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SketchupBlock.jpg

Sketchup is an easy-to-learn program for 3D modeling. While it gives you an easy way to design creatively, it is a bit more challening to design accurately. If you are going to make physical models of your designs, you will need to make them small enough to fit on the tool that will make the part. You can send the 3D models to a number of toos, including the ShopBot, CNC Mill and MakerBot, among others.

If you follow these pretty easy steps, you can get yourself and your students into the habit of designing accurately dimensioned objects. Here is a set of screenshots and a

3DShape.skp

that show the steps of this process.

Open up Sketchup. The default template is probably Architectural/inches. This will give you a massive file. It is easier to work with a smaller file.

Change the snap settings by going to the Window menu and choosing Preferences. Choose Template, and then Inches (Woodworking)-3D. To use the template, open a new file, and it will be using the woodworking inches template. Instead of the person, you’ll see an image of a carpenter’s square. The increments on the square are one inch, you can test this by measuring with the tape measure tool.

Use the Tape Measure tool to make two guides at 2″ from the red and green axes. Choose the tape measure tool. Click on the green axis and pull to the right. If you the line turns red, then you are parallel to the Red axis. Type 2 on the keyboard. This will set the distance to 2 inches.Click on the red axis and pull up. If the line turns green, then you are parallel to the green axis. Type 2 on the keyboard. This will set the distance to 2 inches.

You now have guides for a 2 inch by 2 inch square.

To make the square, use the rectangle tool. Click at the origin, the intersection of all three axes, and drag to the opposite corner. The tool should snap to the intersection of the two guides. You can check to see if your shape is 2 inches square with the tape measure tool. If it is not square, you can move your guides or replace them with new, more accurately positioned guides.

Extrude the square up using the Push/Pull tool, push up the square. Push the square up and type 1.25 to set the height to 1 1/4 inches.

You now have a 3 dimensional shape that is 2 inches by 2 inches and 1 1/4 tall.
If you are designing to cut on a machine, you will want your file to be smaller than the limits of the equipment. If you design your parts with maximum dimensions in mind, you will be less likely to run the equipment beyond its safe limits. You could use a common starting point like this to develop a themed set of student products. The resulting files from these consistently sized objects could then be physically produced locally or remotely through systems like Thingiverse, or other fabrication services like Shapeways or Big Blue Saw.

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Chris Connors

Making things is the best way to learn about our world.


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Comments

  1. Stuart says:

    United States customary units are a blight, I wish they would just die out.

    1. DanYHKim says:

      Maybe off-topic, but WalMart’s ubiquitous retail presence could be used as a force to drag the U.S. into SI measurements. If the company could be persuaded to phase out U.S. units in its products, perhaps as a cost-saving measure that obviates the need for manufacturers to maintain separate product lines, the U.S. consumer public would have almost no choice but to adapt.

      My children have had to “learn metric” in school, and I find that we teach about SI units in the worst possible way: by emphasizing the arcane conversion formulae, rather than the relationship between these standard units and daily living. It’s not important or relevant that an inch is about 2.5 cm. What is good to know is that an adult hand is about 10 x 20 cm, and a liter is about as much as you can rapidly drink before throwing up.

      1. rbean says:

        There’s already a lot of metric stuff in the US. Any serious Maker has both inch and metric tools.

        And conversion factors aren’t “arcane”– except for temperature, it’s just multiplication and division. Every kid has a calculator.

        BTW I work for a printing company, and now that everything is done on a computer, I find some people using decimal inches rather than traditional fractions (eg, 1.2″ rather than 1.25″). I’m thinking of buying a 2ft decimal-inch ruler (yes, they’re available).

        1. Anonymous says:

          1 mile = 6,076.12 feet
          1 yard = 0.3333 feet
          1 foot = 12 inches

          uhm, yeah. I second Stuart.

  2. jj says:

    dunno, but a quick read said get started! INACCURATE design in sketchup, funny….

  3. 3D models says:

    SketchUP is up to the task in hand and makes the 3d modeling a breeze and allows you to be more creative, thanks to its user friendly interface which allows you to put all your thinking behind design rather than on 3d modeling process.

  4. Ryan says:

    Does anyone have any experience in CNCing from sketchup designs? Or are there any shop ninjas out there who could add to this with further advice? Any 100K garages people?

    You can answer in metric if you like!

    1. Chris Connors says:

      Ryan
      We are using Mill Wizard http://www.millwizard.com/default.asp to generate the G code, then milling the parts on a Taig MicroMill http://www.taigtools.com/mmill.html. It takes about 20 minutes to mill the size block described in this post.

      Here is a description of a process to accomplish the conversion: http://dhsfab.pbworks.com/SketchupTogCode

      1. Ryan says:

        That’s fantastic – thanks Chris. Brilliant.

  5. MetricCook says:

    I think American schools should only teach metric, if our students, the future American employees, want or need to learn arcane Imperial based units, than lets force the stupid employer to teach their employees ‘English’ units.

    Lets face it, the problem is though you can not do 50/50 Metric/Imperial conversions, it do not work, causes confusion, and causes problems – bad/wrong million dollar engineering mistakes. Sadly, that is exactly what America is doing now since 1975. You must make the commitment to change and change quickly. Metric is easy to use and learn, there are no fractions, no devision or units of 12, and moving from one large unit down or up to a smaller units only needs to move a decimal. One Meter is 100 centimeters. Moving from volume to cubic units is easy too. One milliliter of water is one cubic centimeter. And yet even after NASA engineers sent Imperial based units instructions to a $125 million Mars orbiter that was build with Metric and Metric instructions that caused it to a crash, NASA still is has not made the commitment to go 100% Metric, and that was in September 30, 1999. NASA still has decided to use both Metric and Imperial measurements. Conversions do not work, Do Not Do It. Use Metric.

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