I am watching the operation of my Cetus2 two-color printer. I discovered a way to implement what I call “shadow-purge” printing. When changing colors with a single nozzle printer, there is a period of time and distance required for one color to cease flow and the new color to fully become full flow. This period is call a purge.
The nozzle design of Cetus2 makes this time and distance very short. But it still exists for perhaps under a second.
The competitor single nozzle printers have a large purge required so typically move to a designated area of the print bed and build a purge tower along side the desired part. This tower is then discarded after the print is finished as waste. The cost of the material is not an issue but many novice printers believe it is. The cost is that material could have been used in the print and it required considerable time to travel to the Purge and travel back to the print.
My Cetus2, because of the very short purge, can use the normally required internal fill area of the model as the purge area. It can’t be seen when finished and it provides a useful function as part the the part’s internal volume.
The internal purge happens so fast I actually can not see it happen -most of the time. Only when it must move a bit more than normal. So it appears to be an almost instant change of colors while printing.
It may not be a perfect way to purge but is far superior to the time required for any other method. I admit I am impressed. This is certainly my now preferred method for changing color.
It is likely un-acceptable for changing different material like dissolvable support filament or other non-compatible filament combinations. The purge tower is not gone.
There are several options for doing a nozzle purge. It is the duty of the print maker to determine which is the best for the print being made. There is no one “best” option and it is very nice to have more than one.