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    Dummy Fingers DIY

    Click image for larger version

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    Due to changing life circumstances, I no longer have the capacity to produce these so I'm giving them back to the community. Print them for yourself, for your friends, for your teammates, for strangers having rollouts at the field, for the benefit of the sport and appreciation of classic equipment. Improve upon them, do better than I could.



    Material -

    I've found a combination of PETG (non-specific brand) and TPU (Recreus Filaflex 82A) the best combination so far.

    PETG provides rigid reinforcement for the outer ring which is clamped in the breach by the barrel. TPU alone is too soft and will deform, either squeezing out into the bore under the clamping pressure of the barrel or pulling into the bore by the friction of the passing paintballs.

    Recreus Filaflex 82A offered the highest tensile strength of the TPUs I found, with the right elasticity/rebound and excellent durability. Other TPU blends did not spring back to their original shape, being more prone to deformation and compression setting. Maybe this isn't as big of an issue as I thought it was, who cares if the fingers stay bent down the barrel or not? It just didn't feel right to me. Definitely matters more for the VM68 detents, which I've included a file for as well. Everyone who's owned a VM68 knows the pain of deformed detents.

    Machine settings -

    I generally followed the recommended print temperatures or slightly higher with the intent to bond the dissimilar materials together, but did not find significant improvement with extreme temperature changes. Other combinations of materials could yield better bonding, but at the time I wasn't able to find any that also satisfied the main requirements.

    I printed everything with 0.4mm nozzles, and the STLs are designed around that extrusion width. My machine has dual print heads which is almost necessary to print these in any large quantities. One side is loaded with TPU, the other side PETG. Switching material and purging would get really tiresome otherwise. I prep one file for each material, and run them back to back. I liked being able to confirm the TPU had printed well before proceeding with the PETG, and to give the TPU nozzle time to cool off so it wouldn't be oozing all over the place for the rest of the print. If these two processes were combined into a single multi-material print file, it would probably work just fine with a perfectly dialed in machine - except there are a couple places where it may be beneficial to run them separately (see collisions later on).

    Process -

    The TPU is printed first. The TPU STLs layers are 0.3mm thick but printed with extrusion ratio increased 5-10%. The aim is to squish the extrusion paths together tightly, flattening the top surface, increasing the bonding strength, and producing adequate thickness. A final thickness of an individual finger should be 0.3mm-0.35mm. Under 0.3mm and the fingers are too thin to provide the needed squeeze and friction to prevent rollouts with modern paintball sizes over a common range of old, overbored barrels. Over 0.35mm and the fingers will squeeze too much, which can actually cause barrel breaks when the paint and barrel meet a "bore-matched" equilibrium. 0.32mm is an ideal target.

    The PETG prints on top of the TPU, again 0.3mm layers. The goal is to interlock the two materials together, but the thin barrels of some markers (CCI, Trracer) really limit your options. Thick autococker barrels have the most area to play with, more potential to interlock the materials. The bottom layer is an outer ring of TPU solidly anchoring the fingers retained by an inner wall of PETG. The PETG actually collides with the TPU fingers while it prints - in theory I hoped this would fuse the two materials more solidly. The Autococker style was the most durable by far, but it was also the chunkiest so I don't know how much collisions contributed to it. Too much collision can also build up backpressure in the nozzle leading to clogs and blobs.... Lastly a 2nd layer of PETG caps off the whole ring.

    Trracer and CCI were always problematic, there's not enough thickness to fit TPU and PETG onto the first layer side by side. Not only that, they're so thin the fingers aren't solidly connected to a solid ring of TPU. The outer perimeter of the TPU usually prints first, and then the fingers after, but there is not enough thickness for a border than encapsulates them together. The CCI ones in particular are just individual fingers, unconnected and "floating."

    Click image for larger version  Name:	_TPU-batch.JPG Views:	0 Size:	160.8 KB ID:	241705 Click image for larger version  Name:	_PETG-batch.JPG Views:	0 Size:	98.7 KB ID:	241706

    Because these are thin little things, there often is a fair amount of rejects, so print them in quantity. Having a perfectly leveled print bed is also crucial to hit that ideal 0.3-0.35mm thickness on as many as possible. However many you choose to print, set up a grid of the TPU shapes for one file, and then a matching grid of PETG shapes for the other file. Mind the orientation of the PETG STLs. Some, like the Autococker, are profiled on one side. Slicers tend to place the flattest side down on the print bed, but the profiled side goes down to interlock with the TPU.

    Quirks -

    CCI - The CCI TPU STL features a razor thin perimeter that the slicer will ignore, but is useful because it gives the TPU shape the same outer diameter and center the PETG ring will have, which is necessary for placement on the print bed in the slicer. I've seen some guy recently came up with his own version of a printed CCI detent which is more of one-piece cap that fits on the barrel, which is brilliant IMO. Makes me wonder if any of the other barrel styles have the clearance to do this....

    Trracer - Trracer barrels are beveled to a sharp edge. Not great for clamping a bendable plastic ring in place. I did hulk barrels on to test and didn't get any to displace, but I couldn't account for any variations in dimension that could possibly occur so I was still concerned. I opted to include an optional "spacer ring" which would limit over-torquing the barrels. The spacer ring needed to be more flexible so it could be forced over the barrel threads without snapping. Nylon worked fine, but NinjaTek Armadillo was better. Great material for anything that needs to be impact resistant and durable, rigid enough for most applications without being brittle. Unfortunately not springy enough for the fingers, IMO.

    VM68 - there's a file for making PETG rings which fit inside the holes of the TPU body, but aren't necessary if you still have the brass rings the orignal detents came with.

    Azodin KP3 - Use autococker barrels, but like a Phantom the ball isn't pushed into the barrel, so long fingers aren't necessary. I experimented with different shapes for fun, but semi-circlular nubs always printed better. I had experimented with triangular nubs as well, but I think pressure concentrated on the tips through repeated firing cycles which could lead to premature failure of the TPU.

    Orientation - Performing destructive testing on a few units per batch was part of my process. I always found the detents to be stronger when pulling the TPU fingers toward the PETG layers. Pulling the TPU fingers away would expose the weakness of the 3D printed design, the tendancy of the layers to peel apart. Therefore I always recommended to "put the flattest side down" when installing into the marker. This may give better longevity, placing more of the stresses on the bending of the TPU than the bonding between the layers.

    Thanks for supporting my hobby for the couple years I was able to produce these. Always stay cool, play hard, and be excellent.

    - Freedummy
    Attached Files

    #2
    I was waiting for you to print another batch so I could buy them from you. Sad to see you go, but massive kudos to you for leaving this legacy to the community.

    In my mind those detents will always be Freedummy Detents, no matter who is actually making them.
    Got Bork?

    Olsson's WTB - Shut up and take my money!

    Comment


      #3
      freedummy Velcor will surely smile upon you for your contribution to the paintball community. May your paint always fly straight.
      Carp 's Feedback
      Carp 's WTB/WTT

      Comment


        #4
        What a guy! These are definitely a needed product.
        Need Inception Designs or Shocktech Products? Let me know!

        MCB Feedback

        old PBN feedback

        Comment


          #5
          Whoever makes these, I'll take 10.
          ๐Ÿ’€Team Ragnastock๐Ÿ’€
          Ion Long Rifle
          Spyder Pump
          BST Feedback
          Brass Thread

          WTB Sheridan Parts

          Comment


            #6
            This is awesome as my son is getting into 3D printing. Thank you because Iโ€™m down to my last one.

            Comment


              #7
              Sticky please Mods This is a very generous mind dump and should be made easy to find in the future. Hey Jake superman now that you have a 3d printer........I think you know where I am going


              "When you are asked if you can do a job, tell 'em, 'Certainly I can!' Then get busy and find out how to do it." - Theodore Roosevelt

              Feedback Link - https://www.mcarterbrown.com/forum/b...del-s-feedback

              Comment


              • Olsson

                Olsson

                commented
                Editing a comment
                Seconded. This should be stickied.

              • lhamilton1807
                lhamilton1807 commented
                Editing a comment
                stickEE! stickEE! stickEE!

              #8
              Not all heroes wear capes! These things are one of my favorite printed itemโ€™s for paintball. Thank You for giving back! I gave away my last one a few months ago to a friend in need. Happy to have the opportunity to get some more made. You Rock!

              Comment


                #9
                Sad to see you're not gonna make them anymore, hope you stick around and really the changing circumstances are for the better.

                Thank you for sharing this awesome gem.
                Love my brass ... Love my SSR ... Hard choices ...

                XEMON's phantom double sided feed
                Keep your ATS going: Project rATS 2.0
                My Feedback

                Comment


                  #10
                  Thanks for developing and making these for us for as long as you did! It's awesome that you've taken the time to give us this well thought out and detailed post too! You're the best!
                  BigRed's feedback

                  Comment


                    #11
                    Alexndl Prints? :3
                    Dealer for: Roasted coffee and TechT products.

                    Comment


                    • Alexndl

                      Alexndl

                      commented
                      Editing a comment
                      I dont have a dual head printer
                      Will still try some test print to see how it goes

                    #12
                    Thank you Freedummy!
                    you made a great product that allowed us to use out old barrel that we loved once again, very generous to share the files and the knowledge
                    take care

                    Comment


                      #13
                      These are the best, I wanted to market them with Freedummy because I loved them so much (the autococker ones at least) now anyone goofing with a 3d printer has a walk through to get some good rings made.

                      Print a bunch and sell em to your friends and on here and everyone can enjoy no-roll-outs.

                      Comment


                        #14
                        Sorry about your current situation, I hope it improves soon.

                        You are leaving quite the legacy with these detents. Thank you!

                        Comment


                          #15
                          These will forever be known as Dummy detents in your honor.
                          ๐Ÿ’€ PK x Ragnastock ๐Ÿ’€

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