Roomba Segmented Snap-On Bumper (updated)

Update

After a discussion with a https://www.printables.com/@PennybridgePioneer (see comments) and some time in between I noticed that I could improve the center piece – read further down what and how.

Problem

We have some obstacles (chair) in our house that allows the roomba to go over most of the times, but also makes problems when the roomba tries to turn around on them and the robot gets stuck after that. 

The solution seems to be a bumper, and there are already some here on printables. But two problems with the existing solutions: I didn't like the mounting options (either glue or screwed with the bumper screws – but those are sh*t with my model and I wouldn't want to open and close them more than once) or the fact, that in my experience, a closed bumper line at the bottom makes problems with the charging station.

Solution

My solution comes with a new mounting option: It snaps-on on the front bumper – first put it in place at the bottom and just snap it in on the top. 

I first also made a full bumper but then realised in testing that it also was not playing nicely with my charging station – it just could not go onto it anymore, and if I put it on the charging station, it wouldn't charge reliably. 

So the second thing is, that I cut my bumper into a segment of ~ 20° piece – and put more than onto the robot. Actually its two different pieces – one center piece and a ordinary piece.

The center piece has a cutout for the sensor that is necessary to find the charging station, and puts a bumper there in the space where the charging station has enough space for that. 

Updated Center Piece:

With the bumper segments mounted, it was sometimes the case, that the roomba bumped pretty hard onto obstacles. Of course the clip on the underside takes away some free space, and I didn't think that I could improve much about that. But recently it occured to me, that it was only bumping hard when going straight into the obstacle. I investigated further and I saw the culprit was, that the original bumper has less free movement space at the front, which was totally taken away by my original center piece:

This is not the case with the other segments:

The solution is now to remove the lower clip, and only have a straight bumper there. To allow to fixate the bumper, I increased the segment to cover a bigger area – we also have to keep the entry to the contact patches of the charging base free – and add the clips only at the outer parts, were the bumper has enough free space to allow a movement even with the clips. The new part got slightly bigger:

As you can see the center part has no clip anymore, giving plenty free space for bumper movement:

Look for CenterPieceV2 if you want this solution, if you do not care too much about harder bumps (I used it this way more than half a year), you can choose  the smaller one as well. 

Printing

So you would need to print 6 ordinary pieces and a center piece. Put the ordinary piece where it is cut and has a nice flat contact. The piece has some curvature, but you can print it easily without support:

The center piece also needs to put on the cut face, but will need support in the overhanging areas: 

The advantage of putting the pieces on the cut face while printing is that the layers will be oriented favorable for the load situation during snap on and when bumping against obstacles and the precision needed for snap on will be easier to achieve.

I still used PLA and this seems robust enough for the use case.

For the center piece V2 this print orientation is quite advanced, but I noticed that this part really does not need to be that strong to survive normal operation, so I would suggest to use for that one a more common printing orientation, laying the top clip flat onto the print bed. 

Mounting

Put the ordinary pieces left and right from the center sensor, just put it in place at the bottom and snap it in on the top. Leave a space free at the center, if you turn around the robot you will see the charging contacts, you will want to have at that area at the bumper free space to allow the robot to drive onto the charging station.

At last put the center piece, with the snaps symmetrically left and right of the lighthouse sensor.