Wildcard week: Composite

The assigment page
The goal of this week was to design a 3d mold, roduce a fiber composite part in it, with resin infusion and compaction.
Fusion360 file

3D mold design
This week I didn't so much time because I had to go to Le Havre for my girlfriend's exhibition.
So I had to find something quick to design and I just looked 2cm right from my screen: an underpot! Or a frisbee.

I opened Fusion and draw a new sketch with 2 circle (one 30cm and the other one 28cm):

I extruded the offset by 15mm.

I made a 15mm offset:

And I use the "loft" command to make the rest of the saucer:

With "filet", I smoothed a bit the design:

CAM and milling
I used 3 settings. A parallel cut for the 3d form but it's making only the slopes, a face to have a flat surface on the top and a 2d contour to cut around the object and cut it off from the material.
I didn't use Rought and Finishing because it's CAM module in Fusion and there's no such option in it. I've managed to have good result with those settings.

Settings used for parallel: 3,2mm flat endmill, 2 flutes Spindle speed: 18000 rpm Surface speed: 180,956 m/min Cutting Feedrate: 1000 mm/min Plunge Feedrate: 333 mm/min Minimum Steep Stepover: 0.16mm Maximum Steep Stepover: 1.6mm Stepover 1.6mm Smoothing 0.08mm

Settings used for face: 6mm flat endmill, 2 flutes Spindle speed: 18000 rpm Surface speed: 339,292 m/min Cutting Feedrate: 1000 mm/min Plunge Feedrate: 333 mm/min Stepover:5.7mm

Settings used for 2D contour: 6mm flat endmill, 2 flutes Spindle speed: 18000 rpm Surface speed: 339,292 m/min Cutting Feedrate: 1000 mm/min Plunge Feedrate: 333 mm/min

I made it with just one pass because the material is foam so it's very tender. The CNC can handle it very easily.

The toolpath is generated and the milling will during 40 minutes:

I put the foam on the sacrificial layer and use depression to fix it to the machine.

I had an huuuuuge problem with the CNC. When I changed tools there's an error displayed in chinese. I try to do the same operation but the machine started to lift the tool directly without deplugged properly from the claw so here's the result:

Hopefully you can screw of tools holder so I tool the 6th one and put in place of the first one (because you have to do the zero with tool 1).

I finally manage to mill my mold properly:

I was not in Amsterdam to do it so I did it on my terrasse to have maximum ventilation:

I used SuperSap CCR Epoxy from Entropy Resins with a CCF (fast) Hardener. You can find the datasheet here.
There's also all the usefull infos here:

-90 min pot life
-24h for curing
-One week for total curing
-100g for epoxy, 43g for hardener.

Let's talk about safety. Epoxy resin is a chemical and it can cause some health hazards according to the datasheet: GHS classification: Skin irritation, category 2. Eye irritation, category 2A. Skin sensitization, category 1. Chronic aquatic hazard, category 2. Hazard statements: H315 Causes skin irritation. H317 May cause an allergic skin reaction. H319 Causes serious eye irritation. H411 Toxic to aquatic life with long lasting effects. Precautionary statements: P261 Avoid breathing dust/fume/gas/mist/vapors/spray. P264 Wash skin thoroughly after handling. Basically, you had to protect yourself from the product. I put a pair of gloves, a long shirt and glasses to avoid skin and eye contact.
I've also wore a mask because I didn't want to breath the chemicals.

Also you can't throw it away in the regular garbage can. "H411 Toxic to aquatic life with long lasting effects" don't throw the liquid remains in the sink!
Brussels trash collecting service offers to take care of chemical trashes.
You have to store the epoxy in a cool and well-ventilated area, and away from foodstuffs.

So, first I filmed the mold and put some vaseline:

I prepared some resin with 80g part A and 35g part B. I put part B directly in part A and mix with a wooden stick.
I cut a circle in a yellow tshirt and put some resin with a dedicated brush:

I cut a green circle and put it on the top. The idea was to have a yellow inside and a green outside:

I covered the mold with hoven paper full of vaseline and put it in the vacuum bag (I have to do it several time because it was never completely sealed):

And here the result 24 hours after. It's kind of floppy so perhaps it's not totally cured:

And the green melt into the yellow but the effect is quite beautiful! I put it back on the mold curing some hours more.
After one week of curing, it's more solid now! I sanded the edges and here it is: