Manufacture complex mechanical parts with strictly tolerances could be very very hard to achieve.
In particular, when the parts are “slim”, the reference planes not reliable, and we must check item “far” from them, it’s changeling keeping tolerances in a repetitive way. The most difficult tolerances to dealt with are:
- Parallelism and perpendicularity between planes
- Positioning tolerances (tol. 0.1 means 0,03mm for each Cartesian axis!)
- Profile tolerances, in particular on instable or curved parts that bent on themselves
But the question is: why it’s so difficult achieve strictly tolerances in these situations?
1.Material deformation, due both to the milling and to the clamp
2.Heating generated by the chip removal and the environment temperature
3.Run out of the tool holder, of the machine chuck and the tool
4.Precision tolerance both of the milling machine and the 3D machine
5.The reliability both of the mechanical support and the manual fixing into the machine
6.Kind of tool and the strategy used
7.The correct manufacturing process
8.The way to check the parts on 3D machine and data analisys
Eventually we must consider a lot of factors that became important when we deal with hundredths of a millimeter.
In the picture below we cut more than 90% of the raw material and achieve the shown tolerances by working on two 5-axis Hermle machines on the same time with 6 different mechanical supports. We check by 100% and find out good the 96% of the parts.