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3D printed gears stress test

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  • #16
    Ok, I switched to an 8 tooth spur gear, giving a 15 to 1 ratio. I couldn't stall the motor, in fact it twisted my lego axle like a pretzel, even deformed it. The 3D printed gear laughed at me again.

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    • #17
      I've used 12mm thick acrylic or plywood laser cut gears in some mechanisms. Never had a stripped tooth.
      Helder Ferreira
      Setubal, Portugal

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      • #18
        I was thinking print some small gears, drive one with a 1/2 square drive, make tte ither unmoveable, mount with key to shaft.
        Now use a 1/2 -torque wrench keep cranking it up in 5 lb increments and pull on the handle till something fails.
        Would that not work ?

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        • #19
          Originally posted by 754 View Post
          I was thinking print some small gears, drive one with a 1/2 square drive, make tte ither unmoveable, mount with key to shaft.
          Now use a 1/2 -torque wrench keep cranking it up in 5 lb increments and pull on the handle till something fails.
          Would that not work ?
          Well, my train gears are 20 DP, yeah, that would work, that would kill most 20DP gears no matter the material. I'd like to test these in a typical home shop machinist project, like a live steam diesel locomotive. I have no doubt Brian could use them on his engines without issue.

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          • #20
            Originally posted by RB211 View Post

            Well, my train gears are 20 DP, yeah, that would work, that would kill most 20DP gears no matter the material. I'd like to test these in a typical home shop machinist project, like a live steam diesel locomotive. I have no doubt Brian could use them on his engines without issue.
            Well that's a thought,
            Maybe Brian could give you dimensions, and you print up a set of crank/cam gears and then Brian can run them as a test. ???

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            • #21
              Originally posted by Ringo View Post

              Well that's a thought,
              Maybe Brian could give you dimensions, and you print up a set of crank/cam gears and then Brian can run them as a test. ???
              That's exactly what I was thinking.

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              • #22
                Can't stop printing gears, too much fun!
                Click image for larger version

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                • #23
                  One of the FIRST Robotics teams is actually making an effort to build their robots entirely from printed parts and they have been playing with 3D printed cycloidal gear reducers which are inherently much stronger than spur gears. They've done some very interesting work.

                  I also have Gearotic and it is a truly amazing piece of software that does lots more than just spur gear teeth. Written mostly by Art Fenerty, the original programmer for Mach 3.

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                  • #24
                    Personal opinion is I think it would be nice to know a ballpark strength comparison vs a cast iron or steel stocked product gear....like Boston Gear etc.
                    If you know that a ××× printed gear is say 60 % shear strength of cast iron or steel , then you can use that in design process..
                    Often application are only light duty use ..like say a waterpump or generator...... but meanwhile there is more severe use like a transmission gear or a rock crushed gear..
                    Where I can see a popular use is a cluster gear for back wheel of a bicycle, but to me it looks like they may not hold up..

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                    • #25
                      Originally posted by RB211 View Post
                      Can't stop printing gears, too much fun!
                      Click image for larger version

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Views:	102
Size:	2.16 MB
ID:	1864199
                      what happen to the 37T/47T lathe gear?

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                      • #26
                        Production molded nylon gears generally can handle about 10ksi tooth bending stress by Lewis formula. This is a design thumb rule.

                        I expect printed gears to be below this value in terms of tooth strength.

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                        • #27
                          Originally posted by Ringo View Post

                          what happen to the 37T/47T lathe gear?
                          Still have it, you never gave me an address to send it to

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                          • #28
                            you got a message? no?

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                            • #29
                              Originally posted by Ringo View Post
                              you got a message? no?
                              Got it

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                              • #30
                                Originally posted by strokersix View Post
                                Production molded nylon gears generally can handle about 10ksi tooth bending stress by Lewis formula. This is a design thumb rule.

                                I expect printed gears to be below this value in terms of tooth strength.
                                I would expect those to be much stronger, after all, we are limited to the fact that 3D printing leaves a "grain" with the layers. I don't claim these things to replace the need for precision machined gears(or molded ones from a precision machined mold) but for many uses are plenty good enough. The largest Lego gear shown costs .65 cents in material to make.
                                For lathe change gears, I do not own a broach, nor gear cutters. Costs a tiny tiny tiny fraction to 3D print one without any additional tooling costs to have needed features like keyways(this is not to say I won't be buying that stuff later)

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