Air-prints on replicator 2

3D Printing 3D Printers
1

Hi all,

I recently replaced my Replicator 2 heater block with a kit from fargo3d. I am now able to print for about 20 minutes before the air-printing begins. I was there at the moment the printing stopped just now, and I heard a small “pop”. Hoping you all can help me track down the cause.

After the failure, I was able to move the filament in and out a bit with the load/unload routine (I don’t have a lever arm), but it was never able to start extruding, nor was I able to get it out from the feeder. So I took the motor out - pictures included. The filament is swollen. When I removed the motor, the filament was broken just above the motor… but i had been moving the filament up and down in an effort to get it out. So I’m not sure if that’s where it actually originally broke.

https://photos.app.goo.gl/nlxyTgBoY6slvLQJ2

Not sure if this is heat creep? The fans are all working fine, are oriented correctly, and the heatsink and spacers are correctly placed. I even put a little thermal paste between the heatsink and aluminum block, but it hasn’t helped.

I also noticed that the heater block is loose when it’s hot. See here: https://photos.app.goo.gl/PzJgNYTKgMJbuZZF2. I took everything out again and tried cranking the metal feed tube into the heater block as hard as I could, and while it’s a bit better now, it’s still a bit loose when hot. When cold, it’s fixed in place.

I’m using cheap PLA, but I’ve been able to print just fine with it recently. There was no tension on the filament feed system when it failed, so that shouldn’t be the issue. The machine is operating in a lab with a controlled environment, so room temperature shouldn’t be an issue either. Any thoughts greatly appreciated.

Thanks,

Alex

2

Did you ever discover the culprit? I have a similar issue and my printer clogs after a minute or two of printing. I had to replace the heater block because I stripped it out.

3

A popping noise during extrusion is most likely Moisture trapped in the filament causing steam to build up in the extruder nozzle, Filament gathers moisture over time, the cheap filament might have been printing fine at first, then a month of sitting on the printer goes by and it prints like crap, thats moisture buildup in the filament, even if your in a low humidity environment, it builds up over time.

As for getting the heater block tight, tightening it cold is your problem. You never replace a nozzle cold, or remove the heater block from the throat cold, or install the nozzle cold, etc. The heater block is aluminum, the throat is stainless steel, and the nozzle is brass (generally), lots of dissimilar metals with different expansion rates. The best practice when replacing a heater block is to screw the nozzle in all the way and back out a full turn, then install the throat so it bottoms out on the nozzle top end, then just snug up the nozzle. Install everything, preheat, snug the nozzle a bit again, and your good. When it cools down the aluminum contracts and it only gets tighter!

If you strip out a heater block your overtightening, and if you did it while replacing a nozzle then you should have preheated. For nozzle replacement, preheat, remove the filament, then remove the nozzle while still hot, replace the nozzle, snug it down tight but dont go 200lb gorilla on the wrench, just snug it good, then reload the filament. If done right it shouldn’t ever come loose or be loose, i print for a month or two before needing a new nozzle, and i use mostly cheap ABS filament or filament that i make myself.

The one thing that Rep2’s and 2x’s suffer from is heat creep, its well known as an issue. However since i replaced my heater blocks with the Fargo3D silicone insulated version i have had zero heat creep issues. I did also replace the fan FET on the mightyboard for a higher current version and put a slightly higher airflow fan on. The original is maybe 7-8cfm, my new extruder fan is more like 12cfm by the rating, but it seems to be moving a ton more air then the original stock fan. However, bigger airflow fans can’t run, or won’t run for long, on the Rep2 and 2X mightyboards because they will blow the fan FET with the higher current demand.

4

My issue wasn’t bad PLA. There was a single pop, which I suspect was from the feeder wheel losing grip on the filament, but not sure. I ended up solving the issue by replacing heater block, nozzle, heater core (i killed it) and feeder mechanism with cheap chinese parts from ebay. And they work like an f’ing dream. My Rep2 hums along beautifully now. Happy to share what I bought with you if you’d like - would just have to look up my ebay history. Found a really helpful seller here in the UK, and would be happy to direct you to him.

Also, I can confirm what crazyhamsales says about mounting the nozzle hot.

5

I discovered the culprit. I had the heat sink behind the fan on backwards. :confused: