Tips to injection mold metallic plastic

Does anyone have tips or resources for successfully molding metallic flake into plastic parts? The parts we mold can be large (up to 3 ft wide) and can have complex surfacing.

Thanks in advance for any help.

Your challenge will be flow lines. Adding the metallic flake will unfortunately accentuate every single flow line coming from surface interruptions.

For a large part like that you may want to consider painting it after molding the part.

Good luck.

Either embrace it (see previous conversation on here about Dyson vacuums and their flow lines) or paint it.

You can work with tooling engineers to try and optimize it as best as possible, but you are always going to have some areas where those flows come together and it will be very visible.

another way to embrace it…

As I understand it, there are magnetic elements in the tool that cause the metal flake to build up more in some areas than others. Wonder where that technique could go with interesting textures

there are a number of tool design tricks that force the material to avoid visible flow and knit lines, but the part has to be freindly to those tricks in the first place.
Samsung has a plastics division (Cheil Industries) that has a metallic material they claim doesn’t create flow or knit lines. we’re looking to run some samples…

I don’t believe that logitech mouse uses metallic plastics, I’m 90% sure it’s a molded black part with some type of IMD or painted surface treatment.

I’ve been using those exclusively and just started taking a razor to the back of one - the bottom edge has a lip that isn’t quite the same finish as the top (almost looks like overspray) and if you scrape it with an xacto you quickly get to black.

I’ll have to take one apart later to be sure.

Looks similar to the fisheye effect when there is a speck of silicon on the surface before painting. Varying surface tension affects the metallic particle distribution?

To the original question. Paint is always the better solution. The metallic particles are basically wasted when mixed into the plastic body as they only show at the surface, and then visually affected/distributed with the flow. Better to use the same particles in paint and only on the surface.

There are metallic films that can be use in the IMD In mold decoration process. Some very authentic looking metal finishes are available. Limited surface complexity however.

let us know… from pics, it sure looks like a metallic additive blemish. If you have one, you’d have a better feel for what was used though

I still wonder if there isn’t a way to control the blemish in an interesting way with metallic flake… maybe it’s too hard to control and that’s why Logitech uses IMD

Thanks so much for all the help!

It looks like possible options are:

• Paint => expensive
• In-mold decoration
• Controlled blemishes
• Embrace flow and knit lines like Dyson
• Work with tooling engineers to minimize flow and knit lines =>possibly limits design. Can anyone offer specific “tricks” or resources?
• New material from Samsung/Cheil Industries => @ no_spec: thanks for offering this! I found the material, it’s called “starex Luminous.” Is this the same as you found? How does the price compare to traditional ABS and traditional metallic ABS? Would you please let us know how your test samples turn out?

that is the same material - I’ll let you know how it compares when we get a part run.
I think you have to compare it’s price to painting to see if it’s a better deal or not, how big is your part?

The parts can be as large as 3’x3’x6". Good point to compare it to painting.

Thanks for the heads up- helpful for a current project.