The X1 and X1 Carbon are capable of printing fast, but in order to do that successfully, the material used for printing also needs to be compatible with fast printing.
There is a balance that needs to be found between printing speed and hotend temperature for silk filaments, and the easiest way to find it is to look at the external layer uniformity of the print. When the silk filament is printed with the right settings, the model should have an uniform shine.
A good indication of too much speed, or a low printing temperature is having matte lines on the external layers, and low layer adhesion meaning that it's easy to break the model in half.
Most silk filament manufacturers recommend a printing speed between 40mm/s to 60mm/s, and this is because how the silk filament performs when extruded.
The composition of silk filament is slightly different from regular PLA as it has some compounds that give the filament the specific shine we love. This additive makes the filament a bit elastic, and layer adhesion is also not that great.
Lowering the print speed will improve the printing results when using silk filament. Because all filaments are different, and different brands have different needs, we recommend starting with the printing speeds recommended by the manufacturer, then adjusting the print speed higher in incremental steps.
Going past ~100mm/s isn't recommended if you want to ensure good layer adhesion and a nice finish, but you might get away with it if multiple external walls are used. To control the speed and allow the material to be properly melted, we also recommend using the “Silent” mode from the screen menu.
Another recommended setting to be changed is the hotend temperature. Regular PLA is usually printed at ~215C with slower speeds, but you might need to increase the temperature to ~220C-225C for a consistent flow and melt rate.
Silk filament usually requires a higher temperature for increased layer adhesion which is usually between ~215C to ~230C. When the model is printed faster (ex: ~100mm/s) the temperature used should be around ~220C to ~225C for best results.