First things first. To print this, you'll need three different kinds of filament: (1) Something rigid like PLA or PETG; (2) Something extremely flexible like TPU or FlexPLA; and (3) Nylon.
There is a design of styling hairbrush that was popular in the 80's through the early 2000's, but which is becoming increasingly difficult to find. The brush component of these brushes consisted of nylon bristles held in place by a typically latex holder that was folded in such a way as to give the bristles good spacing and a reasonable amount of "give" when in use.
For some reason, this style of hairbrush has become increasingly difficult to locate, so I decided to design my own for 3D printing.
In order to have the right amount of "give" while still remaining sufficiently stiff and slick, the bristles are printed in nylon. I don't think there's any reasonable substitute for this, but if you have good luck with some other material, please leave a comment.
In addition to needing a certain amount of flexibility for comfort purposes, the bristle holder needs to be folded under itself after printing for insertion into the handle. I have used TPU for this purpose, although I imagine that any highly-flexible material should work.
The handle can be anything you want, as long as it's stiff enough to hold the bristle holder in place after it has been folded. I used PLA during development, and made my final print with PETG. Both work fine. It is even possible that you could print the handle in nylon if you want something with a little more flexibility.
Finally, this is a compact version of a hairbrush. This is due to the limitations of the printer I'm using, which has a 120x120mm print bed. The design itself is parametric, and although I haven't tested changing dimensions around to create a full-sized hairbrush, the length and number of bristle rows does change appropriately as the parameters in
brush-common.scad are tweaked.
Since these brushes are no longer readily commercially available (at least in the US), I'm considering this a "Life Hack."
This print requires three different materials.
The nylon shouldn't be thick enough for infill to come into play. If you find your slicer doing infill, turn it up to 100%. In my case, I printed the nylon at 245°C, since that's the hottest I can safely get my hot end (which contains PTFE tubing). I printed very slowly, with a max speed of 15mm/s. Using the Inland brand nylon with these settings, I have not had any issues with delamination yet. I printed the nylon with supports turned on, which Slic3r simply turned into a single supporting line under each bristle. It's small enough that I can't really find it to remove after printing.
The flexible material (e.g. TPU) really doesn't need much infill. I printed mine at 10% in a hex pattern, and it works just fine.
The handle should print with your normal PLA or PETG settings. You may wish to turn the infill up to provide more heft and/or strength. I printed my PETG with 30% infill.
Inserting the Bristles
Once all three parts have finished printing, you'll want to take a metal tool (e.g., a 2 mm allen wrench) and ensure that all of the holes in the bristle holder are unobstructed. Clean the strings off of the bristles to the best of your ability.
Taking note that the bristle rows are different lengths, insert the bristles from the back of the bristle holder (the part that was in contact with the printer bed). See the diagram below for the proper orientation.
This can be a bit tricky at first, but after you get one row inserted, you should get the hang of pushing the bristles through the holes. (Note: the "bristle-holder-v2.stl" model has larger holes that makes this process significantly easier than the original design.)
Mounting on the Handle
Once the bristles are all inserted, fold the "wings" of the bristle holder under the surface that the bristles are mounted in. Their curved surface should stretch the bristle holder surface out into a curved arc. Once the wings are folded under the bristles, slide the assembly into the top of the handle, making sure that the back of the brush is in contact with the assembly. When fully inserted, it should look like the picture below.