First of all, I talked a little bit on the fixture side of things, and we have a method and a product that we use here at Makino called continuous pressure hydraulics. There are a number of error proofing methods that are applied within this fixturing process which is why we develop it.
We apply these techniques to most of the turnkeys that we deliver. Our customers purchase this type of a hydraulic supply system for their fixture. Basically, this continuous pressure hydraulic system can provide live hydraulics in the work zone to control a process. This is a Poka-Yoke process because many times, if you're holding the part, there can be the fleximatic curves while you're machining the part.
For instance, the cutting forces due to temperature changes within the part. But if you're able to control the clamping pressure on that part during the machining process, which is what we mean by live hydraulics, then you can improve the process and eliminate errors that would occur because the clamping pressures are consistent, causing a part to deflect during the machining process. This is adding variability in terms of what the finished tolerance of that part coming out of the machine will be. Live hydraulics can control that, and eliminate a problem or an error in the machining process before it happens.
Another aspect of this CPA system is an air circuit that we put into the supply system that can be used for part sensing. We can introduce air and monitor back pressure when a part is put onto the locators of the fixture. We can put in the air circuit and certain locators and gauge the back pressure of the air going to that particular locator, and based on the back pressure of that air sensing system, we can determine if that part is truly properly fixtured up against the locator or not.
If it is not, then the machine can send a warning, via overhead stack light or a visual warning, or if it’s in a system or cell and can send a message to the cell controller and can stop the process and warn the operators that there is a problem, and it can be corrected before a mistake occurs. That’s a clear, good example of Poka-yoke.
Pulling pork through the center is another capability that we built into a lot of fixtures because one of the mistakes in the manufacturing process is mis-setting the part onto the fixture. One of the most common ways of miss-setting a part on a fixture is when there is a chip or something like that in the way of one of the locators. You can miss-set the part by five to 10 thousandths of an inch. Now you're going to get a part that is not consistent with all the others. We can put in coolant flushing systems as part of the CPA process and again, prevent an error before it ever occurs.
Then finally is electronic sequence. The way the CPA is designed is that the clamping system on the fixture can be sequenced electronically or digitally, which means that it’s a very reliable and repeatable method of clamping the part in terms of the clamp sequences. Therefore, the clamping pressures as they come down onto the part, onto the fixture and on the locators is going to be very consistent; again, eliminating the risk of miss-setting the part. It adds predictability, reduces variability and eliminates errors before they even occur. I have a case study example of this, showing a long part that is hollow. It’s an aluminum die cast piece so it tends to be flimsy. It can flexed easily because of the thin walls on this long narrow part. Holding the part and getting good predicability and consistency of part quality was a real challenge. With the CPA system, we were able to do a number of things. Number one, with the electronic sequencing of the clamping motions, we were able to make this very, very repeatable and the parts always at the same place every time, reducing errors that can occur and misplacing the part.
