CNC sample projects

CNC workshop

teaches CNC machining basics for common 2.5 axis jobs in 3+1 sessions. All 3 session represents a major steps from the idea to the part: designing, programming, maschining

Session 1: CNC technology basics, special aspects for designing CNC parts – explained for sample projects, customize sample part for next workshop.

Session 2: Introduction into CNC program generation, generating the CNC program for your parts, milling at least one part.

Session 3: Preparing and operating the machine.

Session 4: DIY & FAQ: Now it’s your turn. For a small project perform all CNC manufacturing steps under supervision and ask all upcoming questions.

Advanced topics are covered upon request after this CNC workshop or by booking a Fablab tutor. Topics may include material and tool selection, PCB milling, 3D axis milling, 4D axis milling

CNC milling – what can be done

- Machining based on 2D vector graphic files (*.svg, *.dxf)

- high precision from mm scale to macro scale objects - PCB milling vs. furniture

- almost unlimited selection of materials -

all kinds of plastics like ABS, Acryl, POM, PTFE, Silicone, rubber, Dibond, fiberglas

wood materials like MDF, multiplex, solid wood including hardwood

Selected allows including brass, copper, AlMg3, AlMg4,5Mn

- various tools ranging from 0.1mm engraving tools to 25mm ball mills

CNC milling vs. 3d print

+ material selection not limited to thermoplastics (FDM) or light curing resin systems

+ very fast machining process – simple parts are finished after a few minutes

+ high precision parts

> simple 2d vector files needed, no 3d information in the file

- postprocessing takes more time – more than just running a slicer

- setup at the machine may be complex

- milling certain 3D objects may be time consuming, difficult or even impossible

CNC milling vs. laser cutting

+ fewer material limitations

+ almost no material thickness limitation

+ no typical laser processing smell or dicoloring

+ high precision parts with rectangular corners

- postprocessing takes more time

- machining to a certain depth is possible

- setup at the machine may be complex

- material has to be mounted on the machine

THIS MASCHINE HAS NO BRAIN – USE YOURS

+ CNC machine is a serious item that can seriously hurt you and others

+ always

think about what you are doing

ask for help if you are not sure what to do

wear safety glass and ear protection when operating the maschine

follow the workshop based guideline unless you have a good reason to not do so

+ in case of doubt

push the emergency stop

report any unexpected maschine behaviour to the FabLab

Designing for CNC - general

+ the drawing only includes contour lines in the right dimension

+ in general you don't have to care about the later CNC machining and tool diameters

+ align and distribute your parts including suitable screw position in your design tool – avoid any path postprocessing in the next toolchain software.

Designing for CNC - tool compensation

+ sharp inner corners will always have a certain radius

+ compensate for this by using 'bone fillets'

+ alternatively compensate the mating part to have an outer radius

+ extend cutout regions beyond the outer shape

Images from Vcarve and 100kgarages

Designing for CNC - Inkscape

+ when creating files in inkscape (suggestion only)

+ use no object stroke, otherwise the size information of the objects is wrong

+ use semi-transparent fill to even see objects hidden by other objects

+ document your design process in different layer, esp. before any boolean

path operations

+ before exporting *.dxf files in inkscape (recommendation)

+ ungroup all group structures

+ unlink all clones

+ convert all objects to path

+ check all path using their stroke

#1 sample project - puzzle

#2 sample project - bear

Usefull links and tips

+ different inkscape tutorials http://inkscapetutorials.org/

+ simple engraving fontset - hershey text extension for inkscape

+ inkscape extensions render function plotter→ → →

+ gcode editor and toolpath visualisation software http://www.cncedit.com/

+ general maschining tutorials http://tomstechniques.com/