software and controls
that the very fi rst blisk manufacturing project you take on us- ing expert blade software will be successful:
One of the biggest issues is making sure that the machine’s rotary axes arrive at the same point at the same time.
Make sure you have a good fi ve-axis post. The post has to be tuned to the specifi c machine’s controller. There are literally dozens of settings that may need to be altered to en- sure that the post and controller are in sync. An experienced post consultant can fi nd which settings need to be altered by running a test piece and examining the results. One of the biggest issues is making sure that the ma-
chine’s rotary axes arrive at the same point at the same time. If you machine a cylindrical test piece and get a wavy pattern that looks like a ghost house, then you can be pretty sure that the rotary axes are out of sync.
Another important issue to be determined during calibra- tion is how accurate the machine is at various positions in the work envelope. It’s common sense, but many users don’t realize that where you put the part on the machine will make a huge difference in how the part will look when it is done. It
is easy to make a good fi ve-axis part in the center of the ma- chine’s work envelope. You just rotate the workpiece at the center, and put the tool next to it, and you will always have a round part. However, as soon as you move the workpiece outside the center, you have to make sure that every motion is mapped correctly to the controller to avoid incremental distortions. There are many other issues that may need to be ad-
dressed during the post/calibration process. The fastest, and usually the least expensive approach to getting a good post, is to hire an experienced consultant to do it or to obtain your expert blade software from a source that makes post refi ne- ment part of the package. Use a clean CAD fi le. In an ideal world, the blisk manu-
Calibrating the machine and post by cutting a test piece is an essential step for assuring that CNC programs generated with expert blade software are safe and effi cient.
facturer would always be working from a clean fi le sent to him directly from his customer’s master CAD system. Many blades are designed in CATIA or Solidworks. However, over many design and prototyping iterations, these models may be directly translated into other CAD/CAM formats or, even worse, circulated to various software packages as IGES fi les. Every time a fi le is translated into a different format some- thing is lost. If there are too many gaps in the CAD model, the expert blade software will be incapable of replicating the design intent of the original model. If you examine the CAD fi le at high resolution and fi nd gaps in the model, then it will be necessary to fi x them or to obtain a clean model from the design’s originator. Set up your simulator. You’ll want to use machine simula- tion to uncover any possible human errors that would lead to clearance issues. Machine simulation based on your CAM software’s output is easy to set up, but you will have to spend a little time “building your machine.” If you are going to be doing a lot of blade work with very complex geometries and surfaces and hard materials, it may also be desirable to use Vericut to do the simulations based on the actual G-code generated by the expert blade program and the kinematics of your machine. This is the more expensive simulation alterna- tive, but also the one with a nearly 100% chance of catching any programming error. Cut a soft part. You won’t always have to do this, but in the early stages of developing your expert CAM capabili- ties, it is recommended as a confi dence-building step. Once you have created, simulated and run your program, cutting wax or some other soft material, you will know for sure that your program is good. Any other issues that might occur on the hard material will involve how the part was set up on the machine and the choice of feeds, speeds, and other basic
62 — Energy Manufacturing 2015
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