I have found myself the lucky winner of the task of replacing the ancient video screen, radio controls & tape drive part of the “navigation & entertainment system” in a 1997 E38 BMW. I’ve so far done all the wiring to haul the head unit connections to the front of the car from the trunk and located a Sony double DIN head unit that will fit in the hole. I’ve done the CAD and have cut out some test brackets (which will be milled from a big block of plastic I have) to adapt the Sony to the ridiculously over-complicated die cast aluminium housing that the old video unit and tape deck lived in to mount it all in the Dash.
My next issue is to cut a suitable bezel to go around the new head unit and clean up the facia. I’ve considered trying to cut the die cast aluminium and walnut veneer bezel from the old unit but it just looks wrong with the Sony screen in it and I’m thinking a matt or silk black finish is likely to be cleaner overall. We plan to occupy the gap on the left with an iPhone holder for the attached Apple Car Play replacing the ancient navigation system.
So, any suggestions on a plastic that will machine well into these complex shapes and maintain dimensional stability and finish as it gets cooked and frozen in the interior of a vehicle pls?
Not intentionally being unhelpful, but use the plastic that the car companies use.
Guessing some type of UV resistant PVC - but agree - do a bit of research as to what dash parts are commonly made of and try to get as close as possible.
PVC, ABS and POM are apparently the go-to plastics, anyone got any experience with whether they machine nicely? (injection moulding for 1 unit seems excessive).
I’ve done a little machining in POM (Acetal, Delrin) but no idea how ABS cuts.
POM seems to be available in 10mm + sheet thicknesses, if it was ABS then maybe an enclosure for the 3D printer and print the bezel?
You could use PVC sheet products and build your part up in layers.
Resins or epoxies may be an option too. Machine the buck for a mold in out of anything suitable. Not sure which ones would work. Dyes would also give you options for colors.
I’ve seen people 3D print, Bondo, sand and paint similar fascia for head units. Not sure how those held up long term though. 3D prints could be used to mold too.
More steps for sure.
3D printed, ABS or ASA, on a textured build plate (i.e. Prusa), would be my go-to. If machining is your only option (or choice), aluminum and paints with a black matte, to match the Sony bezel.
I’m not 100% sure about the finishing process for machining plastics; I’ve noticed slight finish marks when I machine in them. I use them for work holding, testing tool paths, and resin molds, so I’m never concerned about finishes.
I believe the marine grade HDPE from McMaster Carr has a texture to one side, at least the white color did. Max temp 180F.
Might be an option if you left the original face. Machines easy with standard end mills, works great with single flute, and walls are nice and smooth.
ABS sheet usually has a texture, machines well, and can be thermoformed.
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