3D Printing Troubles

By Jayesh

Task: Print Spool/Pulleys for Lift Strap

Today we visited the Dallas Makerspace. They have moved their building though, and now have much more space. Their facility has great tools for us to use in future endeavours. Also, they are very capable people here who listen to our ideas and contribute as well. They have helped us so much, we are going to start considering them to be sponsors. One of our tasks today is to 3D print the spools that drive the ball-lift strap. We then need to mount the spools into the custom brackets that Max printed this week. Then we need to figure out how to mount the brackets to the robot.

Reflections

Our 3-D printing adventures continued today, but with a bit less success. Our hyperbola-shaped design for the spool-bracket failed in the printing because our overhang angle for the top part had a magnitude of greater than 45 degrees and the filament started to fall away from the part. This warping now requires us to either physically make the adjustments to the design or reprint with support turned on so that the slicer program will create a fragile scaffold to support the overhanging layers. This support material should be removable with some simple tools and sanding. Also, the small hole we had inside the spool-holding mechanism was not large enough to fit an axle through it. It only went into the opening a little bit then became stuck. When trying to pull it back out, it broke off. A work-around was to drill the hole out with a 3/16" drill bit. The axle now fits in very snuggly, but there is no flat to prevent the axle from spinning separately from the spool. We'll need to attach an axle hub to the spool to fix that.

We also discovered that the outside rim of the spools are too large. Max says they fit when they were originally designed, but then coach had him change the design to reinforce the tabs that support the axle, and the extra material requires a smaller diameter spool. We didn't re-check the relationship of the separate parts when the design changed. Lesson Learned! So now we will have to change the design of the spools or the bracket that holds them. In the meantime, we simply hacked the spools smaller with a band saw - we don't need the full width. This leaves the ends of the spools open so you can see the filling material. We'll need to cap those somehow or re-print when we get another chance to make it to the makerspace.