Transitioning a Retention Lip for a Robot Scoring Area

On the previous page, we put a rounded edge on the lip that keeps eggs (or balls) from rolling out of the scoring area for a robot contest. Here, we go beyond the call of duty to smoothly transition the lip from the carpet to the posterboard flooring in the nest.

The plastic strip can be placed in front of or completely on top of the floorboard. If placed on top, the robot will have to overcome a taller barrier (1/8 plastic strip on top of 1/16 inch floorboard).

Placing the strip in front of the floorboard is a better choice, since it doesn’t increase the barrier height. Masking tape underneath the floorboard and strip can hold them together to avoid gaps caused by the robot pushing the strip outward as the robot exits the nest.

I chose a hybrid approach, where part of the strip is in front of the floorboard and part of the strip has been milled down 1/16 of an inch to sit flush on top of the floorboard. This turned out well, but was slightly difficult and time consuming. I’m not sure it was worth the extra trouble.

Lots of clamps to hold lip

Lots of clamps to hold lip.

I inserted a long metal bar Ⓑ into the milling-machine vise Ⓐ and held the plastic strip Ⓒ down with four clamps (1,2,3,4). This was necessary to orient the strip in a way that I could mill off a portion.

After milling a test section of the plastic strip, I placed a piece of the floorboard against the strip to check the height. When it reached the correct depth to be flush, I set the vertical stop at the back of the milling machine column.

Checking lip height versus floor board

Checking lip height versus floor board.

This method of creating a profiled lip worked well most of the time. However, sometimes I got sloppy and failed to clamp the plastic strip near enough to the area being milled. In those areas, the end mill occasionally dug into the plastic strip and pulled it up, leaving a nasty gouge. Although disappointing, this is inconsequential so long as the gouges don’t occur very often or near each other, and so long as they don’t reach the other side of the strip, which might cause a break. If merely aesthetic damage occurs, it will be hidden as the underside of the lip is not visible.

Imperfect lip due to milling marks

Imperfect lip due to milling marks.

None of this will matter if the lip becomes detached from the floorboard or nest during the competition. Let’s see how we can reduce the possibility of a robot snagging on the lip.