Molding and Casting Tips / Using Fab Modules

succesful tools relief

This week's assignment is comprised of a four-part process to fabricate a 3D object:

1. Use a CNC mill to digitally fabricate a mold out of wax
2. Create a negative of the mold with a flexible rubber
3. Use the flexible rubber as the mold for the final part
4. Cast the Final Part

Review Neil's class page


Composite Example - see Anna Kaziunas France's Page from last year's Fab Academy


Contents:

Step 1. Create a Positive Mold Model

Create a model of the final part you want to make. You can create a 2D or a 3D file as a starting point for your mold.

General Tips:

3D Models

If you create a 3D file, you need to decide if you want to make a 1 or a 2 part mold.

General 3D Model Tips

3D 1-Part Molds

3D 1-Part Molds Examples (from HTMAA 2011):

2-Part Mold Tips

3D 2-Part Molds Examples (from HTMAA 2011):

2D Models (PNG Images)

2D 1-Part Molds

2D 1-Part Mold Examples:

Tools Relief Example:

black border

Step 2: Mill the Wax on the Modella

Selecting The Appropate Bit

  1. In the computer model / file you created, use a measuring tool (or estimate) the spacing between the parts or detail where you want the bit to pass through.
  2. You need to make sure that the bit is small enough to cut out the detail in your model. You can preview the toolpath in the Fab Modules before you cut it - see steps below -"Fab Modules Workflow for Wax (General Setup / Steps) "
  3. Also pay attention to the depth of your model:
    • Smaller diameter bits have shorter cutting depths.
    • Larger diameter bits (1/8") - standard size used in the fab modules - has a longer shank and can reach deeper into the wax.

Bit Diameters in Milimeters:

Bit Diameter Bit Diameter (MM) Max Cutting Depth Max Plunging Depth
1/16 1.5875 measure cuttng depth measure shank depth
3/32 2.38125 measure cuttng depth measure shank depth
1/8 3.175 measure cuttng depth measure shank depth
1/8 (long) 3.175 measure cuttng depth measure shank depth

Setting Up Your Wax For Milling

Secure your wax to the Modela

General Fab Modules Workflow for Wax (General Setup / Steps)

  1. Open terminal and type "fab" to open the Fab Modules.
  2. Choose the appropiate file type:

  3. Insert the appropiate bit into the Modela. The default size is 1/8".
  4. Position the bit onto the wax using the "move to xmin, ymin" button (just like we did for milling circuit boards.)
    to rml

  5. Zero out your Z axis to the top of the wax. Stop when a few shavings of wax come up.
  6. Set up your rough cut settings:
  7. Execute your rough cut.
  8. DO NOT turn the machine off and on between cuts! We want to retain the Z axis zero setting.
  9. Set up the finishing toolpath
  1. Execute the finishing toolpath.
  2. Remove the wax from the machine.

Fab Modules Settings (Both Rough and Finishing Cuts)

  What the Setting Controls: Rough Cut Defaults Finishing Cut Defaults
diameter
  • The diameter of your tool in milimeters.
  • If you are using a different size bit, make sure to change this value to match your bit diameter in milimeters.
The default is: 1/8" or 3.175mm

The default is: 1/8" or 3.175mm

offset
  • How much material is removed around the model.
The default setting removes all material around your model: -1

The default is 1.

Change this to -1 if you want the box around your model to get a finishing path applied to it.

overlap
  • How closely the toolpaths overlap each other
The default is: 0.25

The default is: 0.5

speed
  • How fast the machine moves.
  • This setting is under "Maker RML"
  • Make sure to crank it up to 20.
  • The default is 20 for both rough and finish cuts if using a STL.
  • If using a PNG - make sure to change this to 20.

STL: The default is 20

If using a PNG - make sure to change this to 20.

STL: The default is 20

If using a PNG - make sure to change this to 20.

in 3D Setting Windows

top height
  • This setting tells the Modela where to begin milling your material.
  • The default setting is: 0 for both rough and finish cuts
  • Starting at zero will begin milling your model at the very top of the wax, where you zeroed the Z axis.
  • I highly recommend starting out -1mm below the surface in order to ensure that you have a smooth top of your model.

The default setting is blank.

I recommend you start at -1 mm.

The default setting is blank.

I recommend you start at -1 mm.

bottom height
  • This must be a negative value or you will get an error.
  • STL: If you are using a .stl file - this setting should be the height of the model in milimeters.
    • For example: if the height of your stl model is 31.75, you enter -31.75 into the z bottom field. This "should" come up by default when you import your model, but double check it.
  • PNG: If you are using an image (.png file) set the z bottom to how deep you want the bottom of the object to be.
You need to set this manually. You need to set this manually.
cut depth
  • This setting determines how deep each individual cutting pass will be.
  • You can make this smaller (for a finer cut) or bigger (for a rougher cut), depending on your model.
  • The finer the cut, the longer it will take to mill the model.
The default settings should be fine for a rough cut. The default settings should be fine.
path
  • This tells the Fab Modlules which plane to use to create the toolpaths for milling.
  • You only need to change this if you modeled a 3D object on a different plane

STL: The default selection is the xy path

PNG: The default selection is the z path

STL: The default selection is the xz finish and yz finish paths

PNG: The default selection is the xz finish and yz finish paths


Workflow for PNG to Modela

  1. Open Fab Modules (from terminal > type "fab)
  2. Select PNG to Roland Modela
    fab modules opened

  3. Click "load PNG" to load your image. The PNG will load in the window.

    to png

  4. Select "rough cut" from the drop down menu.
    png rough cut
  5. The interface will populate with the default settings for a rough cut using a 1/8" bit. If you are not using a 1/8" bit change the diameter. The bit size must be in milimeters. The other settings should be fine.
    png to path

  6. You need to change the 3D settings to work for your model. Click the 3D settings button and a new menu will pop up.
    png 3d default

  7. The top height setting tells the machine where to start milling the top of your file.
  8. The bottom height setting is the how tall / deep you want your model to be. This must also be a negative number or you will get an error.

  9. Example settings shown for the tools mold file.
    tools 3d

  10. Close the 3D settings window and click "make path"
    tools path

  11. You can see from the toolpath generated that this bit is a little too big to get all the detail in this model. Use a smaller bit diameter and generate the toolpath again. You can do this to preview the path. After you can see the detail, you can put the appropiate bit in the Modela.
  12. Position the bit onto the wax using the "move to xmin, ymin" button (just like we did for milling circuit boards.)
    to rml

  13. Zero out your Z axis to the top of the wax. Stop when a few shavings of wax come up.
  14. Click "make rml" and then send it to the machine.
  15. After the job completes, create a finishing pass - select "finishing pass" from the dropdown.
    1. Do not turn off the machine.
    2. You do not need to import / make a .png again.
    3. The machine will retain the Z axis zero setting from the previous job.
    4. If you changed the bit diameter, make sure to change it again.
    5. follow the steps above for the finishing pass.

Milled wax

succesful tools relief

Workflow for STL to Modela

  1. Open Fab Modules (from terminal > type "fab)
  2. Select STL to Roland Modela
    stl to roland

  3. A new window will open. Just like milling circuit boards, work from left to right. Select "Load STL"
    stl to modella
  4. No image will load - just text with the name of the file and the number of triangles.
    load stl

  5. Then click "make png". A PNG representation of your STL will appear. If your model is not showing up, try changing the "side" axis. This depends on how you set up your model.

  6. First do a rough cut. Select your settings from the dropdown menu for the units in your STL, (mm or inches).
    rough cut

  7. The default settings will load for a rough cut with a 1/8" bit in milimeters. If you want to use a smaller sized bit, you can change this value. Make sure the value is in milimeters.
    to path diameter

  8. Next you need to adjust the 3D settings. Click on the "3D settings" button. A new window will pop up.
    3d settings

  9. Use the settings chart above to adjust the settings. The top height of the wax is uneven, so make the top height at least -1 mm or more to make sure the top of the wax is machined away. The bottom height should be the height of your STL model. When you are finished, click "close".

  10. Next - click "make path" to generate the toolpath. You can click "view path" to view the path in greater detail in occular.stl path
  11. Next, make put the Modela in "view" mode and move the xmin and ymin so that the bit is over the wax.
    rml

  12. Manually zero out the Z axis until a little bit of wax comes up.
  13. Click "make rml"
  14. Then send the job to the machine.
  15. After the job completes, create a finishing pass - select "finishing pass" from the dropdown.
    1. Do not turn off the machine.
    2. You do not need to import / make a .png again.
    3. The machine will retain the Z axis zero setting from the previous job.
      • If you do turn the machine off or need to change to a smaller bit, use the xmin, ymin move command to move back to the same starting origin, then zero the bit out so it is close to the surface of the wax, then loosen the set screws and drop it down until it touches the surface of the wax. Then you will know it is zeroed properly.
    4. If you changed the origional bit diameter, for the rough cut, make sure to change it again. (it will defult back to 1/8" when you change to the finishing cut settings.)
    5. Follow the steps above to set up and exceute the finishing pass using the finishing pass settings.

Step 3: Make a Mold from the Wax

Mix silicone and pour into the wax mold - this will form a NEGATIVE mold with POSITIVE space

Oomoo

Other Molding types - read the instructions on the package

Tools Mold in Urathane Rubber (OOMOO mold will be blue)

casting mold

final mold

Step 4: Cast Final Object

Fill the silicone mold with HydroStone to make the final POSITIVE piece.

Hydrostone

SmoothCast 305 - Plastic - read the instructions for the material (on the box)- use mold release if casting in urathane rubber, if using OOMOO, you do not need a mold release.

Chocolate - coming soon.

Final Cast in SmoothCast 305 (white plastic)

final casts

Final Cast in Hydrostone

final casts

Tips and Tricks

Tutorial by Anna Kaziunas France - Fab Academy AS220 Providence, RI - March 2012