SUPER-SIZED ROBOT: SERVOS

NikosGNikosG Posts: 684
edited 2019-11-19 - 22:33:02 in Robotics
Hi all,

Ken announced something about the super-sized robot. He wrote: ".....What are your ideas for making the servos? Keep in mind we could be making up to ten of them. We'd use the 12V motors from our Motor Mount and Wheel Kit. "

My idea is a "fake" servo...

A 3D printed enclosure for the 12V Motor Mount and Wheel Kit in a shape similar to a real servo.
The axle of the 12V motor kit will come out from that "fake "servo-enclosure in the right position like the real servo. And In the same way the cables ...

The question is: will be able the 12v kit to fit inside to the fake servo?
X_Y_chassis_hole.jpg

How much exactly is the dimension (x,y) of the "window" that is supposed to hold the servo in the Supersized robot model?

Comments

  • NikosGNikosG Posts: 684
    edited 2019-11-20 - 00:14:43
    Here is a more detailed model....


    The "fake" servo enclosure is the yellow translucent colour (with the super-sized dimensions, and inside is the 12V motor kit.
    fake%20servo.jpg
    The only we have to do is to print the "Fake" servo enclosure with a Black ABS filament .....
    952 x 689 - 92K
  • With you on the 3d printing idea.
    Returning to Spin after two months of not coding micros at all, forgetting to use :=
  • W9GFOW9GFO Posts: 3,915
    edited 2019-11-20 - 04:04:08
    Maybe something like this...

    Cutaway02%20s.png
    1200 x 937 - 639K
    1600 x 1325 - 1M
    800 x 663 - 405K
  • I think 3d printing the whole thing is impractical.
    I would use a CNC or laser cutter to cut out panels that can be fit together to create the main shape, then perhaps 3d print the "top" part with the mounting flanges and mounting spot for the 12v motor kit.
    This would make it much faster to produce, and less prone to 3d printing failures (which are much more common with such large parts).
  • The 12v motors for the Arlo chassis?

    Judging by some of the pics on fb I'd say there is more than enough room. Unless I'm looking at the wrong 12v motors.

    Thin sheet metal could work for the servo body, or wood. Too much to 3D print for me personally.



  • Roy Eltham wrote: »
    I think 3d printing the whole thing is impractical.
    I would use a CNC or laser cutter to cut out panels that can be fit together to create the main shape, then perhaps 3d print the "top" part with the mounting flanges and mounting spot for the 12v motor kit.
    This would make it much faster to produce, and less prone to 3d printing failures (which are much more common with such large parts).

    I agree with Roy,

    The backside of the servo could be a wooden box painted black and only the top part 3d printed...
    Also, the part of the "servo" that has the four holes in order to be attached on the robot's chassis could be wooden too...
    See the model above from W9GFO and imagine the wooden plate extended left and right in order to fit on the robot's chassis.....
  • The nice thing about 3d printing is that once the design is done, very little work is required.

    I had thought about using a wood plate for mounting the servo to the chassis, but decided against it because the plastic is plenty strong enough and it would interfere with the belt reduction and motor mounting plate - which must be adjustable so that the belt can be properly tightened.

    As for the back shell, sure you could make that out of sheet metal or wood, but why? That is a lot of work to do ten times over, I prefer to let the machines do the work. I guess if you don't have access to a 3d printer then that is a good reason why.

    The large prints sure do take some time though. You gotta have something else to do other than wait for it to finish. The red pulley pictured below took over 30 hours to print but there was no other reasonable way to make it - the pulley is crowned like a bandsaw wheel to keep the belt centered. The servo top only took about 12 to 15 hours.



    Top01.png

    Top02.png

    IMG_3862.png
    1200 x 900 - 2M
    1200 x 900 - 1M
    1200 x 1125 - 3M
  • I'm glad Rich jumped in. I didn't mention in the newsletter that Rich is actually helping us here.

    He's got a solution that will work perfectly. Rich, I need to order some more chassis parts for us. I'll get these to you in the next couple of weeks (I'm going to ask my contact at Sierra College if they're willing to cut a few more for us). How many of these servo enclosures can be made?

    Ken Gracey

  • Ken Gracey wrote: »
    How many of these servo enclosures can be made?

    Probably about four or five per week is realistic, barring any mechanical issues and as long as I can keep feeding the printer with filament. Of course that is assuming that the current design will work. I still need to create a cooling solution, don't want to have the motor (and driver) cooking inside an air tight plastic enclosure.
  • How much filament does one of those servo tops eat up?
    Returning to Spin after two months of not coding micros at all, forgetting to use :=
  • NikosG wrote: »
    How much exactly is the dimension (x,y) of the "window" that is supposed to hold the servo in the Supersized robot model?

    Everything is scaled up 5x, so the size of that "window" is about 210mm X 104mm. The servo body is 203mm (274mm incl. mounting tabs) x 100mm x 189mm. This size was chosen as the smallest that would fit the 12V motors.
  • Nice, I thought it was much larger. That is certainly 3D printable and your print looks great!
  • How much filament does one of those servo tops eat up?

    Just over 3/4 lb, or about 400 ft.
  • Whoa!!
    That's a lot of filament!!
    Returning to Spin after two months of not coding micros at all, forgetting to use :=
  • Looks good Rich, What filament type are you using?
    I've often had issues printing large stuff with ABS (so much warping), which is why I made my earlier post. PLA might be ok, but for structural things it tends to break too easily.
    PETG is what I have settled on for most things.

    Cutting the "box" part of the servo on my glowforge would only take a few minutes.
  • I had read that PETG was stronger than PLA, but when I printed test pieces it broke more easily than PLA. So I use PLA for most everything. I have not found PLA to be lacking in strength. The worst thing about PLA is that it does not take much heat to soften it.

    I would prefer to print in ABS (stronger, withstands heat better and can be vapor smoothed), but that is not possible without a heated chamber. I do intend to get a dedicated ABS printer, don't know when though.

  • In my experience, PETG is much stronger than PLA, but you need to print it hotter and not use the cooling fan as much or you get bad layer adhesion.
    I found PLA to be more brittle, especially around mounting points. I've had PLA parts just snap of flanges, where the same thing in PETG holds.
  • Make some chassis available for sale and see what people come up with.

    Are you going to have 1/5 scale penguins too??
  • WOW -Sorry to arrive late!
    Whit+

    "We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
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