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Otto LC

A Laser cut chassis for the Otto DIY robot.

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Otto LC is a chassis for the Otto DIY robot that can be made using a laser cutter (though the LC). It is primarily intended to be cut from plywood but could also be made from other materials (may be with a bit of tweaking). In addition to the features of the original chassis it also allows mounting a mode switch for looping through different programs.

We wanted to do a robot project for children and found Otto DIY here on Hackaday. While it is a very nice project it uses a 3D printed chassis. While 3D printing is really cool for building one robot it just takes too long for 20 robots. As the chassis is basically made of 3 blocks plus the feet it was a natural step to recreate it in Boxes.py a software to create boxes on a laser cutter.

If cut with sufficient burn correction (aka kerf) most pieces can be put together without glue (but with significant force). This is nice for one robot but turned out to be not very practical for children who often lack the strength (unless you want to hand them a mallet).

Besides the servos and the electronics only two little screws are needed in addition to the laser cut parts.

  • 2 × Screws M3x6mm (or similar)
  • 1 × Micro Push Switch 6x6x4.3mm
  • 1 × Small Sliding Switch
  • 1 × Set of Otto DIY Components without the 3D printed parts See https://hackaday.io/project/11776/components for the list
  • 2 × Additional Jumper Wires female on one side Other side doesn't matter as it gets removed

  • What happened so far

    Florian Festi08/19/2017 at 13:24 0 comments

    When we decided to do a Otto Bot workshop in early 2017 I drafted the chassis pretty quickly. Although the legs are a bit complicated - the body basically is just a hinged box I already had - it quickly looked like a robot. But only with the workshop approaching got the last details fixed - e.g. the holders for the PCB, the "teeth" holding the head shut, the hole for the main switch, the final size of the ankle screws.

    In parallel a group of people was working on a new firmware for the robot and a GUI for moving and calibrating the robot and to create new movement pattern. They currently still lack proper documentation and I have not yet decided whether to make them part of this project here or if they should get their own place - either here on HackaDay or may be just on GitHub.

    As a result of this effort the chassis grew an additional mode switch that allows switching between different programs.

    We also did building instructions in German with a lot of pictures.

    With this in place we did two workshops with 5 kids each.

    Lessons learned:

    • Kids do not that the strength put the part together if they are cut very stiff - adults often do neither unless one uses tools like a vice or a mallet.
    • Pressing the ankles onto the servos is hard and prone to damaging the servo gearing.
    • Pressing on the legs is a bit better as they can get pulled on by a screw.
    • Building the robot takes kids 3 1/2 hours + the soldering of the electronics which we did in fore hand for our second workshop.
    • The legs are pretty complicated with several possibilities to put things together the wrong way.

    Improvements to the chassis since:

    • New driven ankle now uses a servo horn
    • Simplified main switch position
    • Simplified the legs a bit

View project log

  • 1
    Cutting the Chassis

    While Boxes.py allows setting any thickness this is really meant be be cut in 3mm plywood with the exception of servo mounts in the body (the two top most parts) which should be cut from 5mm plywood to get the right depth for the servos. Material with different but similar thickness should also work just fine. Check that the (body) servos will poke through the two layers. Always measure the actual thickness as it often differs from the nominal value. Baltic birch has worked well for us. Poppler is a bit weak but may work now as some weak points in the model have been addressed.

    For the head you do not need to change any settings except the burn value. It depends on the properties of the laser cutter and material you are using. It is possible to cut the parts stiff enough that most joints do not need to be glued together. But then you may need a hammer, vice or press to get things together. If you use brittle material as acrylic this is not an option and you have to use a smaller burn value to get a more loose fit.

    For the legs you have a few settings to consider. The anklebolt diameters are meant for a M3 screw that get threaded directly into the wood. If you are using a different screw size you need to adjust these two.

    The default leg length is 37mm. But we found the robot to be a bit less prone to falling over with shorter legs. 34mm being the minimum - which is what we used in our workshop.

    Note that you may want to add some logo at the side of the head before cutting the head. Just edit the resulting file in your vector graphics / CAD program e.g. Inkscape.

    Depending on your laser cutting software it may be necessary to manually select the order of the parts cut. For the head the rectangular holes in the hinges need to be cut first. Then all the other holes and the outer border of the parts last.

  • 2
    Assemble The Head

    Check if you have all parts


    Start with the top part.

    The hole for the USB port must be on the left of the robot (on the right when you are looking at it from the front)

    When assembling the bottom part put the top part in place before adding the side pieces.


    Glue in the servo mounts and screw in the first two servos.

  • 3
    Solder the electronics



    Solder the pin headers to the Arduino Nano.
    Solder the sliding switch between the battery holder and the break out board using the red wire. Also solder the black ground wire of the battery holder to the breakout board.

    Cut off the headers of two jumper wires leaving female connectors at the other ends. Put them through the push switch mounting plate and solder them to the push switch on the other side:

    Then press the pins of the switch into the holes of the plate.

View all 6 instructions

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