What is the best length of the melting zone in the hotend?

Question

There are many hot end designs out thee and one difference is the length of the melting zone.

The melting zone is that part of the hotend where the pushed in filament is heated up and therefore starts to melt. Is it better to have a short melting zone, or a long melting zone? What are advantages of each solution. And are there materials that benefit from a short/long melting one more than others?

Answer 1

Short melting zone melts material in small amounts which is suitable for thin layers with small nozzles. In opposite, long melting zone can heat a big amount of filament which is needed for fast printing and thick layers.

short melting zone

• less amount of melted material
• thin layer heights
• quality printing with details
• give more precise volume control with less flow/pressure lag and better retraction performance (thx @Ryan-Carlyle)
• nozzles: 0.25-0.8 mm (available for E3Dv6)

long melting zone

• more amount of melted material
• thick layer heights
• fast printing with less details
• nozzles: 0.4-1.2 mm (available for E3D Volcano)

Example

Example of those hotends are E3Dv6 and E3D Volcano

E3Dv6

E3D Volcano with a much longer melt zone than v6

Speed comparison video:

Speed comparison graph:

Update

CNC Kitchen YouTube channel did a review of 0.1 mm nozzle, where the author discusses problems with very low material flow. The main point is the usage of high-quality materials (he uses Polymaker PolyMax PLA) and avoiding materials like PVA, which tend to crystalize under heat.