An all metal BMG Clone Extruder

I had converted my predator to a BMG clone (a fysing one) fairly soon after getting it, after using one on my linear plus. I had purchased the same brand based on the assumption that if the first one works well, why shouldn’t this one. But on receipt, I noticed that the plastic gear fitted to the main shaft wasn’t mounted perfectly concentric. I fitted it anyway and for a few weeks it worked as expected.

I then noticed a piece of plastic had fallen off, and on further inspection, it was the plastic holding in the little bearing on the main body. This missing piece of plastic resulted in a reduction in the amount of pressure that could be applied to the plastic when extruding. After super gluing it back in place, to enable printing to continue, I decided that I should be looking for alternative brand.

That’s when I came across the Sanjiu all metal BMG clone extruder on aliexpress. The main difference between this and other BMG clones is that the whole body is made of machined aluminium rather than being injection moulded plastic. There are even threaded holes to allow you to mount a fan if using it as the heatsink of the hot end (although working with a delta, this isn’t an option). So I took a punt and ordered one.

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When I received the extruder, I stripped it down as far as I could and took pictures of all the components. Everything is made from metal (apart from the roller bearing cages for the one gear). It all assembles really easily and is obviously well made. The main difference between this extruder and a plastic equivalent is the weight. This weighs 68g compared to 131g of a clone. We all know that weight can make a difference but I believe the better rigidity of a metal extruder outweighs the cons of added weight.

I have since fitted it to my machine and I haven’t had any issues with skipped steps. Only time will tell if it works well or not. I shall give an update on it soon.

14 comments

  1. Just assembled mine and all i’ve done so far is steppers and dampers. Have pretty good results out of box, like it far better that my MK3S, not to mention speeds I can reach now. Print bed is a dream, superior adhesion at 40C. Mine came with Trigorilla pro.
    Eventually going to get PanelDue, and maybe fancier extruder.
    Never did any big mods to printers yet, glad I found this blog.

    1. In the long term you’ll want to think about removing the dampers because although they reduce the noise from the steppers, they also introduce play into the system. Play equals loss in accuracy. They also prevent you from getting your belts nice and tight.

      1. Right, reading subj for 3rd day now, going to replace board w Trinamic drivers and will remove dampers. Already ordered v6, bmg extruder and bed insulation. Completed enclosure today.

        Can’t figure out what board to get, either Duet, but I do like that I can do timelapses via webcam with Octoprint, I will miss that feature. Or something like SKR1.3 w Marlin so I can use Octo. Sad thing Duet neither supports webcams nor Octo.

        Since I’ve never modded any of my printers before I don’t know if any of these open firmwares has a capability of 3d rendering from its interface, or even displaying thumbnails of gcodes in file manager, something like my FF Guider 2, but its closed proprietary stuff. I also can do 3d rendering from within Printoid App for Octoprint. If I could do this from board’s native interface…

          1. Thanks a lot I will try.
            Yes I see these processors are really weak, I thought the’re more advanced. Looking forward into release of Revolve boards, if it ever happens.
            2 side enclosure costed me 12$ in 3x corrugated black plastic boards from Michaels Crafts Store as described by this guy https://www.youtube.com/watch?v=fbarSmBh56Q

  2. Hello Jay,
    also ordered one of those “BMG Aeros” for my CoreXY machine.
    How does Sanjiu make the interface to the hot end? The “Mellow” branded extruders are depicted with an M7-to-Bowden adaptor. But your photos don’t show anything like it (neither does Sanjiu on Aliexpress).
    It would be great, if the heat sink would work – but I’m sceptical about this.

    1. To be honest I have no idea how it would interface. Having a quick look at it, the hole isn’t threaded so it may be a case of an unthreaded heat break similar to this which is held in place with a grub screw.
      I have recently had to change the push fit for the ptfe tube as it kept popping out.

      1. Unthreaded doesn’t sound good…
        I have two “smooth” 7mm heatbreaks here. One is a mirror polished Titanium one – but even that coudn’t print PLA relaibly in an XCR BP6 “Hexagon” hotend (much the old E3Dv5, but one cooling fin less).
        An M7 thread would make better contact with the heat sink. And if the bore is 6mm (like for that Winsinn heatbreak), I could cut it.
        Thanks for your answer! I’ll just wait for that packet to get through customs here and take a look at it once it’s here.

      2. My red specimen arrived today. And yes, it has the “smooth bore with two maggot scews” mounting option. The bore is 7mm, so you can’t just re-work it to fit an E3D heatbreak. And a “Mk10” version will be too long. Even the XCR3D one for the BP6 is. Looks like it was made for Kraken/Chimera/Cyclops heat breaks…
        But I won’t try it. Counted the fins and roughly calculated that is has something below 60% of the surface area that E3D heat sinks (especially the Titan Aero) have.
        And if the heat break gets loose, you’ll have to unmount the motor to access those grub screws.
        Guess I’ll just use it like a normal BMG.

        1. I’ll add a note to the blog post about it.
          Just a heads up as well, I ended up removing pneumatic fitting for the Bowden tube and replacing it with another one. I kept having issues with the PTFE tube pulling out. To replace it, I tapped it and fitted a new fitting that way.

          1. Nice little review.
            Why not try feeding some ABS or PLA through it on the bench rather than mounting it up?
            Should give you an idea whether it will actually work or not.
            I’m surprised yours had the plastic guide in. Mine is definitely all metal.

          2. Well, the chinese seem to sell every production run – even their first test batches. So you’ll notice their upgrades with every iteration…
            …or they just forgot it. 😉
            Just designing the part in OpenSCAD, before putting everything together. If it comes to probles with printing flexible materials later, I want to be prepared.

            Yes, also thought about firing up an old RAMPS and loading some random Gcode into it. But as I’ve decided to go for a plain vanilla “BMG direct” setup, I don’t think it is neccessary.

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