Completeness

Make sure you are not missing anything in your design.

If you are new to custom manufacturing or have limited experience, you must exercise great care to specify exactly what you want and not rely on the performance of prior orders.

Specifying exactly what you want and don't rely on prior orders

Specify everything that is important for your part - dimensions, positions, tolerance, GD&T, color, finish and even unusual requirements such as refraction index if needed. Manufacturing and mind-reading don't mix - you must be explicit. For example:

• A customer made a U shaped sheet metal bracket that needed to have a distance between the "legs" accurate to +/- .002". But she never specified this tolerance and only specified a general job tolerance of .005. The parts did not fit.
  
• A customer made a spring that had to be magnetic but this was not specified. The part did not function as needed.
• A customer ordered a sculpture and expected a flawless finish. The parts were machined conventionally. The appearance was not as expected. 
• A customer designed a 90 deg laser mirror reflector holder and assumed the 90 deg angle would be exactly 90 deg and no tolerance was given. The laser beam did not reflect properly.
• A customer designed a flywheel and specified general tolerance but not concentricity - the flywheel wobbled more than expected.
• A customer placed an order with a one-inch hole and a default tolerance of .005". On the first order the hole happened to be on the high side but within spec at 1.005". As a result, a bolt slid thru the hole as desired. On the next run the hole was on the low side at .995, still in spec, but the bolt did not fit. Both orders were in conformance. 
• A customer made a box with a lid. A year later he ordered more lids but the color did not match exactly. No color tolerance was specified. The parts did not match.

Tolerance controls conformance, not prior orders. Just because a first run turned out the way you envisioned does not mean a reorder will be the same. You must specify exactly what you want and the tolerance range.  The eMachineShop CAD software helps you specify most common aspects of design and most designs do not need additional specifications but you must be careful. A reorder might be made by a different machinist using different discretion, a color shade might be slightly different, sizes can vary within tolerance ranges, etc.

Make sure you specify every important detail about your job. We want you to be happy with your parts!