The RP9 is getting a new extruder. The current extruder works well, and I have been very pleased with its performance and durability. I am still using the original extruder on my first 3D prototype printer. However, the person who was making them for me is no longer in business. His design is pretty clever and yet simple and cost effective. The 2 main features that got me interested in this extruder are the PTFE liner that goes from top to bottom and the copper heat sink ( a common plumbing part) remove unwanted heat as you move away from the nozzle. Both of these are key for the extruder. If the heat travels too far up the extruder, then the extruder can clog more easily, and the extrusion amount can vary due to die swell. A small melt chamber yields better performance. The extruder’s copper heat sink removes heat from the stainless steel tube keeping the upper part of the extruder cooler. The liner spans from the SMC connector all the way to the nozzle. The only seam in the melt zone is between the PTFE and the nozzle. With a proper fit, the melt pressure is less at the nozzle ensuring that the easiest path for the melted plastic is used making parts.
So what is different for the new extruder? The first thing you may notice is there is no ceramic insulation. This is not needed with 40 watt ceramic cartridge heater. I also have changed to the NTC 3950 thermistor. The extruder heats up quickly and holds its temperature steady. One advantage of the new setup is that the heater and thermistor can be removed for ease of maintenance by loosening the set screw on the bottom of the extruder. I plan to update assembly instructions with the starting parameters and the new extruder mounts. The other difference is that the copper heat sink is threaded and clamped with the brass nut. This allows for an air gap between the heater and heat sink. This helps keep the heat where we want it.
I have been printing for awhile now with the new extruder and am happy with the performance. I have several put together and the store is open for business.