How do I go about choosing the best metal shop to prototype my first product?

You can try manufacturing aggregators like.
3Dhubs
https://www.3dhubs.com/
They will help you find the right partner for metal fabrication, 3D printing and CNC machining.

Ask them if they see any potential issues with manufacturing your CAD design, including whether they think any weld marks will show through the metal, whether any bend radii are too tight, whether they can foresee any issues in assembling the parts at the end (you should send assembly instructions, or work with them on them) etc.

Ask them what their prices would be for 1, 10, 500, 10k, etc. units, so you know how well you can scale up with them if needed.

If you're in initial discussions with them, find an existing product that exemplifies the quality you would like to get from the shop, and take photos of the example. For instance, it you want the quality and finish of an aluminum Macbook, use that as the example. Make sure to include the color and finish instructions in whatever files you send them.

Ask them for a single sample before a full order, and how much that sample would cost. You're going to want to have a "golden sample" that you approve of, that they will try to match in all subsequent copies. It's also good, if possible, to have "limit samples" which provide high and low bounds of the product's final appearance.

Let me know if you need any more help.

Best of luck.

Hello, good question. It really depends on how accurately the prototype needs to be. The first thing you need to check is that you've taken into account the design guidelines for producing something for CNC. There are a few things to consider for this, namely no overhangs, considering what type of bit they'll be using. The CNC place should give you feedback on this, there's also a few online resources for checking your design - pretty sure there is a good guide here: https://geomiq.com/cnc-design-guide/ The next thing you need to think about is producing the engineering drawings, this basically acts as a contract laying out in numbers what dimensions the supplier must achieve. Finally make sure you try and pay via a platform like alibaba that covers you for any dodgy companies that take your deposit and don't come through with the goods - speaking from past experience! :) If you want to schedule a call I would be happy to help set up your engineering drawing and help you get the best price using these online platforms. Cheers, Alex

Competency-wise, you want to make sure they can hold the tolerances you need for your product, and that they have the quality assurance testing in place to check that they have made the part to your specifications. Double check that they're comfortable working with your metal of choice (many machinists hate titanium, for example).

Business wise, you want to make sure they both support your minimum expected order and can handle room for growth if it takes off like we hope it will. While not strictly necessary, things usually go better if you feel some rapport with the shop and communicate in similar styles.

I'd be happy to discuss more specifics if talking to a metallurgist sounds useful!