Sand Table

Introduction: Sand Table

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Step 1: Items List

Electronics:

Mechanism Hardware:

For the linear slide mechanism, I found the parts separately on OpenBuilds, but I would suggest using the V-Slot linear actuator kit, since it has all of the parts necessary as well as assembly instructions.

  • 1/2" wood base for the mechanism
  • Flange bearing with 1" inner diameter
  • 4x Larger screws and nuts for securing the flange bearing to the base (I found these at my local hardware store)
  • 1" steel pipe
  • 1" right angle adapter
  • Drop in T-nuts (I would suggest definitely getting some M5 T-nuts and any other sizes that you want)
  • Large washers or shims (for balancing the flange)
  • Any other wood/machine screw necessary for securing components

Wood Table Hardware:

  • 1/2" and 1/4" pieces of plywood, birchwood, etc. (refer to the table design)
  • 31" (or any other dimension) circular tempered glass

Optional:

Step 2: Building the Base of the Arm Mechanism

  1. I used a 1/2" piece of MDF wood to act as a strong, heavy base for the arm mechanism. Any 1/2" thick wood could be used for the base (not necessarily MDF). I used a jigsaw (before I bought a woodworking router for better cuts) to cut the MDF board into a rough circle and sanded the edges. Make sure you mark the center of your square before cutting it into a circle.
  2. I bored a 1/2" hole in the center of the circle for the slip ring, and drilled 4 other holes for the screws that will secure the flange bearing to the base. Before securing the flange, you need to insert the slip ring in the 1/2" hole and secure it with wood screws so that the flange and the free-spinning node is on the top of the base.
  3. After securing the flange, insert the metal pipe in the ball bearing and check if the pipe is perpendicular to the base. When I tested this, I found that I needed to insert large washers in different locations under the flange to ensure that it was perpendicular.
  4. I cut the metal pipe to the length that I needed and drilled a hole through the pipe in the location where I was going to mount the main timing belt pulley.

Step 3: Building the Slide Mechanism

If you have acquired the OpenBuilds V-Slot kit or bought part that are similar, use the assembly resources from their website as a good guide for assembling the slide. I bought my parts separately so that I could have a "40x20" V-Slot rail laid horizontally instead of the vertical 20x40 arrangement that the OpenBuilds kit suggests using.

Using a horizontal V-Slot arrangement would allow for a slightly stronger attachment point to the metal pipe rotation axis, but it forces you to design the timing belt system on top of the belt. I will go more in depth to how I designed my custom linear slide, but if you choose to use the V-Slot kit from OpenBuilds, you will have to follow their guide for more information.

After choosing and cutting the length for my "40x20" V-slot, I began mounting the necessary hardware for gantry plate slide:

  1. I made mounting locations for the one of the pulleys that support the timing belt by drilling a hole close to on end of the slide, between the two V-Slot channels. I then used an M2.5 brass standoff with a threaded screw extension and a lock nut to secure a mounting location for the pulley that is elevated off the V-Slot. I used Loctite glue for added strength to the connection, since this pulley will have a fixed location on the slide. Then, it's as simple as mounting the ball bearing pulley with screw on to the standoff (make sure that you don't tighten it too much).
  2. The second pulley will be mounted to the stepper motor on the other side of the slide. I bought a separate flat aluminum bracket that was compliant with my "40x20" setup for mounting the stepper motor on the slide. I mounted the bracket with 2 drop in T-nuts and mounted the motor to the bracket. I used a 1/16" rubber sheet that I cut to the profile shape of the motor to insulate the vibrations from the motor, making the motor quieter.
  3. I bought four separate gantry wheels and a larger gantry plate to be compliant with my "40x20" setup. I mounted the gantry plate in the same way that it's mounted on the 20x40 V-Slot in the OpenBuilds kit. I made sure to adjust the spacing of the wheels by turning the eccentric spacers on 2 of the wheels until the gantry plate firmly secured and would start gliding when the V-Slot was tilted to one side.
  4. The timing belt that I used was a roll of GT2 timing belt (not a loop) that cut to the length that I needed. I mounted 3 more pulleys on to the gantry plate using a different length brass standoff in a V-pattern to maintain the tension in the timing belt. To secure the timing belt to the gantry plate, I used a 1" right-angled piece of scrap aluminum that I cut to about 50 mm in length. I drilled a hole to the same level as the pulleys and used a timing belt fixing bracket to clamp down the two ends of the cut timing belt. I then used belt torsion springs when necessary to increase the tension of the belt.
  5. I mounted the 2 end-stop switches to each ends of the slide by 3D printing a mounting bracket that is compliant with the V-Slot channels. I also 3D printed some bumpers for the gantry plate that extend over the edge of the plate, so that they will contact the switch first.

Step 4: Laser Cutting the Table Legs

I chose to laser cut the legs to be able to achieve the shape that I wanted from the table itself. I wanted them to have a wide base and a shape that flares outward to form a cone-shaped table. I also chose laser cutting to be able to have plenty of mounting holes and connecting braces to make the structure of the table sturdy. I used Fusion 360 to model the structure of the table with the laser cut parts for the legs. I used the laser cutter that I had access to from my local university to make these parts out of 1/4" plywood. I have laid out the necessary parts for 1 leg assembly in the model that can be used to laser cut the parts from a 1/4" 12"x24" piece of plywood.

Step 5: Building the Table Surface

Step 6: Wiring the Electronics

Step 7: Configuring the Software

  1. Download the latest version of Raspbian on your computer, and download Etcher for flashing the Raspbian image onto your Micro-SD card.
  2. In Etcher, select the Raspbian image that your saved and click flash.
  3. In the SD card's directory, create a file called "ssh" (or create a text file and rename it to "ssh"). Then create another file called "wpa_supplicant.conf". Copy the text from below and paste it into the file.

The only library that you should need is the "rpi_ws281x" for LED strip. Install the library onto the Raspberry Pi by using:

sudo pip install rpi_ws281x

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    3 Discussions

    0
    seamster
    seamster

    1 day ago

    This looks like it's going to be awesome. When you've completed documenting the build process, will you let me know? I'd love to see the full details when it's all done! : )

    1
    Penolopy Bulnick
    Penolopy Bulnick

    11 days ago

    Such a fun and beautiful table!

    It looks like a couple of your steps (5 and 6) are missing some directions.

    0
    GrozaR
    GrozaR

    Reply 10 days ago

    Thank you! It's still a work in progress that I decided to publish early. I will be making updates in the following weeks.