Dash Advice

[CriticalB]

Overall, my dash is in pretty good shape, except for a small crack in the passenger corner and a warped split over the passenger speaker grill. The glovebox lid has some minor damage, but given the scarcity of them I can live with it. I don't think the dash damage is bad enough to warrant replacing the whole thing. I'm not sure if it could be repaired - if so, it would probably be more expensive than replacement.

In the meantime, I 3D-printed some low-profile speaker grills to attach over the damage. I'm attaching pics below of the crack, and the rough-print grill. I'm printing a set of larger, finer-detail models at the moment that will completely cover the damage. Once those are sanded and painted, what do you guys think would be the best way to attach them? I know I could glue them on, but they were designed to be attached with screws. Does anyone know what material I'd be drilling into? (metal, plastic, cardboard, etc...I know even plywood isn't out of the question)

55839

55840

[Shep]

You would be drilling into a speaker. Specifically, the right tweeter -- remove it first before going too far, you'll have direct access to the underside that way. I would personally use some of the existing holes in the speaker grille that are still intact to attach the new grille. In your first picture, left, right, bottom-left, top-right. Then, just to match, do the same on the other side. Or if you can adjust the base to take six screws instead of four, that would be easier to fit with the honeycomb pattern.

If you can, oversize the model some more too, especially the base. This will cover the remainder of the crack. The holes can be made way bigger to better match stock appearance too, and to allow your 3D printer to make a more defined edge on it (the bigger the detail, the easier it is to print I've found, this is a universal truth to FDM printing). Sometimes with a lot of extruder head movement, the filament can drag on the nozzle (Q-tip at extrusion temp works well to clean), I don't know if I'm seeing that here or if setting the retraction a bit higher would help more, but it looks like there's unintended filament on a few areas, mostly minor though. Overall it looks fantastic! I'm actually quite surprised at how closely the color matches your interior too, what filament is that if you don't mind me asking?

But as a permanent fix, vinyl repair isn't that expensive. 3D printing is just more modern and awesome :)

[CriticalB]

You would be drilling into a speaker. Specifically, the right tweeter -- remove it first before going too far, you'll have direct access to the underside that way. I would personally use some of the existing holes in the speaker grille that are still intact to attach the new grille. In your first picture, left, right, bottom-left, top-right. Then, just to match, do the same on the other side. Or if you can adjust the base to take six screws instead of four, that would be easier to fit with the honeycomb pattern.

If you can, oversize the model some more too, especially the base. This will cover the remainder of the crack. The holes can be made way bigger to better match stock appearance too, and to allow your 3D printer to make a more defined edge on it (the bigger the detail, the easier it is to print I've found, this is a universal truth to FDM printing). Sometimes with a lot of extruder head movement, the filament can drag on the nozzle (Q-tip at extrusion temp works well to clean), I don't know if I'm seeing that here or if setting the retraction a bit higher would help more, but it looks like there's unintended filament on a few areas, mostly minor though. Overall it looks fantastic! I'm actually quite surprised at how closely the color matches your interior too, what filament is that if you don't mind me asking?

But as a permanent fix, vinyl repair isn't that expensive. 3D printing is just more modern and awesome :)

Lining up with the honeycomb seems like it would be fairly hit or miss. I had resigned to drilling through the outer rim as I wanted to make the grill large enough to cover that crack on the lower left. I ordered a few small grills off of Amazon, but none were a perfect fit.

I've already started a print job with finer detail and scaled the model up to make it larger, which in turn has made the holes a little bigger, but i like the density on this as there's no chance the damage will show through. The top of the grill you see in the picture was on the bottom as it printed, and the other side turned out much smoother, so I flipped the model for this print. I'm using this filament:

https://www.amazon.com/HATCHBOX-3D-Filament-Dimensional-Accuracy/dp/B01N53KX79/ref=sr_1_fkmr0_1?ie=UTF8&qid=1522970356&sr=8-1-fkmr0&keywords=hatchbox+PLA+true+black

The color match was a coincidence - the filament is glossy black, but after sanding it was a near perfect match. I'm sure if I wash it and sand it with a finer grit, it will turn black again.

[Shep]

Oh god no, do NOT use PLA, you are going to regret that decision the next summer day you have. PLA glassing temp is well below the temperature that a car interior gets, you're going to see serious warping issues. And that's in late-model cars, DeLoreans are just ovens. Hatchbox makes amazing filament, I'm surprised it color matches that well, but you're going to want PETG or ABS for this use case bare minimum, PC-ABS I've been reading about too as it avoids some of the difficulty in printing that ABS has while increasing temp range further.

Here's a dash cam mount I made in PLA:
55855

Here's the same mount that miserably failed 24 hours later:
55854

On the alignment: invest in digital calipers, I cannot recommend them enough for 3D printing. Most of what I print is practical use cases, but without exact measurements there's not much point. Here's (https://hackaday.com/2018/03/27/how-to-reverse-engineer-mechanical-designs-for-3d-modeling/) a good article on reverse engineering for 3D printing, and while not strictly related, reverse engineering the speaker hole layout should be dead easy. Believe me, having reverse-engineered a few parts already, DMC didn't exactly make it hard to duplicate their stuff. The calipers at Harbor Freight aren't bad and are fairly cheap too.

Drilling, this is where it could (and may very likely) make a bad situation worse. The vinyl is cracked from age and/or drying out, there's no telling how much it will spread by drilling brand new holes into it, but from the looks of it, given it has started to peel and also branch off in a new direction, it's a fragile area already. Where it currently stands, that one lone section can be repaired for far less than a complete dash replacement (I have seen several "vinyl and leather repair" booths at car shows and expos). I would personally get a few quotes if that were my car just to see what they're asking for that repair. If the quotes come back too high for my tastes, I'd design a PETG grille that matches the stock design.

Keep in mind too: by using a different grille design entirely, the tweeters are even less effective. Every hole in the stock grille that is covered in the new grille is going to cause a more muted and distorted sound. Good analogy: rather than a few people in front of you at a concert, you have a mosh pit full of so many tall loud frat boys that you can't hear squat (sound bounces back when it's blocked). I would wonder at that point if the tweeter would have any useful sound at all, but I can't imagine it would. Under-sizing the holes a bit on the 3D printed grille vs. OEM is one trick to hide the problem better while mitigating its effect on audio quality, but using a square grid vs. a hexagonal grid is going to introduce sound quirks. Not that the DeLorean has decent audio anyway...

EDIT: Forgot to mention, the retraction / nozzle cleaning bit, nevermind that, sanding explains what I was seeing. Interesting thought though, I never considered sanding affecting color.