Another Rebuild

It seems most of the posts on this blog has been about me rebuilding my 3D printer. Well, hopefully this will be the last one in a while as I have several other projects that are in need of parts and I'd rather spend time on them than on another teardown/rebuild.

I were quite happy with the performance on my previous extruder mechanism, although it was supposed to be temporary. Combined with the J-Head I got very nice prints for a while.

When the extruder broke down I tried a couple of e-bay replacements but did not quite get the performance (or fit with my printer) I was looking for. At the same time the J-Head started acting up (leakage and stuff) so I needed to find a replacement for that as well.

After a bit of research I ended up buying a Bulldog Lite Extruder from their Indiegogo campaign and was pleasantly surprised that they shipped them right away with no waiting at all. Although a bit heavy it's beautifully machined and well put together. The "Lite" comes without the gearbox which makes it a bit lighter, but is only suitable for 1.75mm filament. Secondly I ordered the E3D v5 hotend which has gotten great reviews. Going with an all-metal-hotend made sense this time around since there's no peek or PTFE that can melt/be deformed.

One thing about about the Bulldog / E3D combo that isn't perfect is the mating between the two. They are both fabricated to follow the J-Head "standard" so you can just slide the stem into the extruder, but there's quite a bit of slack along the z-axis so I made some shims out of regular plastic. 4 of these did the trick.

It took me a while to get everything put together, as I also switched the printer firmware from my stock Sprinter firmware, delivered with the SUMPOD, over to the latest Marlin.

Now I finally have a working printer again. And I must say, I'm very pleased with the quality of the prints as well as the new functionality in Marlin. The printer even sounds better!

My first print were a camera stand for one of my Raspberry Pi's. This print was sliced with .3 mm layer height so it's a bit rough, but I opted for speed before beauty this time. I've made the design available on Thingiverse as well.

Until next time!

Finally printing again

After several months of not printing I finally have a working 3D printer again - Yay! I can only blame myself for this; since I in my eagerness to improve the printer tore it apart before printing the new parts I needed. Even though my J-Head arrived swiftly I had nothing to mount it on...

J-Head Mk V-BV. Excellent build quality!

The aluminum plate mounted on top of the slide-bearings did not have enough stability using zip ties alone. I tried replacing the zip ties with brass wire (the sort used to hang paintings with), but that turned out even worse since you can't get the wire tight enough.

My best friend Sugru at work again.

Enter Sugru. I had a batch in the fridge that was nearing it's use-by date so why not try that. I made sure to protect the bearings with scotch tape so the sugru wouldn't stick - only support. Apply healthy amount of sugru and wait 24 hours. Worked like a charm!

Next I needed a new mechanism to feed the plastic. The easiest would have been to print something, but without a working printer that proved ... difficult.

Initial setup with the spring mechanism.

After a lot of thought and a fair number of iterations I came up with a design that let me have a spring as tension mechanism on the filament feeder.

Need more springs Scotty!

When calibrating the feed rate I quickly discovered that the original spring didn't have nearly enough force to keep the flow of plastic consistent - especially when the filament spool needed to be unreeled by the printer as well. Adding three more springs fixed that issue neatly - although it doesn't look as pretty any more.

First print: new tension lever.

First thing I printed was the Minimalistic Mk7 replacement by +Whosa whatsis. This is so I have a replacement part ready for if when my cobbled together setup fails.

As for now the feeder seems to hold up pretty good as well as consistent results. I think I'll keep it for a while. The J-Head I'm really impressed with; great build quality and excellent print result!

Print head progress report

Just a quick update regarding the print head from QU-BD. First impression was really good: the assembled hot- and cold end looked professional with a thought through design. I was very eager to try it out, but started off simple, just hand-feeding the filament without engaging the motor.

At 180C the plastic flowed perfectly for about 10 cm (raw filament) - then abruptly stopped! Even using pliers I could not force any more filament through the nozzle. Pulling out the filament I noticed a small plug at the end. Cutting this off and re-threading the filament let me extrude again, but as soon as I made a stop, or after about 10 cm, it would stop again. Feeding and then retracting before feeding again helped some of the time, but no matter of increasing/decreasing the temperature made any difference.

After a lot of fiddling and reading the various threads at Fabric8r I concluded that there was no use even trying the motor before I disassembled the print head. Which was easier said than done considering the plastic had leaked and clogged up the inside of the heater block. Instead of warming it up I soaked it in isopropanol over night - which kind of worked.

Leaked plastic.

More plastic at the bottom and inside.

It's hard to see in the pictures, but you can see the plastic around the brass nozzle and at the top of the heating block. This being caused by the brass nozzle and steel rod not being pressed together tight enough. The leakage apparently causes drag inside the nozzle and makes the plastic hard to press out through the nozzle. When stopping the PLA will expand in the heat and cause total blockage.

Fixing this should be easy enough, cleaning the parts, re-tighten and reassemble the whole thing. Although I'm not going to do that. I'm sure one can get nice prints with this head, but after reading about all the other issues people on the Fabric8r forum are having with not just the hot-head, but the feeder as well I can't be bothered. All very fixable I'm sure, but requiring a lot of fiddling and even then the prints tend to not be that stable between sessions.

So being kind of fed up not being able to print I decided to order a new print head. This time a more proven design: the J-Head Mk V-BV recommended on the RepRap wiki. The one I ordered has a .4mm nozzle and is made for 1.75mm filament. A .4 mm nozzle (the same as I've been using from the beginning) should be easier on the motor as well although I won't be getting as fine details as with a .35mm nozzle (like in the QU-BD head). The bigger nozzle should be more forgiving in regards to filament as well and not clog up as easily.

I got an e-mail yesterday that it has been shipped so back to playing the waiting game...