Hello, I’m a newbie here at Core77 and have a question about engraving. I’ve developed a small consumer product that molded in black ABS and is then vacuum metalized with a chrome mirror finish. I’d like to put specific graphic designs on one of the parts (2" x 1") and though that I could possibly etch or engrave the chrome layer away to reveal the design in the black ABS. My question is how can we do this successfully. I’m not sure how bonded vacuum metalized chrome is on plastic. Would a standard CNC engraver be able to do the intricate designs without flaking the chrome at the edges or would a laser engraver be a better choice? I had heard that the laser engravers hate chrome surfaces so I’m wondering if this would work. Any advice? Thanks.
I think we’re going to need more info because there are tons of options.
first question, have you considered in-mold decoration?
Grab a part.
Grab a dremel tool.
Go to town.
Report back here.
Rotary engraver might be your best bet with the chrome. You’d be using a smaller scale specialized CNC router for that, instead of larger scale machines. The bit’s are very very small so they can do some pretty detailed work. How thick is the piece? What’s the thickness of the chrome surface to the black core?
Keep in mind the VM finish is going to be very thin. You could most likely engrave it, but that will be exposing the base plastic to varying degrees so keep in mind what your underside finish looks like. Also, as mentioned the VM finish is typically brittle, so you may wind up with some issues around the edges.
If you wanted to engrave on a VM part my suggestion would be to try laser etching. That would probably give your best chances of success over a mechanical process - but you are going to face the issue of etching off a consistent amount of VM. If the VM finish is thicker in some areas then others you may not etch all the way through, or you may etch too far and get meltback from the plastic melting.
You will need to tweak the process carefully with your vendor because you will need to understand how thick your VM coating is designed to be applied, and what the substrate will look like when you remove it.
I wouldn’t say it’s not possible, but definitely carries a high degree of risk and process control needed to get it correct.
I’ve seen parts that did similar, dash component knobs for some model year Cadillac. Molding, surface treatment, plating, coating, machining, coating: a very, very expensive part.
Laser’s don’t like reflective surfaces. Laser machine shops I’ve used have refused any job involving reflective material.
Also, laser cutting of plastics is fraught with long term stability issue as the laser depolymerizes the heat affected zone.
There are colour change materials specifically formulated for your type of application, but you get red-beige, blue-white for example.
Can you try thermoforming metalized film and printing, or metallic hot foil stamp and print?
Didn’t even put that together for a polished VM piece…
Are the etched pieces for a one off part (customization?) or just as a process to get a graphic effect?
Thanks for the replies. very helpful. The product will be a mass produced one with options for the buyer to pick one of many designs to go on the chrome side. Doing laser etching is probably prohibitively expensive for this sort of perk. What we’re looking at now is printing directly onto the chrome surface with a flatbed printer. I’ve even had a few suggest we take a CD/DVD carrairge from an old Epson r800 and modify it to take the part in question. The part is just .16" thick and 2" x 1" long so this might be an option to at least try it out. Anyone ever print directly onto a chrome part? BTW - we couldn’t do in the mold design because the chrome plating comes in after the molding.
Sounds like a bit of a science project to be modifying hardware for this. The typical ink used in inkjet printers won’t get absorbed into the material and would rub right off, and I think if you go and start modifying the ink to something that’ll work, you’ll probably have issues with feeding the ink over time.
Laser etching is probably one of the most cost effective methods if you find the right vendor, but the issue of reflectivity is one I hadn’t considered which makes that unrealistic.
What kinds of quantities are you actually producing these in? Right now it almost sounds like the best approach may just be applying a film mask after the VM (which would depend on your part design) and just painting the surface.
Are these customized as one offs? Or are you just making a limited set of designs? You may want to reconsider the VM process entirely and just do a silver IMD that has your graphics applied. Won’t be pure chrome but would be a known process with a known result.