Shaping a model with Meshmixer and printing it

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by Richard Salinas | June 2014 | Cookbooks Open Source

In this article by Richard Salinas, author of the book 3D Printing with RepRap Cookbook, has discussed about shaping a model and then printing it. We're going to take the models that are scanned with 123D Catch and make them better. We'll do this by using Meshmixer, the free program offered by Autodesk. Meshmixer is a 3D modeling program that offers a variety of sculpting tools that manipulate the surface mesh of a 3D model. It also offers a series of tools that are geared to optimize a model for 3D printing. We'll improve the surface of a model by working with its mesh. Later on, in the printing section, we're going to learn how to optimize what we can't see of the model.

(For more resources related to this topic, see here.)

Shaping with Meshmixer

Meshmixer was designed to provide a modeling interface that frees the user from working directly with the geometry of the mesh. In most cases, the intent of the program succeeds, but in some cases, it's good to see how the underlying mesh works.

We'll use some brush tools to make our model better, thereby taking a look at how this affects the mesh structure.

Getting ready

We'll use a toy block scanned with 123D Catch.

How to do it...

We will proceed as follows:

  1. Let's take a look at the model's mesh by positioning the model with a visible large surface. Go to the menu and select View. Scroll down and select Toggle Wireframe (W).
  2. Choose Sculpt. From the pop-up toolbox, choose Brushes. Go to the menu and select ShrinkSmooth. Adjust your settings in the Properties section. Keep the size as 60 and its strength as 25. Use the smooth tool slowly across the model, watching the change it makes to the mesh. In the following example, the keyboard shortcut W is used to toggle between mesh views:

  3. Repeat using the RobustSmooth and Flatten brushes. Use these combinations of brushes to flatten one side of the toy block.
  4. Rotate your model to an area where there's heavy distortion. Make sure your view is in the wireframe mode. Go back to Brushes and select Pinch.
  5. Adjust the Strength to 85, Size to 39, Depth to -17, and Lazyness to 95. Keep everything else at default values. If you are uncertain of the default values, left-click on the small cogwheel icon next to the Properties heading. Choose Reset to Defaults.
  6. We're going to draw a line across a distorted area of the toy block to see how it affects the mesh. Using the pinch brush, draw a line across the model. Save your work and then select Undo/back from the Actions menu (Ctrl+ Z).
  7. Now, select your entire model. Go to the toolbox and select Edit. Scroll down and select Remesh (R). You'll see an even distribution of polygons in the mesh. Keep the defaults in the pop up and click on Accept.
  8. Now, go back and choose Clear Selection. Select the pinch brush again and draw a line across the model as you did before. Compare it to the other model with the unrefined mesh.
  9. Let's finish cleaning up the toy block. Click on Undo/back (Ctrl+ Z) to the pinch brush line that you drew.
  10. Now, use the pinch tool to refine the edges of the model. Work around it and sharpen all the edges.
  11. Finish smoothing the planes on the block and click on Save.

  12. We can see the results clearly as we compare the original toy block model to our modified model in the preceding image.

How it works...

Meshmixer works by using a mesh with a high definition of polygons. When a sculpting brush such as pinch is used to manipulate the surface, it rapidly increases the polygon count in the surrounding area. When the pinch tool crosses an area that has fewer and larger polygons, the interpolation of the area becomes distorted. We can see this in the following example when we compare the original and remeshed model in the wireframe view:

In the following image, when we hide the wireframe, we can see how the distortion in the mesh has given the model on the left some undesirable texture along the pinch line:

It may be a good idea to examine a model's mesh before sculpting it. Meshmixer works better with a dense polygon count that is consistent in size. By using the Remesh edit, a variety of mesh densities can be achieved by making changes in Properties.

Experiment with the various settings and the sculpting brushes while in the wireframing stage. This will help you gain a better understanding of how mesh surface modeling works.

Let's print!

When we 3D print a model, we have the option of controlling how solid the interior will be and what kind of structure will fill it. How we choose between the options is easily determined by answering the following questions:

  • Will it need to be structurally strong? If it's going to be used as a mechanical part or an item that will be heavily handled, then it does.
  • Will it be a prototype? If it's a temporary object for examination purposes or strictly for display, then a fragile form may suffice.

Depending on the use of a model, you'll have to decide how the object falls within these two extremes.

3D Printing with RepRap Cookbook Over 80 fast-paced recipes to help you create and print 3D models
Published: June 2014
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Optimizing infill with Slic3r

Slic3r has the capability of creating seven infill patterns. These patterns can be interesting and fun, but they also serve a practical function. Each pattern will offer different qualities in strength and have a different print time and material usage. In this recipe, we'll learn how to select the infill pattern and adjust its density.

Getting ready

You'll need the toy block that we optimized with Meshmixer.

How to do it...

Open Slic3r and follow the procedure:

  1. Select the Print Settings tab and then choose Infill. The section where we'll be making our changes is illustrated in the following screenshot:

  2. The default Fill density in Slic3r is 0.4. For sampling the infill textures, we'll change this to 0.25. This will create an infill that's less dense and easier for us to visually examine.
  3. Now we'll choose the Fill Pattern. There are seven infill patterns as follows:
    • rectilinear
    • line
    • concentric
    • honeycomb
    • hilbertcurve (slow)
    • archimedianchords (slow)
    • octagramspiral (slow)
  4. Choose each of these patterns and slice the model. Save each one, taking care to label them with the appropriate pattern name.
  5. Now, we'll test the infill density by increasing and decreasing it by 50 percent from our starting infill of 0.25. Choose an infill pattern and change the Fill density to 0.375 and then slice the model. Repeat using 0.125 for the infill.

How it works...

In the following image, we can see a composite of the first 10 print layers and the resulting pattern:

Each of these patterns is going to produce different results. Some of the differences may be as follows:

  • The strength of the pattern: The honeycomb pattern is good for strength. It follows the hexagonal pattern vertically through the print. This makes it generally good for mechanical parts.
  • The print time of the pattern: The line pattern is the fastest at printing infill. It's also a good infill for organic shaped forms.
  • The amount of filament to be printed: The octagram spiral uses the least amount of infill than the others.
  • The amount of vibration of the print head: When printing a pattern like the honeycomb, a lot of vibration can be caused by the rapid short moves of the print head. A pattern such as concentric produces less vibration in the print head.

In the following image, we can see the differences made in adjusting the infill density:

Most models will be strong enough with an infill of 10 to 25 percent. For gears and pulleys, a higher density of up to 50 percent or more may be best for durability. In principle, try to print with as little as possible. This will speed up the printing process and decrease the amount of filament you expend.

Experimenting with the infill as you progress with your future printing would be a good way to see how the infill patterns and infill solidity affect your model.

Summary

In this article, we saw how to shape a model using Meshmixer by using some brush tools to make the model better, thereby taking a look at how this affects the mesh structure, and then we 3D printed the model with the option of controlling the solidity of the interior and what kind of structure fills the model.

Resources for Article:


Further resources on this subject:


3D Printing with RepRap Cookbook Over 80 fast-paced recipes to help you create and print 3D models
Published: June 2014
eBook Price: $26.99
Book Price: $44.99
See more
Select your format and quantity:

About the Author :


Richard Salinas

Richard Salinas is a scenic artist in the film industry, where he has worked for over 20 years on numerous television and motion picture productions.

He was educated at the University of Missouri where he studied sculpture and three-dimensional design. He also has a formal education in the field of electronics. He developed an interest in computers in 1981 when he began programming on his university's mainframe and one of the first affordable personal computers: the Commodore VIC-20.

Since 2012, he's constructed five 3D printers of various designs and hacks. His aim is to explore the possibilities of creating fine art sculpture with DIY technology. You can follow his progress at www.3dprintedsculpture.com.

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