14. Moulding and Casting
Assignments
Here you can find a recording of the lecture from the 23rd of April.
This week's assignments and learning outcomes, see here:
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
You can find the documentation for our group assignments here.
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, and use it to cast parts
Questions to be answered/from Nueval:
Have you answered these questions?
- Linked to the group assignment page and reflected on your individual page what you have learned
- Reviewed the safety data sheets for each of your molding and casting materials, then made and compared test casts with each of them
- Documented how you designed and created your 3D mold, including machine settings
- Ensured your mold has smooth surface finish, that does not show the production process (by postprocessing if necessary)
- Shown how you safely made your mold and cast the parts
- Described problems and how you fixed them
- Included your design files and ‘hero shot’ of the mold and the final object
Hero shot
Hero shots from individual assignment
3D printed mould and casting
I designed a mould and 3D printed it. Then I made two casts of moulds with Zhermack HT 33 Transparent and Zhermack ZA 22 in blue. After that I made casts out of Jesmonite AC100 and Acrystal Prima.
Hero shots from individual assignment
Summary
Tips
Neil gave us some tips in the lecture.
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Important to sheer and absolutely not to scoop, because scooping can add airbubbles to the material.
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Pour in a thin bead. It can be a good idea to paint the first layer of resin and then the other layers will stick to the first layer.
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Wait for all the bubbles to come out.
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A poor mix will not get warm and will not harden completely.
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If you are working with big moulds the heat can damage the mould.
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Remember to slightly angle all faces (draft angle) for easy release.
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Hydrostone and silicone will not stick but check if you need a release agent if you are using another materials.
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Test the materials before beginning.
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Caution! If there is a warning that says the material is not suitable for home use, we should not use them.
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Caution! Read the safety precautions on the datasheet.
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Let material set before disposing.
Some tips from Adrián Torres:
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Add an offset at the top of the mould for easy removal.
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First do a rough milling and then use a finish stepover.
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Make sure that the endmill is long enough not to collide with the walls.
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Use a ball nose.
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You can recycle the wax shavings.
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Use 3D milling settings in Fab Mods or Fab Modules
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Remember that you need a hole to pour in and also a hole/holes for air to excape.
Work process detail
Group assignment
You can find the documentation for our group assignments here. On the group page I documented making the moulds and casting process. Here below is the documentation on designing the 3D mould.
A 3D mould designed in Fusion
I began by drawing a center rectangle and extruding it to 5mm thickness.
Datasheet and pinout for Raspberry Pi Pico
Then I created a new sketch and drew a rectangle on top of the box and extruded it downwards. By using the Cut option under Extrude I made a hole in the cube.
The next step was to create a new sketch and draw another rectangle on top of the box.
Then I chose the outer rectangle and extruded it to create a step around the hole.
Datasheet and pinout for Raspberry Pi Pico
After this I created a new sketch on the bottom inside. There I drew a center circle.
Then I extruded this circle.
Importing a sketch from Inkscape into Fusion
I wanted to put the Fab Lab logo on top of the cylinder. I had the logo ready in my Fab Lab Austurland logo. I saved a copy of that file and deleted Fab Lab Austurland from the file.
I saw that Luc Hanneuse said that he used a .svg sketch and added it to his Fusion file. I tested if I could add the .svg file but it didn't work. Then I thought of how I had exported .dxf files from Fusion in Machine week and imported it into Inkscape. Maybe it would work the other way around. Yes it worked and that is probably what Luc Hanneuse was talking about.
Using a sketch from Inkscape
I exported the logo as a .dxf file and imported it into a new Fusion file. For some reason I could not import it directly into the Fusion drawing I was designing the box in. But I could copy it and paste it into my box file. Then I just had to move it a little bit.
Then I extruded the image and saved the file as a .stl file to use for 3D printing.
3D printing the mould
3D printer and material / filament
Bambu Lab X1 Carbon
I used the Bambu Lab X1 Carbon with a 0.4mm nozzle to print the mould. I used pink PLA filament. Here below you can see the model in the Bambu Studio slicer.
Slicing
Here below you can see the sliced model and that the model did not need any support.
Bed adhesion
Here on the left you can see settings for bed adhesion.
Strength of print
Here on your left you can see the settings for the strenght of the 3D print. I used the preset settings and it worked fine.
Speed
Here on your left you can see the settings for the speed of the print. These settings were preset and I did not change anything.
Learning outcome
Learning outcome from group project
Conclusions
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3D printed mould works very well but the lines from the 3D printed object are visible on the cast.
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You have to think carefully about how you are going to release your cast object from the mould.
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It is hard to get rid of bubbles if you don't have a vacuum chamber.
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You have to work fast with materials that have a short pot time/working time.
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Make moulds that do not use more material than needed.
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Create a step at the top of the mould. This thinner edge makes it easier to get the cast out of the mould.
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Be careful when you pour the material into the mould. Bubbles can easily get trapped in the cast.
