Metal 3d printing: lock escutcheon

Billtodd · Sep 7, 2022

I've been ask to reproduce a lock escutcheon for a friend's classic Bentley Continental, which is apparently unobtainable else where.

I think I can model the part ok, but I'm seeking experience of others as to the best material. The original is a zinc alloy chromed, so would either something that could take plating or ,at a stretch, would polish to a mirror finish.

memphisjed · Sep 7, 2022

Brass takes a nice chrome, relative easy to cast or machine. See a faucet for an example.

Billtodd · Sep 7, 2022

Yes if I had to carve one from solid, that's what I'd choose.
I don't think I have seen 3d printing with brass ??
Edit: of course, yeah lost wax casting is available 8⁠-⁠)

Scottl · Sep 7, 2022

Apparently the way to create brass objects through 3D printing is to 3D print a wax model and investment cast it.

Brass 3D Printer: How To Get Brass 3D Prints

Brass is poor man's gold. With a bold face rivaling the appearance of precious metals, it proves that all that glitters is not gold, but in a good way. Here's the scoop on brass and how to 3D print with it.

all3dp.com

This article explains why copper alloys are unsuitable for 3D printing.

3D Metal Printing: Alloys and Powder Types and Specs - Belmont Metals

Whether creating prototypes for application components, precision gears, or jewelry, more manufacturers are turning to the capabilities provided by 3D metal printing. Also called additive manufacturing, this process relies on technology that uses a metal powder in a layering process to produce...

www.belmontmetals.com

For a simple part such as the one you have I'd suggest making a silicone mold directly off the original (after padding any defects with epoxy, shellac, wax, or even clay) and then casting a wax investment pattern to send out for casting in brass.

MCritchley · Sep 7, 2022

If you go back a generation in cars to the “brass era” parts like that were brass casings filed to perfection and nickel plated. I just built some parts for a Pope Hartford touring car and noted the high level of fit and finish on each part. The guys building car must have worn out a lot of files!

If I was making a one off, it would be a CNC mill project from brass and a bunch of hand finishing.
If I didn’t have a CNC I would just rough the part out and file it to shape. It won’t take long, and you’ll get really good with a file.

Billtodd · Sep 17, 2022

Thanks guys.

I've modelled the escutcheon, and printed a couple for testing.

I've sent the file to a firm in India to be cast in brass and will report back with the results

implmex · Sep 19, 2022

Hi Billtodd:
That is not a difficult part to machine from barstock, so I would have simply farmed it out to a local CNC milling shop.

You already did all the hard part by modeling it...cutting it is not very demanding by comparison.
Since you are vendoring it out anyway, it makes some sense to me to pick the process that will get you the closest to a finished part as you can get.
You could have it milled out of 303 or 316 stainless and polish it nicely...no need even for chroming it, unless you need an exact colour match to an existing part.

If it must be perfect, you cannot avoid the chroming step...even a mirror polished stainless part will be noticeably different if it's sitting in close proximity to a bunch of chromed parts; the luster and colour of chrome is really hard to mimic perfectly.

So another option to consider...you've already committed to the "cast in India" route, but if that is not successful, this is another alternative.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

Billtodd · Sep 19, 2022

This needs to be chromed, since it's one of the parts where the customer meets the job, and the there's a number of other parts that are being chromed in any case

I thought about making in from barstock, manually (I could cnc the profile, but only have a 2axis machine in my garage) , but didn't fancy carving two, and farming out to cnc (i.e taking it to the works and persuading someone to make it for me, would have cost too much in favours ;⁠-⁠))

The cast in India route is cheap enough to fail 8⁠-⁠)

implmex · Sep 19, 2022

Hi again Billtodd:
Did you know that you can get very close by running waterline toolpaths if all you have is a 2 axis machine.
If you do it in something like Fusion 360, you can adaptive rough it with a small step up like 0.005" or so, and run it with 0.001" of stock on it and a nice gentle feedrate with a small radial DOC as well.
The 3D adaptive roughing strategy is a waterline strategy with the added benefit of taking only very small bites if you need to.
It will get you a part that you can hand finish with ease...not as good as finishing it with a Scallop toolpath on a VMC, but still pretty damned nice

So all the toolpaths in that Adaptive Roughing strategy are XY toolpaths.
I don't know if that's what they're called in Fusion...I'm running HSMWorks which is basically the same thing.
Check it out...it's pretty cool.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

Billtodd · Sep 20, 2022

Hi Marcus, Thanks for the suggestion. No I didn't know fusion could do that .

Well worth a look. Thanks

implmex · Sep 20, 2022

Hi again Billtodd:
Here's a picture of a part in 316 Stainless I'm just cutting now:

The top is being cut with a 1/8" bullnose with a 0.010" corner radius and is a scallop toolpath with a 0.005" stepover.

The bottom half is what it looked like after roughing from a solid lump with 1/2" of stock on it in places.
It was roughed with that 3D adaptive strategy using a 3/8" bullnose with a 0.010" corner radius with a 0.005" stepup and leaving 0.010" residual stock for the finishing cutter to clean up.
Radial DOC was 0.0075" and I ran the rougher at 120 IPM with MQL (refined vegetable oil).
As you can see from this shot, the roughing is already pretty good...if I was able to cut every detail with the 3/8 cutter, I could be almost good enough to polish it right from the roughing with a big buffer and coarse Greystar compound.

There were only XY moves done to get this result, and it's quite a complex surfaced part:
Here's the other half:

It's part of a freaky sex toy...(don't ask!) :willy_nilly:

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

Billtodd · Sep 29, 2022

Well they're here 8⁠-⁠)

And , I'm very pleased with the parts . I need to finish the top surface , I left myself material to grond back and polish, and sensibly they put the riser on that surface, so ideal.

These worked out at just under £25 a pop so not cheap but there are features that would require some thinking about to cnc.

Billtodd · Sep 29, 2022

After a hour polishing

implmex · Sep 29, 2022

Hi Bill:
They look very nice indeed!
Are they good dimensionally too?
I realize for this project it probably doesn't matter, but there may be other projects where it does.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

Billtodd · Sep 29, 2022

There's a little bit of shrinkage, expected, the onl critical part here was the stem 15.00 - 14.98 5.50 - 5.48 but chromium will fatten this back to size .

Metal 3d printing: lock escutcheon

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