MK7 fan holder/ print cooler

The design is a version of the great fan block from timmytool.

It has some additional features like:

• fan ejection nozzles on both sides of the MK7 heater. It provides more even airflow over the printing area and MK7 radiator;
• wider ejection nozzles. Again, more air out - better cooling;
• optional connection to additional air supply (compressor) for delicate prints.