Does your E3D v6 need Z-Hop?

[gwatson1990 1]

I recently switched to and E3D v6 on my Ender 3 and I'm running Cura 4.3. I've never had any issues with stringing until now with PLA, but after the switch it took me a while to get the stringing down to an acceptable level (Small hairs that can be blasted with a heat gun). The changes in my other settings I could make sense of such as shorter retractions and slower retract speeds, but what I can't figure out is why I suddenly need Z-hop to get the same results as the stock hotend. Is there something that I may be overlooking in my Cura settings or a difference in the hot ends that require the z-hop? I'll attach my profile below, any input would be greatly appreciated!

Ender3ProfileE3DV6.curaprofile

[TheodorK 11]

I also have a old prusa i3 (from 2014) which I recently upgraded with an UM2+ feeder and an e3d v6 hotend. I also use a z hop when traveling from one side of the print to another.

The only reason I can think of that a z hop could reduce stringing is that the nozzle is not moving over already printed parts, these printed parts then could stick a little to the remaining plastic inside the nozzle end could sort of "pull the plasic out" and with a z hop this is not the case. 

 

This same effect is visible when printing a flas square with some holes for example, when the nozzle travles it oozes a little when moving, leaving spots of filament on the surface. When moving over an object, instead of a surface these become strings, resulting in stringing.

[gwatson1990 1]

Previously this was not needed though, which is why I'm puzzled a bit. Is it due to the design or is there an issue with my hardware?

[TheodorK 11]

by previously you mean before you switched to the E3D v6?

 

It once happened to me that there was not enough airflow flowing past the heat sink of the hotend (cold zone) which allowed heat to creap up past the heatbreak, this caused my filament to stick to the walls of the heat sink, making retractions a lot harder. This could be the case but that totally depends on the design of the hotend/extruder.

 

In most (older) hotend designs this was not much of an issue because a PTFE heatbreak was used to isolate the filament from the metal parts of the hotend, the E3D V6 is an all metal hotend, and thus without a PTFE heatbreak, making propper cooling even more important.

[gwatson1990 1]

Yes, before the V6 I had a PTFE heatbreak which was very forgiving. I recently noticed that the mounting set up I was using wasnt allowing the fan to properly mount in the heat sync so I'm hoping that will help.

[TheodorK 11]

I hope so.

If you are looking for inspiration, this is the design I used as a base for the redesign of my hotend:

https://www.thingiverse.com/thing:2023947

 

This design allows for a restricted and good airflow past the fins of the heatsink, however make sure that the fan is always spinning, of start to spin when the nozzel temp is above 40 degrees C.