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  1. #1
    Join Date
    9th December 2015
    Location
    Fullerton, CA
    Posts
    68

    3D printing conformal rail guides - Plastic question

    I really like the conformal rail guides that Wildman sells, but refuse to pay $14 shipping for them, so I've designed my own that are very similar and will be 3D printing them.

    My question is, which type of filament should I use for them? I know several vendors also make and sell 3D printed rail guides, does anyone know what they use? I prefer printing rocket parts out of PETG, but I know that has issues with epoxy adhesion (These will be going on a MD rocket, so I can't mount them with a screw). PLA doesn't have the bonding issues, but I'm not sure if it's tough enough for the task (J motor on a Go Devil 38). Would ABS be the best choice, or should I modify the bottom of the guides to have places for the epoxy to grab hold of?

    Any thoughts or suggestions would be appreciated. Thanks

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  2. #2
    Join Date
    19th January 2015
    Location
    Northern Virginia
    Posts
    84
    I've been printing similar guides for about a year ( http://www.thingiverse.com/thing:1413165 ) and I've printed them in PLA, ABS, Nylon (Taulman 910) and even Carbon Fiber Reinforced ABS. I've played with CF Nylon but the filament was really brittle to work with. My preference now is Taulman 910

    While to my touch the nylon seems slicker, I can't really see any difference in the way they perform. In the long run I suspect that the nylon ones will be the strongest and most wear resistant. The CF reinforced guides are very rigid even when printed with standoffs ( http://www.thingiverse.com/thing:1984960 ). Some of my students launched a 5.5" 5 lb HP rocket with them and had 0 problems.

    We did test them for adhesion and actually destroyed a body tube without detaching the guides. The mounting procedure we used was as follows:
    1) Wrap a piece of coarse sand paper around the body tube, grit out, and sand the mounting surface to remove any residue, create a roughened surface and contour the guide to the tube
    2) lightly sand the body tube in the mounting area. Essential if the BT has a glassine coating.
    3) Optional, not for MD - Use a map pin to punch several holes in the BT to create "glue rivets"
    4) Use a proper adhesive, I've used epoxy and PolyZap successfully.

    BTW, the notch in the top edge makes it easy to align the guides by dropping a ruler into a pair of guides. I designed this using the dimensions listed for regular rail button and looking at the ACME guides. At the following launch another rocketeer had the Apogee guides that are very similar (and look 3D printed), a kind of simultaneous invention

    Last edited by dcullen; 3rd February 2017 at 12:39 AM.

  3. #3
    Join Date
    19th January 2009
    Posts
    890
    Nylon would be my first choice, then ABS. If you already have PETG, try a test with epoxy bonding. I was able to glue PETG to another PETG part with hobby epoxy. I have not tried to glue it to anything else though. Even a bit of raft or skirt is enough for an initial test. Wait 24 hours, then destructively test. If it holds, print a guide and do it again. My concern with PLA wouldn't be toughness, it's good enough for this. It's heat. If you launch in hot weather, that can weaken the PLA and let it deform a little. That could cause it to hang up on the rail or let go, causing you to go skywriting.

  4. #4
    Join Date
    17th December 2013
    Location
    Slagle, La
    Posts
    1,128
    Give Tim at Wildman's a call to discuss shipping. He may be willing to drop some in an envelope and send em on their way. He has called me before to save me money on shipping. I always leave a note in the comments to use cheapest shipping available anyway.
    As for the 3D printing, I know little about all that.

    Mikey D
    Nothing is foolproof to a sufficiently talented fool.
    TRA #16513
    Level 1: Danger Close ---AT H123W to 1240'--- 29 OCT 2016

  5. #5
    Join Date
    9th December 2015
    Location
    Fullerton, CA
    Posts
    68
    Thanks for the suggestions. I will check out the Taulman 910 filament, and will be conducting tests with epoxy adhesion on the PETG. If all else fails, and I don't have any luck printing somethign that I'm confident in, I'll give Tim at Wildman a call to see about shipping.

    Thanks!

  6. #6
    Join Date
    31st January 2009
    Posts
    4,212
    There are, of course, many other considerations, but here are some filament strength tests by "Maker Dan". PLA is, interestingly, stronger in tensile strength than ABS.

    https://www.youtube.com/channel/UC2Z...yWVZwqw/videos
    "I don't make jokes. I just watch the government and report the facts." - Will Rogers

    "If you don't read the newspaper, you're uninformed. If you read the newspaper, you're misinformed." - Mark Twain

  7. #7
    Join Date
    23rd February 2014
    Location
    Eastern Shore, MD
    Posts
    262
    The older PLA with print temperatures 175-195C will soften in the sun, I found out the hard way when my first av-bay sled deformed. I mainly use PETG these days with mechanical connectors (ie screws). Mayham just made me a set of 98mm rail guides out of Taulman Alloy 910 to test for him, that 910 is extremely tough and he had great layer adhesion.
    Dennis Kingsley
    NAR #97251, MDRA #064
    L1 - Madcow Torrent
    L2 - Madcow Sensor
    L3 - Extended Madcow Stinger

  8. #8
    Join Date
    6th June 2011
    Location
    San Diego. CA.
    Posts
    6,387
    Quote Originally Posted by SoCalChris View Post
    Thanks for the suggestions. I will check out the Taulman 910 filament, and will be conducting tests with epoxy adhesion on the PETG. If all else fails, and I don't have any luck printing somethign that I'm confident in, I'll give Tim at Wildman a call to see about shipping.

    Thanks!
    If you need help with testing the Taulman, I'd buy a pair and pay to defray the cost of materials/time, if that helps

    TRA 2383
    Somebody told me I was on the watch list-I hope I get a Rolex.....
    The road to Hell is paved....you're welcome.
    I can't remember the last rocket I built, because I haven't built it yet.....

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