Close



Results 1 to 6 of 6
  1. #1

    Creating a negative from a positive .stl file

    Hey everyone!

    I found some mask files I want to use for some projects, my only problem is that they are 3d printing models with the texture on the outside. I am looking to carve these masks out of a block of plaster/silica material. The problem I'm having is all the texture is on the outside of the model, and I need that texture to be in the bottom of the cavity after I route the design.

    I am not sure if I'm explaining this properly, but I essentially need a way to create a specific dimension block inside of autocad, and "extract" the mask from the block, leaving the design in the bottom of the block. I will then be filling this plaster/silica block with crushed glass in order to get all the texture of the mask on the outer facing side (once I remove the glass from the mold).

    If anyone can help me, or explain to me how to accomplish this, I would appreciate it!

    Best Wishes

  2. #2
    Technologist
    Join Date
    Aug 2015
    Posts
    193
    That's called a boolean action, subtracting one solid from another


  3. #3
    Engineer ralphzoontjens's Avatar
    Join Date
    Nov 2013
    Location
    Tilburg, the Netherlands
    Posts
    428
    Follow ralphzoontjens On Twitter Add ralphzoontjens on Facebook Add ralphzoontjens on Shapeways Add ralphzoontjens on Thingiverse
    HI, I sent you a PM

  4. #4
    Staff Engineer
    Join Date
    Jan 2014
    Location
    Oakland, CA
    Posts
    867
    I'm not sure you really want to be carving that plaster-silica material. It will make a big mess, with toxic dust all over the place, and the abrasive silica won't be good for your CNC machine either. I'd suggest you carve the masks as positive forms (the way they come) in machinable wax (or 3D print them), build a wall around them out of clay, pour in the plaster-silica mixture, letting it set up before you remove the clay and the positive form. Aside from saving your machine and your health, doing it this way will also allow you to make as many of these molds as you want from the same model.

    Andrew Werby
    Juxtamorph.com

  5. #5
    Engineer Marm's Avatar
    Join Date
    Sep 2014
    Posts
    635
    Add Marm on Thingiverse
    In sketchup, creating a negative from a positive takes like 30 seconds.

    Import the STL. Draw a 3d box that completely incorporates the object. Click "Intersect faces with model". And you're done. Then you can split and manipulate your mold as needed.

  6. #6
    Engineer ralphzoontjens's Avatar
    Join Date
    Nov 2013
    Location
    Tilburg, the Netherlands
    Posts
    428
    Follow ralphzoontjens On Twitter Add ralphzoontjens on Facebook Add ralphzoontjens on Shapeways Add ralphzoontjens on Thingiverse
    As above said, it's always good practice to create negatives from reusable master molds.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •