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14. Molding and Casting

Hero Shot of the Week

Summary

Work Process

Calendar

Date To be done What was done
Thursday - 10h local meeting
- Fusion design
- CNC positive mold
Friday - FabLab normal work - negative mold
- casting
- thermo vacuum
Saturday - moving houses
Sunday - cleaning old house
- documenting
- chocolate cast
Monday - documenting
- 3D print + coating
Tuesday - FabLab normal work
Wednesday - 12h Local
- 13h Regional
- 15h Global

Introduction

Saco and Henk made an introduction.

Important parts for a cast

  • parting lines
    • where you take apart your cast
  • vent
    • to get out air
  • (open) riser
    • to check the level of your liquid stuff
  • angle to release your stuff from the mold
  • type of resin to use
    • resistance & co

Tool to compare different Smooth-On products.
Really useful.

This guys expendable model is really weird and funny.

Pressure casting

Trying to understand how pressure casting works. I get vacuum chamber as you get out the air from the material but with pressure I suppose you compress your resin until air is out ?

Safety

Know your pictograms !!!

Another person FabAc page with really good safety instructions and other helpful stuff.

My work

Here is my Lab setup.

Setup

  • Lab extractor
  • vacuum chamber
  • resins and co

First Version - with CNC

I first started by checking Nicola's page.

Fusion

So I started with importing a STL file that I found on thingiverse into Fusion. I converted it into an object, patched the holes, and tried to create a positive mold. Only tried because I had a lot of trouble, as the mesh to object conversion created a weird object. I even asked the help of my colleagues but it was more complicated to resolve it than to start rom scratch.

So I started from scratch. I created my 3 sided dices, chamfered it. Than I did a positive mold from it.

At this point I was getting confused on what and how I am going to CNC it.

And after reflection I got to the point that I need a mold for my mold. This was not a logical thing when I started the project but seems logical looking back to it now.

Than I looked what mills I have, encoded them into Fusion and tried different tool paths to found what was working and what wasn't.

Fusion

Some of the errors encountered :

Errors

Error: The negative value for Ignore Stock Less Than must be smaller than the tool radius.

Did not understand. I had this error when using flat end mills with Adaptive Clearing. But not with ball end mill...

All of this took me quite a lot of time.

CNC

So I started milling with a 1/16" round head mill.

I fucked up. There was an electrical issue in the FabMan bridge so the CNC lost power. And I wanted to reset the position of the head but instead I zeroed it...
But the positive mold seems to be complete.

CNC

After I got my two molds, I went home for the day.

Molding the mold.

I went through the resins we had with Axel

In the end I used SORTA-Clear 37 to create my mold.

I used this as Axel recommended me this one and OOMOO 25 but one of the resin part was dried up so from two recommendation only one left.

So I poured it out.

Mixed.

Mixed

Degassed.

Poured into the positive mold.

Poured

And waited.

Than after more than 4h I tried to de-mold it with the help of a knife. It was half success. I think I was too optimistic with the size of my CAD designs and made the whole thing too small.

DeMold

Casting

After that I needed to cast something into the mold.

I choose hard resin GlassCast 50 as it seemed to be compatible with SORTA-Clear 37.

Reading the notice I understood that the resin has crystallized and I first needed to give him a heat bath.

So I did.

Hot Bath

Than I mixed the two parts together and with the help of a syringe I poured it inside of the mold.

Casting

And I left it to harden over the weekend.

DeMold

The de cast did not go that well. My object is full of buble, like the top half of it. #Gravity But the bottom is quite smooth.

And the seam is quite pronounced.

Seems like the buble came from the seam.

And the dice does not seem to be equilibrated.

vacuum forming

I also tried vacuum forming.

Setup

So I first needed to found a simple object that could be used for it.

We had some FabLab keychain goodies so I tried it with them.

An error that I made was to not wait enough time so the heater wasn't heated up correctly at my first try. This resulted in a failed mold.

Failed

For my second try I waited enough. And now I have a food compatible mold.

Success

At home I made a cupcake with chocolate so before adding the eggs and flower I poured the molten chocolate into the mold. Left it to cool down. And demold it when it hardened.

Chocolate

3D Print

3D Printing

I tried a 3rd method where I 3D Print my object. Smooth it. And make a mold with the help of the 3D object.

So I am using a coating agent from Colido.

Setup

Than wait as it cures.

Machinable Wax

We do not have Machinable Wax but I want a place to safe keep this links so:

Learning Outcome

Assignment Check

  • group assignment:
    • review the safety data sheets for each of your molding and casting materials, then make and compare test casts with each of them
    • compare mold making processes
  • individual assignment:
    • design a mold around the process you'll be using, produce it with a smooth surface finish that does not show the production process toolpath, and use it to cast parts
      • done
    • extra credit: use more then two mold parts
      • Done even if not successfully