Two hexagon hot ends (both brand new) are different lengths

So I am in the process of putting together clough42's dual extruder so I ordered two hexagon hot ends. Unfortunately the two that I received are different lengths from the heat sink to the heater block. More specifically, they are 0.84mm different in length. You can see this in the picture below. I emailed Colin over at Makerfarm since I bought both of them from him, but haven't heard back yet (jeez, it has been a whole 10 minutes). Does anyone know of a way to safely modify the length of the pipe which is exposed between these two sections?

http://3dprintboard.com/attachment.p...tid=4442&stc=1

And to answer other questions that may come up, they are both completely unused. They have set screws on the side of the heatsink, but I can't seem to figure out what those are for.

Any help would be much appreciated.

By set screw, are you really referring to the one on the aluminum block? That's there to hold the heater cartridge in place, pushing it up against the side that is most valuable in applying heat to the nozzle side. If there's really a set screw on the heatsink, provide a picture. That must be something new.

Technically, the distance from the bottom of the heat sink to the top of the aluminum block really doesn't matter. What's important is the overall length of the hot end from the mounting plate end to the tip of the nozzle. The aluminum block can be repositioned as desired or necessary on the M6 threads of the heatsink, and the nozzle threads should bottom out against the tube extending from the heatsink. To ensure everything is tight, IMO it's actually best to NOT have the brass nozzle flush against the aluminum block. If you tighten the nozzle against the heat sink tube, the exact position of the aluminum block doesn't matter.

If the overall length truly is different - yeah, that'll be a problem for the dual extruder. One thought would be to carefully sand away some of the threaded end coming out of the heatsink after removing it from the aluminum block. Another option would be to add a shim of sorts at the mounting plate end of the one that is shorter - at least to the extent that the mounting plate will allow you to do that. My single hex was a loose fit in the mounting plate, and I used several layers of kapton tape in a similar way that this shim would be used... A combination of both to get the two hot ends to match might be something to consider.

remove both nozzles. tighten both heater blocks on the heat sink tubes as far as they will go. then reinstall the nozzles and tighten. See if they are still different.

If you bought two at the same time from the same vender, I'm thinking you should get two identical units? How about calling their support line and suggesting they figure out how to make it right?

Thanks to everyone for the responses.

printbus: I have a new picture that shows the set screws (or what seem to be set screws) on the actual heatsink. The hexagon has had a definite tweak with what Makerfarm is selling now vs a few months ago. It also comes with a shorter heater cartridge (perfect length for the hex), quick disconnect cables, and the silicone jacket for the heater block. Unfortunately the overall length from the top of the heatsink to the tip of the nozzle is different, and is caused by the different lengths of tubing which are exposed between.

TopJimmyCooks: I did make sure to tighten everything down as much as is safe, and this didn't change the difference between the total lengths.

Toxy: I am in contact with Colin over at Makerfarm, hopefully I will be able to figure something out with him. I would hate to have to hack something together to get these brand new units to match with each other.
http://3dprintboard.com/attachment.p...tid=4446&stc=1

Yeah that hole on the heatsink is something new. The heater cartridge is no surprise; my old hex came with the shorter cartridge. They're harder to find though, and it could be the hex ships with whatever reprapdiscount has on hand.

Someone had posted a picture of a broken hex hot end before. The tube you see entering the heatsink passes all the way through the heatsink, and for a few people the mechanical hold of the heatsink on the tube has broken. I don't know if it's threaded, expoxied, or what. If that's really a set screw on the heatsink, it's possible that it now forms the mechanical connection and the length is in fact adjustable.

I have the impression clough42 only checks in on threads where he's subscribed. This could be a significant enough issue that I'd mention it in the double extruder thread to make sure he's aware of it. Since the outcome has major impact on the viability of the dual extruder design, it could be that he'd want to have direct communication with reprapdiscount on the extent that the overall length of the hex extruder is specified and checked during manufacture.

That is a good point. I will reference this thread on the dual extruder thread so that clough42 sees it. I will also make sure to check back in here once I hear back from Makerfarm on the new design.

Hmm that's an interesting issue. I'm not familiar with how the mounting process to the dual extruder goes, but could you just modify one side of the dual extruder plastic to make them level? I would actually be surprised if any hotends in a dual setup didn't need some calibration to get them to match up perfectly.

With C42's dual extruder, it seems in order to "level" two hotends of different lengths, you have to "unlevel" the whole X axis by turning one or the other of the Z threaded rods.

I had the same issue with one hex being longer than the other. What i did was to shim the Double Groove Mount on the side that the long hot end was on.