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Part of the freedom I’m longing to experience this year is simply putting the fun back in what I do. Not everything needs to be solemn and extremely important, at least not all the time. So, with that in mind, I was working on this model of a hairbrush, just for the sake of practicing and having fun. I must admit, given the kind of item it is, I also thought it could provide a few examples on using patterns. I have a few patterns in there, as you will see in just a few moments. Some of them are feature patterns and there are also a couple of  component patterns, as well. I had a particular brush in mind, so I tried to make it look exactly like the real one.

First, I started with a simple extrusion. I sketched an ellipse on the Front plane, centered on the origin to take advantage of symmetry, and extruded it to create the part of the brush where the bristles will be. I made a couple of extruded cuts on both ends, using arcs that were sketched on the Top plane. In this image you can see the sketches in pink.

After that, I sketched a circle on a plane parallel to the Front plane and used it to create a loft between it and one of the edges of the elliptical extrusion, as you can see in the following image. I used the start constraint normal to profile (start profile is the circle) to shape the loft a bit and make it look more like the brush I own.

After the loft, I shelled the whole thing to a thickness of 0.18 in, because my real hairbrush is hollow.  Notice that I didn’t remove the circular face on the other side, but only the one highlighted in blue in the image.

Next step was to create the zigzag cuts on the hairbrush. For that purpose, I sketched a zigzag line on the Top plane, symmetrical with respect to the Right plane, and used Offset (look for it in the Sketch tab) to transform it into a slot with circular capped ends, as you can see in the following image.

I used the sketch of the slot to extrude a cut through all in both directions (up and down) and then, after filleting the edges a bit, I used Linear Pattern to reproduce the cut and the fillet features nine times along the body of the hairbrush, as you can see in the image. I used the line of symmetry in the sketch to specify the direction of the pattern.

Trying to make holes for the bristles was the fun part. In the real hairbrush, there are nine holes per row (except at the top where there’s only seven) and they are all located along a zigzag line that follows the same shape of the slots used for the cuts. At first, I thought about simply sketching a zigzag line or offsetting the previous one on the Top plane, drawing some circles along that line (still on the Top plane), and using them to extrude cuts for the bristles. However, this approach would not work fine, because I overlooked the fact that these holes would be created with projections of the circular sketches and would therefore deform and/or show in a position different to the one I expected.  So, what I ended up doing was to offset the first zigzag line (the one for the slot) and then project it on the face of the hairbrush, to have as my guide for the holes.

I also created a couple of reference points on the face of the hairbrush and right in the middle of two of the line segments, such as the one you see in this image.

Using those two points and the points at the end of each line segment, I created a series of planes that were tangent to the face of the hairbrush and that passed through each those points.  One plane per point.  On each plane, I sketched a circle and used it to make a hole for the bristle on that location, as you can see in this image.  These holes are not deformed like previously.  I only had to cut half of the holes in the row and then mirrored with respect to the Right plane to create the other half.

Once I had all the holes in place in that first row, I used a Linear Pattern again to recreate the holes nine times along the body of the hairbrush in one direction. Again, the direction for the pattern is specified by the same line in the slot sketch that I used before.

I used Linear Pattern one more time to recreate a row of holes in the opposite direction, only this time, as you can see in the image, I left out the hole on the edge, because that one doesn’t fit on this row. This step only created half the row, so I had to mirror the other half with respect to the Right plane.

After adding a few fillets to the brush, just to make it look a little nicer, I continued with the handle by creating a second loft, this time between the circular edge of the brush and an ellipse sketched on a plane parallel to the Front plane, as you see in this image. I used start and end constraints to shape the loft a bit. By the way, the start constraint “Normal to Profile” simply means that, on that side of the loft, if your surface was a mesh of parallel lines going from one profile to the other, the lines would try to remain normal to the elliptical profile, at least for a while, depending on the start tangent length.  On the other side of the loft, the end constraint “Curvature to Face” means that the surface of the loft is trying to follow the same curvature of the face of the brush that is highlighted in blue, at least for a while, also, depending on the end tangent length.

OK, so, let’s continue with the handle. Next, I offset the elliptical edge a bit and created an extruded boss for the handle. I also added a Dome feature at the end. On another plane parallel to the Front plane, I created to ellipses by using Convert Entities on the edges of the handle and the second loft. I used this sketch to extrude a cut on the handle, as you can see on the image.

Once again, I used a linear pattern to recreate this cut thirty times along the handle, in order to create the ridges I saw on the handle of the real brush.  Next, I cut a circular hole on the part of the handle without any ridges on it. I guess some people may use this hole to hang the brush from a hook. Personally, I keep mines inside a drawer. Anyway…  I sketched a couple of circles on the Top plane and used them to extrude a little edge around the hole, as you see in the following image. Notice the end condition on both side is “Offset to Surface”, where the surface is the one in pink, this way the extrusion follows the shape of the handle.  I had to select the options “translate surface” and “reverse offset” in order to make it work.

The last step was to create a bit of a “ridge empty” surface on the handle, for the brand or tag. I did this by sketching a slot on the Top plane and extruding it, just as before, using Offset to Surface as the end condition. Only this time I didn’t select translate surface, however, as that would’ve resulted in my new surface having ridges just like the rest of the handle. 

The bristles were created separately. Well, I must actually say “bristle”, singular, because I only created one and inserted nine instances of it to an assembly I created from the hairbrush body part. I mated all nine bristles on their correct holes in one of the rows and then used a Feature Driven Component Pattern to reproduce bristles in their correct holes in all other rows, as you can see in the image. This is only in one direction, because my driving feature is the Linear Pattern I used previously to create holes in these rows, remember? I guess I could’ve done something similar by simply using a Linear Component Pattern instead, but by doing that I would’ve had to enter the correct distance to the holes, etc. This way, this pattern will be linked to the other one and if that one changes, this one will update with the right information.

I did the same on the other direction, to create the last row of bristles, only I didn’t pattern the bristles on the edge, since there’s no room for them on that row. And that’s it! I hope you found this useful, or at least fun.

This is how the brush looks like finished, without appearances.

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