounting variations, the temperature reading is not affected by the fans operation.
Having this modification one can implement the full advantages of the improved firmware, where I did some updates coming from Marlin V1.1 and some own improvements.
The temperature can be hold stable within ± 2°C under operation and ±5°C even under fan operation.
I implemented a pressure advance mechanism, which makes the retraction handling in most cases unnecessary. Besides the large temperature deviations this is one of the major mechanisms which leads to clogged nozzles.
Some more informations can be found here: http://ddd.k8400.hoehnemann.net/index.html
Since I see more and more topics which are related to the poor thermal control I checked the possibility to make this design available to the Vertex community. For 50 € + shipment I can provide the heating block, the temperature sensor and supporting material (more details: http://ddd.k8400.hoehnemann.net/Heizblock%20EPCOS.html). However, I need at least 20 fixed requests to start this activity.