Monthly Archives: January 2022

11th Commandment

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THOU SHALT NOT KID THYSELF

Usually this issue does not surface before the casting plant is making a loss. At that point in time it is no longer possible to lower the performance bar to the level that mediocre performers like. Many of them survive by coloring the reporting metrics instead of improving their personal performance. If you are a player who actually wants to improve the viability of the casting plant that funds your livelihood, you start to succeed when you ignore the colored reporting data and begin gathering data you need to guide your efforts.

My preamble sounds really pessimistic. The actual issue is how do you get out of the downward spiral. It starts with the shot counter that you cannot reset. This US$ 23 dollar item is mounted in every die cast machine electrical panel. It is wired to the control output that activates the fast shot. One count is added every time the fast shot is activated. The fact that the counter cannot be reset frustrates the players who want to color the data. If you cannot get these counters installed in your machines, it is time to start looking for other employment. It is easier to land a new job when you have one. The stated purpose for installing this counter is die life tabulation. Knowing how many shots are on a set of cavities is absolutely necessary for planning cavity replacement. You are ahead of the game if you already have shot counters that you cannot reset on your machines.

The first law of data gathering applies- Only those who gather the data believe it . Waste as little of your time as possible gathering data for others. They won’t believe it anyway. There also is a lot of gurus out there selling courses on how to spend more time gathering data. These techniques can be very useful for the singular individual who needs to employ them one time. Start simple. Record the shot counter at the start of the shift. Record it 8 hours later. Do not be surprised if the number of shots made is less than would be predicted by dividing the 8 hours by the cycle time. The best die cast results occur when even cycles occur continuously. The accounting group can tell you how many castings of each part number are sold each year. The die life report tabulates how many shots. Surprise, surprise, Not every shot turned into a sold casting. When you begin analyzing the numbers, be aware that many casting plants are only 30% efficient. (Yes it is possible to achieve 81% efficiency running 364 days/yr for 5 yrs in a row which was the track record for the plant where I learned die casting)

Keep the insight that you gain from gathering data to yourself. You are the only one that is going to believe it anyway. Especially in a plant that is not making a profit. Mediocre players are on the hot seat. Politically defending yourself will distract you from making actual improvements

SCALE

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die cast machines evolved from steam engines

High pressure aluminum die casting is a thermal process. Our melt furnaces add a lot of heat to make aluminum molten. During each casting cycle this heat is transferred to the casting die solidifying a casting. In each casting cycle the heat added to the casting die must be removed so that the die is ready for the next casting event. Evaporation of water is the most common heat removal method. Die spray systems and cooling towers remove this heat Because the thermal conductivity of die steel is low the majority of the heat is removed by die spray when it is used. This article is focusing on the heat removed by the thermal passages within the die

Fluids flowing through the thermal passages in the die remove heat. Cooling tower water is the most commonly used fluid because water has a high heat transfer capability. Other fluids used are hot oil or compressed air. The properties of aluminum castings are enhanced by rapid cooling. In many casting dies careful placement of internal thermal cooling passages is needed to create quality castings. These dies only produce quality castings when proper heat transfer flow occurs through clean passages.

Cooling tower water has some disadvantages. The evaporative cooling tower concentrates minerals in the water. These minerals then deposit within the casting die as scale. I always use individual return lines so that a once a shift check for plugged thermal passages can occur. Visual management is better than nothing, but it can result in whole shift of scrap castings. No heat removal is occurring if the passage is plugged with scale. It is even more frustrating when you need to pull the die once per shift to clean out scale build up -happens when boiling occurs in the passage.

The emergence of structural castings and 3D printed conformal cooled inserts is causing a rethink. Some players are trying to set up a HPDC process more like injection molding. ( The die temperature is totally set by the TCU (thermal control unit) More internal die cooling is designed in to eliminate the evaporative spray cooling. As with any new technology being developed there are growing pains. Scale build up being one of them. Starting my career as a piping engineer I suspect the solution for scale build up will come from our “Engineering” roots. Engineers are the people who ran the steam locomotives. Eliminating scale mineral buildup is a lot easier if you circulate water that does not contain them. Sounds like boiler feed water .https://en.wikipedia.org/wiki/Boiler_feedwater

Having made a few million aluminum castings without using evaporative spray cooling, I can report some benefits. The casting plant is no longer a steam bath in the summer. Spray lube induced porosity problems disappear. Beyond that there is a fresh water shortage .https://www.bbc.com/future/article/20170412-is-the-world-running-out-of-fresh-water