best practice for nozzle replacement on Replicator 2X?

[Gian Pablo]

I'm going to replace the extruder nozzles on a Replicator 2X - I'm putting in the "high lubricity" ones to work with carbon filled ABS.

Wanted to double check what a good replacement procedure is. In particular, how do you grip the hot blocks so that you don't break the ceramic insulation?

Here's what I understand the steps are:

1. Unload filament
2. Detach the extruder assembly from the carriage, so that you can reach the nozzles
3. Preheat the extruder you are going to work on
4. Use a 7mm wrench to remove the nozzle
5. Let it cool down
6. Insert the new nozzle and lightly tighten
7. Preheat again
8. Tighten the nozzle against the thermal barrier

I'd heard that you could remove the heater cartridge, and insert a metal rod, but then how do you preheat the extruder? On my Rep 1 I have a metal rod that fits exactly between the two hot blocks, so I use that, but on the Rep 2x the spacing is different. Maybe I just need to find another  metal rod!

[TobyCWood]

Not having a 2X I can't comment on how to hold the hot block. You have some very delicate thermal covers that break easy. Holding the hot block in place to get the nozzles to seal against the thermal tube inside... hmmm... Talk to Ryan. You may need to remove/replace the thermal covers.

Regardless, why bother with letting it cool down? Remove the old nozzle screw on the new one.

On a side note, I'd be less concerned about switching a "high lubricity" nozzles just for printing carbon filled ABS. Are the OEM nozzles not working with ABS and you are trying to get t to work? have you tried using the OEM nozzles?

[Scott Booker]

As noted, the ceramic insulators are the problem on the R2X.

I have replaced nozzles two different ways on these machines.  I have found an Allen wrench that just fits between the two hot blocks.  The good news is that the sides of the blocks are exposed so you can put the Allen wrench in there with little fear of damaging the ceramic.  Then I run the sucker up to temperature and see if I can get the nozzle to budge using the 7mm socket.  Two out of three times this has worked and the swap-out was easy (no need to take the extruder assembly off of the carriage.. all done in-situ).

On the third machine the nozzle wouldn't budge and I was afraid I was going to bend the thermal tubes.  So the extruder assemblies came off of the carriage (I didn't un-bundle the cabling)....  I slid the heater cartridge out and put the shank of a #2 Phillips screwdriver (about 1/4") through the hole.  I was then able to remove the nozzle "cold" using the socket wrench.  I put the heater cartridge back in, put the extruders back on the carriage, heated it up.. and installed the new nozzle using the Allen wrench mentioned above.

Hope this helps!

[Ryan Carlyle]

I have typically done exactly what Scott just described.

At a certain point though, I got tired of dealing with the R2x blocks with their oddball shape and delicate insulation (broke one, tried a silicone sleeve off ebay, it got torn up too...), and I just stopped using them. I have Carl's dual threaded thermal barrier version with his T hot blocks for my workhorse, and a cheap Mk10 PTFE-lined dual bar from Monoprice as a backup. Plus a few oddball assemblies for experiments -- for example, my stock "straight tube and clamp" cooling bar got converted into a watercooled hot end by running a copper tube through one clamp and using the other as usual (I think with an E3Dv6 block, don't recall). Worked ok, not great.

[Gian Pablo]

That sounds like a good solution. I've ordered Carl's parts as you describe.

[Jake Clark]

This video may help: Rep 2x Hot Block Replacement

Just make sure you're two heads are level to each other.

-J

[Gian Pablo]

Did you notice a significant performance difference?

My Rep 1 and Rep 2x are basically in sync as far as upgrades (Carls alu x-ends and carriage, bottleworks z-arms and hbp, 3in1 extruder, etc) but the Rep 1 is able to manage a much wider range of materials/quality/temperature. At this point the key difference is the hot end, and specifically how the thermal barrier is clamped in place.

I've ordered all the parts you mentioned, and am very curious to see how a Rep 1 style cool block + thermal barrier affects performance.

For parts in the middle of the "envelope" (ABS, 0.2mm layer height, standard speeds and temperature) the quality of the parts is the same from both printers - but the Rep 1 can more easily handle more challenging cases (PETG, 0.1mm layers, dual extrusion).

On Tuesday, January 26, 2016 at 9:08:42 PM UTC-8, Ryan Carlyle wrote:

[Ryan Carlyle]

Yep, you've got it right, the clamp on the R2x messes up the head-shedding from the cold zone, which can cause jams. It works fine for ABS because ABS is a very tolerant material to non-optimal extrusion conditions. Carl's threaded version should make it possible to print everything. 

[Gian Pablo]

Good to hear. How did you mount the thermocouples? 

It looks like using the threaded thermal barrier AND the stock thermocouples is going to require a bit of a song and dance to twirl them into place. Did you just remove the thermocouples from the wire harness, screw them in place, and put them back in the harness?

[TobyCWood]

I would have screwed them in before installing the block.

[Ryan Carlyle]

I have thermocouple plugs in my wiring harness. Makes life much easier. For example, you can swap out everything attached to the cooling bar without any re-wiring if you get a jam or whatever.

Digikey:
Male k-type thermocouple plug: 290-1985-ND 
Female k-type thermocouple plug: 290-1986-ND

Without adding plugs, you'll need to remove the TCs from the mainboard or put a bunch of reverse twists into them so they'll untwist as you screw them into the hot block. (Count the threads on the thermowell.) This is a pain though. 

Alternatively, use a non-thermowell mounting style, such as clamping the tip between the two set screw holes in Carl's T-block, or pick up some E3Dv6 blocks. (You'll probably want to use E3Dv6 nozzles if you use E3Dv6 blocks since the thickness is a bit different.)

[Gian Pablo]

Cool, that looks practical. Any specific instructions for wiring in the thermocouple plugs? Can you just cut the thermocouple wire and attach it to the screw terminals in the plug?

[Ryan Carlyle]

Yep, cut and strip the wiring, install into the screw terminals, and it's done. Two tricks:

1) Use a small, strong magnet to tell the two metals apart. One wire and one plug terminal sticks to magnets, one does not. So it's easy to tell which wire goes where. (The color codes are theoretically standardized, but are pretty inconsistent by country of origin.)

2) Before firing up the heaters, use your hand (or a heatgun, or whatever) to warm up the tip of the TC a little. If the reported temp drops, you wired something backwards. 

[Gian Pablo]

Awesome, thanks! I was wondering which metal went where. The magnet trick is really helpful.

I note that the thermocouple plugs seem to be standard across a range of devices, so I should be able to plug into my handheld thermometer which has a thermocouple plug. Useful for calibration and sanity checks...

[Gian Pablo]

Everything works fine with the OEM nozzles, it's just that the carbon filled plastic will wear away the nozzle, and so I might as well change it now. As little as 10 hours and you can see the nozzle aperture start to deform.

[TobyCWood]

Really? That soon? We need to talk about that.

[Gian Pablo]

Yeah, when you think about it the tip of a Mk8 or similar nozzle goes to a point, so it's actually not a lot of metal surrounding the nozzle opening. It's abraded by the plastic flowing through, but also mostly by the plastic moving laterally across the sides of the nozzle. Some colleagues found that with very few hours of printing the nozzle sides were eroded enough that the nozzle was shortened by almost 1 mm. See the picture below (blue represents filament, yellow represents brass):