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Thread: Onyx X build thread

  1. #11
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    Re: Onyx X build thread

    Or try cutting sheet and bending it in a brake, just like how most of the other frames are made for bots. I expect that Fusion 360 has a sheet metal forming capability just like Solidworks. You can adjust the radius for each bend to make sure things line up and then unfold everything into a flat drawing ready to mill.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh

  2. #12

    Re: Onyx X build thread

    Yes, I was looking at sheet metal, and tried some 5052 aluminum, but:
    - on the waterjet, it delaminated on pierce-through
    - on the mill, I get edges that are too rough -- 5052 is a pain to machine
    - also, workholding of sheets on the mill is a pain. The least bad is mitee-grip wax paper, but it's not a slam dunk

    The good news is, a few hours at the Tech Shop today came out really great for femur brackets (separate for the two sides, as in the picture):

    The first step required one clamp and three tool changes per piece (2.7mm drill, 3/8" milll, 1/4" mill):


    The second step required no tool change (it's all 3/8" milling) but two clamps per piece:




    I didn't bother with soft jaws, so the second clamp was by eye only and a bit was sticking out of the vise and vibrating more than I'd like. But it got the job done :-)

    (Other things you may be able to see:
    - The first bracket, I had forgotten to add the cutout for the center of the MX-64 horn, so I did those by hand and they're bigger than the design.
    - The third bracket, I clamped too hard in the vise so it buckled, and didn't get fully faced by the 3/8" endmill)

    Anyway, a good use of three hours!

    With soft jaws and a fly cutter instead of end mill for facing, these would have been perfect. But I'm not going for perfection :-)
    Last edited by jwatte; 02-09-2017 at 10:29 PM.

  3. #13

    Re: Onyx X build thread

    Alright, back to the actual build! I've been a good boy, and spent almost zero time looking at what it would take to build my own 433 / 916 MHz Xbee-like device out of the $2.80 Atmel parts ...

    I've decided to build a single host board for plugging everything else in. Because I have 190mm of covered area inside the body, there's enough room for almost everything. Even a 4S battery. (Yes, I may go back to trying 4S this time! I'll develop on 3S, and if I feel lucky, pre-discharge the 4S to 16V or less, and run with that.)

    So, the inside fits battery, controller (OpenCM 9.04,) power switch, control XBee, and scoring board, as well as the yaw servo for the turret. This will keep center of gravity lower, which is good for stability. I've lasercut 3/32" Delrin to fit, and figured out where all the screws go, so I'm ahead on that front, too.

    Because of all the radios inside (I may add a third one, to get telemetry back, at least while developing) I will likely stay with the Delrin for the body.

    I've learned KiCad, and the OSH Park submission seems to come out alright in the previews, so there is that. Also, DXF files exported from Fusion 360 somehow double up all the strokes, and I found a shortcut in how to remove the doubles in Illustrator. Select it all, then press "outline" in the Pathfinder tools. Magically, single outlines of all the paths are created! Great for lasering.

    Tomorrow, Big Blue Saw starts a Valentine's sale, where 1/8" 6061 aluminum parts will all have the quantity discount applied.
    Given all the radios I'm applying, I don't know whether I want aluminum, though. The turret will contain video transmitter, camera, and the gun, as well as the hit indicator lights. The body will contain everything else. Plastic seems better (but less rigid.)


  4. #14
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    Re: Onyx X build thread

    Nice parts! Do you plan to sandblast them?
    Kåre Halvorsen aka Zenta
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  5. #15

    Re: Onyx X build thread

    Onyx 3 was sandblasted and powder coated black. People thought the parts were plastic :-)

    This time, I'm going for functionality; bare metal, no treatment. Two months to go!

  6. #16
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    Re: Onyx X build thread

    Good call. A working unpainted robot is better than a non-working painted robot.

  7. #17

    Re: Onyx X build thread

    Iterating on the base plates using paper models and Delrin turns out to be quite effective. I think I have all the cable routes and standoffs and screws accounted for, now.

    There's also a tension between "holes to make it possible to poke at things without disassembling the robot" and "must be ruggedized against an incoming onslaught of plastic pellets." I may put more holes on the bottom, and less on the top, perhaps. (Except the top is where the wiring to the turret needs to be.)

    Representative image: (yes, this process is messy! and involves kitchen tables!)


  8. #18

    Re: Onyx X build thread

    I'm a careful fellow. I use simulation software for my machine tool paths. I run air passes so I don't crash the mill. I fix all compiler warnings in my software, and turn on as many warnings as I can. I run design checks in my electronics CAD. At least, that's what I tell myself.

    Last Sunday night, pretty late, I was finishing up the main board of Onyx X, having just learned KiCad.
    OSH Park actually allows you to just upload the kicad_pcb file to their site now; no need to generate Gerbers, so that's cool!
    When dry fitting everything, I realized I had no 3.3V power connector for the aiming laser. Not liking to tap into other traces/pads with patch cables, I dropped a 2 pin header onto the board, into a free area of GND fill (and +12V fill on the top side) and routed 3.3V into it, and sent it off for the Monday morning board run.

    I opened up the board yesterday to check something out, and pressed the "DRC" button. Which I had forgotten to do after the final adjustment last Sunday. Here's the story in three pictures:











    The solution will be to Dremel out the copper around that pad on the top layer before I do anything else when I get the boards back. Here's hoping I remember to do that! And test continuity.

    Now, I got this in 1.6mm 1oz copper. Fourteen servos plus a bunch of radios actually draw a fair bit of power, at least at peak, so I may want to re-spin it on 0.8mm 2oz copper anyway. The idea was to fit everything, and make sure it works, and then get that next order in and finished before RoboGames mid-April. There will still be time, but it might be tight ...

  9. #19

    Re: Onyx X build thread

    Ouch! Been there

    I have not learned KiCad yet - still using Diptrace. So I still have to generate Gerber files. So I run the diptrace verify functions first, then generate gerbers and then I run viewmate (older version) by pentalgix to make sure that the gerber generation did not totally screw up.

    But I still miss some!

  10. #20

    Re: Onyx X build thread

    So far, KiCad has very few annoyances, and mostly works great!

    Forward- and back-annotation is not automatic between schematic and PCB layout, though -- you have to press about three buttons to go each way -- which is the only real annoyance I've found.
    I can think of large projects with many enginers where a carefully staged process for going back and forth would be useful, but forcing it on everybody seems clunky.

    Also, when I moved parts around into hierarchical sheets, they got re-numbered (more accurately, the numbers got set back to ?, and I auto-renumbered them.)
    Then, when going through "export netlist" -> switch -> "import netlist" all the nets ended up being screwy, because "pad 3 of J5" was something totally different now.
    There actually exists a solution for this in KiCad; you can associate parts by "timestamp (id)" rather than "name," which would have solved this, but it's not the default, and I didn't know/realize I had to use it.

    Power tools, indeed.

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