I recently went to MFG.com and tried to get a small run of parts made. I found 2 different suppliers — 1 in the US, and one in China, and had them try and do the work. The work was CNC milling of some HDPE plastic blocks — hardly rocket science.
Here’s the Skinny — the cheapest US shop came in with a bid of $191 for the job, with $7,000 as the most expensive. The modal bid was around $500. In China, the cheapest shop came in at $2.00 for the job, the most expensive at $3,000, and the modal bid was around $50. I was doing a small run — 1 set of samples, then no more than 100 final parts.
First problem — hardly anyone knew how to read the 2d drawings. These are old drawings that have been used to produce parts for about a decade. They were professionally drawn, not something I just whipped together, a longtime ago. I was trying to build a few copies of an old machine that I happen to like, and found the original blueprints for. These were standard isometric drawings, with a top, side, front, and back view of each part. In almost every case, both the American and Chinese shops could not read them. They kept thinking the views were front views of individual parts — even though each view was properly labeled and numbered! An example would be “Part 001, Front view”. Almost no-one provided quotes for the parts. I had to explain that these were 2d blueprint drawings, not 3d models.
Second problem — everyone wanted 3d models. This is an old machine, and 3d drawings didn’t exist back then ( they did, but just barely ). No-one knew how to quote from drawings, and everyone wanted 3d models so they could put it into their CAM packages and get time estimates. In fact, in order to quote the part, I’m sure many of these people took the drawings and made cheap/dirty 3d models. Since almost all of the people doing bids on the job were likely sales people, and not engineers, none of these estimates were right.
Third problem — no one delivered. At all. The US folks didn’t deliver. The Chinese didn’t deliver. Finding manufacturing partners that can do the job and deliver on time is a difficult task. If you look at Kickstarter, this is perhaps the most common problem why “widget” type projects are late. The manufacturing partners can’t deliver on their commitments.
This experience has taught me something — I understand why manufacturing APIs work now. The humans are doing terrible jobs at basic tasks like reading blueprints — a computer can’t do it any worse. There are only a few companies I have worked with that I trust to do the job, get it done on time, and in budget — the ones that have hardly any humans in the process at all. Job intake is by computer, job quoting is by computer( and instant ), job scheduling is by computer, job is done by an automation, and the human is only loading/unloading the blanks. The few shops that do this are rare and expensive, but worth it.
In the mean time, here’s some tricks that may help you if you try to manufacture things:
1. Have 3d models. STEP files for CNC, not STL. Most CNC shops can’t handle STL files. STL files only work in additive shops ( laser sinter/fused filament shops ).
2. Have a high budget. A small run of a part will cost 10-100x the unit price of a production run.
3. Pick 3 manufacturers, all at the modal price. The lowest bidder is highly unlikely to deliver. Even a modal bidder is unlikely — but they’re a bit more serious.
Personally, I think I’ll manufacture all parts myself from here on in, or from the few trusted suppliers that have delivered on time and in budget. If I ever start a job shop, this will be my number 1 concern — all jobs on time and in budget( and as few humans as possible in the process to ensure this is so. )