No progress last few weeks:

  • no time for me (and a heavy tiredness),
  • the Prusa printer is under maintenance,
  • issues in printing PLA material: I’ve to redesign some parts by adding among other things a duct to blow on the ongoing printed part; no part seems to by used “as it ” on the 1.5 rework and I need to redesign somes,
  • and so on

I got samples from Igus® to replace the LM08uu bearings of the 3D printer, and some LM10uu ones for the CNC machine – I’ll take the maintenance opportunity to change them.


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Cyclone CNC factory: a CNC project

On the website of somebody I’m following, one speaks about a small spanish origin CNC machine, the Cyclone PCB factory (link to the website); I found this project quite interesting for several reasons:

  • While it has been designed for PCB manufacturing at the begenning, its uses can be extended to other applications: engraving, cutting of soft and thin materials, drawing, and so on,
  • Plenty of parts come from 3D printing,
  • A lot of parts are common to 3D printers (bearings, threaded rods, smooth rods, endstops, electronic card amoung others), and since I’ve some extras …
  • It’s a way to be initiated to such tooling at a low cost, and another way to take advantages of our 3D printers,
  • A lot of links exist on the numerical softs to drive this CNC, all “free”.



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Spider Robot

The “Spider Robot” project (original designer : Regis Hsu) is a quadruped robot with 12 degrees of freedom (DOF), which uses 9 grams servos, a mini-pro Arduino card, a HC-06 bluetooth module and 3D printed parts, that made the project complete and relatively inexpensive (note it has ever been one of the goals of the designer).


Regis Hsu shares all the needed files in the Instructables website and in his blog : from the STL files up to the Arduino files, passing by the silk screen for the PCB making: open-source & open-hardware development at the true term meaning – thanks to the designer for this.



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FreeCAD: free CAD modeler

In our new Fablab, CAD initiation courses will be offered : I’ll do ones on FreeCAD modeler that is probably the closest one to professional tools such as Solidworks® or pro-engineer/creo® for example; while we’re a bit disoriented at the beginning, we remain in familiar territory (Sketcher, protusions, booleans, and do on).


Without having all the features of the professional CAD modeler, it remains sufficiently provided for our needs; remember that FreeCAD is developed and maintained by the community.


One of the essential plug-ins is the Assembly2 module developed and maintained by Hamish2014 (you need to install it yourself).


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Robotic: First release

For some time involved in a FabLab creation, I’ve found there number of interesting and fascinating things compiling various fields coming from the CAD (to design and to realize the 3D parts), to the 3D printing (to make the parts), the embedded electronic (servo control by electronic cards such as Arduino one or raspeberry py one), the programming (of the previous electronic cards for the robot behaviour), and so on.

Number of potential projects can be made ….

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fillet calculation in 2D

Fillets are commonly used in mechanical engineering in order to avoid singularities and then stress concentrations.


The goal is here to “put down in writing” methods I’ve been using to analytically  calculate fillets; these are one solution among others (and not necessary the best ones or the simplest ones), but I’m good with them and they answer to my needs (if some of you want to share other methods, I’ll be pleased to devote a specific section and the author will be cited).


There are different types of fillets; the simplest of them is the arc of a circle that answers to a practical need, the use of a ball-nose cutter. In the meantime I’ve discovered other methods for curves transition, notably used by topographers in the design of road networks or railway ones for example (it uses clothoids or Cornu’s spirals – the later ones are also called Euler’s spirals especially in the English speaking world).



1- Fillets using an arc of a circle

1-1 The basis

The figure here after presents a fillet in arc of a circle.



It be characterized by 2 straight lines \left[ BA \right] and \left[ BC \right], by its radius R, by its centre O and by the points of tangency D et F we have to calculate.


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Extruder number 1

Until I ahve my new PSU, I decided to assemble my Bowden Airstripper extruder ; I’ve chosen to replace the diesel hose by springs (After different trials of some types of spring, I finally decided to cut some loops in order to fit a correct length – the stiffness topic will be treated afterward).


In a first step, I noticed that the motor axis has no flat surface; a file plus a little bit of elbow grease and the business is done (all that fuss to save one machining step  😕 ) :

extruder_flat_surface1 extruder_flat_surface2

Motor axis with its new flat surface
view 1

Motor axis with its new flat surface
view 2


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