Ball Launcher using XRP

Students are using the XRP to launch foam balls at targets


Thanks for sharing this sample of student work with the XRP. I am excited to see it.
Is this activity part of class or club?
Will the students share some of their designs and insights?

This is a challenge I created for my high school C.A.P.P.S. (Chemistry and Physics Problems for Seniors) [C.A.P.P.S.]. I will keep this thread updated with design and insights.

1 Like

Is it a challenge in the style of ‘The Game 2023’ (The Game 2023 - Google Docs)?
Do you have similar challenge instructions for the XRP Throw-bots?
I look forward to seeing more!

Other explorations in “throwing”


Fantastic to see the diversity of approaches to solving the challenge! I especially appreciate the mixed prototyping media: XRP (of course), 3d printing, Lego Technic parts, and others.

Have they custom designed some XRP-to-Lego connectors? For example, XRP motor shaft to Lego axle (yellow cylinders in IMG_6042)?

Yeah the students are using Onshape to
Design all custom pieces

Some of your students’ parts build on design features of the XRP. For example, the red stilt legs of the first project you shared use the rail-clip system recommended by XRP.

Are your students typically starting from the .3mf files that XRP provides (Printables)? Or are they requesting the original Solidworks files?

Or, are they starting from scratch with new Onshape designs?

The students at starting from scratch. The .3mf/.step files available on Printables Don’t play well with Onshape.

They seem to have mastered essential elements of the 3d design process. What kind of preparation have they had to get to this point?

I have tried to fork some of the XRP files using Fusion 360 and found it to be challenging. At times, I wondered whether it would be easier to start from scratch, too.

Added a second channel tab to support vertical as well as horizontal orientation of boards.

Is that designed to hold a printed circuit board?

I have been contemplating recreating the ‘connector’ in OpenSCAD (to make a printed circuit board holder of some sort) - but have not yet done so.

Ultrablox: Yes. In response to one of your posts, @TFossDK wrote about a project adding supplementary circuit boards to the XRP. I used one of the .stl files to make this modification of the holder.

1 Like

Ultrablox: Do you use parametric design tools in OpenSCAD? That concept ( seems to support flexibility in designs without proliferating dozens of idiosyncratic .3mf files.

Ah, yes, I had looked at that article, but had somehow forgotten that it included designs for pc board brackets.

While I don’t have the specific Qwiic boards referenced in that article, I will try printing those for comparison with the line follower holder that is ‘native’ to the XRP, to help inform my own modelling.

I recently upgraded my 3D printing capabilities with a Bambu Lab P1S and I’m currently coming up to speed with it - for example, I’ve printed the “Alpha -holey- Single Part Frame V1.4” XRP chassis with which I could make use of pc board mounting techniques that utilize the added holes as an alternative to using the ‘insert connector tab into rail’ method - but I’d like to experiment with a variety of pc board mounting options.

Your modifications to support both vertical as well as horizontal orientations are certainly of interest…

While in the past I have typically built custom “one-off” models that would not be of interest to anyone else, it would not have been much of a stretch to make them more general by explicitly parameterizing the models along the lines described in that article.

I do have some ideas for future projects which could absolutely benefit from that approach.

I’ve been tinkering with OpenSCAD in order to build a parameterized script for creating pcb-holder brackets with one or two connectors that plug into the XRP rail, similar to the line-follower pcb holder that comes with the XRP and also similar to the ones shown here (that you directed my attention to a couple weeks ago):

What I’ve coded is not really ready for prime time, and it’s not pretty, but I can indeed use my OpenSCAD code to create customized sizes of pcb holders, with one or two “connectors” that plug into the rails on the XRP chassis, and with those connectors located on either the side wall or the base of the part.

I plan to continue refining it - but I will probably put together some more details soon and create a separate post in the robot hardware section of this forum to describe my work so far.

I will have to spend some time understanding the creative commons licenses - I have not remixed anyone else’s files, and I don’t think that it would be considered an ‘adaptation’ of someone else’s work, inasmuch as I have coded the OpenSCAD file for creating the part completely from scratch - but I’m not completely certain that I’ve covered all of the bases.

I’ve printed some sample pcb holder brackets on my Bambu Lab P1S printer - using a layer height of 0.2mm and a nozzle diameter of 0.4mm - but I suspect that using 3D printers with different characteristics, different slicers, etc. may require tweaking of the parameters to dial things in properly.

Also, I haven’t implemented all of the parameters that I’d want to support in a more finished project.

But I did want to let you know that your inspiration led me to actually roll up my sleeves and get some workable code, even if it’s still in a rough state.

A few quick photos - showing a pcb holder that I created for an Adafruit “perma-proto” board, and a couple of smaller pcb holders showing rail ‘connectors’ on either the base or the side of the holder, all created from my parameterized OpenSCAD script.


Thank you! They look precisely as I imagined when I asked you about parametric designs!

I have been working in parallel trying to use Fusion 360 to develop similar designs. You have made much more progress than I. Congratulations.

I succeeded in creating parameters for width of this holder but not yet for the height:

I’m pleased to hear you say that you are refining your work and plan to share the details in a future post. I may have to return to OpenSCAD when you share the code. If you want to have an independent test of some of your designs, I’d be happy to try printing at my local library using a Prusa printer and slicer.

1 Like

Absolutely. It would be great to have a ‘sanity check’ as well as to get feedback on potential changes or enhancements to improve its utility.

I’m looking into the possibility using either the Thingiverse “Customizer” or the similar built-in OpenSCAD “Customizer” tool to simplify the selection and range-checking of parameter values, including the use of UI tools such as sliders and entry fields to make adjustments, with interactive preview of the effect of making such changes, along with a button to directly generate and export an STL file.

FWIW I see that Thingiverse has come in for a great deal of online criticism, both in general as well as for sometimes flaky operation of their Customizer. I don’t have enough experience with either to have any opinion about those criticisms, however.

For example, this is a Thingiverse “thing” that permits customization of word selection as well as other options:

There is (or was) an alternate site that was billing itself as an improvement on the Thingiverse Customizer, however sadly it looks like that site is about to be shuttered because it was not meeting its creator’s revenue goals:

It would be nice if someone else could pick it up rather than having it disappear, but I’m not really in a position to do such a thing. I may consider attempting to contact the site owner to see whether it may be possible to somehow keep it alive. I have no experience actually using that site, however.

I am exploring a different customization approach. Don’t yet have anything to share but will keep you posted if it looks like it might work. Would you mind sharing one of your small OpenSCAD bracket designs so that I can test my approach? Thanks!

1 Like

@SCSpaeth I sent you a Discourse private message

1 Like