Class 14 - Composites

Table Of Content

Assignment

3D Model

I decided to go for an “off-the-shelf” model in order to save time for hands-on part of the assignment.
I took a 3D model of a mask from thingiverse. With Rhino I prepared the model for milling

rhino1.PNG

rhino2.PNG

rhino3 20x30.PNG

Machining

I used Cut3D software to produce the files to control our LinuxCNC milling machine.
First load the stl files made with Rhino:

cut3d1.PNG

I defined a new tool with 4mm diameter. I set a pretti high feed rate since the machine will not encounter much resistance milling styrofoam

cut3d2.PNG

I also defined a finishing toolpath with same speed and tool of roughing phase.

cut3d3.PNG

Finally I exported the file for LinuxCNC using a special profile Linuxcnc_mm.pp that i downloaded from LinuxCNC website.

cut3d4.PNG

Linux CNC has a simple interface to move axis and start/stop a job

linuxcnc1.png

linuxcnc2.png

This is the control box LinuxCNC is connetcted to:

milling_machine1.jpg

This is our milling machine:

milling_machine.jpg

I made the mold the wrong way since I milled the negative (as molding and casting) instead the positive

milling1.jpg

milling2.jpg

milling3.jpg

milling4.jpg

Milling in operation. Very very noisy

Preparing the mold

I used 10 layers of wax in order to avoid that the resin attaches to the styrophone

wax.jpg

wax1.jpg

Layering

First I put a thin plastic layer in order to ease de-attaching

layer1.jpg

mold.jpg

I made the resin mixing 40 g of Hardner and 80 of Epoxy

resin.jpg

I made small pieces of fabric in order to position them better on the mold

pieces.jpg

I made about 5 layers

mold1.jpg

Then I followed these instructions:

layers-theory.jpg

layers.jpg

valve.jpg

Finally I put everything in a bag

bag.jpg

Sealed it with mastic

vacuum1.jpg

Switch the vacuum pump on and let it work for 7 hours

vacuum.jpg

vacuum-pump.jpg

Finishing

The mold was broken since the bottom was very thin and it didn’t stand the force of the vacuum machine

broken.jpg

broken1.jpg

broken2.jpg

Tha mask was not perfect but still I decided to finish it to see how it looks the final result

extracting mask.jpg

finishing mask.jpg

mask.jpg

Let’s have a try!

mask_try.jpg

Class sources

composite_tutorial.pdf
Finishing Toolpath4mm45 - Top.ngc
Linuxcnc_mm.pp
Linux CNC website