Cleaning my Extruders

My Replicator hasn’t been functioning well lately. I switched back to some older filament and couldn’t get much out of it before the nozzle would stop extruding. I am beginning to believe that this is a common problem that everyone calls “clogging”, but I know that in my case, the drive gear just slips on the filament and it loses pressure.

One of the reasons that I love the Original Makerbot Replicator is that it is incredibly user serviceable. Getting to the drive gear is a piece of cake with a few hex drivers.

Once I got to my drive gear I could see how dirty it was. I’m not sure if it functionally makes a difference, but I suspected that the powdered plastic sitting inside the teeth was decreasing it’s ability to bite and drive.



For those of you unfamiliar with the extruder design, the filament comes into the top left in the following picture and is pressed between a delrin plunger and the toothed gear at the end of a stepper motor. The gear bites into the filament and forces it into the hole that you can see below it. This is the entry into the hot end where the plastic is melted and driven out of a tiny nozzle to make the part.



Using a small wire brush (Harbor Freight has them cheap) I cleaned inside the gear teeth and dusted off the filament guides. You can see in the lower picture that there is a groove running down the face of my plunger. Apparently this is normal wear. However I will be going the route of using a bearing face to press it into the teeth instead. Fortunately Thingiverse has me covered.IMG_1111Please note that on the back side of the plunger there are a number of tiny tiny washers. Four in my case. And I spent an hour on the floor trying to find them.



Spotty Charging on a Kindle

A good friend of mine had a Kindle that refused to charge easily like a good piece of hardware. You could get the charge LED to come on for a second or so if you wiggled the mini USB plug, but otherwise it was a crapshoot to get the unit to charge for any length of time.

Being quite a hassle, she asked me if I could fix it and gave me one of those pretty smiles that I’m such a sucker for.

Enter the Kindle.

The first 5 minutes was me looking around the perimiter trying to find any hidden screws that might hold it together and experimentally wedging my fingernails under the edge looking for pop latches. Once I got one edge to come up, I went around the entire perimeter carefully popping the back cover off.



The USB receptical is located on the underside of the green PCB that makes up the brains of this little unit. I was impressed at the size of the battery on here, but my job was under the PCB. Eight little phillips screws later and some care to remove the plugs and ribbon cables gave me my first look at the connections.

Here is the offending USB port.

Here is the offending USB port.

Some little reflow unit was a bad boy.

Some little reflow unit was a bad boy.


All five of the pins for the USB receptacle had broken their solder joints. This actually happens somewhat commonly in electronics. The amount of heat needed to reflow the solder paste for the tiny components is small compared to the thermal mass of something as big as a plug. I’ve seen a lot of times where the ground pins never get properly soldered to the board and the receptacle is left wobbling until it breaks its own connections. In this case every single pin had come loose. Looking closely, I think the problem might also be that there was not enough solder paste applied to the pads before the component was set on top of it and the solder just couldn’t flow properly as a result. Either way, I found the issue and I knew how to fix it.


The pins were too close together to easily solder separately. I tried. Unfortunately the only tip on my soldering iron that would decently fit onto a pin was too small to carry enough heat to the part to make a good solder joint. I used a trick originally taught to me by Dave Jones of the EEVblog and just soldered all of them at once. This allowed me to use a larger tip to carry enough heat down to the pins and ensure that each one is soldered well and good. There was just one problem.

The Horror!

The Horror!

Now don’t worry. There is this wonderful material called solder wick, and it pretty much does what you think it does. I applied a little amount to the solder blob I just made and put my soldering iron back to the part. Solder wick works by pulling solder into the fine braids of wire through surface tension and capillary action. The beauty of using it in this case was that those same forces also existed between the pads of the PCB and the pins that were sitting on top of them. The result was that most of the solder above the pins was wicked away while the solder under the pins (i.e. the good solder) remained.

Kindle Connection FinishedNow in the interest of full disclosure, I did go back and touch up the pins individually after the solder wick did its job and before that last picture was taken. Once each pin had been properly wetted with solder it responded to my overly large iron tip well enough to carefully confirm that it was free of solder bridges between the pins.

I cleaned off my excess flux (the secret to good soldering) and did another visual check for solder bridges. I reassembled the kindle and confirmed it indeed worked and couldn’t even interrupt charging when I tried.


And I got another pretty smile too.