Yes, I have! I use the variant with the V6 nozzles and my reworked hotends are quite a bit shorter than the original ones.
Since I want to be able to mix those as I need them and since I use my shortened variant of the cooling nozzle which is tuned to blow out just below the heat block to keep it out of the air flow as much as possible, I needed to do that - otherwise I would have to switch the fan nozzle together witch the hotend. Apart from that, I want the hotends to behave identical.
How many different hotends are you using with your J1?
I have two sets - one with the standard 0.4mm nozzles and one currently equipped with 0.2mm nozzles. Since I never missed anything bigger than 0.4 in the past (and only used the 0.4mm nozzle in my old printer), I suspect this will be fine. Otherwise I will change the nozzle only, I found this works really fine even in cold state - I simply tighten the new nozzle with a torque wrench to 1.5ā¦ 2Nm.
I made another version of the covers for the fanducts. This version is with adjustable z-heigh for non standard nozzle heights. The old ducts positioned on the side of the toolhead can be repositioned +/- 5 mm.
Unfortunately the ducts positioned on the back of the toolheads can only be lowered (10 mm.) So for a higher nozzle position than standard, one would need to remake the backside ductsā¦ Iām sharing the step file here so anybody can do it themselvesā¦
Thanks for your new design.
While these slotholes make it possible to adjust the duct to any nozzle height, you have to carefully measure and adjust the height during installation. With your old design the height was set.
I think the majority of J1 owners use either the stock hotend or the mod with the copperhead heatbreak and Bondtech nozzle which is 3.5 mm shorter. And those with additional hotends will use all either stock or have modified all with the copperhead/Bondtech mod. So no need for an adjustable version.
Just 2 sets of your old design, one for the stock hotend and one for a 3.5 mm shorter hotend would be better. In case someone has modified his hotend differently and needs another height, he could easily move the holes for the attachment points of the ducts in the STEP file and have a custom solution for his mod.
Furthermore I donāt think, it is an easy task to change the backside ducts from the STEP file without access to the source file. Looked inside the STEP file and there is no straight vertical area in the duct where I could cut out 3.5 mm and then reconnect the parts. According to the filename of your picture it seems youāve used Fusion 360 for modeling the fanduct. I assume youāve used a loft along a path to create the tip of the duct and adjusting the height would then be possible by simply adjusting that path. If you donāt want to do it yourself I could try to do this if you post the f3d file.
Well, the same situation applies in order to create a fixed working solution for the copperhead setup.One would have to reloft the ducts for the backside of the toolhead. Therefore, If I were to make a cooling setup specificly for the copperhead mod, it would probably just use the standard coverā¦
Unfortunately, Fusions shell function and fillet function are not very good, so the part has been through a couple of exports and imports. There is no usable design history. 
I used objects of specific shapes and in specific locations in order to control position and output angles of the ducts.
I still have the old loftobjects if you want to have a look?
As for "installing a z-adjustable duct, one could simply just hold a piece of thin paper or string in front of the nozzle. Then adjust the heigh of the duct accordingly. 
Thatās was my proposal. Standard cover and 2 sets of ducts, one for stock and one for copperhead.
But it is probably too much work especially if you have no use for a copperhead version yourself.
Ah ok I see. I must have read too quicklyā¦ Then we are in agreement.
Maybe I will make the modification and the ducts for it sometime in the futureā¦
I can confirm you can still swap out hot ends with your fan mod. @Rwide
Extremely pleased the mod as a whole.
@Plasticrap3d thanks for testing.
@Rwide Just want to let you know that I will print your initial version. I will do the copperhead mod but with AP3X nozzles instead of the Bondtech CHT. The length of the modded hotend should then be almost identical to the stock hotend. Canāt speak for otherās who have done the mod with Bondtech CHT nozzles but for me you donāt have to do the modification with the shorter ducts.
Alright, great. I hope the ducts will perform! 
I just realized that the bedholding flaps might be in the way when doing z-offset calibration. So beware of that. Might be wise to loosen them a bitā¦
hello everyone, does anyone have a printhead model in the format .Step ???
This might be a starting point: https://www.myminifactory.com/object/3d-print-3d-model-of-snapmaker-j1-hotend-module-282895
thank you very much for your help, I have it, I thought maybe someone has it completely assembled with the full body of the head
