CNC wheel diamond cut machines

What does the CNC lathe machine do on the wheel? 

It makes an original surface from an injured or repaired surface. 

When I start a rim repair service do I have to buy a CNC diamond cut lathe machine to cut wheels?

The short answer no; many shops have only rim straightener machines to repair structural damages. On the other hand, all professional, comprehensive rim repair shop has wheel Diamond cut lathe machine.