3rd February 2017, 12:09 AM
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
3rd February 2017, 12:33 AM
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.
3rd February 2017, 04:47 AM
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.
3rd February 2017, 04:47 AM
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.
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6th February 2017, 06:08 PM
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.
6th February 2017, 07:07 PM
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.
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6th February 2017, 07:56 PM
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.
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6th February 2017, 09:22 PM
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
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