I had a rather strange thing occured to me recently that I have never encountered before.
We recieve a lot of part files from our customers that we either mill or cut from.
This time was no different.
I recieved 24 different files, and all parts were laser cut according to their part file.
These 24 different parts all required a measuring report, and this was when we found out one of the parts missed its tolerances - by over 1mm.
All others were approved.
Well, first thing I did was to make a new one. Instead of laser cutting the part this time, I milled it instead. Putting these two parts, the lasercutted and milled, next to each other you could clearly see these were 100% identical. And as expected, the new milled part failed the measuring too.
I then began looking into the part file instead, and discovered what I at first thought was a resulotion error in SolidWorks.
It looked like this:
You can clearly see some kind of shadow next to the edge.
I never put much thought into this as I disregarded it as a resulotion error.
But when I did a 1:1 print on A1 paper of the part file, and aligned my milled and lasercutted parts onto it you could clearly see the 1mm miss that the measuring report got.
So I did a new part file based upon the original sketch in the original part file, milled a new one - and this time it was approved.
So what happened?
The measuring was done upon the original part file, and both the milled part and lasercutted part was machined according to the same part file.
How can our CAM software (both milling and cutting) read the part file wrong? .. and not the measuring software?
Has anyone ever experienced anything like this?