Yesterday I spend sometime at my local #fablab #fablabnordvest learning to know their Chinese Laser cutter. I used 4mm. white acrylic.
The design was made with #iDraw and exported to SVG (You can download the SVG here Body.svg). But my Chinese friend only speaks DXF or AI. After importing the converted AI file, I realised that I needed to do some cleanup of the path. Some of the patterns appeared twice(?).
Anyhow, it’s always mesmerising to watch a machine do it’s work.
After playing with the assembly, I want to redesign the way the lid is attached and I will like to make a smaller version for 9g servos. Probably the easiest way to do this is to use OpenSCAD to create a parametric model with the size of the servos as a dynamic variable, and then create a projection which I can export to DXF.
Today I made a stand for Felix. Like the rest of the parts this is designed as a “2 1/2 D” structure. It should be easy for everybody to cut the parts with at laser cutter, a desktop CNC or easily convert the design to something you can print on your 3D printer.
Or, you can just print it, glue it to plywood and cut it with a bandsaw or jigsaw.
I have used plywood and powertools until now, and done some small corrections with a knife and sanding.
Next week I plan to visit our local fablab (http://fablabnordvest.dk) and laser cut my templates on 4mm. acrylic. I’ll be able to test if everything fits “right out of the oven” or if the design needs some adjustments. I’ll post the final templates as SVG.
Made the structure even simpler. Now it’s time to play with Johnny-Five & @nodebots
Today I finished the new design for the body. I began to use iDraw for this project, and until now it has been a very positive aquaintance. I used to be a competent Illustrator user, but jumped of the Adobe wagon some years ago. iDraw fells very familiar and stay out off my way.
You can download the pattern here: FelixBodyPattern.svg
To test the dimensions and the range of movements, I cut the pieces from 4mm plywood using the pattern as a template, then put it all together using bolts and washers.The servos are fastened with 3mm. bolts and the knee with 2mm. Below you can se af video of the assembly process.
I run a bit out of steam while tinkering with the gaits. The write/compile/upload/test cycle on the Arduino took some of the fun out of it. For the new leg I have to rewrite the IK and control to accommodate the new servo’s setup. So instead of doing this as Arduino sketches, I decided to give NodeBots (http://nodebots.io) and Johnny-Five (https://github.com/rwaldron/johnny-five) a try.
Furthermore Johnny-Five have an Animation module (https://github.com/rwaldron/johnny-five/wiki/Animation) that looks like a perfect fit for managing Felix’s walking cycles.
Lately I have had some time to revisit Felix’s leg design. I wanted to experiment with a simplified version without linkages to increase movement precision. A positive side effect of this, is that by moving half the servos closer to ground I can rely on less powerful servos (HiTEC HS-422).
Another step to increase precision (and repeatability) is to move from an aluminium (hand made) based hardware to laser-cut acrylic. I’ll be posting SVG files of the design as I move along.
I don’t have a Laser Cutter at home, the leg on the picture was made with my scroll-saw to test the geometri and basic movement. Once I’m happy with it, I’ll borrow one at my local Fablab (http://valby.copenhagenfablab.dk).
Finish the other legs and completed the body assembly. The servos are hold to a piece of plywood with plastic straps and the battery holder is fixed to the “belly of the beast” with double sided tape.