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This page presents the assignments for week 17 of Fab Academy 2020: “Mechanical Design” and “Machine Design”.

To do list:


Week 17 "hero shot":

Figure 0: Foam cutting machine

Table of Contents

Week 17 files:

motor_block.stl (group work)

end_block.stl (group work)

carriage_block.stl (group work)

Group assignment

This week I worked with Jonah on machine design.

I was interested in the design of a foam cutting machine to be able to cut wing section for my final project.

Besides, Jonah already made a nice Instructables on how to make a hot wire machine

Trying modular kit

I first wanted to reproduce Nadya Peek modular foam cutter, but then realise that we cannot easly machine metal at the Fab Lab.

So I wanted to try her cardboard kit version of the foam cutting machine to build the machine.

The design are available on this page

Laser cutting the cardboard part

frame part

frame parts
Laser cutting the parts was easy and fast.

Folding the cardboard parts

Here the two-fold cardboard available at the Lab didn't reacted well to the folding.

It seems nice

wait, no...
We then decided to stop testing this cardboard module to manage time well.

If there is some time left I will try to make other test with tri-fold cardboard.

First design

I used OpenSCAD to design a foam cutting machine from scratch with inspiration from the modular cardboard kit machines of Nadya Peek.

Second design

Given the time frame for this week and following Jonah advises we adapt design around already existing parts of a machine.


So we first check the parts we could use from an old and unused Ultimaker 2.0 at the Fab Lab Digiscope.

3D printer before scavanging

Dissasembling the ultimaker 3D printer

Dissasembled ultimaker 3D printer

Scavenged motors

Belt and axis


The figure below show the design step of the foam cutter:

Linear threaded actuator

Linear belt actuator

Full foam cutter
We designed the parts to addapt to the scavenged pieces from the Ultimaker 2.0.

3D model visualization

A 3D model visualization is available on scketchFab!

3D model of our foam cutter

3D printing

We use the 3D printer to make stiff and custom frame parts.

3D printed parts

3D printed and scavenged parts

Assembling the frame

3D printed parts and actuators

Screw worm frame

Belt frame parts and assembled

All modules

Foam cutting machine


We use a pre made controller board for the nema motors : the TinyG.

Jonah added some limit switches.

We used the stabilized alimentation of the lab to power the TinyG and the hot wire.

TinyG board connected to the 4 motors

TinyG board and linear actuators

Limit switch

Zoom on the limit switch and servo harm on the moving part

Lab stabilized alimentation

User interface: webpage CNC controller Chilippeper

We used Chilipeppr for the user interface.

It is a webpage CNC controller.

We run a local JSON script to allow the website to acces the COM ports.

We followed this github tutorial for TinyG Configuration for Firmware Version 0.97.

Chilipeppr interface

JSON script running

Chilipeppr configuration modifications


Testing belt linear actuator

Testing threaded linear actuator

Testing all modules

Cutting a little foam wing section

To test that everything worked to we wanted to cut a simple wing section.

I used OpenSCAD to produce a .dxf file of a wing section.

Jonah then use the software Cambam to generate a Gcode from the dxf file.

He then make everything related to the Z axis zero, and set the start point.

CamBam software

Wing rib cutting (10 times faster)

Chilipeppr interface (10 times faster)

Foam wing section in Jonah hand!