Two-shot, Co-Injection, or In-Mold Decorating?

I would like to know the pros and cons when comparing two-shot (two-color), co-injection, and in-mold decorating to each other. What is the general cost and availability if manufactured in the United States?

I have designed overmolded parts (plastic with elastomeric overmold) in the past. This required the plastic part to be designed with a mechanical interlocking features so the elastomeric material would bond to the plastic. I am guessing overmolding would be more costly that the previously mentioned injection-molding techniques.

If two identical, but different color, materials are used (ex: PP, PC/ABS, etc.) for a plastic housing, which process would you recommend and why? The two different colors where suggested by an industrial designer to improve the aesthetics of a part, and the part will probably need to be dishwasher safe (i.e. utensils).

I haven’t used or quoted co-injection.

Of the other two, for a lower volume (10k-100k), two-shot is more reasonably priced. You have to get multiple cavities or molds made, but we are talking no more than 2x the price of a single mold.

When I quoted IMD in NA, the price was 8x what we normally pay for a mold. I didn’t follow up too much, because that was way beyond my budget, but I did notice the quote included hot runners, which would certainly add to the cost.

To sum up: it seems that IMD only pays in large quantities.

From your response, is the cost of two-shot approximately the same as over-molding (elastomeric material bonded to plastic substrate)? I believe over-molding increases the cost by approx. 50% more than that of a standard mold.

Is a two-shot part designed like that of an over-molded part? Where can I find a design guide on the two-shot process?

Two shot is overmolding. If different cavities aren’t used, the first shot would fill the entire cavity.

Are you working with a supplier already? Do you have a design in mind? Designers will typically only be able to give you some broad idea of cost and capability, the mold shops are the experts.