Prototype #4: The Last One?

After a long overdue wait I finally have the pieces of prototype #4 in my hands, ready for assembly, and they are looking great!

Fresh from the Shop and Looking Good!

Prototype #4 has a number of design changes from the previous prototypes originating from a variety of tests, feedback, and research:

• Magnetic base and cap (it works very well...not sure how I overlooked this design initially)
• Slightly longer for a combination of aesthetics and to hold long-style USB boards if I ever need to
• Hole in the cap for a lanyard attachment
• Slightly simpler interior design for cheaper production (at a small cost of strength)
• Very high strength materials (Aluminum 7068-T651 and Titanium Grade 5)
• Hard anodized Aluminum (dark red)
• Laser engraved logo and serial number

Close-up Showing the Laser Engraving Details

The production itself was basically flawless with only a few minor issues encountered:

• Thread in base was 0.05" deeper than specified (makes assembly a little trickier)
• Threads in the Aluminum base were a bit tight (re-tapped manually after anodizing)

Other than the smaller quantities (10 Aluminum and 5 Titanium) the production process was identical to that of the (hopefully) eventual larger order. This minimizes any surprises and gives me a good idea on the base material cost and time required for assembly.

All that is left now is the final assembly of the USB boards and epoxying before I can get back to destructively testing a few units for fun!

Prototype #4 Production: How to waste 4 months....

I haven't updated this blog in a few months as I was waiting for a small production run of prototype #4 to be completed. I only expected this to take a few weeks but it ended up being a annoyingly painful 4-5 month process.

The Quotes

I originally tried to get quotes from 5 different machine shops from (names have been removed to protect the guilty):

Shop 1	Shop 2	Shop 3	Shop 4	Shop 5
High-end CNC shop Used for prototype #3 Al = $70/set for x100 Ti = $130/set for x50	Advertised as a large, high-volume CNC shop Did not respond to several quote requests and inquiries	US company via internet Has simple CAD software for instant quotes Al = $25/set for x100  Ti = $80/set for x50 Many production issues	Local machine shop Took 2 weeks to respond to initial quote request Could not source desired Al alloy Al = $160/set for x100 Ti = $350/set for x50	Local machine shop Did not source or work with desired materials

I don't understand why I never got a response back from shop #2 despite them looking like a large and reputable shop. I guess they're doing so much business they don't need to reply to quote requests although a simple "We cannot do this order for you at the moment" type reply would be nice.

I tried shops #4 & 5 as they are close in the area as me but both had issues with my material choices. I understand not wanting to work with certain materials, like Ti Grade 5, but I'd expect a machine shop to be able to source materials better than an amateur like myself can. ...or perhaps I'm overestimating how commonly Al 7068-T651 is used. Even with cheaper materials shop #4's quote is more than double that of shop #1 and 4-6 times that of shop #3.

I've used shop #1 for a large number of orders in my previous job as well as for making two pieces of the VIUD prototype #3. They produce excellent quality parts and are very easy to work with. I've always considered them as an "expensive" shop although after this episode I've warmed up to their prices...you get what you pay for after all.

An Unfortunate Choice

Given the wide range of quotes I went with the cheapest one from shop #3....unfortunately I choose poorly. Shop #3 has a slightly different operating practice than most other machine shops. It supplies a very simple custom CAD program that you use to create designs and submit them for instant quote requests. While their CAD application is very limited compared to SolidWorks or AutoCad it works well enough and being able to get instant quotes for simple parts is very convenient. Their quotes for the parts were also far cheaper than anything else I could find by over a factor two.

While shop #3 appears to have a lot going for it they had multiple issues actually delivering them. Trying to contact an actual person is difficult and usually you end up talking with someone who can't, or doesn't, actually answer your questions. Their lead time was longer than most shops at one month but this was extended twice to two and three months without explanation.

Oh....but it gets so much worse. After finally actually completing my order of 15 pieces after 3 months there were three serious quality control issues:

1. Knurling was the incorrect type (straight instead of diamond)
2. The internal thread in was made at the incorrect depth



Worst Knurl Ever

3. The depth of cut in the threaded plug was wrong.

I could probably live with the incorrect, and poorly made, knurling but the other two issues were a deal breaker. I know that mistakes happen in production but these parts are so simple and the mistakes so basic I'm at a loss to explain how they might of occurred. Call me crazy but I expect a competent shop to have the basic ability to make things according to the drawing, especially trivial parts like this. Coincidentally they messed up on each of three parts.

I asked, and the agreed to remake everything, but after another few weeks and several more manufacturing issues I was told they "couldn't find anyone to make it" and I had to cancel the order. The only nice thing I can say is that it didn't cost me anything...except 3 months of time.

The End Result

So +3 months after placing the order for prototype #4 I had nothing to show for it. At this point it is close to Christmas which scratches off another couple of weeks before I can source and place an order with shop #1. I finally get the 15 pieces in my hands some 5 months after the initial order with shop #3.

This whole process highlights a simple wisdom I've learned over the years:

Supplier relationship is often more important than price

Shop #1 may not have had the best price but they are incredibly easy to work with and produce excellent quality work (the prototype #4 pieces look great). I'm looking forward to using them in the future for larger production quantities of the VIUD.