Finished my first DIY: Hephaestus the 3D Printer

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    @frank26080115 fantastic and great set of pictures here, also 😍


    love the custom splash screen!

  • it was looking so promising, but alas you lost me at the clothes peg springs i'm afraid...

  • Are those springs that bad? The stuff I'm printing now looks fine. My 5 year old $2500 Ultimaker 2 has them integrated into the sliding blocks internally.

    I designed this just now:


    Belt slots in, a M3 screw and a captive M3 square nut will be inserted and press against the belt, pushing it out the opening at the top. The whole thing will be zip-tied to the belt. The screw and the belt will have something between them so the metal edge of the screw doesn't damage anything (probably a piece of 1/4" PTFE tube cut in half lengthwise).

  • @frank26080115 Adding lumps of mass to a tensioned belt may enable you to increase the tension, but will add yet another potential source of resonance that will tug at the belt (you're adding a weight to a spring). It would be better to make the tension adjustment by means of fixed parts, like sliding a pulley or motor until the belt is tight, then locking it down.

    I would never tell you that the static tension on one side of a belt loop is different from the tension on the other side. 😉 I paid attention to the teacher in high school physics class.

  • The only way I could accomplish that is to install the belts another 2mm or 4mm tighter before installing the rods, so I am kind of screwed unless I rip apart the entire upper half of the printer. It'll also make installing the rods a pain in the ass, if not impossible.

    The point of using springs is to take up the slack that builds up over time. The disadvantage is it could result in backlash. But I don't see any indication right now that it's happening so I'll keep the springs. Maybe add a second one if I really do need to.

    It's insanely tight right now too

    My X and Y steppers are being driven at 1600mA in case you are wondering. The Duet is actively cooled. It's done two 12 hour prints so far.

    I think I have a lot of headroom for barbarian solutions

  • @frank26080115 Those springs make the belt act like a rubber band. Depending on the mass of the printing head & x axis, it may not be noticable.

  • Yea I know, that's the disadvantage. But without them the belt itself becomes a very loose rubber band. With them, the belt feels like a stiff rubber band. So far it prints fine after some tuning, acceleration is at 1500 instead of 3000 and I see no oscillations any more.

    It is possible for me to tighten the belt without the springs but it'll be too difficult (tearing down the entire top of the printer) for too little gain. The part I just designed is another easier (retrofitted) solution, I don't think the added mass is a problem. I'm just reluctant to remove the springs, they are actually insanely tight right now and I'd rather cut them off instead... though all the small cutters I own are meant for soft metals and not hard metals. I've ruined my Lindstroms before making that mistake...

    As I said before, the springs have an advantage because they take up slack over time. Ultimakers, $3000+ printers, has the same springs built into it, hidden from view, and mine is 5 years old and printing smoothly. I'm quite positive that the lack of problems is because springs are being used. My gantry is actually covered with a fine rubber mist from the age of the machine.

    With that said, I don't actually see how it would be possible to retain tension on an Ultimaker-like design without using springs. It's not like you can just move the rods. The gantry kind of depends on being slightly overconstrained anyways. Adding tensioning idlers would be challenging if you've seen just how efficiently the Ultimaker uses available space, they'll end up with less build volume or wasted material building a bigger printer.

    Maybe Ultimaker could adopt how I built in that screw into my sliding block, but perhaps give it more travel.

    If we are doing a tradeoff between less frequent maintenance and print quality, I pick less frequent maintenance.

    And if I had to favor print quality instead, the best bet is probably the part I just designed in the previous screenshot. Or some variation of it where it is lighter. The mass is insignificant compared to the actual extruder.

    I've seen people use simply three zip-ties, but I fear that might damage my belt from pinching it.

  • Hi,

    Looks good.

    I've not seen a printer like that before. What is the name for this type of setup?

    And I think you need to more nuts and bolts holding it together. 🙂


  • @fcwilt I'm not an expert on 3D printer style naming, but from what I see on the market, Ultimaker prefers this style, and other people who build this style always kind of make it sound like "Ulti" in some way. Example: Monoprice Ultimate. Not sure if Ultimaker invented it though.

    I call it Ultimaker-like

    It's cartesian as far as electronics/firmware is concerned.

    The RepRap wiki calls the Ultimaker's kinematics "parallel kinematics"

  • @frank26080115 said in Finished my first DIY: Hephaestus the 3D Printer:

    The RepRap wiki calls the Ultimaker's kinematics "parallel kinematics"

    I understood parrallel kinematics referred to an actuator system where the source of the motive force for the axis was stationary. I think core xy and maybe delta printers are parrallel kinematic systems.

    ...goes off to check...!

    Edit: after a re-read the quote from the reprap article is acurate, but it doesn't intend to suggest the ultimaker kinematic arrangement is the only way of achieving a parrallel kinematic system. It is saying that the ultimake style is one example of a parrallel kinematic system.


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