15. Molding and Casting - Week 13

15.1. Assignments

Molding and Casting

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

  • extra credit: use more then two mold part

15.2. Group Assignment

Group Page about Material Safety

15.2.1. Mold making processes

We tried out 2 processes (how to make the positive):

15.2.1.1. Milling

When milling, we use the part we want to make and first decide, how many sides we need. In our case it was just one side. Then we model the positive in combination with a cavity, which also needs to be slightly angled for the mill, so it can reach the bottom of the mold cavity.

IMAGE_MODEL_WITH_CAVITY

Then to generate the G-Code, I’ve chosen FreeCAD. There it is a bit tricky to generate a rough and a fine path in a fast way. It’s way easier and faster to generate it in Fusion 360.

15.2.1.1.1. Fusion 360

Also Ferdi made a tutorial for doing it in Fusion 360: Ferdis Doc

15.2.1.1.2. FreeCAD

First you go to the CAM Workbench, presse JOB Setup and setup the needed tools, workpiece and initial feed rate and RPM.

IMAGE_JOB_SETUP

For creating the Path, it’s not as easy as in Fusion but I tried to mimic the way fusion generates a path (at least for the adaptive clearing). I first added a roughing job with the adaptive clearing (which is not as powerful as as in fusion) for everything above the model:

IMAGE_ADAPTIVE_CLEARING IMAGE_SETTINGS

Then I did the same for the rest next to the SPACE symbol:

IMAGE_ADAPTIVE_CLEARING_2 IMAGE_SETTINGS

15.2.1.2. 3D Printing

For 3D printing there are 2 possibilities to produce a smooth surface:

  • SLA Printing (event though it is not perfectly smooth, but extremely)

  • normal FDM printing and then post process the print

We used FDM printing to get used with the process.

There you have the possibilities of applying some material on the print to make it (like paint or similar) or you use a material, that smoothen the current print by reacting with it and dissolve it. We used the 2nd approach with ABS and Aceton-Fume, where the Aceton fume reacts with the ABS and smoothens the surface, when applied correctly:

IMAGE_PRINTED_FABBY

You need:

  • Aceton

  • A closed container (which optionally can be heated)

  • the part on something, you can attach on it (to get the maximum surface that should get smooth)

  • OPTIONAL something to heat the container

IMAGE_PARTS_FOR_SETUP

I then put a good amount of Aceton in the container. The I used a professional and completely normal Setup for keeping it in the container:

IMAGE_THE_SETUP

And then occasionally rotate the piece. And it its to slow, you can heat up the aceton-container (we use a portable stove top).

After a while, it gets quite smooth:

IMAGE_SMOOTH

TODO

15.2.2. Casting A mold

15.2.2.1. Silicon

IMAGE_TU_MOLD_HARD IMAGE_TU_MOLD_HARD IMAGE_TU_MOLD_FINISHED

15.2.2.2. Gelatine

IMAGE_GELANTINE IMAGE_GELANTINE IMAGE_GELANTINE IMAGE_GELANTINE IMAGE_GELANTINE IMAGE_GELANTINE

FREEEZING

IMAGE_FABBY_MOLD IMAGE_FABBY_MOLD

15.3. Individual Assignment

15.3.1. Creating a Space Mold Model

15.3.1.1. Inkscape Preparation

IMAGE_SPACE_PATH IMAGE_SPACE_OUTLINE

15.3.1.2. FreeCAD Path Generation

IMAGE_SPACE_MILL_OBJECT

IMAGE_SPACE_FREECAD_PATH IMAGE_SPACE_FREECAD_PATH IMAGE_SPACE_FREECAD_PATH IMAGE_SPACE_FREECAD_PATH IMAGE_SPACE_FREECAD_PATH IMAGE_SPACE_FREECAD_PATH

IMAGE_CAMOTICS_PATH IMAGE_CAMOTICS_SIM

15.3.1.3. Milling the Mold

IMAGE_WAX_MILL

IMAGE_WAX_MILL IMAGE_WAX_MILL IMAGE_WAX_MILL

15.3.2. Casting a Mold

IMAGE_MOLD_FINISHED IMAGE_MOLD_FINISHED

15.3.3. Casting Plaster

IMAGE_PLASTER IMAGE_PLASTER IMAGE_PLASTER IMAGE_PLASTER IMAGE_PLASTER

15.3.4. Casting Chocolate

IMAGE_HEAT_CHOCOLATE IMAGE_HEAT_CHOCOLATE IMAGE_HEAT_CHOCOLATE IMAGE_FINISH_CAST IMAGE_FINISH_CAST IMAGE_FINISH_CAST IMAGE_FINISH_CAST

15.4. Notes

  • matt wax for milling

  • for metal casting

    • cerrotru (tin)

    • zamak

  • mixing

    • use 3 glasses to mix without sheering

  • when casting, think about air, should entweichen

Parts of casting

  • sprue: da wird reingegoßen (konisch)

  • runner: distributes the casting material

  • gates: connects runner to part

  • riser: out for the air while poring

  • part

Materials Easy:

  • GIPS

  • WAX (candle)

  • Chocolate

  • Nougat

  • Soap

  • Silikon

    • use quickly all material after bought -> datasheet -> unusable after a time (splits material, hard to rühren etc…)

  • always 2 components because of the hardening

  • Pot Life: time you have, until it should be casted

  • Cure Time: time until hardened

  • mixed ratio: for the 2 components

Safety infos

  • what happens when on skin/mouth, how to treat, safety equipment needed

2 components

Designing 2 Sided Molds

  • rahmen zum verbinden

Becher

  • Rührstab nicht zu dünn, stabil wegen umrühren -> chopsticks good

  • stabil, flacher Boden

  • molds should be high enough -> we use 1cm -> when entgasen dann 3x volume

  • think about air comming out -> needs to have holes

  • Sachen mit Öl einreiben, damit sie leichter rausgehen