After my recent discovery of blue painter tape for the build plate and how it can almost Eliminate Warps and Slips I found myself a new problem this week.
Everything I’ve printed so far was in my clear MakerBot PLA or my glorious purple RoboSavvy PLA. The clear is great for seeing the intricate honeycomb infill pattern I use and the purple has a really nice smooth glossy finish. I can recommend both.
Anyway, I switched over to green just to try it. After printing a few things for other people, more key rings and combs :), I switched back to clear to have another attempt at printing the Rook (castle chess piece) with a spiral staircase inside and a twisted pair of wires inside that.
Where’s the Plastic Gone?
All was going well until the extrusion stopped after only a few layers and no plastic was being extruded, it was effectively air printing nothing. Then the classic stepper motor clicking sound appeared which basically means there is some kind of jam or blockage.
There is a section about cleaning the drive gears, which although the index pointed me to the wrong page I eventually followed. It was pretty clear and only involved removing two screws holding in the cool end fan, heat sink and stepper motor.
This is a routine task by the way so it’s not too stressful and it’s good to get used to doing it. You’ll also learn a lot about how your extruder mechanism works.
There was indeed a little plastic in the drive gear mechanism which I removed and then gave it a little brush out as the manual suggested.
Lesson #1 – when unloading filament and loading the new filament take your time as I think this was the cause of my jam. When unloading filament (maybe to swap to a different colour) be slow and try to pull out as much plastic as possible before it breaks off. You’ll be amazed at how much plastic can come out and expect it to be all stretched and malformed. I think I did this too quickly and it left some old plastic in the drive mechanism, so always be sloooow and careful.
The Real Problems Begin
Just a quick note before reading this, don’t be alarmed by the problems I’m about to report, because as you’ll see it was mostly my fault, but was a massive lesson learned…
To cut a long three day story short, from this point on I couldn’t print anything. Extrusion wasn’t smooth when I tested it (load filament and continue extruding for a while) and when it came to printing there was no extrusion at all.
After removing the fan, heat sink and stepper motor again there was PLA plastic in the thermal barrier tube but it wasn’t budging, even when pushing it manually and the heated core was at the working temperature of 230 degrees.
MakerBot YouTube videos show how to do this manual extrusion, but it didn’t work for me. All I could conclude is that I had a nozzle blockage, stopping the PLA going any further. I couldn’t push the PLA in or pull it out, because it had broken flush with the top of the thermal barrier tube, oops.
MakerBot show you how to remove the nozzle (there are various ways of cleaning them) but only for the Replicator and the Replicator X. For the Replicator 2 you have to contact support. I suspect this is because it looks more difficult to hold the heated core in place on the Replicator 2 because it only has a single extruder.
So, I logged a support ticket with MakerBot and waited… and waited. At this time of writing this I’ve waited three days and still no response. This isn’t great.
It was time to have a good think and try a few things myself which I know wouldn’t do any damage. I eventually used a pair of pliers to stick a pin down the middle of the PLA in the thermal barrier tube. I then let it cool a little and pulled the pin out. The PLA came out with it and the blockage was gone, result.
I’ve not seen this idea documented anywhere but it worked really well for me and if in the same position again I’d certainly do it again.
What really confused me was that everything now looked fine and as good as new, but it still just wouldn’t extrude properly and would block the thermal barrier tube within seconds of trying to print. Testing did show that the extruder was clear though and plenty of PLA could be extruded, but it still looked rough.
After taking the usual bits off for probably the fifth time I noticed the stepper motor on the ‘cool’ end was warm. Hmmmm, that’s not right, as the name suggests it’s at the ‘cool’ end of the extruder. What was going on here?
My Admission of Guilt
I think it’s time to jump straight to my next big lesson learned…
Lesson #2 – when replacing the cool end heat sink make sure it’s the right way, with the vents facing the fan and the flat side touching the rectangular aluminium block. Yeah yeah, I know, how stupid am I for not realising and yes I’m embarrassed to tell you this. However, I did promise at the beginning of this series to tell it how it is, my mistakes too, so that’s what I’m doing.
Ultimately, the fan was being blocked and the heat sink wasn’t even touching the part it was meant to be cooling. This meant the cool end (including the thermal barrier tube) was too hot. PLA was melting slightly in the tube and blocking it. What PLA was being extruded was probably far too hot by then and wasn’t extruding smoothly. You get the picture by now, it was all screwed up due to my mistake.
After a quick rebuild (the correct way), I levelled the build plate and gave it a few minutes to let it all cool. Everything was great again with perfect prints every time. I even printed another comb to compare the quality with a pre problem comb and it was perfect.
I call it my little Ice Castle. Incidentally, some people print using glow in the dark plastic and insert LEDs into their prints afterwards to light/charge them up. They look stunning and I’m really looking forward to trying this myself.
First things first though, I’m going to browse Thingiverse to try and print something more ambitious. I also want to try adding Support Structures and Rafts so I’ll report on those as they happen. I’ve learned a lot this week, probably more than I would have liked after only 5 hours of printing, but it was an experience. As for MakerBot support, I’ll let you know if/when they get back to me, even though I solved it myself.
Thanks for reading and feel free to Like and Share this article if you found it useful. Also you can download my FREE Beginners Guide to 3D Printing at Home eBook if you wish.