To Scott_bob: Hi, this is Randy. Let me ask you a question? Have you ever done an impact test on a machine tool cutter assembly (Stackup) and then diagnosed a FRF or Stability Chart that was produced by that process to use for the machining process, in conventional or HSM?
I have done it hundreds of times, I am on the floor right along with the machine operator doing real time measurements, improving the machining operation. I have worked with many different machines, conventional and HSM, all kinds of controllers, all kinds of cpu’s, all kinds of cutters, etc. It doesn’t matter to me what machine tool is used I still get the results of the machine dynamics in the end at the end of the tool tip because that is where it all shows up, period. I agree that it is a good idea to use the best controllers, cpu’s etc that one can purchase but it still doesn’t tell you what RPM to run the cutter at to maximize. Lets face it, no company is using the same controllers and cpu’s on their machines and that certainly does not tell the operator or programmer what RPM to use.
It takes only a few minutes to do an Impact Test and get the results, it is not time consuming as you might feel. It is just as useful on a single mold as it is for production runs. If your running the wrong RPM then the depth of cut will suffer along with finish and MRR. I am not sure what your statement of “the vibration or acoustic signature must be taught to the system before compensation dynamics can offer benefit” means? The dynamic signature measured at the tool tip is a direct result of the overall machine tool system, there is no being taught applied, it is what it is and it can be measured to tell one what RPM and Depth of cut to take in a matter of seconds.
The statement “Molds are never production items where a process can be monitored and tuned to optimum performance. Who has time for this? In a production run, that’s a different story” That is an assumed statement which is not true, if you have ever done an Impact Test or an Audio Chatter Recognition reading then you would not be saying that. This is the kind of attitude that I have dealt with of many companies and the one greatest reason why they are not maximizing operations, it is sad that it is so common place in the industry. Hence, it is why I always start off my presentations to audiences with” Forget antiquated ways, go beyond your comfort zone”.
Here is just one instance of going out of ones comfort zone: 1” ball cutter, steel cutter body with abrasive particle diamond attached, machining what is called a T-shirt – composite material, running 4,000 rpm, HSK 63A interface, 18,000 rpm max spindle, 6” OAL gage length, lots of noise and vibration during the cut, operator scared to run it due to unstableness. Myself, sitting in the tool crib about 30 yards away, I hear the noise and decide to try something. I use my laptop and audio chatter recognition software, stick the microphone out the door and take a reading. This took about 60 seconds to do, a dominant chatter frequency shows up, the software suggests an RPM, I walk up to the operator, give him the RPM to try – 8,000 RPM. He freaks, says no way, was really scared now but agreed. I take the Stackup tool and check static balance, it is in a standard TG collet holder, checks okay, put the Stackup tool back in the machine and the operator runs it at 8,000 rpm. Result, cut stabilizes, operator resumes cut and finishes part in a timely manner now, I document parameters on my dynamic database for that tool so programming will know what rpm to use of this Stackup again. All this occurred in about 3 minutes and saved one heck of a lot of time on the machining operation, let alone the wear and tear on the machine tool, cutter and part. I have done this many times over for one piece jobs, this was a mold shop by the way.
I suggest you have a reputable person come in and show you how to use an Impact Test or Audio Chatter Recognition or you take a class on it - so you can experience the process. Forget antiquated ways, go beyond your comfort zone.
See video's of the process at:
http://members.cox.net/camminc/