Quickbuild Number 3

So, we have this board full of header pins that hold a vertical board full of leds, unfortunately the pins protrude too much outward from the vertical board, and we had to cut them down for the fifty prototypes. The board has 70 pins, and cutting them by hand is just silly…(and as always, one of the topmost thinking heads, valorated cutting them by hand…yeah, they’re so naive sometimes.)

So, here it is, Quickfix number 3, weekend improvised miniature circular saw/grinder:

109b - circular grinder sawYeah, it’s kinda botched, isn’t it? well, this is what I was cutting before the laser exploded (i.e. pressure cracked) so I had to make do with the piece and a half I had cut, and leftover pieces lying around. Add some RC parts (10Amps brushless driver and a cheapass servo tester), machine an adaptor (3mm to M2 screw) and there you go. (yes, they pay the material AND time I spend making these things at home, isn’t that wonderful?)

109 - circular grinder saw
Super transformer to hold down the thing, as it doesn’t have much mass in itself.

Since the laser died, I was unable to cut the pieces as I would have liked, so, instead of adjustable depth, I glued a pair of FR4 strips to the top surface and finely adjusted disc position through spacers (wich make a pain in the ass to change discs, by the way).

You can’t know by the photo, but I’m wearing two pairs of gloves, because the leftovers where so hot they burned my skin! I didn’t had better gloves around, so I had to make do with those two pairs. I still felt some really hot ones, but was just bearable.

Once I have the laser operative again, I’ll redesign it all, putting an engine guard against dust and add adjustable depth, amongh other things. A thing to note, I never thought about header pins and magnetism. Be careful with a setup like this (with no guards) header bits might get between the windings and magnets, and shatter something.

And then, when my least favourite boss comes around, asks “Does this really cut?”

After all these years and you still ask that kind of questions when I’m involved?…Really??

Part 2:

What was all this cutting for?

9 responses to “Quickbuild Number 3

  1. Pingback: Tiny Improvised Grinder/Saw Packs a Punch

  2. Nice thing you got there! I’m guessing that your motor driver is powered with a wall adapter? What is the model of the motor you are using?

    • Almost!, instead of a wall adapter (wich would work perfectly) I used a variable power supply, we have plenty of those at work, so I can’t loose it when the “tool” gets stored for some time.
      The motor is from ebay, for a tricopter I had around. It’s a “MAX CF2822″ with around 1200Kv. I bought four at the time, so I can spare one for the grinder, and still have some left for the tricopter, the day I get into finishing it ^_^U

  3. Great to see, but your boss would have finished before you even started your first cut:
    70 pins, 3 pins per cut, 2 seconds per cut, 50 boards. That totals to 45 minutes….
    glue a spacer to the pliers and he will finish before the end of his lunch.
    Don’t get me wrong. I love the build and RC parts, but why being such a smartass in public?

    • Yes, but cutting pins with pliers has a major drawback, the cut will leave a pair of tiny bits on each side of the cut, wich will make for difficult insertion in very long boards because the pins won’t slide as easy through the pads. For short boards that doesn’t matter, but for 50cm boards, since the pins do not sit perfectly in their pads, the room you have for wiggling around the board is none, so, adding a bit of resistance per pad, can become very annoying. Grinding pins leaves them absolutely flat, so insertion is way easier.
      Apart of the legitimate reason, I get paid to be a somewhat smartass at work (really! XD). If those protos become a production, one person cutting with pliers for hours, will get tired after…what, four hours? (not taking into account the degradation in performance over time and cumulative hand strain). With the grinder, I don’t even feel any bibration on my hands, so I can keep cutting for hours if necessary.

  4. I like the project and re-usability for future requirements…
    My concern is no vacuum or other means of drawing the metal dust and pin remnants away from the electronics. Tiny slivers of conductive ‘pin swarf’ – can be very hard to find when they short out under IC legs etc.

    • Yes, that’s especially true for low pitch boards. This one has quite big components (for SMD) so dust is not especially a concern. Leftover pins could pose a more serious problem, but a heavy shake after cutting, gets rid of them (and makes for a sparkly floor! XD)
      Interestingly, the tight fit (so to speak) of the disc, generated a bit of vacuum, wich gathered dust of the cutting on the small hollow area under the sliding surface. Hadn’t that happened, dust might have become a more serious concern.
      When the laser is back to life, I’ll add a centrifugal extractor to the shaft itself, so it really absorbs dust when cutting. :)

  5. I’d probably sooner strapped my dremel tool to something and just gotten on with it. Congratulations. You just reinvented the wheel.

    • Yeah, but still, you’d need more time to strap your dremel to something and mount some kind of smooth slider for the boards, than I needed to design, cut and assemble this. (If hadn’t kill the laser)

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