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3D printed metric gears ???

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  • 3D printed metric gears ???

    Can someone tell about the relatively new 3D printed metric transposing gears for your lathe?
    I have a Logan 9" and the 127 tooth original, metric gear is still available for the cost of 1 arm + 1 leg.
    Now enter the Ebay offering of 3D printed gears for less money.
    Will plastic gears do the job?
    Is the technology in 3D printing such that these will actually work?
    is this a waste of money?

    ​​​​​​https://www.ebay.com/itm/Logan-9-10-...MAAOSwFZddzKbu
    Last edited by Ringo; 02-09-2020, 11:12 PM.

  • #2
    Hard to tell from just the pictures what the print process was. My best guess is its an FDM print, which personally i dunno id trust for a change gear. X and Y strength axis on an FDM print arent bad, but the Z axis is, so no matter what your gear will always be prone to breaking in some direction.

    Another downside, the seller doesnt see fit to say what the gears are made of beyond "plastic". A nylon gear might be strong enough to use, a PLA print probably isnt, but the fact that the typr og filament used isnt listed has me suspicious

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    • #3
      I haven't tried them, but as they come relatively early in the geartrain, I'd suspect they're stronger than you might think, simply from the mechanical advantage of the rest of the drivetrain between them and the apron.

      And for a lot of people, they tend to be a "one use" proposition- that is, the person just needs them to last long enough to do one or two threads, and are likely rarely, if ever, used again. You might not be able to hog out a coarse thread in steel with them- I have no idea- but you can almost certainly make it work with multiple light cuts.

      Doc.
      Doc's Machine. (Probably not what you expect.)

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      • #4
        I've been seeing a LOT of 3D printed home-shop machine parts, at least listed on eBay. Spindle nose thread protectors, which are apparently pretty hard to find in metal (always wondered why no one's machined a run from aluminum) threading dials, metric gears, and especially QC toolpost block holders in about ten different styles and a dozen sizes. I've even seen people make the tool blocks themselves, albeit only for the sub-AXA sizes, like commonly used on Sherlines and 7x12s.

        On the strength of the gears, a lot of the Asian lathes all come with a nylon initial geartrain- This Old Tony made some pretty substantial cuts, in steel(!) on a mini-lathe with nylon gears, one of which turned out to have been already cracked, pretty much from the factory. My old 9x20 when I had it, had a big molded plastic gear to go from the banjo to the QCGB, and I had no trouble threading or turning with it.

        And my Sheldon- among others, I'm told- came from the factory with a phenolic gear, supposedly in part to quiet the geartrain down a bit, and also as a "fuse"- that is, the soft plastic gear would shear in a jam, saving the more expensive and harder to replace gears. (Mine was replaced by a shopmade brass gear when I got the machine, but I picked up some phenolics from an HSM'er a few years back, and have been meaning to swap one in.)

        Doc.
        Doc's Machine. (Probably not what you expect.)

        Comment


        • #5
          The on;y downside of the 3d printed gears in this use is the consequence of failure. You often thread after doing much of the other work, so you have a bit involved in time and materials. When a change gear breaks the leadscrew stops moving and the thread gets a nice groove cut into it at that point. Depending on the project that can still be salvaged since in many cases one missing thread out of 8 will not cause problems.

          Dan
          At the end of the project, there is a profound difference between spare parts and extra parts.

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          • #6
            If you have a STL of the gear you need, I will print you one out of PETG, you just pay for shipping.
            I don't have a good way of producing gear tooth profiles in Fusion yet, otherwise I'd draw one up for you.

            Comment


            • #7
              Thanks, good points all.
              I hadnt thought that the cheapie asian machines come with factory plastic gears. They seem to work just plain ok. Little Machine Shop has quite a business in that sort of parts.
              Apparently the forces in the tooling are not as demanding as one would assume, I remember seeing a video of a guy freehand turning metal such as the wood lathe would do.
              Perhaps the plastic gears are just plain ok.

              Comment


              • #8
                MrPete222 has videos on printed change gears.

                https://www.youtube.com/watch?v=V6Aq0d1070I

                https://www.youtube.com/watch?v=NpO16KhiBak

                Comment


                • #9
                  Originally posted by Ringo View Post
                  Perhaps the plastic gears are just plain ok.
                  Fair warning - GearSnob opinion to follow...

                  First, I will stake $10 that a correct profile and size was not used to print them. I have yet to meet or correspond with anyone that is selling them to the public that actually has half a clue what an Involute is, much less how to properly construct one in CAD. Most ( possibly not all ) are using shared files to create these pseudo tooth wheels in complete ignorance.

                  Next, I will stake my reputation that they are not actually correct, from their printer.

                  As well, my personal opinion is that they are sh|te, and more than likely to break. That is admittedly supposition, though.

                  Phenolic is a magnitude of order better the choice for materials.

                  What do you consider a fair price for a quality 127T gear that fits a SouthBend 9 inch lathe? I happen to know a guy that could make quality ones and has been known to help people out in the past.




                  Last edited by Zahnrad Kopf; 02-10-2020, 10:01 AM.

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                  • #10
                    A few weeks ago as a result of a topic on the Model Engineer forum (search 'Creality') I drew a One Module 30 tooth gear for a Hobbymat that is a small lathe with plastic gears anyway. I used Freecad which has a built in involute design feature. Takes minutes or less to draw the gear. The Freecad utility will calculate DP for you in the entry box.
                    I got someone to print it at work on a £1500 printer in PLA which at 80% density took 50 minutes. The result has two runs in the wall and compares closely with the manufacturer's injection moulded original (that is 30 yrs old), meshes well, but I haven't tried it in anger.
                    The ME forum thread also has examples of printed Meccano gears which are 38DP and actually work though down there with a 0.4mm nozzle you can't expect pure involute.
                    I have drawn up gears at 14DP but can't get access to the printer so will have to buy one soon (only £200 type though). I'd like to try a dividing head pre-master disc and a few patterns for bronze casting.... Damn it I'm getting excited again, did I save that ebay listing.

                    Comment


                    • #11
                      Originally posted by Zahnrad Kopf View Post

                      Fair warning - GearSnob opinion to follow...

                      First, I will stake $10 that a correct profile and size was not used to print them. I have yet to meet or correspond with anyone that is selling them to the public that actually has half a clue what an Involute is, much less how to properly construct one in CAD. Most ( possibly not all ) are using shared files to create these pseudo tooth wheels in complete ignorance.

                      Next, I will stake my reputation that they are not actually correct, from their printer.

                      As well, my personal opinion is that they are sh|te, and more than likely to break. That is admittedly supposition, though.

                      Phenolic is a magnitude of order better the choice for materials.

                      What do you consider a fair price for a quality 127T gear that fits a SouthBend 9 inch lathe? I happen to know a guy that could make quality ones and has been known to help people out in the past.



                      Zahnrad, you buy them, and fairly test them, and prove they are inferior with evidence, and I will send you $10.

                      Comment


                      • #12
                        Originally posted by mattthegamer463 View Post
                        Zahnrad, you buy them, and fairly test them, and prove they are inferior with evidence, and I will send you $10.
                        Don't really GAS enough to. But I will happily provide the result for someone that does. I put my money where my mouth is daily. Let's see someone else do it, too.

                        Send me a 3D printed gear from one of these guys and I'll provide you with Involute Form, Index, and Lead chart results.

                        I don't see anyone else making that offer, or the other.

                        ** - I should point out that I've been here, before. I _have_ actually done this test. More than a handful of times. And I have posted the results publicly. Been a few years since I have, but nothing has changed with regard to the factors that people keep trying to shortcut.
                        Last edited by Zahnrad Kopf; 02-10-2020, 11:02 AM.

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                        • #13
                          Why don't you just ask the seller what material the gears is made of?

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                          • #14
                            Uhm, why would a 3d plastic gear need to have a perfect form? It will deform and conform to the metal gears it meshes with. Y'all over thinking this. 1$ in material to turn some metric threads. They are throw away, consumable. If you have a 3d printer, doubt you'd care how much better a proper wheel is.

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                            • #15
                              How about using them to simply index a setup that cuts actual involute profile teeth in metal blanks? And then you will have the proper metal gears with the right tooth count and profile.

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