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Hidden button in a bumper

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This is one of the designs I tested during input week to detect balls in a bumper.

Using a button should be the simplest system. The only problem is that it needs a switch that is pressable from every direction. The actual pinball switches do it with more complicated assemblies, but I decided to test if some kind of seesaw on top of two buttons would work.

Started by editing my previous design with the bumper.

I created new variables: buttonWidth, buttonHeight, buttonDepth, seesawThickness.

Extruded the same area that is used for the paddle, but from the floor. Height seesawThickness, taper -45 and offset clearance.

Started a new sketch on the undersurface of the extruded seesaw. To make the pivot, I drew to rectangles, defined its y-axis length as pivotWidth == 1.2mm. Constrained its outer edge midpoint to the end of a construction line that goes throught the object. Constrained the inner edge of the rectangle to be in midpoint with the rectangle that cuts the hole for the paddle legs.

Similarly, to make way for the buttons, I drew two rects with size buttonWidth x buttonDepth, and constrained them to be in tangent with the inner circle, and their top and bottom edges to be symmetrical over the diameter contruction line.

Extruded them all. The pivot with join and distance of clearance and buttonSlots with cut and distance of buttonHeight.

At this point, I noticed that the first extrusion with taper angle had gone terribly wrong, and it had tapered both sides of the extrusion (as it always does). To fix it, I removed the taper angle from the extrude command from the history and redid it with chamfer command on the top edge, with the distance of seesawThickness.

Printed it. I printed it upside down to make sure that the only contact to the bed is not the pivots. Noticed a few problems:

  • The wobble was a bit too small.
  • The buttons did not fit in their slots
  • The button slots were too high, it couldn’t press the button down.
  • The slots for the paddles legs were too tight.

To fix them I needed to increase the pivot length. I went to history, and changed the extrusion distance to pivotHeight = clearance *2, i.e. I named the measurement and doubled its size.

To fix the legs, I selected modify -> offset face to all 6 faces in the slots, and offset them by -clearance.

Then I increased the value in buttonWidthvariable by 2 mm to 8mm to make the button fit its slot. At the same time, I decreased the height of the slot by changing to extrusion for slot buttonHeight to buttonHeight - pivotHeight.

Printed the design, assembled and tested it. I used the same code for testing that I had used for the shorting

When pressing the button with my finger, the button works as expected.

But when launching a ball toward it, the button did not activate. There might be many reasons for it:

  • The ball is too light
  • The ball comes from wrong direction, thus the force is not applied to the button.
  • When ball comes, the seesaw rises from the opposing edge so much, that even the pivot point rises.

Fixing any of the last two should solve the issue, but they would require a complete rehaul of the bumper design. Lets leave that for now, and come back to it if necessary.