Purpose: Use the tools learned in part 1 to make a basic cut file from scratch. The final application is to run a job on the FlowJet.

Tools: AutoDesk AutoCAD 2012

Step 1: Let the Games Begin

CAD software involves a bit of command prompt and confirmation since the software goes step by step, and you have the opportunity to address all of the variables in order to have complete control of the results. Everyone starts with rectangles. Rectangles are also boring, so we will start with drawing a circle. Effectively you are telling the software, “I want to draw a circle” <where?> “here” <how big?> “this big”.

Translated into CAD-speak: “circle, ok” <where?> “here” <radius?> “5, ok”.

Simplified to actions: <C> <spacebar> <left-click> <5> <spacebar>

While that is technically five actions, how fast can you type? That command is roughly 1.6 seconds once you get the hang of it. Hunting for buttons can really eat up your time, so while the keyboard might seem a bit weird at first, it will drastically save you time in the long run, and good habits start early. Also remember that for “circle” you can still type the full word, but one letter saves time over six letters.

Step 2: Circle, Offset

This circle is going to be turned into an object! To quickly make a concentric circle with the same center point, “offset” the existing line two inches outward (AutoCAD default units is inches). [1] [2]

Conversation: “I want to offset” <how far?> “2” <what line and which side?> “this line, going this direction”.

Actions:<O> <spacebar> <2> <spacebar> <click desired line> <click desired side of line>

Remember that the software doesn't know what action you want to do, what objects are affected, and the numerical values involved until you explicitly tell it. Prompts are always listed in the bottom left of the screen, so the next step is outlined for you.

Now repeat the offset command using the same line as before, but this time change the distance from 2 inches to 1.5 and offset towards the interior of the circle instead of the exterior. [3]

Step 3: Line, Mirror, Trim

We are going to turn these circles into a gear, which will require including teeth. First step is to draw a line from the center of our circles, up. [1] Note that my cursor is hovering over the actual circle in order for the center snap to be visible. Also note that when a green snap point appears, the action you take next will occur at that location. This means I can click where my mouse is currently and I don't have to move over to the snap location.

Following the line command, one click to start the line and a second click to determine the end point. [2] In the image you will see a few things worth mentioning. The green dashed line indicates that the line is perpendicular, the highlighted window indicates the line's length, and the other dialogue box shows the exact angle (pressing <tab> will move between the dialogue boxes). For now the length of the line is arbitrary, but I made sure the top was far enough away from other parts of my drawing such that the snap points wouldn't conflict. A line is a highly common action, so the software keeps you in the command to allow for drawing multiple lines.

Actions: <L> <spacebar> <left-click> <left-click> <escape>

Since the gear we are drawing is just for demonstration, the angle for the next line is not critical and I just eyed it. Draw the line extra long so as to avoid unwanted snaps (zooming in can help if conflicts are arising). [3] To ensure that the other side of the cog is symmetrical, we are going to “mirror” the most recent line across the vertical line. [4]

Conversation: “I want to mirror” <what object?> “this line” <where does the mirror plane start?> “this point” <where does the mirror plane end?> “this point”

Actions: <M><I> <spacebar> <left-click> <spacebar> <left-click> <left-click> <spacebar>

The final portion of this step is to “trim” off the excess portions of the drawing in order to have a single cog. You will pick the two angled lines and the two outer circles. All that should remain of the outer circle is the portion between the angled lines, and the angled lines should be reduced to the portions between the two circles. [5] [6]

Conversation: “I want to trim” <what are the cutting edges?> “these lines” <what do you want to remove?> “these sections”

Actions: <T><R> <spacebar> <select lines> <spacebar> <left-click>(x5)

Step 4: Array, Trim

Everything looks great, but we only have one lone cog on our gear! While you could do a series of “rotate” and “mirror” commands, the quick way is “array”. This command can be a little trickier than most, so don't be surprised if you need to try it a few times to get it looking the way you want.

The full command for a circular array is “arraypolar”. Honestly I don't use the command enough to remember the full name, but typing in “array” is enough as I see a round looking icon down the list. [1] First select the set of lines you wish to include in the array. This can be done clicking on the individual lines one at a time or better, dragging a window around them (left to right in this case). Identify the center point that you are rotating around and then number of copies to be made. The software starts an array at vertical and will default to 360 degrees unless specified otherwise. [2]

Conversation: “I want to array in a circle” <which objects are included?> “these lines” <what is the center point to rotate around?> “this point” <how many copies?> “10” <how far around the circle?> “360 degrees”

Actions: <ARRAY> <select ARRAYPOLAR from list> <select objects> <spacebar> <left-click center point> <10> <spacebar> <spacebar> <spacebar>

Spacebar is hit three times because the first confirms 10 copies, the second confirms a default of 360 degree rotation, and the third confirms the end results are correct. If you don't know the exact angle you can also click on other lines as reference points. This is also one of the more complicated, multi-step commands. If you were successful, congratulations – the rest of AutoCAD is going to be easy. If you struggled, don't worry – the majority of AutoCAD is a lot easier.

Technicality: The outer portion of the of the cogs should not be rounded. This is just a fun drawing and should not be inferred to be a functioning bit of engineering.

Step 5: Clean Up + Commands

Now that everything has been drawn, we can clean up the drawing by removing portions that are no longer needed. The vertical line can simply be deleted (<delete> not <backspace>), and the circle that appears inside the cogs can be trimmed out. There are a few different ways that this can be completed successfully, but I find the quickest is to drag a window and select everything as cutting edges. Simply put, the lines not involved in cutting wont cut so there is no harm in including them, plus dragging one window is much faster than clicking on twenty individual lines.

Conversation: “I want to trim” <what are the cutting edges?> “these lines” <what do you want to remove?> “these sections”

Actions: <T><R> <spacebar> <select lines> <spacebar> <left-click>(x10)

Additionally if you want to group this entire entity together, select everything and type “group” or “g”. Success!

As a bonus, here is a list of common commands and their shortcuts:
line <L,space>
polyline <PL,space>
rectangle <REC, space>
circle <C,space>
copy <CO,space>
trim <TR,space>
extend <EX,space>
move <M,space>
mirror <MI,space>
rotate <RO,space>
regenerate drawing <RE,space> (If you are zooming in and out a lot, AutoCAD simplifies the drawing so that it doesn't lag. You did not lose information, it was just compressed in a way.)
zoom extents <Z,space,E,space>

The project continues with part 3!

For more resources, tools, and training, head over to TechShop!

FlowJet Series Part 1: AutoCAD Basics
FlowJet Series Part 3: Converting an Image to Vector
FlowJet Series Part 4: Cleaning Vectors for FlowPath
FlowJet Series Part 5: Manual Pathing in FlowPath
FlowJet Series Part 6: Using FlowNest

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