Fail! The Son of Replicator (2) A tale of molten plastic...

[Kenneth Jamieson]

Hey all!

First off, before my tale continues I want to thank Jetguy for all his information and advice. In fact this whole community has been awesome in helping me get up to speed, and I feel like I have a better (but obviously imperfect) grip on this stuff.

As some of you recall, my Replicator 2 started to develop temperature issues, and then began failing prints. In an attempt to fix this, I embarked on a series of upgrades... not all were directly related, but I was on a roll).

• Printed out and installed the "upgraded" official Makerbot extruder. Using the hardware kit from Makerbot themselves.
• Upgraded the print bed to glass (from Performance 3D) - my acrylic one was warped. 
• Added the aluminum bolt on arm stiffeners from Performance 3D.
• Added a new nozzle from Performance 3D.
• Added the 3-in-1 aluminum extruder upgrade.

It was the nozzle that added another problem. The fault is entirely mine. I simply did not know enough, and installed it wrong. I "bottomed out" the shoulders of the new nozzle, but did not know how to check the seating against the threaded tube. So, in addition to it's other issues my hot end now started filling with and burning PLA inside the threads. Whether my somewhere along the line, I started getting "Heat Error" messages.

Makerbot replaced the part for me for free. What I did was call the retail store sales line, and tell them I wanted to buy a thermocouple. Since they do not have it ont he site, they had to transfer me to support to place the order. I opened a ticket, and mean while aimed a few less than flattering tweets at @Makerbot. Int he end, they offered to ship me a new hot end, and I took them up on it.

When it arrived, I installed the Performance 3D nozzle, then put the whole thin in my printer and got on my way. The printer worked fine, and my prints looked good. In the meantime I was educated on the proper way to install a nozzle - and realized I had NOT done it correctly... again. I set aside time to rebuild the extruder to fix this, right after I printed out another fan duct so I could swap it while everything was apart.

Bad idea :)

I printer developed a huge plastic "booger" on it, as it spend 90 minutes accumulating molten PLA on the hot end. Whild this seems to have done no damage (and in fact after cleaning it I did in fact print the duct) there is a lot of PLA inside the insulation tape and Klapton. Clearly it all needs to be replaced. Since I was unmounting it anyway, I took the hot end apart (carefully!) and sure enough - I had been leaking PLA into the threads again.

My current plan is...

• Order new Klapton tape (McMaster-Carr 7648A725) - I think this is the right stuff. I cannot find anything obviously higher temp. Amazon also seems to have some but I am unsure of it's specs.
• Order new insulation material (McMaster-Carr 87575K84 or  87575K85 depending on 1" or 2") - I can find no equivalent on Amazon.
• Clean the threaded tube and aluminum block (with TC and heater removed) using a heat gun to melt out any PLA that is clinging inside. I am open to other ideas about how to do this. 
• Order a new heat sink fan (mine seemed a bit slow to start last print, though it seemed to run well enough, but why take chances?) - I found one at Robotshop. 
• Order new 40mm grills for the heat sink fan. I don't need these, but the black appeals to my vanity :)
• Re-assemble correctly :)

What I am unsure of now is if I should use the Performance 3D nozzles or the one from Makerbot that came with my new extruder. They both seem brass based and as such should seal correctly but the P3D version seems to be a different alloy, so I am unsure if it is too "hard". I am also unsure if "arctic silver" or some other compound is good to use on the threads themselves to help heat transfer.

The fan and grills are on the way, I will order from McMaster later today (Monday) and do the work Friday (assuming the parts show up).

We'll see how it goes :)

[Ryan Carlyle]

Don't put thermal grease on the hot block threads. The carrier grease cooks out, leaving behind a dry powder that probably hurts you more than helps you. 

Conduction across the threaded interface in the hot block is not likely to be a bottleneck that we care about. The tight threaded brass/aluminum connection produces fairly good thermal contact even without thermal grease -- much better than the heat conduction through the filament itself.

Now, on the cooling bar side of the thermal barrier, you should definitely use thermal grease. You need every iota of conduction you can get in order to prevent heat creep with PLA.

[Kenneth Jamieson]

Ryan,

Thanks! I appreciate you takign the time to comment, I added your caution to my ever growing OneNote file :)

Ken

[Kenneth Jamieson]

On a happy side note, it turns out I am only an hour drive away from McMaster-Carr! My "need a part fast!" life just got a LOT easier.

Ken