CAD Design v.s CNC Machining
Hello everyone,
I am new to this forum so let me introduce myself. I recently started helping my brother run his CNC Machine Shop. He gave me the task of doing the QC Inspection on parts and I am learning a lot. My job is to please the Engineers( you guys), but it's not an easy job. So here I am trying to understand really what it is that the engineers want. I have a few questions. And I don't mind answering any questions that maybe a few of you might have for me as well. I think this can be a win-win discussion. I can also tell you how we(cnc machinist) feel about mechanical engineers. ;) Disclaimer: I just started this job so please excuse anything I say that is wrong.
1. We are provided both CAD drawings and STEP files. But sometimes they don't match up. My brother say ultimately the STEP dimension is more correct than the CAD drawing. This can be confusing as I am writing my CMM program to match up with the dimensions on the drawing but the CMM is telling me the dimension on the STEP file is off. What is going on your side that might be causing this? Or is this just the engineer's fault?
2. We have drawings from a client that call out A LOT of true positions, which my brother said I can just ignore since it is very hard to achieve. There is a thing call propagated error. The parts are slightly out of its tolerance of true position and the parts are never rejected. Which reconfirm my brother's judgement, you guys don't really care. Do you guys really care about true positions or is this just a rookie's job thinking he can make the part as perfect as he want?
3. We get parts that may look simple, but to the CNC machinist's perspective can be very tricky. Do Mechanical Engineers have any training at all on what is capable from a CNC machine? We had a part that cost $900/EA just to make and it is just an aluminum frame.
4. Just any tip/advice for me in general to please our customers( you engineers). Thanks.