I have a DeWalt DWS779 Miter Saw and the dust deflector (part number N630004) kept breaking on it. It would break whenever something I was cutting would get caught by the blade and end up slamming into the deflector. The part is not expensive or anything, it is just annoying to have to buy them from random sites and wait a week for it to arrive.
I emailed DeWalt and asked if they would consider sending me the CAD files for the part so I could just print it myself (and I offered to pay them for it), but they never responded; so I designed it from scratch. Having never designed anything in CAD before, this part took 8-9 hours to finish using my calipers and Fusion 360.
I have included the STEP file so anyone can make modifications to it if they want. It is possible this part might work on a DeWalt DWS780 (because it’s just a DWS779 with laser guides), but I can’t guarantee it since I don’t have one of those.
For best results, reduce the Support Density to 10-15%. The default support density is just a little difficult to remove from such a small part. Supports should be Touching Build Plate and have an Overhang of 45 degrees. If you want to increase the part strength increase the wall count or wall thickness, don’t increase the infill.
I printed at 50 mm/s, but 75 mm/s still gives you near/perfect results.