Ok, time for some pictures and movies. First, here’s a picture of the very first cut which I’d posted last week on facebook, where I cut the length of brass threaded rod for my heater barrel:
To make the heater barrel you need to drill a small hole in one side and then hollow it out from the other side with a larger bit, which I think has typically been done with a lathe, but I don’t have a lathe. So my idea was to take a 2×4, drill a hole slightly smaller than the brass threaded rod, and screw it in strong enough to hold it up. Here’s the section of rod screwed into the wood, along with the 1/32″ bit I used to drill the nozzle hole (1/32″ was the closest I could find to 0.5mm – I’m a bit worried whether that will affect my prints since that’s around 0.8mm).
I own a drill press which I’ve almost never used, and I also borrowed a mini-drill-press-for-your-Dremmel thing from a friend.. I ended up using both:
I used my Dremmel in the mini-drill-press-fixture, with the 1/32″ Dremmel bit, to cut the nozzle:
At the end though it was a bit off center (and I didn’t taper off the edges first, like I should have):
I screwed the nozzle side of the barrel into the wood, put the 1/8″ bit in the Dremmel, and tried hollowing out the barrel. It was very loud, and around 3am at this point, so I stopped with it looking like this:
The next day when I resumed, the Dremmel was making insane noise and generating a huge amount of heat (I had no cutting lubricant. 🙁 ).. It also turned the barrel deeper into the wood. At one point it caused a little smoke and I stopped the whole thing. Here was the hole in the wood after it cooled and I removed the barrel:
Instead I found a regular 1/8″ bit for my real drill press, and tried it there (on a new piece of wood). Night and day difference. It was quieter and cut through like it was butter. (in this video the wrench was an improvised heat sink, not that it was necessary with this drill):
The aftermath..
Success! Kind of..
Just a bit more work.. So I tapered off the nozzle side as best as I could without a lathe, and it looks good, although the barrel does seem a bit bent, and the offset nozzle does look like the molten plastic would turn a bit – not sure if that’s a big deal.
Excellent documentation Jeff!!! This is the kind of stuff you hope to find while searching the web when seeking info. Can’t wait for more! What’s the typical hole size at the end of the heating tube that people have made?
Thanks. The specs at
http://reprap.org/bin/view/Main/ThermoplastExtruder_2_0#The_heated_brass_barrel
say that the nozzle hole is supposed to me 0.5mm. I couldn’t find metric bits (at least not at Home Depot) so the best I could do was a 1/32″ Dremmel bit, which translates to 0.79375mm.
The other side of the barrel is different too – it’s supposed to be 3.5mm (I believe the filament that goes into it is 3.0mm), and I ended up using a 1/8″ bit, which translates to 3.175mm. I don’t even know whether to think that’s bad or maybe good – maybe when doing the metric version they wanted to get smaller than 3.5 but couldn’t. Time will tell.. I have no idea what the measurements are on the MakerBot or other RepStraps.
Jeff, Exactly how is it that your reprap is going to be able to reproduce what you went through to drill the hole in the thredded metal thing?
That part is pretty cool. There’s an SD card on the motherboard that contains a 16384-bit cryptographic private key unique to that RepRap. When the RepRap needs to print the barrel, it moves the extruder head out of the way, creates a packet representing a print_barrel request, encrypts it with its private key, and broadcasts it over a small multi-spectral antenna wire on the board. Presumably someday our nanotech-assembler arm will become small enough that it can manipulate quantum foam to open a micro wormhole, then expand it with a huge amount of energy. Children RepRaps will know all previous locations of their ancestors at every moment in time (which is why we have the GPS module in the motherboard now, which apparently isn’t fine resolution enough because none of this has worked yet). They periodically will open these small holes, listen for encrypted part requests, validate that they indeed came from their ancestor, and vote on which current sibling device will handle the request. The vote winner assembles the requested part, pushes the part through the hole via an extender arm, placing it now in the open area on the print bed. Simple. Again, though, the GPS coordinates are pretty coarse now, so it hasn’t worked yet. 🙁
Anyway, here are some of the real answers. A RepRap is something that can print the majority of its own parts (not necessarily 100%). Current RepRap versions require certain “vitamin” parts – things that currently need to be added externally to create another functioning RepRap (examples include circuit boards, steel bars, nuts, bolts, timing belts, and stepper motors). Having future versions of the RepRap design reduce the number of vitamin parts is good (if it reduces the cost and complexity of building a RepRap), because it helps the spread of the RepRap movement. So people are working on that. Gears are being RepRapped, there are even thoughts about printing stepper motors, etc.
Maybe some future RepRap has a permanent mold piece made of some low-temperature-yet-slowly-melting metal that takes a while to melt/solidify or something, some layer of plastic is injected inside it as a lubricating barrier, metal is melted and injected, and the inside piece cools before the mold would melt. The point is, that can be pushed off until later, since 100% replication isn’t a necessary part of this project for it to be interesting.
Another goal has been to make the design such that someone in a third world country without access to specific suppliers can still make one. Even though I’m waiting for Makerbot Industries to get more Stepper Driver v2.3 boards in stock, for instance, I could still go download the PCB design (which is GPLed, as is everything else), etch my own board, buy components from wherever, and get up and running. Reducing the RepRap to cheap local parts is more important (from one point of view anyway) than being able to replicate each and every piece.
In this particular case, the piece I was having problem with was made from a simple piece of brass threaded rod – I could have just used a brass screw from a hardware store. I made mine without even needing a lathe..
Or, maybe part of a future RepRap design is that it prints out a mold for you that you fill with some ceramic material?
Still not awake – sorry that reply was all over the place. 🙂
Excellent!!! And we all slept through it…not so noisey afterall. Much quieter than video games 🙂
..and quieter than a broken subwoofer!
This is the story of one man’s epic struggle… to drill a hole in a threaded rod.
Dude next week I will have my bench. The length of the entire basement wall!!!
You know what happens after that…
Sweet! Seriously, another big part of what pushed me off a year was my damned basement and not even having working lights in there. I had never fixed/replaced large fluorescent light fixtures, so I didn’t even know what a ballast was or that it was replaceable; my cousin fixed the lights for me while Laurie and David were in the hospital etc, and a consequence of that is that I have space to work!
The barrel bent most likely from the heat of your first try.
My suggestion is to do it again only go for the drill press earlier.
It is also possible that it was bent either before or during cutting. I’ve cut that type of rod myself and it is rarely consistant.
Good luck! Give it another go!
Glad I tried again (see later blog postings). Hadn’t really thought much about the whole piece melting into a bent piece. 🙂 Thanks
Hi, hopefully that barrel will work fine, but if you ever need to make another one there is a much simpler way. If you put the brass threaded rod in a pillar drill, you can drill down onto a clamped drill bit, it acts like a lathe to give a perfectly centered hole.
Cool idea having the barrel itself spinning (to make sure it’s straight). I already now have smaller metric drill bits, and somewhere in the mail I have a metric tap and die kit, so soon I’ll create a few more extruders (and keep a few as backups). I bought some vice jaws and hopefully that will make it easier to hold either the barrel or bit.
I was just looking through old comments to see what I hadn’t responded to during lunch, and came across your comment and my reply. I now see that in my reply I missed the point of your comment entirely – the idea of spinning the rod wasn’t to make sure it’s straight, but rather to get that self-centering behavior that happens when a stationary point comes into contact with a spinning larger piece; some give in the bit allows it to bend slightly, and it gravitates towards the center of the moving piece since there’s less resistance there. Still haven’t tried this, but now that I have small metric bits I may just remake my heater barrel before gluing anything to my Mendel extruder piece!
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