The meat and potatoes of this presentation, from a fixture designer standpoint, begins with what we like to call fixture economics. Inside of fixture economics we're looking at cycle time versus the number of parts per fixture. Basically we're trying to figure out exactly where and how many parts we should have on a fixture to optimize the process as well as get the maximum output per dollar spent that we can from the machine tool and for the particular process that you are trying to run. We're gonna look at how non-cut time amortization figures into that equation. Obviously, the fixture costs and number of parts per fixture has a great impact on that. We need to consider process issues and quality, and then of course maintenance considerations.

First consideration when looking at a fixture design is to determine the number of orientations per fixture required. You need to know how many parts on a fixture there are going to be. You have to understand what cutting forces you're gonna be imparting on the part and those that will be transmitted into the fixture, and then of course you also have to know your locating and clamping points and where those are going to be arranged on the fixture to accept all those cutting forces that you're going to be inducing into the part.

When we consider the number of orientations or number of parts per fixture you can look at a graph like this, and if you think of the left side of this graft as cycle time as well as number of parts per fixture and the horizontal part of the graph is number of parts per fixture and cost of fixture, you can kind of lay in a line that says as I go across from left to right the more number of parts I put on the fixture the less cycle time that I have per part on that fixture. Now a lot of factors go into how steep or not steep this curve ends up being. The type of part that it is, be it aluminum or steel or cast iron or nodular iron is going to change the slope of that curve considerably. The non-cut time or the time that the spindle does not stay engaged in the part is much higher on aluminum parts than it will be on nodular iron part, so the shape of that curve changes with each different type of material that you'd cut on a fixture.

You can look at this next bar that's on the graph as fixture costs. Obviously as you increase the number of parts per fixture the cost of your fixture goes up, not only in terms of the capital costs at the beginning but also your maintenance costs in the future. The more part orientations you have on a fixture the harder it is to maintain. You may sacrifice rigidity to increase the density of the parts per fixture, those types of considerations. So if you look at the intersection of these two lines, which we like to call the optimum configuration point, or the sweet spot, you're looking at a fixture that has the maximum number of parts per fixture that gets the most benefit for the cycle time reduction for those number of parts. Now I'd love to tell you that there is a simple mathematical formula that you could use to determine this, but with, with each case it's different; with each different part material, the number of parts, the size of the machine, it varies greatly, but time needs to be spent to study what the cycle time reduction is per part as you stack the parts up versus your fixture costs to determine this optimum configuration point. That's kind of a brief overview of what we like to call fixture economics.