I like my Printrbot, but there are certain tasks that I wish were easier. I often go back and forth between larger, less detailed prints and smaller, very detailed prints. Generally, I like to keep each print to around an hour or two, so I often switch my nozzles between .2mm, .4mm and 1.0mm.
A few months ago, I upgraded my Printrbot Simple Metal to the Ubis13 hot end and while I was at it, I bought a bunch of the new tips because they were much cheaper than the old Ubis (ceramic) style tips. I bought all of the sizes they had at the time which were .2, .4, .75 and 1.0mm. Since then, they have come out with almost every size from .2 to 1.0mm.
The Ubis13 (and Ubis13s) have an all metal design which makes them heat up quicker and maintain temperature better than the ceramic hot end did. I definitely get more consistent results with this hot end. When changing the tips, you have to make sure you heat up the hot end to 200c before trying to remove the tip (to allow for thermal expansion). This is easier said than done, because handling a tiny piece of brass that is red hot can be tricky.
At first, I just used a pair of needle nose pliers that I keep around for cleaning the nozzle tips from hot plastic, but then I had an idea. If I could use a socket wrench to loosen the nozzle, it would make it quicker for me to change the tips and prevent the scratches that are slowly obscuring the tip size that is engraved on the side.
Step 1: The Problem...
The nozzles on the Printrbot's Ubis13 hot end are round with 2 flat sides. When you remove the nozzle tip, you have to turn it pretty hard to break it loose and the best way I have found is with a pair of curved needle nose pliers. They give me the leverage I need, while keeping my knuckles clear of the hot end and other obstructions. The downside to this method is that there are only 2 flat sides, not 6 like a normal hex bolt. If you've ever been frustrated by a square bolt or nut, this is even worse. Because of the 2 sides, it's pointless to try to use a regular open ended wrench. The worst part about the pliers is that they will scratch up the sides of the nozzle, obscuring the markings that indicate what size the nozzle is.
Step 2: Modifying the Socket
In most cases, if you have a tight space where you can't easily maneuver a wrench, you should be able to find a socket wrench that will do the job. Unfortunately, there aren't any sockets for semi-rounded squares or semi-flattened cylinders. I thought about taking a larger socket, filling it with epoxy putty and pressing the nozzle into it for an exact fit socket, but then the epoxy probably wouldn't hold up to the heat required for the hot end while changing the tip.
I thought a better solution would be to cut the sides out of a standard 7mm hex socket. This size socket works perfect for the brass nozzles. I think an 8mm socket will work for the steel ones, but I haven't gotten to make the other adapter yet.
Step 3: Using the New Socket
Currently, I am still using the Allen key as Printrbot recommends to hold the Ubis13 in place and prevent twisting. The socket fit snugly on the nozzle and prevented any more scratches as it easily broke the nozzle loose. I'm very happy with the result.
Step 4: Future Enhancements
There are 2 things I would like to add to this little socket wrench to make it perfect. The first is a battery powered socket wrench. The reason for this is that once the nozzle tip breaks loose, there is no more tension to allow the ratcheting of the socket wrench. In the meantime, I can just use a small screwdriver socket handle and move the Z arm all the way up to get under it.
The second thing I would like to build in the future is a set of pliers that have a short nub that would fit into the holes on the outside of the hot end. Currently, I am still using the Allen key as instructed by Printrbot, but I think it would be nicer to have a more solid grip on the hot end to isolate the twisting motion to the tip. I've thought about modifying a small set of pliers or snap ring pliers to have a nub or two that would fit into the holes around the throat of the hot end. I thought either something like that or like a miniature version of the oil filter wrench in the picture above would do nicely.