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10. Molding and casting

Task:

Group assignment:

  • Review the safety data sheets for each of your molding and casting materials
  • Make and compare test casts with each of them

Link to this week’s Group Assignment

Individual assignment:

  • Design a 3D mold around the stock and tooling that you’ll be using, mill it (rough cut + (at least) three-axis finish cut), and use it to cast parts.

Is good practice to plan molds to be:

-“Soft inside hard and hard inside soft.”

-“Silicon only sticks to silicon”

Three part procedure:

  • Negative/milled

  • Positive

  • Outuput

Molds

Types

  • “Molde envolvente - 2 caras” - Wrapping mold

(Plan to have pins to ensure less burr / “rebaba” will be leftover, e.g. Dangerous Popsicle in Instructables — see link below)

  • “Molde simple - 1 cara (ángulo)” - Simple mold

  • “Molde simple - 1 cara (vertical)” - Simple mold

3D Milling

With 3D milling, the three axes can work simultaneously, to create different shapes

CNC // 3D Step Process:

Note:

Ball endmill for finishing and flat endmils for roughing

  • Rough cut flat

  • Rough cut around

  • Finish cut around

Roto casting

Process // Overview one sided mold) 1. mill wax mold (+) 2. cast silicone mold (-) 3. cast object (+)

Need to leave 0.25” of wax on each side, that highly depeds on the silicones used and retraction of the casted materials

// Battle of bubbles Mixing silicone is all about avoiding bubbles

You can have little worries about getting the silicone out when all the walls are straight up and down and you can have a struggle between the silicone and the wax mould when it comes the time to releasing it. The silicone can be al lot sturdier than you think it will be [xa: please complete this sentence]

The use of wax is ideal to make moulds since it is completely recyclable almost indefinitely.

// Errors - Rough output in foam using CLIMB style of cutting - use conventional milling instead [xa: please add an image here of the two types of milling]

MOLDING AND CASTING TECHNIQUES

Casting // Release assignment Applying a release agent to the mould before casting not only helps release the cast, it minimizes wear and tear on the mold.

Needs to be compatible with the mould materials Need to take into account the future purpose of the mould, in order to ensure it stays ‘safe and clean’]

How to use it: [xa: please finish adding the rest of the information, including the three steps]

// Pressure

The only way to ensure 100% bubble free casting every time is to pressure the cast resin. Needed: Air compressor with hose, Preassure tank large enough to accommodate your mould and withstand 100 PSI.

How it works

The most dangerous bubbles are those at the surface of the mould.

// Essential Know your mixing ratio Pot lifetime: Lets you know ho l of the mix before it expires Durometer: Viscosity: [xa: check and add a link and comment on the SSC Technical overview template]

// De/Unmoulding Afte the rubber has curated, it is time to remove our original model from the finished mould, or “de-mould”

//Mixing

Mixing and pouring liquid plastics Two component system that needs to be mixed throughly Know the “set time of your material” “When you think your mix is done, mix a bit more” ~Josep Know the set time of material Get used to timing everything, in every part of the procedure

DESIGN OF MOULDS

Full // Process

Mould // Types Simple: Models ‘with no undercuts’ [xa: por favor agrega una imagen que ilustre las diferencias] Envelope: Models ‘with undercuts’

// Soft-materials A draft angle is a slight taper (angle) in from what would be a perpendicular line drawn from the bottom edge of the model up away from the moulding

// Design Pouring and vent holes These holes are mandatory to allow the material flow evenly through te mold in closed moulds as

Centering holes/pads Be sure they are aligned Allignment is best when rounded shape vs. squares or chamfersfered shapes mix of male and female parts in order to get a mold that can be used twice with the same casts // Chamfers Rounded corner swould leave a lip around the edge of my bowl, and stop the interior and exterior molds from registering cleanly

Overall shape loose due to material flexibility [xa: por favor termina de escribir y agrega una ilustración]

Mold // Machinable wax Color coded to know the hardness, milling specifications, height melting points mixed with plastics Blue: excelent finish Purple:

Soap can be used as well

no need to lubricate the machine, is good cleaning is less of an issue keeps end mills stay in good shape and don’t get dull

// Hard - materials Synthetic plywood Polyurethane Tooling board Featuring

[xa: pf agrega el resto de la información]

FLEXIBLE MATERIALS Casting: Latex

Natural rubber extracted from rubber trees

Silicone rubbers (Smooth-Sil Series) are two-component systems (base plus curative; A+B)

Polyurethane Sticks a lot the casting MATERIALS

Gelatine / Bioplastics

Hard materials

Liquid Resin Plastic

Metal

Low temperature metal Mold made with a specific silicone (harder and more difficult to work but functional)

Problems

Failure

Wheat went wrong with your mold? 1. Bubbles in the surface 2. Bubbles on the mixture 3. Mold bubbles on back

  • Start pouring from a corner.
  • Pour creating a thin continuous line

  • Silicone on top of silicone

  • Cast not completely filled Material hardened

Safety

Always check the safety data sheets of your materials Always use gloves for handling the materials Clean space Ventilation

Check there is no unwanted chemical outputs

Work very carefully

Fabrication

  1. U

Softwares

3D CAM -Cambam -Rhino CAM -Aspire

MODELA Player 4 stl files Define origin in Z on top Modeling Form - Everything to X0 Y0 Start creating operations (New Process Creation) Use UP Cut flute Do not use scan lines, use “contour lines” Feeds and speeds:

Finishing

  • most likely ball mill
  • normally selected “scan lines” for Finishing
  • Select “X” and “Y” for the best finishing. which will create both dimensions? -use magnifing icon to see simulation

Research

[XA: por favor agrega el enlace de la presentación ] Add: Rotocasting - how to make a lightweight cast from youtube

Code Example

Use the three backticks to separate code.

// the setup function runs once when you press reset or power the board
void setup() {
  // initialize digital pin LED_BUILTIN as an output.
  pinMode(LED_BUILTIN, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {
  digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(1000);                       // wait for a second
  digitalWrite(LED_BUILTIN, LOW);    // turn the LED off by making the voltage LOW
  delay(1000);                       // wait for a second
}

End mills No go Milling Waxes Wax Milling Vacum Chamber_01 10. Vacum Chamber_02 Monedas 1 Monedas 2 Monedas 2 Monedas 3 Monedas 4

Last update: October 5, 2023