Introduction: Create a Finger Bed for Your Lie Detector

The following information is a single lesson in a larger project. Find more great projects here.

Return to Previous Lesson: Prototype the Circuit

Lesson Overview:

Now we'll build a finger hold for the detector!

Step 1: Create the Base Shapes for the Finger Bed

Your test subject’s digits need a place to rest during the test!

  1. Drag a box shape to the Workplane.
  2. Scale the box larger to a size of 30 x 40 mm.
  3. Reduce the height of the box to 5 mm.
  4. Drag a paraboloid to the Workplane.
  5. Resize the paraboloid to 28 x 10mm.
  6. Increase the height of the paraboloid to 38 mm. This will become the finger rest!

Step 2: Add Base Shapes Together

Group the shapes together to create a custom cavity.

  1. Change the paraboloid into hole mode.
  2. Rotate the paraboloid 90 degrees on the horizontal axis.
  3. Move the paraboloid so that it hovers above the rectangle.
  4. While holding the Shift key, select the red rectangle. Both objects will be selected.
  5. Using the “Adjust - Align” tool, align the oval end of the paraboloid with the short side of the rectangle.
  6. Using the “Adjust - Align” tool, align center of paraboloid with the center the rectangle.
  7. Lower the paraboloid until it is 1mm above the workplane.
  8. While holding the Shift key, select the red rectangle. Both objects will be selected.
  9. Click the “Group” button to merge the two objects, creating a custom cavity in the red rectangle.

Step 3: Create Grooves for Your Finger Bed

Add some grooves to help your finger bed stay nice and snug.

  1. Click on the finger bed to select the object.
  2. Rotate the object 180 degrees so that the flat side of the rectangle is facing up.
  3. Drag an orange cylinder to the Workplane.
  4. Resize the cylinder to 2 x 3mm.
  5. Increase the height of the cylinder to 30mm.
  6. Rotate the cylinder 90 degrees on the vertical axis.
  7. Rotate the cylinder 90 degrees on the horizontal axis.

Step 4: Add the Grooves to Your Finger Bed

Add the grooves to your finger bed

  1. Change the cylinder to hole mode.
  2. Duplicate the cylinder by holding down the Alt key while clicking and dragging the cylinder.
  3. Place the duplicate cylinder 7mm to the right of the first cylinder.
  4. Duplicate the cylinder again by holding down the Alt key while clicking and dragging the cylinder.
  5. Place the duplicate cylinder 7mm to the right of the second cylinder.
  6. While holding the Shift key, select the first two cylinders. All three cylinders should be selected.
  7. Using the “Adjust-Align” tool, align all three cylinders along the close oval edge.
  8. While all three cylinders are still selected, group the three objects together to create one compound object.
  9. Move the compound cylinders to hover above the red rectangle. Move the compound cylinders so that the right-most cylinder is about 2mm from the right edge of the red rectangle.
  10. Lower the compound cylinders 10mm so the compound object hovers 4mm above the Workplane.
  11. Holding the Shift key, select the red rectangle. Both objects will be selected. Using the “Adjust-Align” tool, align both objects along the top center axis. This will center the compound cylinders with the red rectangle.
  12. With both objects still selected, click the Group button to create three cylindrical cavities.

Step 5: Create the Top and Bottom

Duplicated the shape to create two finger beds.

  1. Select the finger bed.
  2. Holding the Alt key, click and drag the finger bed to create a duplicate shape.

Step 6: Prepare to Print

Prepare the finger beds to be 3D printed.

  1. While holding the Shift Key, select both finger pads.
  2. Rotate both finger pads 180 degrees on the vertical axis so the finger beds are facing up. This orientation will result in a cleaner 3D print!

In the next lesson you will learn to build the detector!

Next Lesson:Build Your Lie Detector

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