LEGO Mindstorms "Projectile" ball replacement

A ball replacing the original Technic Bionicle Ball included in the Lego Mindstorms EV3 set.


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LEGO Mindstorms


In the Lego Mindstorms EV3 set (#31313) there are three red plastic balls ("Technic Bionicle Ball", #54821) used as projectiles for a ball shooter ("Technic Bionicle Weapon").
As it can be expected they have an almost magical ability to disappear just to reappear in another part of a house or in a left winter boot stored in a shoe cupboard since the last winter.
I designed this simple replacement piece to worry no more. I can always print some new munitions for my sons robot wars.
In order to obtain a good geometry and surface finish I split the ball into two halves. They are assembled by press fitting the male and female halves together.
I used a small vice with soft padding between vice and the part. I did not see a need for any glue but to be sure that the halves do not split a drop of CA glue can be added before joining the halves.
Doe to a rougher surface the projectile to projectile shooting precision might vary more then for original parts.

It is also recommended to smoothen the ball around the split line with a fine sand paper to avoid jams during shooting.

Materials and methods

Printing (shown sample):
- Ultimaker 3 with:
Extruder 1 - a 0.4mm AA print core, material: Ultimaker Black PLA,
Extruder 2 - a 0.4mm AA print core, material: Ultimaker White Breakaway,
- fine resolution (0.1mm),
- standard UM profile with following modifications:
Generate Support ON
Support Extruder Extruder 2
Support Pattern Grid
Support Density 30%
Support Z Distance 0.0mm
Support Stair Step Height 0.1mm
Support Horizontal Expansion 1mm
Support Interface Resolution 0.1mm
Build Plate Adhesion Type Raft
Build Plate Adhasion Extruder Extruder 2
Raft Extra Margin 7mm
Raft Air Gap 0.0mm



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Mini wp 20130113 003Piotr published this design ago