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Kevin Kennedy: Hey there, it’s Kevin
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Kennedy, and welcome to episode
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number 1 of Practical Prints, a
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new 3D printing series where I demo
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designing for 3D printing in Fusion 360.
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By the end of this video, you’ll
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know how to create custom spur gears.
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I’ll show you how to create the
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gears, including setting the number
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of gear teeth, the gear thickness,
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adding joints and motion, and more!
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[Logo Chiming]
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When it comes to creating spur
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gears in Fusion 360, you could
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technically create a gear tooth
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and circular pattern the sketch.
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However, there’s a better way
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that will save you a lot of time!
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When you downloaded and installed
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Fusion 360 there were a couple add-in
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samples installed along with it.
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Fortunately, one of those pre-installed
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add-ins is a gear creator.
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While in the design workspace you
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will need to select the “tools” tab.
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You will then find the Scripts
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and Add-ins option in the toolbar.
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You can also hit the keyboard
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shortcut letter “S,” as in
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Sierra, for the shortcuts box.
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Where you can simply search
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for scripts and add-ins.
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Within the Scripts and Add-ins
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dialog, you will want to select
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the “Add-ins” tab and scroll down
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until you see the SpurGear option.
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Because this is a sample script, you’ll
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see they’ve included one written in
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C++ and a second written in Python.
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You can use either one of these
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add-ins, as they work exactly the same.
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For the sake of following along, I’m
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going to select the one with the blue
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and yellow Python logo.
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Once selected, you can click the
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“Run” button to start the add-in.
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However, you’ll notice that it says
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the add-in is now added to the “create”
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dropdown list of the design workspace.
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Back in the solid tab, you’ll see it
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appears at the bottom of the list.
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The best part about this is the fact that
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it will now show in the shortcuts box.
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I frequently use the shortcuts menu, and
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I prefer that over having to activate
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the scripts and add-ins dialog each time.
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Let’s now take a look at all the details
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that we can specify to create a spur gear.
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I want to save time to show you how
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to test the gear with joints and
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motion, so I won’t be discussing all
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of these options with great detail.
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To learn more about the terminology
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of each option you can check out
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this tutorial’s resource page
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at productdesignonline.com/p1.
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That’s productdesignonline.com/p
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for printer and the number 1.
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Just a quick side note, all the
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new tutorials for this practical
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prints series will have a URL that
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corresponds to the episode number
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after the slash and letter P.
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The first option in the dialog is the
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ability to select English or Metric units.
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For this tutorial, I’ll be
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using the default of metric.
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Next, is the pressure angle, or the
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angle in relation to the gear teeth.
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Again, to keep the focus of this tutorial
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on using Fusion 360, you can read more
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about the pressure angle on my website.
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Just note that the default of
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20 degrees is the most common
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pressure angle for spur gears.
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You can also use the standard
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14.5 degrees or 25 degrees.
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You also have the ability to
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specify a custom pressure angle,
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but I wouldn’t recommend that
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unless you know what you’re doing.
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To understand the next two settings,
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the module and the number of gear
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teeth, you should first note that
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these determine the pitch diameter
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at the bottom, which is read-only.
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The pitch diameter is the diameter
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of the gear used for spacing the
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gears, as you can see in the diagram.
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It’s important to note, this is not the
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same as the outside diameter of the gear.
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Notice with all the defaults
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that the pitch diameter is pretty
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large with a diameter of 304mm.
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For this sample print, I want to create
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two gears, with a 2 to one ratio.
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We can set the first gear to have
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32 teeth, but I want the pitch
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diameter to be closer to 60mm.
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Therefore, we’ll have to adjust the
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module option, because the module is
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the ratio of the gear’s pitch diameter
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divided by the number of teeth.
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If I drop the module down to
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2, you’ll see that it leaves us
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with a pitch diameter of 64mm.
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The Backlash option is the defined
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clearance between this gear and the mating
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gear, or the gears that it will touch.
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This is very important, as with a 3D
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print we need to built-in tolerances.
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I’ve found that .15mm works well
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for this size of 3D-printed gears.
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Remember that this will give us a
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total of .3mm since we’ll have the
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same tolerance on the second gear.
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This does also depend on your printer
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settings, you may need to increase this to
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.2 or .25mm based on your print results.
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The next option is the “Root Fillet
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Radius,” or as you can see in the
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diagram, the radius where the gear teeth
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meet the root or the base of the gear.
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If you type a large number in here
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you’ll see a warning message at
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the bottom of the dialog stating
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that the radius is too large.
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We need this to be less than
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1.1mm, so I’ll type out 0.9mm.
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Generally, you want to make the root
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radius as large as possible as it
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will make the gear teeth stronger.
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However, if you make it too large,
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per the warning message, then the
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teeth of the second gear won’t be
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able to fit within the opening.
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The gear thickness is
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pretty straightforward.
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This defines the extrude depth
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or the total height of the gear.
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If you’re making a replacement
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gear for something that broke then
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you would want to make sure the
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gear is the same thickness so it
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fits within the required space.
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To save on printer filament for this
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example gear, I’ll set this to 5mm.
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Lastly, we have the hole diameter, which
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is the hole in the middle of the gear.
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Also pretty straightforward, but one
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trick with this is that you can set this
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to 0, which will omit the hole creation.
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Sometimes I find it better to not
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create a hole with the add-in and
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to instead use the hole command.
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The hole command offers more
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options and makes it easier
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to adjust the size later on.
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For now, I’ll set the hole to 6mm
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as we’re going to create a simple
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pin for this gear to revolve around.
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We can then click “OK” and the
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SpurGear add-in will generate the gear.
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If you look at the timeline, you’ll
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see that the add-in essentially
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automates the process of creating
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the tooth and the pattern feature.
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This last sketch also represents the
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pitch diameter, so we can reference
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this to align the second gear.
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I’ll reactive the spur gear
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tool with the shortcuts box.
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As you can see it’s a little bit
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quicker than going back to the add-ins.
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If you prefer speed, you can also use the
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marking-menu to repeat the gear add-in.
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You’ll first notice that all of our values
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are set to the gear that we just created.
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There are only two things you
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need to change if you’re creating
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gears with a 2 to 1 ratio.
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First, we need to lower
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the number of teeth.
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The first gear has 32 teeth so I’ll
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set this second gear to 16 teeth.
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We also want to drop the root fillet
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radius to half, to make sure we don’t
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end up with an undercut on our teeth.
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I’ve put more info about
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undercuts on my website.
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In short, you want to avoid an undercut
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shape of the teeth or the gear teeth
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will not smoothly roll off each other.
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After changing the root
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radius you can click “OK”.
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The SpurGear add-in will always place the
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newly created gears at the origin point.
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We’ll need to move this second
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gear into place before we can
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create a base and add joints.
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I’ll right-click the smaller gear in
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the Browser to select “Move/Copy”.
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For the X distance, we’ll need to type
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out the larger gear’s pitch radius
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plus the smaller gear’s pitch radius.
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If you remember our larger gear’s pitch
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diameter was 64mm, so I’ll type out the
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radius of 32mm, the plus symbol, and then
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the radius of 16mm for the smaller gear.
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As you can see, if the gears are
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positioned correctly, the reference
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circle of the pitch diameters
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should line up with one another.
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Now, all we have to do is rotate the gear
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so the teeth are in the correct place.
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In the dialog, I’ll select the
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rotate option for the move type.
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You’ll then need to select
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the inner cylinder of the
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gear for the axis of rotation.
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We can then type out 11.3 degrees
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to rotate the gear into place.
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The .3 comes from that tolerance
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that we set up earlier and the 11
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came from guessing and checking.
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There are formulas you can use to figure
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this number out, however, there are
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many factors in play, so it's often
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easier to simply guess and check.
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Let’s now create a simple base
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and pin for these gears so
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we can add joints and motion.
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I’ll first create a new component for
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the base and I’ll make sure the component
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is active before doing any work.
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I’ll just draw two center circles off
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the bottom of the gears, making sure
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they’re slightly larger than each gear.
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I’ll then create two lines
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tangent to each circle.
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If the lines don’t snap into place
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where its tangent, then you can
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always add the tangent constraint.
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I’ll then hide each of
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the gear components.
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This will allow me to click and drag
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over all the profiles so I don’t
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have to select them all one by one.
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I’m going to hit the keyboard letter
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“E,”’ as in Echo, and then we’ll want
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to define an extrude distance of 3mm.
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I’m also going to change the
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start option to “Offset,” with
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an offset distance of 3mm.
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This will give us a gap in between
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the gears and the base plate so
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there isn’t as much friction.
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We’ll also add a riser when we create the
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pin so the gear has a spot to rest on.
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I’m going to turn the gear
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components back on for now, so I
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can use them to create the pin.
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To reference our hole cutout in the
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middle of the gears we can project
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them to the top face of the base.
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I’ll hit the keyboard shortcut
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letter “P,” as in Papa, to
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activate the project command.
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Then, I’m going to select the top face
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of the base to create the sketch on.
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Select both of the gear
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holes and I’ll click OK.
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I’ll hide the gear components again
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so that I can use the keyboard
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shortcut “O,” as in Oscar, to
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activate the offset command.
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I’m going to offset both of
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these projected circles -.2mm, so
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the pin has a tolerance, ensuring
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that we can slide the gears onto
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the pin after this is printed out.
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I’ll then extrude the pins up to 10mm,
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making sure they join to the base.
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These are going to stick up well past the
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gears so gears don’t fly off while the
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gears are spinning with this sample part.
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Ideally, you could spend a bit more
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time to create a threaded cap to
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ensure they don’t fly off, and then
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you’d have a nice 3D printed gear toy.
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To create the first riser,
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I’ll offset the base of the pin
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to 10mm for the larger gear.
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I’ll then offset the pin
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of the smaller gear 5mm.
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I’ll extrude both of these
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up 3mm to create the riser
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that the gears can rest on.
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Depending on your project and gears,
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you may even find it beneficial to
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add the riser to the gears themselves.
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I should state that this is not
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necessarily the best or most efficient
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way to place gears, but I wanted to make
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it simple for this first gear tutorial.
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I’ll likely do many more tutorials on
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gears or projects with gears incorporated.
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If you’d like to see other types of
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gear tutorials or have other ideas for
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designing for 3D printing then let me know
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by commenting them below on this video!
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We can now activate the top-level
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component to add some joints
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and motion to the gears.
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This is a great way to test out
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gears before you print them out,
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especially if you have a gear chain
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consisting of more than 2 gears.
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I’m first going to right-click
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on the base component and I’ll
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select the “ground” option.
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This will ensure the base can’t be
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moved while we spin the gears around.
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From the assemble dropdown,
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I’ll select the as-built joint.
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You’ll need to find the
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revolute option from the list.
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Select the large gear and the base
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component and then select the pin
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cylinder for the position of the joint.
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Notice that gives us a nice
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animation preview and as long as
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it’s set to the Z-axis the gear
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should be spinning around the pin.
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We now just need to apply the
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same joint to the smaller gear.
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I’ll use the marking-menu to repeat
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the as-built joint and I’ll apply
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the revolute joint in the same way.
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Once both joints are applied,
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we’ll want to add a motion link.
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The motion link will tell the program
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that when one object is moved the
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other object should move accordingly.
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I’ll activate the motion link
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from the assemble dropdown.
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To add a motion link you
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simply need to select the two
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joints that should be linked.
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Now you can see that both gears are
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turning together at the same time.
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However, we need to alter the
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motion link so that the larger
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gear spins at a slower rate.
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To do this, we can type out an
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equation for the degree angle.
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I’m going to pause the animation as well
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so it’s easier to focus on the dialog.
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We need the 360 degrees as we want the
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gear to go all the way around, then
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we’ll multiply 360 by the number of
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teeth on the small gear divided by the
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number of teeth on the larger gear.
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So we have 16/32.
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We also need to place
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the 16/32 in parenthesis.
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Now that we have the degree defined we
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can resume the animation and you’ll see
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that the gears are now properly linked.
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However, we also need to make
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sure that the reverse option is
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checked, as this will ensure that
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one gear is going counter-clockwise.
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You can close out of the motion link and
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if you manually drag one of the gears
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they should now rotate accordingly.
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Another thing you may consider when
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working with 3D printed gears, especially
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ones with a larger size, is reducing
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the amount of material on the inside.
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I’m going to activate the larger
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gear component so that I can cut
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out some of the inner material.
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There are several ways to do this
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and a lot of it is going to depend on
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your project and how strong you need
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the gears to be, or how the gears
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fit with the rest of the assembly.
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You could even shell or hollow
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out part of the gear if you
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don’t need them to be as strong.
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For now, I’m going to create
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an offset sketch, using the
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perimeter circle from the gear.
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I’ll also offset this again to be a
00:16:05
couple of millimeters away from the hole.
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I’m essentially going to create
00:16:11
four spokes, that connect the
00:16:13
inner area to the outer area.
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I’ll create a construction
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line down the middle.
00:16:20
Then, I’ll create a regular
00:16:21
line on the left side of it.
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I’ll mirror the line over to the right,
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which will allow me to then use the
00:16:28
circular pattern sketch feature to
00:16:30
pattern this profile around 4 times.
00:16:42
From here, I’ll extrude this out to
00:16:44
the top of the gear, using the “to
00:16:45
object” extent type, while also making
00:16:48
sure the operation is set to cut.
00:16:58
You may even want to consider adding
00:16:59
a fillet radius to these inner edges,
00:17:02
not only making them stronger but
00:17:04
likely producing a better print.
00:17:10
Another quick tip if you’re looking to
00:17:12
3D Print gears for a project would be
00:17:14
to check out the McMaster-Carr add-in.
00:17:18
From the insert dropdown, select
00:17:19
“insert McMaster-Carr component.”
00:17:23
Simply search gears and you’ll see
00:17:25
there are hundreds of gear options.
00:17:28
I would recommend using the plastic
00:17:30
gears section, as these gear designs
00:17:32
have been optimized for plastic.
00:17:34
You’ll see there are even
00:17:35
gear railings and miter gears.
00:17:39
Once you find the optimal gear,
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you’ll need to view the product
00:17:42
details, make sure the dropdown is
00:17:45
set to “STEP-File” and save the file,
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which will place it in your design.
00:17:59
It took about 3.5 hours to
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print out these sample gears
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and the base that they rest on.
00:18:04
As you can see, the final
00:18:06
printed gears work well.
00:18:09
To summarize this video,
00:18:11
here are three takeaways to
00:18:12
consider when 3D printing gears.
00:18:16
#1 - Never have fewer than 13 teeth on
00:18:18
your smallest gear, or you’ll likely
00:18:20
end up with an undercut on the gear
00:18:22
teeth that will prevent proper rotation.
00:18:26
#2 - Always include a
00:18:28
backlash or tolerance, based
00:18:30
on your 3D printers’ setup.
00:18:32
You’ll likely need to print a few test
00:18:34
gears to dial in the optimal tolerance.
00:18:39
#3 - Always consider the thickness
00:18:41
and width of your gears, which greatly
00:18:43
impacts the strength of the gear.
00:18:45
When possible, consider adding a
00:18:47
backing to strengthen the gear teeth.
00:18:50
Last but not least, I want to give a
00:18:51
shoutout to those who supported the
00:18:53
channel over the last few weeks by
00:18:54
joining my Patreon or contributing
00:18:57
to my Buy Me a Coffee page.
00:18:59
Special thanks to the new Patrons.
00:19:01
Mark Smith, David Steeves, Brett
00:19:04
Vitaz, Dave Outlaw, Terry Norton,
00:19:07
Martin, Alex Parton, and Adam Whipple.
00:19:11
And thanks again to those
00:19:12
who bought me coffee.
00:19:15
Highfly!, David Brim, Dennis Murphey,
00:19:17
Heinz Somplatzki, Gary Hensley, and
00:19:19
all of the anonymous contributions.
00:19:21
[Upbeat Music]
00:19:24
I hope you’ve enjoyed episode
00:19:25
number 1 of practical prints!
00:19:28
Be sure to subscribe if you’re not
00:19:30
already, click the thumbs up icon if
00:19:32
you learned something, and click on that
00:19:34
playlist in the lower right-hand corner to
00:19:36
keep track of the practical prints series.
00:19:39
[End Upbeat Music]
