This is a prime example of the phrase "Computers don't make mistakes, people do".
I ordered a batch of custom made parts from a shop that uses a CNC laser/plasma machine to cut steel and other metals.
With laser/plasma cutting, there has to be a tolerance for the "burn out" which is a small gap (about 1/16" to 1/8") between the raw material and the actual dimensions of the finished part. Very Important: The burn out tolerance is determined by whether the critical dimension is on the inside or the outside of the part and that detail must be properly entered into the CNC guidance instructions.
For example, is the machine cutting a circular hole in a finished plate (and the circular piece is scrap) or is the finished part itself circular and the plate will be scrap. This makes a Hell of difference in setting the burn out tolerance!!!
Cutting to the chase, I received the finished parts and there is a constant 1/8" error throughout every part. After analysis, it looks like the operator reversed the burn out tolerance for both the inside and outside dimensions. As a result, the outside dimension of the part is smaller than specified, but the holes are oversized.
The bottom line: Whether you're running a CNC or manual shop, remember the old saying "Measure twice, cut once".
I ordered a batch of custom made parts from a shop that uses a CNC laser/plasma machine to cut steel and other metals.
With laser/plasma cutting, there has to be a tolerance for the "burn out" which is a small gap (about 1/16" to 1/8") between the raw material and the actual dimensions of the finished part. Very Important: The burn out tolerance is determined by whether the critical dimension is on the inside or the outside of the part and that detail must be properly entered into the CNC guidance instructions.
For example, is the machine cutting a circular hole in a finished plate (and the circular piece is scrap) or is the finished part itself circular and the plate will be scrap. This makes a Hell of difference in setting the burn out tolerance!!!
Cutting to the chase, I received the finished parts and there is a constant 1/8" error throughout every part. After analysis, it looks like the operator reversed the burn out tolerance for both the inside and outside dimensions. As a result, the outside dimension of the part is smaller than specified, but the holes are oversized.
The bottom line: Whether you're running a CNC or manual shop, remember the old saying "Measure twice, cut once".