Cheap Hot End Modification Allows Easy Future Repairs

printrbot simple metal fix

We’ve seen a lot of experimenting with 3D printers over the years, and that is a good thing. However, [Tyler] has had a bad experience with experimenting. He has a Printrbot Simple Metal and decided to try nylon weed wacker line. Since he wanted to get straight to printing, he skipped the apparently important step of drying the trimmer line before printing. This experimentation ended in several clogged nozzles. Removing and cleaning the nozzle several times put undo stress on the Ubis hot end wires and they broke. Things were not going well.

In an effort to make his printer more repairable, [Tyler] ordered up an aluminum RepRap heater block, heating resistor and thermistor. The heater block was tapped with standard M6 threads but the Ubis was 1/4 inch. This was remedied by drilling and tapping the M6 hole to 1/4-20.

Now for the nozzles, [Tyler] bought a handful of cheap brass acorn nuts. He drilled a hole for the molten plastic to exit the nozzle, then used a Dremel to grind the acorn nut’s dome into a cone. He reports it only took him about 5 minutes per nozzle.

It looks like [Tyler] got back to printing with a little creative thinking. Unfortunately, the Ubis and J-Head hot ends are not interchangeable. A couple of other ex-Ubis users have made J-Head adapters for their Printrbots.

24 thoughts on “Cheap Hot End Modification Allows Easy Future Repairs

  1. Seems like a lot of effort when a new E3D knockoff is about $10 on AliExpress. Those are completely modular, easily disassembled, and fit the same mount as the PrintrBots — and they’re much better hotends too in my experience. Or if you’re willing to spend the $80, a real-deal E3D v6 is fantastic.

    1. I’ve seen the e3d hotends. They look great.

      (prints a dual extruder carriage for $.30 in plastic and time)

      Now, I can run dual extruder for $22 using the knockoffs, bowden at your choice of filament diameter. Real e3d would set me back $160. NOPE.

      1. It’s a matter of taste. I’m running a genuine E3D because my “extrusion chain” is the weakest link, and is all that holds me back from >200mm/s printing. If I could, I would use a $10 knockoff. Similarly, if my steppers or electronics were annoying, I might pay more for those.

  2. I tried nylon weed wacker line in my printrbot and suffered the clogged hotend issue, but I tried drying the line and it didnt help so surmised it was down to strands of fibreglass chopped into the line to reinforce it.
    I keep meaning to buy some taulman or similar to try again as the results until clog were great but havent got round to it yet.
    IircI held the hot end lightly with some padded curved plierswhile undo’ing the nozze as I could see the wires fracturing so I was lucky it seems.

    1. I’ve been using Taulman Bridge Nylon and cannot recommend it enough. By far my favourite filament and fairly cheap too. Pity it only comes in one color, but you can dye it pretty easily. It is really strong stuff and quite easy to print too.

    1. I actually once used a MIG welding tip to make an ejector for a DIY heat pump. It helps that the tips are 1/4″ diameter (fits into common ACR plumbing) and very easy to shape with a drill and file as a makeshift lathe.

  3. weed whacker line will ruin your nozzle. As MrFluffy points out, it has fibreglass as well as other additives in it, which will clog and even grind the nozzle.
    Taulman nylon on the other hand, is a dream material.

  4. The Ubis is a total piece of shit. There is too much hot metal close to the print, the rim around the hole at the nozzle is too wide and usually poorly centered. Switching to E3D v6 makes the PB into one of the most accurate printers on the market. Knockoffs I’d avoid, they are prone to jam.

    1. > Knockoffs I’d avoid, they are prone to jam.

      Bullshit. I had a Metal Magma. I pretty much ragequit on my printer because of that thing. When I ordered from Aliexpress, it was a last ditch effort before I sold the printer off to someone else.

      $11.20 including extruder, heater, therm, and fan assembly. This is a bowden but they sell both. And they work exceptionally well. All the parts are standard thread so I can swap as needed. And they’re all metal, so I can work with nylon and polycarbonate. And if I ruin a hotend, it goes in a MEK/acetone bath for an hour. Comes out sparkly.

      Oh, and I can buy thermistors in a 10 pack for $1.30 , so I JB weld those in the hotend therm hole.

      With the cost of making a printer, I can now make one for $300 that can handle a variety of materials, and is easily modded. So, meh to your $80 hotend.

      1. Can you toss me a couple aliexpress listings for a reasonably good 3d printer “kit”? I have two CNC machines, and would like something to monkey around with but am not too knowledgeable about what’s best to play with whilst getting good results.

          1. If you want a full kit for cheap that works I’d say go with the folgertech prusa i3 kit. If you don’t mind piecing it all out yourself I’d reccomend grabbing an i3 graber frame. It’s more rigid, but based off the same design. You could even cut one yourself on one of your cncs.

        1. Look up Sintron on eBay. Their shipping is fairly timely from China, not like some sellers over there that’ll take 3 weeks or more. I got a kit with hot end, bowden extruder, Arduino Mega clone, RAMPS, “discount” LCD with SD slot, MK3 heat bed, one motor for the extruder (I had them delete 4 because I already have 4 steppers), thermistor, 6 mechanical end stops (limit switches), wires cables etc. for $159. With 5 motors it’s $219 USD.

          You do have to provide your own power supply and mechanical parts, or buy one of their complete kits.

          I’m building my own frame with a formerly expensive flooring sample impact tester as the core on which the rest will mount, with the bed and hot end sliding on THK HSR rails.

          Don’t bother with the old Prusa design made with all the threaded rod. It is quite frankly, crap.

        2. I’ve not seen any listings for a kit, or at least I haven’t looked.

          I’d instead figure out what kind of printer you’d like to build. The #reprap irc channel on freenode is essential for assistance.

          From there, you can get the bill of materials (BOM) and start picking up parts where you can. Obviously, Aliexpress is caveat emptor, but can potentially be very highly cost cutting.

          After some looking around, I did see some deltabots that had a good price (~ $350). Those are good due to being able to design tall stuff. My prusa i2 cannot do very tall stuff at all.

          1. I think I’ll poke around and look since I’m in no rush.
            Sometimes I don’t want to learn everything there is, but since I’m not needing anything anytime soon I might as well find what I’d like.

            I won’t mess with threaded rod. Acme or bust. I have been tooling with building my own frame with thomson shafts, oolite bushings, and ballscrews for a small CNC/3d printing thing for fun (I’m 22 so I still mess around). But no time to really give it a shot until I move, and my wood CNC routers won’t hold the .001″ I want for slightly crazily overbuilt desktop machine.

            I might just opt for something ready to go, and know each Chinese seller is different.
            I asked a Taiwanese friend about the business practices since I’ve been buying more from Aliexpress. More or less you must hold your ground. In my case they’ll fudge with shipping or if something is damaged unless you press them to what they promise>

            Anyways thanks for the input, I’ll look into everything this morning, and see where things go.

      2. He’s somewhat right that the knockoffs are prone to jamming. All-metal designs in general are more prone to filament jams, especially with sticky plastic like PLA, than hotends with a Teflon liner…it’s just physics. Even with good cooling there’s always a chance of the hot plastic getting hung up on metallic burrs somewhere in the barrel. Closer tolerances in the barrel/heatbreak and heatbreak/nozzle joints will help, as will a higher quality finish on internal surfaces. Suffice it to say that Chinese knockoff parts don’t often display great attention to detail.

        Also, the E3D guys are constantly improving their designs, and from firsthand experience I can tell you that the V6 is a more reliable design than the V5. There are a variety of little mechanical details that make this the case, and you really have no idea whether an AliExpress copy has all of these features implemented properly or even at all.

        FWIW, the most reliable hotend I’ve ever used was a MkV J-head. I don’t think I had a single actual jam in two years of heavy usage (PLA only) on that tool. E3Ds are pretty reliable (and very precise) when you get the filament path set up properly and ensure that your cooling system is doing its job, but they do still jam once in a while.

        1. +1 to this. Exactly the same experience here.

          I switched to an e3d when I ran the Jhead a little too hot and got melted PEEK everywhere… Though I’ve also melted an e3d heat block due to a detached thermistor.

          The clones are usually made to work with both 3mm and 1.75 mm and the result is they don’t work as well with either.

  5. Trimmer line having fiberglass can be resolved with stainless nozzles.

    The big problem is additives to make fiberglass compatible with nylon could be dangerous when melted.

  6. Uhh, printing at the temps required for melting nylon means nearing/crossing the 250C mark. This also means that the PEEK / PTFE in the hot end will start to deteriorate giving off poisonous fumes. It is NEVER a good idea to print high temp plastics in any hot end that is not fully metal. For you or the hot end.

    That being said, I love my Ubis… for PLA.

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