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12. Moulding and Casting

Group assignment:

  • Review the safety data sheets for each of your molding and casting materials

  • Make and compare test casts with each of them

  • Compare printing vs milling molds

Individual assignment:

  • Design a mold around the process you’ll be using, produce it with a smooth surface finish, and use it to cast parts.

Download Design Files

Click here to download my design files folder

Group Work Reflection

This work helped me to consider the difference in processes for mold making (using a 3D print and casting the final product in it vs. using a 3D print, casting and creating a mold from it to later be able to cast the final product in it). It also helped me to consider what type of materials are necessary with respect to the final product’s desired result: flexible or hard.

For example, for my individual project I wanted to make a flexible cover for my I2C LCD electronic. If I were to do a two process mold and cast, I would 3D print a mold that was an indentation of my desired final product and then cast a flexible material in it. If I were to do a three process mold and cast, I would 3D print an extrusion of my desired final product, cast a hard material over the 3D print, and then use the newly casted, hard mold and cast a flexible material into it as the final product.

Mold Material Data Sheets:

Link to Group Work Page

CAD Mold Model

https://www.thingiverse.com/thing:3505029/files

Making the Mold

Prusa 3D Print

I sliced my stl file in PrusaSlicer to create my gcode and then sent it to the Prusa 3D printer.

The mold 3D printed:

insert prusa mold pic 1

insert prusa mold pic 2

Formlabs 3B Print

To use the Formlab’s resin 3D printer, I first opened our lab’s site and went to our Lab Equiptment tab. From there I opened the Formlabs Form3B printer workflow.

The steps I followed are detailed below, slightly modified to my process.

Workflow

Setting Up Job in Resin Printer (updated 2/21/23)

  1. Go to printer and clean build plate then lock it in

  2. Then hit “Prime”

  3. Follow the steps provided ie, locking build plate and opening vent

  4. Open FormLabs PreForm 3.28.1 on a computer in Charlotte Latin School Fab Lab.

  5. Under “Job Setup” select “LearnedFish” Printer preset

    • Settings are Form 3B, Durable V2, and layer thickness of 0.100 mm or 0.050 mm

    insert job setup tab pic

  6. Open model file (either .STL or .OBJ).

    • Go to File–> Open. Bring a file in. It will place the file in the virtual workplane.

  7. Orient the model for the best printability

    insert orientation tab pic

    insert layout tab pic

  8. On the right side of the screen, verify “Printability”. This should be green in color.

    • Add supports if needed:

    insert supports tab pic

    insert supports pic

    insert supports pic 2

  9. On the left side of the screen, click on the orange “Start A Print” button.

  10. Select a printer; this should say “LearnedFish” since it’s already been configured

    insert print pop up pic

  11. Then “Upload Job”.

  12. Go to printer to confirm that the print is running

  13. Wait until step 5 of the checking process

After Job Is Complete

  1. Pull the entire build plate out

  2. Press “Open” for the washer and slide the entire build plate on the ledge

    • If not using the basket, please remove basket and place it on some paper towels

  3. Start washer for twenty-minute cycle

  4. Once wash cycle is finished, put on disposable gloves

    • If the build plate is still sticky, the wash didn’t cover the entire print. Fill more alcohol into the wash and re-wash the print

  5. Carefully pry the print job from the build

  6. Place print job (alone) in curing machine for sixty minutes

  7. Wash the build plate with alcohol and put it back into printer

Problems/Solutions

while trying to print with the Formlabs Form 3B printer, I got a dispense error:

insert dispense error pic

To fix this, I ended up pushing on the tank down a little, checking the vent cap, and clicking retry. I used this article as reference. 

insert tank pic

Casting

Moldstar

The mold material I used was 15 Slow Mold Star Series which would create a soft cast. It is necessary that I did a soft cast because I did hard molds.

Parts A and B need to be mixed together in a 1:1 ratio. Before I put them together, though, I took part A and part B and put them in seperate cups (while wearing gloves!). I stirred them for a few minutes each with their own popsicle sticks. I then poured them together in a cup and mixed them together with a third, clean popsicle stick.

I then slowly poured the mix into the mold that was placed on a sheet of cardboard to protect the table. Once it was poured in, I carefully hit the mold on the table a couple of times to help remove bubbles.

Prusa Mold

insert pic of prusa mold + pour

insert pic of prusa pour cured

I then took a popsicle stick and carefully removed the cast from the mold.

insert pic of prusa mold out

Here’s it on the IC2 LCD; it worked perfectly!

insert pic of prusa mold in use

insert pic of prusa mold in use 2

I wanted to see if I could put screws through the silicon so I tested it on this one. It worked well! I want to be able to protect the LCD and also secure it in my final project so this working was a big relief for me.

insert pic of prusa test screw

Formlabs Mold

Reflection

This week definitely put me out of my comfort zone. The 3D printing I didn’t mind so much, however, the molding & casting materials made me rather anxious – I definitely caught myself feeling nervous to mess up the ratios or even, when I felt heat coming off the mold (because it’s an exothermic reaction), I was nervous that it was going to burn my hand or something. The concept of chemicals and things happening without a clear physical indication frightens me a bit… I think it’s cool, but scary. It’s a similar feeling to when there’s a flame so hot you can barely see it – it’s un-nerving. But anyways, this week helped me push past that and feel more comfortable with the whole process – the resin 3D printer, molding & casting materials, and creating a mold through two or three step process.

References

https://docs.google.com/document/d/1DYqllYFakSBZHtUzX5VQ_bdxNAiNJWOl/edit?usp=sharing&ouid=104030110969759880306&rtpof=true&sd=true

https://www.thingiverse.com/thing:3505029/files

Last update: May 11, 2024