STEM Robotics 4 All

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Construction lines, more sketches and extrusions

Our purpose is to draw a circle centered on the top face of a box we have extruded. The “end product” will look like this:

How can we do this ? SolidWorks helps us to find the middle of various entities. If it were some other proportion, we would need to compute it, and request a specific distance from some reference point. First of all, carefully look at the figure and notice

  • the bottom-left red system of small coordinate axes. The “horizontal” one is shorter (that’s a SolidWorks convention we can put to use when we build the construction line).
  • The dashed horizontal line segment
  • The circle centered in the middle of the dashed segment

So, we can do all that one by one (just two elements: the dashed line and then the circle). Before we do it, one more ease-of-use trick. We can always first select a tool, then wait for SolidWorks to ask its questions, and then proceed — here we would select the sketch and then we would be asked on what plane we want to sketch. However, to go faster, we can first select the face (or plane) we want to sketch on, and then click on ‘Sketch’ — this makes SolidWorks go right ahead to allow us to sketch in that plane or face, without asking. The same will happen with the extrude, if we do that before concluding the sketch.

So, on we go.

We click on the top face, and it turns light blue (from the regular grey).

We click on Sketch in the grey tool bar line, and then on the ‘Sketch’ “button” in the middle toolbar with “boxes”, the same way we did it the first time.

Then we go to select the ‘Line’ sketch element, and the usual nice animated pop-up explains to us how this is going to happen:

Once we click it, before we go ahead and start sketching the line itself (by clicking to get the start point, etc.), we go to the dialog in the left bar, and check the ‘For construction’ box. This means this line will not be part of some contour to be extruded or to be otherwise used for 3d-building operations, but will only be used geometrically, to help us find specific points (middle, intersections, perpendicular, parallel, etc), for further construction or 3d processing). We also check “Horizontal” (instead of ‘As sketched’), which constrains the line to be horizontal (thus parallel to two of the edges of the top face), making our life easier.

Then we simply go and hover above the left edge of the top face. As the edge line becomes orange (by simply hovering on it), also its middle becomes apparent, as a square yellow dot, with two tiny diagonal lines:

This is help from SolidWorks to allow us to start the line from there. The line will be horizontal no matter how we move the mouse. Note that we do not even need to keep holding the left button down.

We only need to click once more when we want the segment to end. We will do that when the other edge becomes orange:

Then the line is “ready to be validated”: if we glance at the left dialog, we see the now familiar green check mark (and the red x), inviting us to make the “decision”: we approve this or we change our mind. Ok, we approve it, and then we need to draw the circle. We want the center of the circle to be in the middle of this line, which itself is parallel to the edges of the top surface and goes from middle to middle. We go and press the Circle button, and, before clicking to set the center, we again use the fact that SolidWorks highlights the middle, this time of the construction line segment we just drew.

We click on it and start drawing the circle, by enlarging the radius (we can release the left button, the circle will follow the mouse until we click once more).

Then we click to finalize the circle, and, before clicking on the green checkmark from the left dialog bar, we go into ‘Features’ and ‘ExtrudedBoss/Base’, and click on it. This will extrude it right away:

And now we can validate it, once we are happy with its height. The last few things to do are to make a hole in it, to be able to place pencils and pens, and to make the edges less sharp. We’ll do that in the next lessons.

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