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Where have we been? Wheels of course.

A project log for Micro Robots for Education

We aim to make multi-robot systems a viable way to introduce students to the delight that is robotics.

joshua-elsdonJoshua Elsdon 02/01/2017 at 15:002 Comments

Hello,

If any of you have been following this project you may have noticed that the main problem we need to overcome is making the wheels for the robot. If you scan through previous logs there are something like 4 full posts on the subject (I have lost count). Today may be the last, one can only hope.

The wheels in question need to be very small, and they have a very fine module gear teeth running around the perimeter to engage with the motor pinion. I have tried to date: Model wheels (friction driven), stamped out rubber disks (friction driven), printed on Roland DLP printer, cast from a negative printed on the Roland, printed on a zcorp (glue dust together) printer, and finally - building my own printer for the express purpose of producing these wheels.

Quite the journey, the result: look for yourself!

You can see that the teeth on the wheel is as well defined as the teeth on the pinion. The pinion gear comes with the motors and are presumably injection moulded in a big fancy factory. These were printed with FunToDo Deep black (settings: 20u layers, ~70u pixel size, 27s exposure per layer). The detail is pretty crazy, though at ~35s per layer they are not quick to print, so I will work on optimising the print parameters such that they take a more sensible time. Check out the printer on my other project page CLICK HERE FOR PRINTER DETAILS , though I warn you the project is likely to be rather more sparse than this one for details, though all the info you would need to build it is on the page, it is really just one linear slide in a box, so I am sure you clever people can fill in the gaps!

The primary use for the printer till it gets decommissioned is to produce wheels, though maybe it will also produce some useful jigs for small scale manufacture.

These layers are 70u, and they are stretching how thick is possible for this resin. This is because it is so black all the UV is absorbed before being able to cure more deeply than this. With some optimisation it might be possible to get to 100u at around 30 second cure time (I found the projector was on Eco before, doh!). Also seeing as I wish these wheels to be printed directly on the bed I may modify the model to account for the wider-than-designed first layer.

Discussions

deʃhipu wrote 02/03/2017 at 01:27 point

Very nice! Good to see you have solved the problem. I'm a bit disappointed at the non-fancy design of the spokes -- I'm sure that with 3D printing a much nicer design is possible -- but I understand this is the first iteration. I also wonder whether it wouldn't make sense to 3D-print a mold and try casting again?

I suppose the tire is just some rubber O-ring?

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Oskar Weigl wrote 02/02/2017 at 16:26 point

Cool!!

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