A look inside the magic box
March 25, 2014 by Dick Morley
When I first learned that this issue of Manufacturing AUTOMATION was going to focus on the power consumption of the automatic process, I shivered. “Goodness, I’ll have to be politically correct,” I thought. But then I decided to focus my column on the factors to consider when trying to reduce power consumption with the “magic box.”
The magic box, in this case, is the discrete products box, the “stuff” box — all refineries or any system that converts raw material into needed products in the marketplace. It is a box that has four fundamental surfaces — power input, waste output, raw material input and product output.
Inside the box we can imagine many things for improving efficiency and reducing costs. One of the most obvious is improving the power factor — the balance between current and voltage. Make sure you don’t use excess current to deliver the required power. We must make the magic box look like a non-inductive resistor. Since most of the factory boxes have motors, inductive loading is high. Correction where capacitance is added by third-party packages improves the efficiency of the system.
Do you remember your j or i homework? These are the power factor considerations to reduce power usage. When I was a machinist working my way through college, I noticed the capacitors hanging from the ceiling correcting the power factor. The power company knew about this and would charge for the apparent power used rather than the real power used. Higher-than-necessary currents also require larger wires and more dissipation in the distribution system.
Another consideration is when terminal systems are not being used or, as mom says, “Turn the lights off when you leave the room.” It is also important to size electric motors correctly. Matching the tool to the job is always an efficient decision. But why stop there? If you increase the frequency beyond the classic 60 Hz, efficiency will go up. I would recommend that you look at 400 Hz and 2,400 Hz. Yes, I know, the motors are more expensive, but they’re smaller and less energy is used to hold the magnetic field during the switches between pulses. These pulses are the cycles on the line. Some of that is helped by multiple phase sources, but this higher frequency can generally only be used in greenfield projects.
Let’s try something else and examine what it is we are making. My favourite story is one about Toyota (I hope the story is true). I heard that Toyota was making aluminum engine blocks — not for performance, but for efficiency. Aluminum is easier and less expensive to machine and ship, and the machines to machine them are smaller and cheaper. They win on the cost of power, machinery and shipping, and pay for it with the increased cost of the material. Aluminum is one of the most prevailing elements in the surface of the earth. If, in the design, we think about the production process, we can substantially reduce the costs of materials, product and power.
I recently had a mechanic complain about having to replace the entire mechanism of the headlight just to replace a bulb. If we only have to replace the bulb, the energy to make that area of the automobile increases. Removing separate items is a key to retained energy. The computer and TV set were made with many components. When it breaks, we replace the whole thing. There is no way to make part of a TV screen small. Keeping the number of separate parts down requires less information and saves on transportation.
Let’s now look at “just-in-time” manufacturing, which reduces standing inventory. A car company should only have 10 of its models in the parking lot of its sales outlet. You point to the one you want and the next day it appears on the lot. We keep minimal inventory and transport to the needs of the day. A concept that I like is called “the moving now” — deal with it now and pay less for the past and the future.
There’s much more to learn about the magic box. Look at both inputs to the box (power and raw material) and outputs (waste and product). Most of the power can be reduced by considering design factors. But, as you know, there are many other considerations when trying to reduce energy. So much to do, so little time.
This column originally appeared in the March/April 2014 issue of Manufacturing AUTOMATION.