The material presented in this video are some highlights from NADCA’s online webinar - Process Control: Introduction to Process Control.
The first part of this series will provide a brief introduction to process control techniques. The need for the application of statistical techniques to controlling variation in the die casting process will be emphasized.
For information on purchasing a downloadable copy of this webinar in its entirety, please visit: http://www.diecasting.org/store/detail.aspx?id=WEB299
(Transcript of the highlight.)
And so, this is a more modern way of thinking about Process Control Theory. The idea is to utilize feedback loops on all the inputs. As we said, the process is out of control if we've not got any assurance that the machine is actually doing what we want it to do.
So, here's the input. Again, maybe the input is the fast injection speed of four meters per second we talked about before. Then we make the process produce the casting. But instead of looking at the casting itself, what we do is, we look at the input. We measure the input and again, it's 3.5 meters per second. We compare it to the desired value and then we adjust as required. Again, we could adjust it real time or we can adjust it on the next shot. The idea behind this modern thought of Process Control Theory is that by controlling all of the inputs, therefore the output will be predictable. Therefore the output, in this case our casting, doesn't need to be measured.
Now, maybe we still want to do a statistical sample to make sure there's nothing really strange happening, but the idea is now we don't need to do 100% inspection. The idea is if, when we set the die casting parameters for a new die for a new part, we need to identify the speeds, the pressures, the times, the temperatures. The idea being is if none of those vary, if none of those change, or at least change significantly, then the process is going to be under control. If every shot is made at four meters per second and we have defined that four meters per second makes a good casting, then we should be producing a good casting as long as all the other process parameters are also under control.
That's the idea behind Modern Control theory and obviously it really is very important that therefore we measure and monitor and control all our inputs to the process. Now, one of the questions, of course, is as we've just talked about before, we're going to see some level of variability. Everything is going to vary. So the speed, maybe the speed varies by 0.1 meters per second. 3.9 to 4.1. Maybe it varies by two meters per second. It goes from two meters per second to six meters per second. Are those significant? Well, the problem is at the moment we don't have enough data.
We'll talk about this a little bit later, but at the moment we don't have enough data. I would think that if you go from two meters per second to six, that's going to have a significant impact on part quality, but not necessarily. You think that going from 3.9 to 4.1 would be okay, but again, not necessarily.
What we're going to do is talk about, a little bit later, talk about how we define what's an acceptable tolerance range on those kind of parameters are and therefore when our process is in control, and we can be relatively assured of making good castings, and when our process is out of control and therefore we ought to do something about it.
To purchase access to this course, visit the NADCA marketplace at www.diecasting.org/store. Purchasing a course through the Online Education System grants you one year of access to the recording, presentation, support material, and test when applicable.
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