Machine start behavior in this revision will be different from previous. The machine will now preheat the top plate to reach a temperature of 32°C before probing the bed which may take upwards of 10 minutes when ambient conditions are cold and it is the first print of the day. Additionally, the machine preheats to three different temperatures throughout the preprint procedure, which may include periodic pauses, please note this is normal operation.
Improved Nylon reliability, strength, and surface finish
Drastically reduced bed scarring on bed probing
Improved bed probing for reliable perfect first layers
Shrinkage compensation for better dimensional accuracy
Previously, the nylon temperatures have slowly been pushed hotter and with more part cooling to chase higher volumetric speeds, but we have recently found issues with nozzle jamming due to filament burning when deposition rates slow down in certain parts of a print.
To restore reliability, we have reduced the volumetric flow rate from 20mm^3/s to 10mm^3/s, allowing us to drop print temperatures by 20°C. To maintain fast print speeds, acceleration is set high at 8000mm/s^2.
Lower print temperatures have allowed the need for substantially less part cooling, down from 35% to 20%. This combined with lower volumetric limits actually results in stronger parts than previous, while maintaining excellent quality and overhang performance.
In the past month extensive testing has been performed on the mesh levelling performance and first layer quality and reliability. The following summarizes key learnings:
The nozzle starts to damage the PEI and create divots at temperatures above 210°C. At 210°C, there is virtually no wear/damage even after 1000 probes
The printhead carries a linear relationship between the probed Z value and the nozzle temperature
Probing performance is best when performed at the actual print temperatures (nozzle and bed) on a plain steel bed (no PEI)
Probing performance is poor at elevated (print) temperatures on PEI (due to scarring)
Filament accumulation on the nozzle tip will impact probing performance if the nozzle temperature is too low (material is solid and not malleable)
The machine must be preheated to ensure thermal expansion of the motion system has taken place
With these key takeaways in mind, a new bed probing strategy has been implemented using the start gcode in the printer settings:
the machine will heat the bed and wait until the top plate has reached at least 32°C
the ideal probe temperature is at 210°C to minimize PEI damage, but these temps are too low for filament on a dirty nozzle to be squished out of the way as the material will be solid, so instead the machine will probe above the melting point of the material (220°C for PETG, 240°C for nylon). These temperatures are set using the idle temperature box in the filament settings tab
after probing, the machine will then preheat to the actual print temperature before printing, but due to the elevated temperature, the hotend will expand downwards resulting in too low of a first layer height, a fixed, tuned offset is applied (+0.02mm for PETG and +0.05mm for nylons). These offsets are found in the custom g-code of the Filament settings tab for each material
We have added our first new feature to Pantheon Slicer: shrinkage compensation. The new value is found in filament settings and has been tuned for each material to scale parts in XY to achieve improved dimensional accuracy.